Home > Products > State Listing > Illinois Data
Latest:
 AFDLOT |  AFDILX |
  [top]

000
FXUS63 KLOT 230308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LINE OF SCATTERED TSRA MOVING THROUGH BETWEEN 0345Z AND 0500Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.


//DISCUSSION...UPDATED 03Z...

THE LINE OF SCATTERED STORMS IS MOVING SOUTHEAST ACROSS THE AREA
AND WILL MOVE THROUGH ORD AND MDW PRIOR TO 05Z. COVERAGE HAS BEEN
ENOUGH TO MENTION IN ORD AND DPA TAFS. BUT ANY STORMS LOOK TO BE
SHORT-LIVED. NOTED ON KMKX AND TMKE RADARS IS THE SECONDARY COLD
FRONT SHIFTING WINDS TO THE NORTH-NORTHEAST RACING DOWN THE LAKE
AT AROUND 30 KT. THIS WILL LIKELY MOVE INLAND INTO NORTHEAST IL
AND NORTHWEST IN BUT POSSIBLY SLOW SOME. HAVE TIMED THAT AS WELL
IN TAF AMDS.

PREV DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN TSRA IMPACTING ORD AND LOW YET IF AT MDW.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY TEMPORARY MVFR CIGS IN THE COUPLE HOURS AFTER FROPA.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 10 AM THURSDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 230308
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LINE OF SCATTERED TSRA MOVING THROUGH BETWEEN 0345Z AND 0500Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.


//DISCUSSION...UPDATED 03Z...

THE LINE OF SCATTERED STORMS IS MOVING SOUTHEAST ACROSS THE AREA
AND WILL MOVE THROUGH ORD AND MDW PRIOR TO 05Z. COVERAGE HAS BEEN
ENOUGH TO MENTION IN ORD AND DPA TAFS. BUT ANY STORMS LOOK TO BE
SHORT-LIVED. NOTED ON KMKX AND TMKE RADARS IS THE SECONDARY COLD
FRONT SHIFTING WINDS TO THE NORTH-NORTHEAST RACING DOWN THE LAKE
AT AROUND 30 KT. THIS WILL LIKELY MOVE INLAND INTO NORTHEAST IL
AND NORTHWEST IN BUT POSSIBLY SLOW SOME. HAVE TIMED THAT AS WELL
IN TAF AMDS.

PREV DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN TSRA IMPACTING ORD AND LOW YET IF AT MDW.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY TEMPORARY MVFR CIGS IN THE COUPLE HOURS AFTER FROPA.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 10 AM THURSDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





  [top]

000
FXUS63 KILX 230205
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 904 PM CDT Tue Jul 22 2014

A boundary and the main front will still move through the area
tonight. Any thunderstorms that have developed along these
boundaries have not amounted to much as ILX 00Z sounding shows
high cape, but also very high CIN/capping in the lower layers.
Middle layers of the atmosphere are also very dry. So
storms/showers fizzle quickly and do not get much vertical
development. So will be updating pops for the overnight period.
Will be keeping chance, but have removed likelies. Confidence is
lower than earlier this afternoon. Remainder of forecast looks
fine, including temps and winds. Update will be out shortly.

Auten
&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten
&&

.PREV DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230205
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 904 PM CDT Tue Jul 22 2014

A boundary and the main front will still move through the area
tonight. Any thunderstorms that have developed along these
boundaries have not amounted to much as ILX 00Z sounding shows
high cape, but also very high CIN/capping in the lower layers.
Middle layers of the atmosphere are also very dry. So
storms/showers fizzle quickly and do not get much vertical
development. So will be updating pops for the overnight period.
Will be keeping chance, but have removed likelies. Confidence is
lower than earlier this afternoon. Remainder of forecast looks
fine, including temps and winds. Update will be out shortly.

Auten
&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten
&&

.PREV DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230205
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 904 PM CDT Tue Jul 22 2014

A boundary and the main front will still move through the area
tonight. Any thunderstorms that have developed along these
boundaries have not amounted to much as ILX 00Z sounding shows
high cape, but also very high CIN/capping in the lower layers.
Middle layers of the atmosphere are also very dry. So
storms/showers fizzle quickly and do not get much vertical
development. So will be updating pops for the overnight period.
Will be keeping chance, but have removed likelies. Confidence is
lower than earlier this afternoon. Remainder of forecast looks
fine, including temps and winds. Update will be out shortly.

Auten
&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten
&&

.PREV DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230205
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 904 PM CDT Tue Jul 22 2014

A boundary and the main front will still move through the area
tonight. Any thunderstorms that have developed along these
boundaries have not amounted to much as ILX 00Z sounding shows
high cape, but also very high CIN/capping in the lower layers.
Middle layers of the atmosphere are also very dry. So
storms/showers fizzle quickly and do not get much vertical
development. So will be updating pops for the overnight period.
Will be keeping chance, but have removed likelies. Confidence is
lower than earlier this afternoon. Remainder of forecast looks
fine, including temps and winds. Update will be out shortly.

Auten
&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten
&&

.PREV DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 230107 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.

//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 230107 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.

//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 230107 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.

//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 230107 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
807 PM CDT TUE JUL 22 2014

.MESOSCALE DISCUSSION...
807 PM CDT

THE HIGHEST THETA-E SURFACE AIR MASS OF THE YEAR HAS ADVECTED INTO
THE AREA IN ADVANCE OF A SOUTHWARD MOVING COLD FRONT ADVANCING
TOWARD THE CWA FROM SOUTHERN WISCONSIN. AN AXIS OF MID TO EVEN SOME
UPPER 70 DEGREE DEWPOINTS IS POOLING ACROSS NORTHERN ILLINOIS JUST
AHEAD OF THE FRONT. THE VERY HIGH THETA-E JUXTAPOSED BENEATH AN
IMPRESSIVE EML WITH VERY STEEP LAPSE RATES IS RESULTING IN A CLASSIC
LOADED GUN SITUATION WITH VERY STRONG INSTABILITY THAT IS CURRENTLY
LARGELY BEING HELD IN CHECK BY THE STRONG CAP AT THE BASE OF THE EML
BETWEEN 900-800 MB ON THE DVN EVENING SOUNDING. FRONTAL
CONVERGENCE ALONE HAS NOT BEEN TERRIBLY EFFECTIVE AT BUSTING
THROUGH THE CAP THUS FAR...THOUGH A FEW CELLS HAVE MADE STOUT BUT
RELATIVELY SHORT LIVED EFFORTS.

AS THE FRONT MOVES THROUGH THE CWA THIS EVENING WOULD NOT ANTICIPATE
MUCH BOUNDARY LAYER STABILIZATION TO TAKE PLACE AHEAD OF THE FRONT
DUE TO THE VERY HIGH DEWPOINTS IN PLACE LEADING TO RELATIVELY
LIMITED DIURNAL COOLING. WATER VAPOR IMAGERY THIS AFTERNOON AND
EVENING HAS SHOWN VERY WELL DEFINED SHORTWAVE TRACKING
EAST-SOUTHEAST FROM SOUTH DAKOTA NOW INTO NORTHERN IOWA AND SOUTHERN
MINNESOTA. AS THIS FEATURE CONTINUES EAST-SOUTHEASTWARD AND BEGINS
TO CATCH UP TO THE SURFACE FRONT...THE INCREASING LARGE SCALE ASCENT
ASSOCIATED WITH THE SHORTWAVE COULD RESULT IN A WEAKENING OF THE CAP
AND AN INCREASE IN STORM COVERAGE THIS EVENING ALONG THE FRONT AS IT
MOVES INTO OUR CWA. CONFIDENCE IN THIS SCENARIO IS NOT OVERLY
HIGH...SO NOT GOING TO MAKE ANY CHANGES TO POPS AT THIS POINT...BUT
THAT IS THE REASON THAT DESPITE THE PALTRY STORM COVERAGE THUS FAR
THAT I`VE BEEN RELUCTANT TO LOWER POPS. IF CAP DOES WEAKEN AND
SUSTAINED STORMS CAN FORM...THE VERY STRONG INSTABILITY AND MODEST
EFFECTIVE SHEAR WOULD BE ENOUGH TO SUPPORT AT LEAST A PULSE SEVERE
THREAT.

IZZI

&&

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.

//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.

//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KILX 230006
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
706 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230006
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
706 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230006
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
706 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 230006
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
706 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 705 PM CDT Tue Jul 22 2014

Believe VFR conditions will prevail at all sites next 24hrs. A
small area of showers is slowly moving through the area this
evening. In addition, a frontal boundary is still back along the
Mississippi river. With lots of moisture pooling along and ahead
of the front, thunderstorms are still possible this evening. So,
will keep at least a VCTS in all the TAFs for this evening til
around midnight. The limiting factor for thunderstorms is that it
is too warm at around 5kft. So any storms or showers that develop
will not be able to get much height. So do not expect them to last
very long. Then after the front moves through skies will scatter
out some. Then expecting cu to redevelop during the morning hours
with some high cirrus. Winds will be southeast til the front moves
through, and then become northwest and then north-northeast tomorrow.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 222341
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.


//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.


//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 222341
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* A CHANCE FOR TSRA BETWEEN 0200Z-0430Z.

* GUSTY NORTH-NORTHEAST WINDS DEVELOPING BEHIND COLD FRONTAL
  PASSAGE LATE THIS EVE AND PERSISTING THROUGH WEDNESDAY.

* SMALL CHANCE FOR TEMPORARY MVFR CIGS OVERNIGHT.


//DISCUSSION...UPDATED 00Z...

A COLD FRONT DRAPED ACROSS CENTRAL LAKE MICHIGAN THROUGH SOUTHERN
WI AND INTO IA AS OF 2330Z WILL MOVE SOUTHEASTWARD THIS
EVE...PASSING THE TAF SITES BETWEEN 0230Z AND 0500Z. ALONG AND
JUST AHEAD OF THIS FEATURE WILL BE POTENTIALLY ENOUGH CONVERGENCE
FOR LIFT TO OVERCOME THE STOUT ATMOSPHERIC CAP. COVERAGE SHOULD BE
SCATTERED AT BEST ALONG THE BOUNDARY. FEEL VCTS WAS STILL THE
PROPER WAY TO HANDLE IT AS WE ARE ABLE TO FOCUS IN ON FRONTAL
TIMING MUCH BETTER NOW GIVEN THE OBSERVATIONAL TRENDS. THE WIND
DIRECTION WILL TURN NORTHWESTERLY BEHIND THE FRONT AND THEN NORTH-
NORTHEAST WITHIN AN HOUR OR TWO OF FROPA. STRONG PRESSURE RISES
SHOULD LEAD TO PERIODIC GUSTS EVEN IN THE OVERNIGHT HOURS. THE
GUSTY WINDS WILL CONTINUE THROUGH THE DAY WEDNESDAY. WHILE THERE
MAY BE TEMPORARY DUE NORTH WINDS EARLY IN THE MORNING
WEDNESDAY...A 020-040 DIRECTION IS PRIMARILY EXPECTED FOR MUCH OF
THE DAY.

ANY MVFR CIGS OVERNIGHT ASSOCIATED WITH THE INITIAL COLD AIR
ADVECTION SHOULD BE SHORT-LIVED AND ARE NOT EXPECTED TO MAKE IT
INTO THE MORNING RUSH HOURS...AT LEAST AT THE BROKEN CATEGORY.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW IN TSRA IMPACTING OR EVEN BEING NEAR THE AIRFIELD BUT IF IT
  OCCURS HIGH IN TIMING AND THAT IT WOULD BE BRIEF.

* MEDIUM IN TIMING OF WIND SHIFT TO NORTH-NORTHEAST. HIGH IN WIND
  FORECAST FOR WEDNESDAY.

* LOW IN ANY MVFR CIGS OVERNIGHT.


//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...

THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...CHANCE OF TSRA DURING THE NIGHT.
SATURDAY-MONDAY...PERIODIC CHANCES OF TSRA.

MTF

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 222212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SSW WINDS INTO THE LOW 20 KT RANGE THROUGH LATE
  AFTERNOON.
* CHANCE OF SOME ISOLATED TO WIDELY SCATTERED THUNDERSTORMS
  DEVELOPING IN THE AREA THIS EVENING AHEAD OF A COLD FRONT. BEST
  TIMING APPEARS TO BE IN THE 01 TO 04 UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB/MTF

//DISCUSSION...UPDATED 20Z...
WE HAVE OPTED TO DROP THE TEMPO GROUP FOR THUNDERSTORMS THIS
EVENING AT THE TERMINALS. THE LATEST AMDAR SOUNDINGS OUT OF KORD
AND KMDW INDICATE AROUND 14 DEGREE CELSIUS TEMPERATURES AT 700
MB...WHICH IS PROVIDING A VERY STRONG CAP IN SPITE OF THE
PRESENCE OF 90 DEGREE TEMPERATURES AND LOWER TO MIDDLE 70S DEW
POINTS. WITH THIS IN MIND...IT APPEARS THAT ANY ACTIVITY THAT
DEVELOPS BY EARLY THIS EVENING MAY BE JUST AHEAD OF THE COLD FRONT
AND OF LOW AREAL COVERAGE (ISOLATED TO WIDELY SCT). AT THIS
TIME...I WILL CONTINUE THE VCTS TO ACCOUNT FOR THE POTENTIAL FOR A
FEW CELLS NEARBY.

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIME FRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* LOW CONFIDENCE IN TSRA AT A GIVEN TERMINAL AS AREAL COVERAGE MAY
  REMAIN FAIRLY LOW.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB/MTF

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 222212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SSW WINDS INTO THE LOW 20 KT RANGE THROUGH LATE
  AFTERNOON.
* CHANCE OF SOME ISOLATED TO WIDELY SCATTERED THUNDERSTORMS
  DEVELOPING IN THE AREA THIS EVENING AHEAD OF A COLD FRONT. BEST
  TIMING APPEARS TO BE IN THE 01 TO 04 UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB/MTF

//DISCUSSION...UPDATED 20Z...
WE HAVE OPTED TO DROP THE TEMPO GROUP FOR THUNDERSTORMS THIS
EVENING AT THE TERMINALS. THE LATEST AMDAR SOUNDINGS OUT OF KORD
AND KMDW INDICATE AROUND 14 DEGREE CELSIUS TEMPERATURES AT 700
MB...WHICH IS PROVIDING A VERY STRONG CAP IN SPITE OF THE
PRESENCE OF 90 DEGREE TEMPERATURES AND LOWER TO MIDDLE 70S DEW
POINTS. WITH THIS IN MIND...IT APPEARS THAT ANY ACTIVITY THAT
DEVELOPS BY EARLY THIS EVENING MAY BE JUST AHEAD OF THE COLD FRONT
AND OF LOW AREAL COVERAGE (ISOLATED TO WIDELY SCT). AT THIS
TIME...I WILL CONTINUE THE VCTS TO ACCOUNT FOR THE POTENTIAL FOR A
FEW CELLS NEARBY.

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIME FRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* LOW CONFIDENCE IN TSRA AT A GIVEN TERMINAL AS AREAL COVERAGE MAY
  REMAIN FAIRLY LOW.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB/MTF

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 222016
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
316 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 1243 PM CDT Tue Jul 22 2014
VFR early this afternoon, with cold front moving in later this
evening and showers and thunderstorms possible ahead of the sfc
boundary. Issues with the models...some of the shorter term higher
resolution models are actually downplaying the thunder potential.
With the amount of instability available to the boundary, and the
expected convergence along it...keeping the thunder in the TAFs
from near 00z into the evening. Winds shifting first to the east
and then to the north by morning. Timing issues abound with this
particular forecast so narrowing the time frame for the thunder is
problematic. Confidence is low and forecast is conservative as a
result.

HJS

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 222016
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
316 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 228 PM CDT Tue Jul 22 2014

The main forecast concern for the next few days is a shortwave and
attendant surface cold front approaching central Illinois from the
northwest this afternoon. This will sweep across central and
southeast Illinois this evening through tonight bringing a period
of thunderstorms. Following the cold front, temperatures will
lower several degrees and humidity will decrease significantly for
Wednesday and Thursday, along with dry conditions. Chances for
thunderstorms will arrive again Friday through the weekend as
another low pressure system moves across the region.

SHORT TERM...Today through Thursday:

Cold frontal boundary moving toward the northwest corner of
Illinois is currently initiating scattered thunderstorms over
eastern Iowa. Ahead of the front, dewpoints range up to the mid to
upper 70`s yielding heat index values in the upper 90`s. This
evening the front will reach the Illinois River around mid-
evening...and southeast Illinois early Wednesday morning. A few
hours of scattered thunderstorms are likely at each location as
the feature moves through. Severe wind and hail remain as a slight
risk as a result of high surface temperature and dewpoint combined
with strong mid-level lapse rates in the region the front is
moving into. Mitigating the severe weather possibilities are a
strong cap evident in the KILX morning sounding which has
precluded convective activity from western Illinois this morning
from spreading into central Illinois.

For Wednesday...cool and dry northerly flow push into central
Illinois for drying conditions, cooler temperatures, and much less
humidity through Thursday. Nighttime temperatures should dip into
the 50`s again.

LONG TERM...Friday through Tuesday:

A strong 500 mb low will move across the northern Plains and
Canada before moving into the great lakes region and carving out a
deep trough over the eastern U.S. through early next week.
Models fairly consistent bringing MCS remnants through Illinois
late Friday into Saturday...then a cold front arriving around
Sunday should bring another chance for thunderstorms. Yet another
round of cooler and drier conditions expected to follow for early
next week.

Onton

&&

.AVIATION...
ISSUED 1243 PM CDT Tue Jul 22 2014
VFR early this afternoon, with cold front moving in later this
evening and showers and thunderstorms possible ahead of the sfc
boundary. Issues with the models...some of the shorter term higher
resolution models are actually downplaying the thunder potential.
With the amount of instability available to the boundary, and the
expected convergence along it...keeping the thunder in the TAFs
from near 00z into the evening. Winds shifting first to the east
and then to the north by morning. Timing issues abound with this
particular forecast so narrowing the time frame for the thunder is
problematic. Confidence is low and forecast is conservative as a
result.

HJS

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KLOT 222012
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THROUGH LATE AFTERNOON.
* CHANCE OF SOME ISOLATED TO WIDELY SCATTERED THUNDERSTORMS
  DEVELOPING IN THE AREA THIS EVENING AHEAD OF A COLD FRONT. BEST
  TIMING APPEARS TO BE IN THE 01 TO 04 UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 20Z...
WE HAVE OPTED TO DROP THE TEMPO GROUP FOR THUNDERSTORMS THIS
EVENING AT THE TERMINALS. THE LATEST AMDAR SOUNDINGS OUT OF KORD
AND KMDW INDICATE AROUND 14 DEGREE CELSIUS TEMPERATURES AT 700
MB...WHICH IS PROVIDING A VERY STRONG CAP IN SPITE OF THE
PRESENCE OF 90 DEGREE TEMPERATURES AND LOWER TO MIDDLE 70S DEW
POINTS. WITH THIS IN MIND...IT APPEARS THAT ANY ACTIVITY THAT
DEVELOPS BY EARLY THIS EVENING MAY BE JUST AHEAD OF THE COLD FRONT
AND OF LOW AREAL COVERAGE (ISOLATED TO WIDELY SCT). AT THIS
TIME...I WILL CONTINUE THE VCTS TO ACCOUNT FOR THE POTENTIAL FOR A
FEW CELLS NEARBY.



//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIME FRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* LOW CONFIDENCE IN TSRA AT A GIVEN TERMINAL AS AREAL COVERAGE MAY
  REMAIN FAIRLY LOW.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
300 PM CDT

LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO DEEPEN AS IT
MOVES ACROSS QUEBEC TONIGHT WHILE HIGH PRESSURE MOVES OFF THE MID
ATLANTIC COAST. A STRONG COLD FRONT ASSOCIATED WITH THE LOW WILL
PUSH SOUTH DOWN THE LENGTH OF THE LAKE TONIGHT. MODERATELY STRONG
SOUTH TO SOUTHWEST WINDS WILL VEER TO NORTHERLY FOLLOWING THE
FRONTAL PASSAGE WITH WINDS INCREASING TO 30 KT WITH OCCASIONAL 35
KT GALE FORCE GUSTS POSSIBLE. A SMALL CRAFT ADVISORY ASSOCIATED
WITH THE STRONG NORTH WINDS WILL GO INTO EFFECT LATE TONIGHT AND
REMAIN IN EFFECT THROUGH THURSDAY MORNING WHEN WINDS AND WAVES
WILL TAPER OFF AS HIGH PRESSURE BEGINS TO BUILD ACROSS THE
REGION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT TUE JUL 22 2014

.DISCUSSION...
233 PM CDT

FORECAST FOCUS PRIMARILY ON SHORT TERM HEAT AND HUMIDITY AND
CONVECTIVE CHANCES THIS EVENING. AFTER THUNDERSTORMS TONIGHT...WE
WILL HAVE A COUPLE DAYS OF DRY AND COOLER CONDITIONS...FOLLOWED BY A
RETURN TO A POTENTIALLY MORE ACTIVE PATTERN FOR THE LATTER HALF OF
THE WEEK AND THROUGH THE WEEKEND.

THE LARGE UPPER RIDGE IS BEING FLATTENED BY AN UPPER WAVE
PROGRESSING THROUGH THE NORTHERN LAKES. DEWPOINTS ARE POOLING OUT
AHEAD OF THE COLD FRONT APPROACHING FROM THE NORTH AND WEST...SO
READINGS ARE GENERALLY WELL INTO THE 80S TO AROUND 90 AND DEWPOINTS
IN MANY AREAS INTO THE 70S WHERE IT STARTS TO FEEL QUITE
UNCOMFORTABLE...EVEN ALL THE WAY TO THE LAKEFRONT. LINGERING CONVECTION
FROM EARLIER TODAY IS SINKING SOUTH AND WEAKENING ALONG THE IA/MO
BORDER. RECENT THUNDERSTORM DEVELOPMENT HAS BEEN ONGOING IN
CENTRAL AND EASTERN IOWA OUT AHEAD OF THE COLD FRONT. THE STORMS
ARE TRYING TO GROW AGAINST THE CAP BUT HAVE OVERALL BEEN
RELATIVELY UNIMPRESSIVE ON SATELLITE TO THIS POINT. LATEST SPC/RAP
MESOANALYSIS SHOWS AN AREA OF VERY HIGH MIXED LAYER INSTABILITY IN
EASTERN IOWA AND EXTENDING INTO FAR NW ILLINOIS WHERE DEWPOINTS
ARE IN THE LOW TO MID 70S. UNFORTUNATELY IN THIS SITUATION THE BEST
MOISTURE CONVERGENCE IS NOT JUXTAPOSED WITH THE BETTER HEIGHT
FALLS AND STRONGER WINDS ALOFT ASSOCIATED WITH THE DISTURBANCE
GLIDING BY TO THE NORTH.

SHORT TERM GUIDANCE STILL REMAINS MIXED TO THIS POINT AS TO HOW
WIDESPREAD THE COVERAGE WILL BE...BUT ANY THAT DO FORM STILL HOLD
THE POTENTIAL FOR STRONG WINDS...LARGE HAIL DUE TO THE MODERATE MID
LEVEL LAPSE RATES...AND LOCALLY HEAVY RAINFALL AS PWAT VALUES HOVER
ABOVE 2". WHAT WE CAN SAY WITH DECENT CONFIDENCE IS THE TIMING OF ANY
STORMS. SOME HI-RES GUIDANCE SUGGEST A BRIEF WINDOW OF THE CAPPING
TO BE ERODED IN NORTH CENTRAL INTO NE ILLINOIS IN THE 6-7 PM TIME
FRAME...MOVING THROUGH METROPOLITAN AREA BETWEEN 8-11PM...AND THEN
SHIFTING SOUTH AND EAST INTO NW INDIANA. CONFIDENCE IS LOW ON A FULL
LINE DEVELOPING AS SOME MODELS INDICATE AS THE CAPPING HOLDS IN OUR
SOUTHWESTERN AREAS WHERE WEAKER LOW LEVEL CONVERGENCE AND UPPER
FORCING WILL HAVE A HARDER TIME WITH THE CAP. STILL BELIEVE THERE
WILL BE SCATTERED ACTIVITY DURING THIS PERIOD. WOULD LIKE TO BE MORE
DEFINITIVE WITH THE POPS AT THIS TIME FRAME BUT WILL GENERALLY
CONTINUE THE 40-50 POP/SCATTERED COVERAGE FOR MOST AREAS AS THE CAP
LOOKS TO KEEPS THINGS IN CHECK AT LEAST AT THIS POINT. CLOSER TO
THE LAKE WE MAY GET SLIGHTLY BETTER HEIGHT FALLS LATER THIS
EVENING ALONG WITH THE FRONT.

THE FRONT WILL BE RATHER PROGRESSIVE...THUS THE WINDOW FOR STORMS
FOR ANY ONE AREA APPEARS TO BE PRETTY SHORT.  BY DAYBREAK THE FRONT
SHOULD LARGELY HAVE PASSED THROUGH THE ENTIRE COUNTY WARNING AREA.
THERE MAY BE SOME LOWER CLOUDS BEHIND THE FRONT ESPECIALLY CLOSER TO
THE LAKE IN THE ONSHORE FLOW PATTERN. COLD ADVECTION CONTINUES
THROUGH THE DAY THUS EXPECT SOME WARMING WITH SOLAR INSOLATION BEING
STRONG...BUT WE WILL LIKELY HAVE A QUICKER DROP OFF IN THE AFTERNOON
AND EVENING. LOOKS LIKE A DRY AND SEASONABLY COOL DAY WITH NW FLOW
ALOFT IN PLACE WHILE THE UPPER RIDGE IN THE CENTER OF THE COUNTRY
AMPLIFIES INTO SASKATCHEWAN AND MANITOBA.  NOT MUCH OF A CHANGE IN
THE PATTERN FOR THURSDAY AS HIGH PRESSURE MOVES OVERHEAD AND SHIFTS
EAST...MAINTAINING COOLER THAN NORMAL CONDITIONS UNDER ONSHORE FLOW.

THE UPPER DISTURBANCE THAT IS MOVING BY TODAY WILL MERGE WITH A
LARGE UPPER LOW IN THE HUDSON BAY AREA THAT GETS BLOCKED BY A RIDGE
IT THE ATLANTIC BASIN. MEANWHILE AN UPPER LOW OFF THE PACIFIC COAST
WILL MOVE THROUGH THE CANADIAN PRAIRIES. WARM ADVECTION AHEAD OF A
SURFACE LOW EJECTING OUT OF THE NORTHERN ROCKIES ON FRIDAY LOOKS TO
TRIGGER A ROUND OF SHOWERS AND STORMS. A BIT MORE UNCERTAINTY TO THE
EVOLUTION ON THE WEEKEND AS A SURFACE WAVE ASSOCIATED WITH THE
PACIFIC LOW IS HANDLED QUITE DIFFERENTLY...THUS SOME TIMING CONCERNS
AS TO WHEN THE ASSOCIATED COLD FRONT SLIDES THROUGH...WHICH WILL
PROVIDE ANOTHER OPPORTUNITY FOR SHOWERS AND STORMS.

BEYOND THAT FORECAST CONFIDENCE INCREASES SOMEWHAT WITH
MODELS/ENSEMBLES DEPICTING A HIGHLY AMPLIFIED FLOW PATTERN WITH A
LARGE RIDGE IN THE WEST AND AN ANOMALOUS LOW IN THE EAST KEEPING THE
REGION UNDER NW FLOW FOR COOLER THAN NORMAL CONDITIONS WITH PERIODS
OF CLOUDS AND SHOWERS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 AM WEDNESDAY TO 10
     AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 AM WEDNESDAY TO 10
     AM THURSDAY.

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 AM WEDNESDAY TO 10 AM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 221753
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1253 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 1051 AM CDT Tue Jul 22 2014
Cold front approaching the Midwest but an overnight disturbance to
the northwest brought some showers and thunderstorms down into the
region. IR sat imagery showing warming cloud tops and slowly
weakening thunderstorms on radar as well. Upped some of the pops
over the far west for some rainfall and sct thunder. Diurnal swing
doing well in the forecast... updated a bit for the west with
current conditions. Updates out momentarily.



&&

.AVIATION...
ISSUED 1243 PM CDT Tue Jul 22 2014
VFR early this afternoon, with cold front moving in later this
evening and showers and thunderstorms possible ahead of the sfc
boundary. Issues with the models...some of the shorter term higher
resolution models are actually downplaying the thunder potential.
With the amount of instability available to the boundary, and the
expected convergence along it...keeping the thunder in the TAFs
from near 00z into the evening. Winds shifting first to the east
and then to the north by morning. Timing issues abound with this
particular forecast so narrowing the time frame for the thunder is
problematic. Confidence is low and forecast is conservative as a
result.


HJS
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 221753
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1253 PM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 1051 AM CDT Tue Jul 22 2014
Cold front approaching the Midwest but an overnight disturbance to
the northwest brought some showers and thunderstorms down into the
region. IR sat imagery showing warming cloud tops and slowly
weakening thunderstorms on radar as well. Upped some of the pops
over the far west for some rainfall and sct thunder. Diurnal swing
doing well in the forecast... updated a bit for the west with
current conditions. Updates out momentarily.



&&

.AVIATION...
ISSUED 1243 PM CDT Tue Jul 22 2014
VFR early this afternoon, with cold front moving in later this
evening and showers and thunderstorms possible ahead of the sfc
boundary. Issues with the models...some of the shorter term higher
resolution models are actually downplaying the thunder potential.
With the amount of instability available to the boundary, and the
expected convergence along it...keeping the thunder in the TAFs
from near 00z into the evening. Winds shifting first to the east
and then to the north by morning. Timing issues abound with this
particular forecast so narrowing the time frame for the thunder is
problematic. Confidence is low and forecast is conservative as a
result.


HJS
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KLOT 221738
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 PM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221738
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 PM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221738
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 PM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221738
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1238 PM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR A BRIEF PERIOD OF LOW CIGS BEHIND FRONT.
* NORTHEASTERLY WINDS (020-030 DIRECTION) AROUND 14 KT WITH SOME
  GUSTS UP TO 20 KT ON WEDNESDAY.

KJB

//DISCUSSION...UPDATED 18Z...

A COLD FRONT IS EXPECTED TO MOVE ACROSS THE TERMINALS THIS EVENING.
THE ATMOSPHERE AHEAD OF THIS FRONT IS BECOMING VERY WARM...MOIST AND
HENCE VERY UNSTABLE. THEREFORE...THE THREAT FOR AT LEAST SOME
THUNDERSTORMS IS STILL ON TAP FOR THE AREA AROUND THE EARLY TO MID
EVENING HOURS TODAY. THE MAIN QUESTION THAT REMAINS...HOWEVER...IS
HOW WIDESPREAD THE THUNDERSTORM ACTIVITY WILL BE ACROSS THE TERMINAL
AIRSPACE THIS EVENING. IN SPITE OF THE PRESENCE OF A VERY UNSTABLE
ATMOSPHERE...WARMER TEMPERATURES ALOFT WILL ACT TO INHIBIT
DEVELOPMENT UNTIL VERY LATE THIS AFTERNOON/EARLY EVENING WHEN THE
SURFACE FRONT AND AN ACCOMPANYING MID LEVEL ATMOSPHERIC DISTURBANCE
APPROACH THE AREA. IT APPEARS THAT ALTHOUGH THE FORCING FOR ASCENT
FROM THIS APPROACHING DISTURBANCE WILL REMAIN VERY MODEST...IT SHOULD
BE ENOUGH TO ALLOW SOME THUNDERSTORMS TO DEVELOP ACROSS NORTHERN
ILLINOIS...SOUTHERN WI AREA AROUND THE 00 UTC TIMEFRAME...THEN SHIFT
EAST-SOUTHEASTWARD. HOWEVER...IT APPEARS THE AREAL COVERAGE COULD BE
FAIRLY LOW INITIALLY DUE TO INHIBITING FACTOR OF WARMER AIR ALOFT.
THEREFORE...THIS SHEDS SOME DOUBT AS TO WHETHER OR NOT THE TERMINALS
WILL BE DIRECTLY IMPACTED BY ANY OF THESE STORMS. IN SPITE OF THESE
UNCERTAINTIES...I WILL CONTINUE WITH THE MENTION OF THUNDERSTORMS
AFTER 00 UTC THROUGH AROUND 04 UTC THIS EVENING.

ONCE THE COLD FRONT SHIFTS ACROSS THE AREA BY LATE EVENING THE WINDS
WILL BECOME NORTH-NORTHEASTERLY OVERNIGHT AND INTO WEDNESDAY. IT
APPEARS THE WINDS WILL REMAIN GUSTY BEHIND THE FRONT...WITH
NORTHEASTERLY (020-030 DIRECTION) WINDS EXPECTED DURING THE DAY
WEDNESDAY...WITH GUSTS UP TO 20 KT.

KJB


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1112 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 221612
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1112 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD

//PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY SSW WINDS INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT. BEST TIMING APPEARS TO BE IN THE 01 TO 04
  UTC TIME FRAME.
* WINDS SHIFTING TO NORTH THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KILX 221554
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1054 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 1051 AM CDT Tue Jul 22 2014
Cold front approaching the Midwest but an overnight disturbance to
the northwest brought some showers and thunderstorms down into the
region. IR sat imagery showing warming cloud tops and slowly
weakening thunderstorms on radar as well. Upped some of the pops
over the far west for some rainfall and sct thunder. Diurnal swing
doing well in the forecast... updated a bit for the west with
current conditions. Updates out momentarily.

HJS
&&

.AVIATION...
ISSUED 649 AM CDT Tue Jul 22 2014

A dissipating line of convection approaching from the NW should
continue to weaken over the next few hours, with mainly mid clouds
drifting into central IL from that complex. Some MVFR fog at CMI
will dissipate by 13z as it has the last few mornings. Then VFR
conditions should prevail through the day and into the evening
hours.

Storm chances will increase this evening from NW to SE as a cold
front arrives. Storm coverage may be limited by the amount of warm
air in the mid levels of the atmosphere, but if any storms do get
going, they could quickly become strong with winds and hail. VCTS
was included in all TAFs beginning at 01z in PIA and expanding
east to CMI at 03z. There should mainly be a 3-4 hour window of
storm chances for PIA and BMI, but farther east and south the
front may slow down and rotate slightly, keeping storm chances
through 08z-09z for the SPI/DEC/CMI corridor.

Forecast soundings are showing some low level moisture behind the
front possibly creating some MVFR ceilings for late tonight into
Wed morning.

Winds will be S-SW today, with speeds increasing to 12-14kt
sustained by late morning. As the cold front arrives from the NW,
wind speeds should diminish in the vicinity of the front to less
than 10kt, then veer to the W-NW behind the front later this
evening and overnight.

Shimon
&&

.PREV DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.

SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.

LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 221554
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1054 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 1051 AM CDT Tue Jul 22 2014
Cold front approaching the Midwest but an overnight disturbance to
the northwest brought some showers and thunderstorms down into the
region. IR sat imagery showing warming cloud tops and slowly
weakening thunderstorms on radar as well. Upped some of the pops
over the far west for some rainfall and sct thunder. Diurnal swing
doing well in the forecast... updated a bit for the west with
current conditions. Updates out momentarily.

HJS
&&

.AVIATION...
ISSUED 649 AM CDT Tue Jul 22 2014

A dissipating line of convection approaching from the NW should
continue to weaken over the next few hours, with mainly mid clouds
drifting into central IL from that complex. Some MVFR fog at CMI
will dissipate by 13z as it has the last few mornings. Then VFR
conditions should prevail through the day and into the evening
hours.

Storm chances will increase this evening from NW to SE as a cold
front arrives. Storm coverage may be limited by the amount of warm
air in the mid levels of the atmosphere, but if any storms do get
going, they could quickly become strong with winds and hail. VCTS
was included in all TAFs beginning at 01z in PIA and expanding
east to CMI at 03z. There should mainly be a 3-4 hour window of
storm chances for PIA and BMI, but farther east and south the
front may slow down and rotate slightly, keeping storm chances
through 08z-09z for the SPI/DEC/CMI corridor.

Forecast soundings are showing some low level moisture behind the
front possibly creating some MVFR ceilings for late tonight into
Wed morning.

Winds will be S-SW today, with speeds increasing to 12-14kt
sustained by late morning. As the cold front arrives from the NW,
wind speeds should diminish in the vicinity of the front to less
than 10kt, then veer to the W-NW behind the front later this
evening and overnight.

Shimon
&&

.PREV DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.

SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.

LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KLOT 221532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1032 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD


&&

.PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1032 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD


&&

.PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1032 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD


&&

.PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1032 AM CDT TUE JUL 22 2014

.DISCUSSION...
1011 AM CDT

.UPDATE...
JUST SOME MINOR TWEAKS THIS MORNING TO ACCOUNT FOR SOME ADDITIONAL
CLOUD COVER SLIDING THROUGH THIS MORNING OUT AHEAD OF THE COLD
FRONT. THIS MAY ACT TO KEEP TEMPS FROM GETTING INTO THE LOW 90S. OTHERWISE
HIGHS IN THE UPPER 80S TO CLOSE TO 90 SEEM REASONABLE...SO HEAT
INDEX VALUES SHOULD GENERALLY REMAIN AT 100 OR LESS.

WITH REGARDS TO CONVECTIVE TIMING THIS EVENING. MODELS ARE SHOWING
A BRIEF WINDOW OF THE CAP BREAKING FROM NW TO SE THIS EVENING.
BEST TIME FRAME WOULD SUGGEST STORMS BEGINNING IN SOUTHERN
WISCONSIN IN THE 22-23Z TIME FRAME AND SLIDING SOUTHEAST...MOVING
THROUGH THE METRO AREA BETWEEN 1Z-4Z...OR 8 TO 11 PM.  STILL SOME
MIXED SIGNALS ON SHORT TERM GUIDANCE AS TO HOW WIDESPREAD COVERAGE
WILL BE...ESPECIALLY FARTHER WEST/SOUTHWEST WHERE THE CAP IS
STRONGER AND HEIGHT FALLS ARE WEAKER. HAVE GONE WITH LIKELY STORMS
CLOSER TO THE LAKE. GIVEN STRONG INSTABILITY...MODERATE SHEAR...EXPECT
STORMS THAT DO DEVELOP TO HAVE THE POTENTIAL FOR STRONG
WINDS...LARGE HAIL...AND HEAVY RAIN.

KMD


&&

.PREV DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221355
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
855 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 221355
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
855 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD/KB

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* MEDIUM-HIGH WITH WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM WITH THE GENERAL TIMING FOR TSRA THIS EVENING BUT LOW
  CONFIDENCE IN COVERAGE.
* LOW WITH MVFR CIGS BEHIND THE COLD FRONT.

BMD/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 221149
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
649 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.

SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.

LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart


&&

.AVIATION...
ISSUED 649 AM CDT Tue Jul 22 2014

A dissipating line of convection approaching from the NW should
continue to weaken over the next few hours, with mainly mid clouds
drifting into central IL from that complex. Some MVFR fog at CMI
will dissipate by 13z as it has the last few mornings. Then VFR
conditions should prevail through the day and into the evening
hours.

Storm chances will increase this evening from NW to SE as a cold
front arrives. Storm coverage may be limited by the amount of warm
air in the mid levels of the atmosphere, but if any storms do get
going, they could quickly become strong with winds and hail. VCTS
was included in all TAFs beginning at 01z in PIA and expanding
east to CMI at 03z. There should mainly be a 3-4 hour window of
storm chances for PIA and BMI, but farther east and south the
front may slow down and rotate slightly, keeping storm chances
through 08z-09z for the SPI/DEC/CMI corridor.

Forecast soundings are showing some low level moisture behind the
front possibly creating some MVFR ceilings for late tonight into
Wed morning.

Winds will be S-SW today, with speeds increasing to 12-14kt
sustained by late morning. As the cold front arrives from the NW,
wind speeds should diminish in the vicinity of the front to less
than 10kt, then veer to the W-NW behind the front later this
evening and overnight.

Shimon
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 221149
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
649 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.

SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.

LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart


&&

.AVIATION...
ISSUED 649 AM CDT Tue Jul 22 2014

A dissipating line of convection approaching from the NW should
continue to weaken over the next few hours, with mainly mid clouds
drifting into central IL from that complex. Some MVFR fog at CMI
will dissipate by 13z as it has the last few mornings. Then VFR
conditions should prevail through the day and into the evening
hours.

Storm chances will increase this evening from NW to SE as a cold
front arrives. Storm coverage may be limited by the amount of warm
air in the mid levels of the atmosphere, but if any storms do get
going, they could quickly become strong with winds and hail. VCTS
was included in all TAFs beginning at 01z in PIA and expanding
east to CMI at 03z. There should mainly be a 3-4 hour window of
storm chances for PIA and BMI, but farther east and south the
front may slow down and rotate slightly, keeping storm chances
through 08z-09z for the SPI/DEC/CMI corridor.

Forecast soundings are showing some low level moisture behind the
front possibly creating some MVFR ceilings for late tonight into
Wed morning.

Winds will be S-SW today, with speeds increasing to 12-14kt
sustained by late morning. As the cold front arrives from the NW,
wind speeds should diminish in the vicinity of the front to less
than 10kt, then veer to the W-NW behind the front later this
evening and overnight.

Shimon
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KLOT 221135
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
635 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SSW WINDS BECOMING GUSTY LATER THIS MORNING AND INTO THE LOW TO
  MID 20 KT RANGE THIS AFTERNOON.
* SCATTERED THUNDERSTORMS DEVELOPING IN THE AREA THIS EVENING
  AHEAD OF A COLD FRONT.
* WINDS SHIFTING TO NW THIS EVENING WITH COLD FRONTAL
  PASSAGE...THEN NORTHEAST.
* POTENTIAL FOR LOW CIGS BEHIND FRONT.

BMD

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE LIES OVER LAKE SUPERIOR EARLY THIS MORNING WITH A COLD
FRONT TRAILING SOUTHWEST INTO IOWA. AHEAD OF THE FRONT...MODERATE
SOUTHERLY WINDS ARE EXPECTED TO INCREASE THIS MORNING WITH GUSTS
INCREASING INTO THE LOW TO MID 20 KT RANGE THIS AFTERNOON. THE COLD
FRONT WILL START TO MOVE INTO NORTHERN ILLINOIS THIS EVENING. A
STRONG CAPPING INVERSION WILL BE IN PLACE AHEAD OF THE FRONT AND
WILL PREVENT ANY THUNDERSTORMS DEVELOPING THIS AFTERNOON. HOWEVER...
MODELS SUGGEST THAT THUNDERSTORMS WILL DEVELOP OVER NORTHERN
ILLINOIS THIS EVENING IMMEDIATELY AHEAD OF THE FRONT. A FEW MODELS
SUGGEST THAT IT MAY EVEN DEVELOP LATER IN THE EVENING SOUTH OF THE
TERMINALS. GIVEN THE UNCERTAINTY WILL MAINTAIN PROB30 FOR TSRA ON
STATION FOR NOW. ONCE THE FRONT PUSHES ACROSS THE TERMINALS WINDS
WILL VEER ALL THE WAY AROUND TO THE NNE. AS COOLER AIR FILTERS INTO
THE AREA COLLIDING WITH THE ANTECEDENT MOIST CONDITIONS...MVFR
CEILINGS ARE POSSIBLE...BUT GUIDANCE SUGGESTS THAT IF IT DOES
DEVELOP IT WOULD ONLY LAST A COUPLE HOURS BEFORE DRIER AIR ADVECTS
INTO THE AREA.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM-HIGH CONFIDENCE IN WIND TRENDS/TIMING/MAGNITUDE.
* MEDIUM CONFIDENCE ON THE GENERAL TIMING FOR TSRA THIS EVENING
  BUT LOW CONFIDENCE IN COVERAGE.
* LOW CONFIDENCE IN MVFR CIGS BEHIND THE COLD FRONT.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
FRIDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220907
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
407 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220907
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
407 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 220818
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
318 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
317 AM CDT

LOW PRESSURE IS MOVING INTO THE WESTERN GREAT LAKES EARLY THIS
MORNING AND WILL DEEPEN SLIGHTLY AS IT REACHES QUEBEC BY TONIGHT
WITH A COLD FRONT PUSHING SOUTH ACROSS LAKE MICHIGAN THIS EVENING.
SOUTH TO SOUTHWEST WINDS WILL CONTINUE TO RAMP UP THROUGH THE DAY
TODAY...ESPECIALLY OVER THE NORTH HALF OF LAKE MICHIGAN WHEN WINDS
TO 30 KT ARE EXPECTED AND A FEW GALE FORCE GUSTS REMAIN POSSIBLE.
BEHIND THE FRONT...WINDS TURN NORTH TO NORTHWEST TO AROUND 30 KT.
WINDS WILL BEGIN TO TAPER THE LATTER HALF OF THE WEEK AS HIGH
PRESSURE BEGINS TO BUILD ACROSS THE REGION.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 220758
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
258 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.


SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.


LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 to 10 kts.

Smith

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$






000
FXUS63 KILX 220758
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
258 AM CDT Tue Jul 22 2014

.DISCUSSION...
ISSUED 257 AM CDT Tue Jul 22 2014

Clear skies once again across the forecast area early this
morning, with some shallow dense fog mainly along the Indiana
border. An advancing area of mid/high clouds was ahead of the main
frontal boundary, which extends from an MCS in northeast Minnesota
southwest into Nebraska.

Initial forecast concerns involve the heat index across the
northwest CWA today, and rain chances tonight/Wednesday morning.
Longer range, the timing of rain chances through the weekend comes
into play.


SHORT TERM...Today through Wednesday:

2 am surface analysis showing 70-75 degree dew points not too far
away across Iowa and northwest Missouri. Should start to see some
of this coming into the areas along/northwest of the Illinois
River by late morning. With highs in the lower 90s, heat index
values of 100-105 are likely in that area. This is just shy of
advisory criteria, and with some question as to how much the
incoming clouds will affect the temperatures, will hold off on any
advisory for now.

Cold front expected to arrive in the northwest CWA mid to late
evening, and be through nearly all of the forecast area before mid
morning Wednesday. Strength of the cap appears to limit much of
the convection until the front is nearly on top of us. SPC 4km WRF
and ARW models, as well as the NAM, show the best chances of
storms developing over northern Missouri and and perhaps clipping
our far southwest counties as they track southeast. Looks like
best chances for rain in our area should be focused in the 9 pm to
4 am time frame. Rather healthy CAPE`s will be available but shear
will be a little more modest, so severe weather threat is a bit
lower this far south. Think the rain should be limited to areas
along/south of I-70 by morning, and out of the forecast area by
midday.


LONG TERM...Thursday through Monday:

Upper ridging expected to amplify across the Rockies through late
week, before being squashed by a strong 500 mb low which will be
coming into the Pacific Northwest beginning on Wednesday. This
should become an open wave late in the weekend by the time it
starts heading our way. Broad trough across the Midwest will bring
much drier conditions late week with temperatures well below
normal, but not as cool as the peak of the last cool spell. More
of a cooling trend will become established next week as a large
upper low settles into the Midwest.

Dry conditions expected Thursday, but an MCS is expected to form
Thursday night to our northwest along the 850 mb thermal gradient
over Iowa, dropping southeast. Thinking this should stay northwest
of our area until the remnants arrive on Friday. Better rain
chances expected with the next MCS Friday night and Saturday, as
the surface warm front becomes pronounced over the area. Sunday
is a little more questionable with rain chances, but some 30%
chances are warranted with the arrival of a cool front.

Geelhart

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 to 10 kts.

Smith

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$





000
FXUS63 KLOT 220735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 220735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 220735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 220735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT TUE JUL 22 2014

.DISCUSSION...
233 AM CDT

TODAY THROUGH TONIGHT...
THE FOCUS FOR TODAY WILL BE ON THE DEVELOPING CAP IN THE
ATMOSPHERE...AND WHEN IT MAY BEGIN TO WEAKEN AND ALLOW CONVECTION TO
DEVELOP LATER THIS AFTERNOON INTO THIS EVENING.

WARM/HUMID START TO THE DAY WITH TEMPS EARLY THIS MORNING STRUGGLING
TO DIP BELOW THE UPR 60S...WITH A HANDFUL OF POINTS HOLDING ARND 70.
DEW PTS HAVE HELD IN THE MID/UPR 60S...WITH THE 70 DEG DEW PTS
BEGINNING TO KNOCK ON THE DOOR STEPS OF THE WESTERN CWFA EARLY THIS
MORNING. PRESSURE GRADIENT CONTINUES TO BE HELD JUST WEST OF THE
FORECAST AREA...AS THE SFC RIDGE NOW CENTERED OVER THE MID-ATLANTIC
REGION WAS STILL PROVIDING SOME INFLUENCE EARLY THIS MORNING. THE
GRADIENT OVER THE CENTRAL PLAINS WILL SHIFT EAST AND ARRIVE OVERHEAD
LATER TODAY...WITH INCREASED MIXING AND A STEADY SOUTHERLY FLOW OF
WARM/MOIST AIR ADVECTING ACROSS NORTHERN IL/NORTHWEST IN.

IR/WATER VAPOR IMAGERY EARLY THIS MORNING DEPICTS THE CHANNEL OF
ATMOS MOISTURE STRETCHING FROM OKLAHOMA NORTH THROUGH THE UPPER
MIDWEST...AS A COMPLEX OF THUNDERSTORMS WAS SLIDING EAST TOWARDS
LAKE SUPERIOR/UPPER PENINSULA THIS MORNING. FOR OUR AREA TODAY
ABUNDANT SUNSHINE IS EXPECTED...WITH JUST SOME HIGH BASED CLOUDS.
STRONG THERMAL RIDGE ARRIVES WITH 850MB TEMPS NEARING 20-22 DEG C.
SFC TEMPS HAVE BEEN CONSISTENTLY PROGGED TO APPROACH 89-92 DEG
ACROSS THE CWFA...AND THIS COUPLED WITH THE ANOMALOUSLY HIGH DEW PTS
NEARING 73-76 DEG...THE POTENTIAL EXISTS THAT HEAT INDEX VALUES OF
ARND 100 DEG WILL DEVELOP THIS AFTN. FOR A FEW LOCATIONS WEST OF
I-39...HEAT INDEX VALUES COULD HOVER ARND 102 DEG THIS AFTN
BEFORE SUNSET. MIXING HEIGHTS SHUD INCREASE TO ARND
2500-3000FT...WHICH COULD BRING SOME SUBSIDENCE TO THE SFC. IF THIS
WERE TO MATERIALIZE THEN SFC TEMPS COULD RISE ANOTHER 1-2 DEG TO
PERHAPS 92-95 DEG.

NOW THE FOCUS TURNS TOWARDS THE CONVECTIVE POTENTIAL. IF STRICTLY
FOCUSED ON THE SFC CAPE/MID-LVL CAPE...GUIDANCE WOULD POINT TOWARDS
A VERY UNSTABLE ATMOS. HOWEVER THE MONKEY WRENCH IS THAT A STRONG
CAP CONTINUES TO BE PROGGED TO DEVELOP LATE THIS MORNING IN THE
MID-LVLS WITH CIN ARND 200J/KG LINGERING INTO THE EVENING HOURS. LCL
ARW8KM SOUNDINGS SHOWS THIS CAP HOLDING INTO THE EARLY EVENING
HOURS...WHICH WOULD LESSEN THE POTENTIAL FOR CONVECTION. THEN ARND
3Z WED THE CAP SHUD BE STEADILY WEAKENING AS GUIDANCE HAS BEEN
CONSISTENT IN THE THERMAL RIDGE DIMINISHING JUST AHEAD OF THE
FRONTAL BOUNDARY ARRIVAL. AFT 21Z 0-6KM SHEAR INCREASES TO NEARLY
30KTS OVERHEAD...SO THERE WILL EXIST A HAIL/WIND THREAT IF ANY
STORMS CAN BECOME STRONG/SEVERE. THE SPC HAS UPGRADED THE ENTIRE
NORTHERN IL/NORTHWEST IN FORECAST AREA INTO A SLIGHT RISK OF SEVERE
WEATHER TODAY. GIVEN THE PWAT VALUES OF ARND 2"...WHATEVER
CONVECTION IS ABLE TO DEVELOP BRIEF HEAVY DOWNPOURS COULD LEAD TO
FLOODING CONCERNS.

CONFIDENCE IN TEMPS...HIGH.
CONFIDENCE IN STORMS/TIMING/INTENSITY...MEDIUM.

WEDNESDAY THROUGH FRIDAY...
FRONTAL BOUNDARY ARRIVES EARLY WED MORNING ALONG WITH THE MID-LVL
TROUGH...AND A BUILDING BROAD SFC RIDGE. THIS WILL FRESHEN UP THE
AIR OVER THE REGION WITH MUCH COOLER/DRIER AIR EXPECTED ALONG A
NORTHERLY FLOW...WITH HIGHS GENERALLY IN THE 70S WED-FRI.

DRY CONDS LOOK SOLID THRU THURSDAY NIGHT...THEN FRI THE SFC RIDGE
WILL BEGIN TO DRIFT EAST WITH FLOW TURNING SOUTHERLY/SOUTHWESTERLY
ALONG WITH THE MID-LVL FLOW TRANSITIONING INTO A MORE FLAT/ACTIVE
FLOW. GUIDANCE CONTINUES TO POINT TOWARDS A WEAK WAVE DEVELOPING IN
THE CENTRAL ROCKIES EARLY FRI AND ARRIVING FRI AFTN/EVE OVER THE
FORECAST AREA. WHICH COULD BRING THE NEXT CHC FOR PRECIP/CONVECTION
THRU FRI NGT.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
ENSEMBLES HAVE MAINTAINED A HIGH CONFIDENCE WITH MINIMAL SPREAD IN
THE LATER PERIODS WITH RESPECT TO THE MID-LVL FLOW TRYING TO
FLATTEN...HOWEVER THIS MAY ONLY BE FOR A BRIEF PERIOD THRU THE
WEEKEND. HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC WEAKENS
FRI/SAT...WITH ENSEMBLES DEMONSTRATING THIS FEATURE REDEVELOPING
LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL LIKELY ALLOW THE
HIGH AMPLITUDE RIDGE TO RETURN TO THE WESTERN CONUS AND STRETCH
NORTH THRU THE CANADIAN ROCKIES. BETWEEN THESE TWO RIDGES WILL
LIKELY EXIST A TROUGH OVER THE GREAT LAKES REGION IN THE EARLY NEXT
WEEK TIMEFRAME.

THE UPCOMING WEEKEND APPEARS TO BE RELATIVELY ACTIVE WITH THE
SEMI-ZONAL MID-LVL FLOW...SO HAVE LOW CHC POPS THRU THE WEEKEND INTO
MON. TEMPS SHUD WARM INTO THE LOW 80S SAT/SUN...ALTHOUGH
CLOUDS/PRECIP COVERAGE COULD HOLD TEMPS DOWN A LITTLE. THEN MOVING
INTO EARLY NEXT WEEK TEMPS SHUD COOL BACK INTO THE LOW/MID 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 220532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT TUE JUL 22 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

//PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 220532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT TUE JUL 22 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

//PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* SSW WINDS BECOMING GUSTY FROM LATE TUESDAY MORNING THROUGH THE
  EVENING...THEN WINDS SHIFTING TO THE NORTHWEST THEN EVENTUALLY
  NORTHEAST TUESDAY EVENING/NIGHT.
* SCATTERED THUNDERSTORMS IN THE AREA TUESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

OVERNIGHT...EXPECT RELATIVELY UNCHANGING WEATHER WITH VFR CONDITIONS
AND LIGHT SOUTH WINDS. CANNOT COMPLETELY RULE OUT SOME PATCHY FOG
AGAIN TONIGHT MAINLY AT GYY WHERE THE GRADIENT IS WEAKEST...BUT THE
SOUTH WINDS SHOULD STAY UP ENOUGH TO INHIBIT FOG BECOMING TOO BIG A
PROBLEM. INCREASING GRADIENT AND MIXING DURING THE DAY TUESDAY WILL
RESULT IN GUSTY CONDITIONS WITH LOW TO MID 20 KT GUSTS POSSIBLE AT
TIMES...ESPECIALLY DURING THE AFTERNOON HOURS. STRONG INSTABILITY IS
PROGGED TO DEVELOP AHEAD OF AN APPROACHING COLD FRONT BUT A STRONG
CAP WILL ALSO BE IN PLACE MOST OF THE DAY KEEPING A SOLID LID ON
DEEP CONVECTION. CIN ERODES SOME DURING THE EVENING AND MAY ALLOW
THUNDERSTORMS TO KICK OFF DURING THE EVENING...HOWEVER GIVEN THE
OVERALL STRENGTH OF THE CAP IT IS UNCERTAIN HOW MUCH COVERAGE THERE
WILL BE...AND IT MAY END UP BEING ON THE LOWER END AS IT COMES
ACROSS THE TERMINALS WITH BETTER COVERAGE DEVELOPING LATER TO THE
SOUTH OF TERMINALS.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH CONFIDENCE ON WIND TRENDS/TIMING/MAGNITUDE.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH MUCH OF THE
  PERIOD...OUTSIDE OF TSRA CHANCES TOMORROW EVENING.
* LOW-MEDIUM CONFIDENCE ON SCATTERED TSRA TOMORROW EVENING AT OR
  NEAR THE TERMINALS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KILX 220417
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1117 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 t 10 kts.

Smith
&&


.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 220417
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1117 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 t 10 kts.

Smith
&&


.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 220417
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1117 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 t 10 kts.

Smith
&&


.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 220417
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1117 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

&&

.AVIATION...
ISSUED 1105 PM CDT Mon Jul 21 2014

MVFR vsbys possible in ground fog again late tonight, roughly in
the 09z-13z time frame, otherwise, VFR conditions will persist
thru the forecast period. Best threat for fog, at least based on
the latest temp-dew point spreads appears to be along and east
of I-55, which would encompass BMI, DEC and CMI. Latest HRRR
forecast hitting the lower vsbys the hardest from MTO to DEC
to just east of BMI by morning. What fog the does form during
the early morning hours should be gone by 13z most areas. After
that, some mid and high level clouds will track in from the
west but it now appears the showers that models were depicting
earlier this evening out to our west by dawn will stay west of our
TAF sites.

Secondary concern will be in the 00z-06z time frame as a cold
front shifts across the area and TSRA chances along it. At this
time, with such warm temperatures aloft, it appears that
thunderstorm coverage will be too limited at this point. As a
result, will include VCTS at the TAF sites during the time frame
that the front will be moving thru. Surface winds will be out of
the southeast at 5 to 8 kts overnight and then turn into the
south and southwest tomorrow at 12 to 17 kts with an occasional
higher gust during the afternoon. Winds should diminish quickly
towards evening and then gradually turn into more of a southwest
to west direction at 5 t 10 kts.

Smith
&&


.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 220259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

//PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

//PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 220212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

&&

.PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

&&

.PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

&&

.PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 220212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 PM CDT MON JUL 21 2014

.DISCUSSION...
911 PM CDT

EVENING UPDATE...

HAVE MADE NO MAJOR CHANGES TO THE GOING FORECAST FOR TONIGHT. MAIN
FOCUS IS ON THE HEAT AND HUMIDITY ON TUESDAY AND THE THREAT FOR A
FEW SEVERE STORMS MAINLY TUESDAY EVENING. THERE IS SOME POTENTIAL
FOR DEBRIS CLOUD COVER FROM UPSTREAM CONVECTION TUESDAY
MORNING...BUT OVERALL SHOULDNT BE SIGNIFICANT IMPACTS ON FORECAST
HIGHS IN THE LOWER 90S. DEW POINTS POOLED WELL INTO THE 70S OUT TO
OUR WEST TODAY...SO THE LOW-MID 70S IN GRIDS BY AFTERNOON APPEARS
ON TRACK. THE TEMPERATURES AND DEW POINTS YIELD HEAT INDEX VALUES
RANGING FROM 95 TO 105 DEGREES...HIGHEST IN THE NW CWA. GIVEN THE
FAIRLY COOL WEATHER OF LATE AND THE OVERALL LACK OF HIGH HEAT AND
HUMIDITY THIS SUMMER...HAVE ISSUED AN SPS FOR AN EXTRA HEADS UP.
AT THIS TIME...NOT APPEARING WE WILL NEED AN ADVISORY FOR ANY
PARTS OF THE AREA...THOUGH WILL NEED TO MONITOR FOR HIGHER TEMPS
AND/OR DEWPOINTS THAT COULD PUT FAVORED NW AREAS AT OR SLIGHTLY
ABOVE 105 DEGREE HEAT INDEX CRITERIA FOR A HEAT ADVISORY.

REGARDING THE THUNDERSTORM/SEVERE WEATHER POTENTIAL TOMORROW
EVENING...STILL A FAIRLY CONDITIONAL THREAT DUE TO PRESENCE OF
VERY STOUT CAP AS AN EML IS ADVECTED OVER THE REGION. SOME
GUIDANCE SUCH AS 18Z GFS ACTUALLY DEVELOPS LITTLE OR NO QPF OVER
THE AREA DURING THE EVENING...BUT THIS COULD BE OWING TO SFC TEMPS
BEING COOLER THAN WHAT WILL LIKELY OCCUR. BEST UPPER FORCING WILL
PASS TO THE NORTH...THOUGH INCREASING BOUNDARY LAYER CONVERGENCE
WITH APPROACH OF COLD FRONT AND SLIGHT MIDLEVEL COOLING SHOULD BE
SUPPORTIVE OF SCATTERED TSRA COVERAGE. FOR ANY STORMS THAT ARE
ABLE TO OVERCOME CAPPING AND BECOME MORE INTENSE...HIGH CAPE AND
STEEP MIDLEVEL LAPSE RATES ALONG WITH MODEST DEEP LAYER SHEAR WILL
FAVOR A THREAT OF LARGE HAIL...AND STEEP LOW LEVEL LAPSE RATES A
THREAT FOR DAMAGING WIND GUSTS. AS ALLUDED TO IN THE AFTERNOON
AFD...HEAVY RAIN RATES WILL ALSO BE A CONCERN IN MORE INTENSE
CONVECTION DUE TO PWAT VALUES INCREASING TO CLOSE TO OR ABOVE 2
INCHES.

RC

&&

.PREV DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.

//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 220200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

Smith
&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&

.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$




000
FXUS63 KILX 220200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

Smith
&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&

.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$




000
FXUS63 KILX 220200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

Smith
&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&

.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$




000
FXUS63 KILX 220200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 850 PM CDT Mon Jul 21 2014

Hazy, warm and humid conditions prevail over a good portion of the
region this evening with the main thunderstorm activity well to our
north across North Dakota and northern Minnesota. Watching a band
of mid level clouds now over Iowa which short term models suggest
may develop into some elevated showers and storms over parts of
Iowa as the low level jet and 850 mb moisture convergence increases
as the night wears on. 00z ILX sounding showing a fairly decent
warm layer in place already around 700 mb with our temperature near
+12 degrees while Davenports was up to +14 degrees C. Most models
suggest any of the elevated storms that do develop out to our west
will be fighting an uphill battle as the 500 mb ridge temporarily
builds east into central Illinois and forecast soundings continue
to show a stought capping inversion in place tomorrow morning. What
activity that is able to develop well out to our west will probably
not make it into western Illinois tomorrow morning so will continue
to keep the forecast dry late tonight into Tuesday morning.

00z surface analysis indicating 75 to 80 degree dew points out over
west central Iowa into Minnesota ahead of the cold front that is
forecast to push across our area tomorrow evening. The pooling of
the higher dew points is expected across our area tomorrow afternoon
and evening just ahead of the boundary. The combination of afternoon
temps in the lower 90s and surface dew points expected to be at
least in the low to mid 70s, our apparent temperatures will soar
into the 97 to 102 degree range by mid afternoon thru the early
evening hours. Since this is the first time we have seen the more
widespread high apparent temps this Summer, in addition to coming
off a stretch of cooler temperatures over the past 3-5 days, will
issue a Special Weather Statement highlighting the threats from
the high heat and humidity levels.

Have made only minor tweaks to the current forecast for the overnight
hours, not enough to warrant an updated ZFP this evening.

Smith
&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&

.PREV DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$




000
FXUS63 KLOT 212335
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
635 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.


//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 212335
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
635 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* GUSTY SOUTH-SOUTHWEST WINDS TUESDAY AND TUESDAY EVENING.

* SCATTERED TSRA PROBABLE TUESDAY EVENING.


//DISCUSSION...UPDATED 00Z...

LOW PRESSURE IS DEVELOPING INTO WESTERN MN EARLY THIS EVE WITH A
COMPLEX OF SEVERE STORMS MOVING EASTWARD JUST NORTH OF THIS LOW
CENTER. SOUTHERLY WINDS WILL INCREASE IN SPEED TUESDAY MORNING
WITH GUSTS EXCEEDING 20 KT MUCH OF THE AFTERNOON. THE ATMOSPHERE
LOOKS TO BE WARM AND PROVIDING A CAP TO ANY THUNDERSTORM
DEVELOPMENT DURING MUCH OF THE DAY. AS THE SYSTEM COOL FRONT
APPROACHES FROM THE NORTH...CONVERGENCE WILL INCREASE AND LIKELY
SERVE AS A FOCUS FOR AT LEAST SCATTERED EVENING INTO EARLY
OVERNIGHT STORMS IN THE REGION. ONE POSSIBILITY TO STILL CONSIDER
IS IF AN OUTFLOW WERE TO EMANATE SOUTHWARD FROM THE
AFOREMENTIONED STORM COMPLEX LATE TONIGHT....AS THAT COULD CAUSE
AN EARLIER FOCUS AND WEAKENING OF THE CAP FOR STORMS. ON THE OTHER
HAND...THE CAP LOOKS TO BE QUITE STRONG. SO CONFIDENCE IN PRECISE
TIMING OF STORMS IN THE AREA FOR THE TUESDAY EVENING PERIOD IS
LOW. SOME STORMS IF THEY CAN DEVELOP COULD BE STRONG GIVEN THE
AMOUNT OF INSTABILITY THAT WILL BE PRESENT AND BUILDING THROUGH
THE AFTERNOON. BEHIND THE COLD FRONT...LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING...A PERIOD OF AT LEAST MVFR CIGS IS PROBABLE FOR
CHICAGO AREA TAF SITES AS FLOW TURNS OFF OF LAKE MICHIGAN.


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM IN WINDS.

* LOW ON SPECIFIC TSRA TIMING TUE EVE. IT IS LIKELY TO BE A 2-3
  HOUR WINDOW FOR THE MOST PROBABLE TIME.


//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...MORNING LOW CLOUDS. GUSTY NORTHEAST WINDS.
THURSDAY...NORTHEAST WINDS.
FRIDAY...CHC OF TSRA DURING THE NIGHT.
SATURDAY-SUNDAY...CHC OF TSRA.

MTF

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 212318
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
618 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&


.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KILX 212318
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
618 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.AVIATION...
ISSUED 605 PM CDT Mon Jul 21 2014

May see a few hours of MVFR vsbys in ground fog in the 09z-12z
time frame, otherwise, VFR conditions are expected for this TAF
period. Rather quiet weather expected into tomorrow morning then
we will have to see if any showers develop out west of the
Mississippi River as a few of the short term models suggest. For
now will just introduce a mid level cloud band over PIA as support
for any shower activity will remain to our west tomorrow morning.
Surface winds will be southeast at 5 to 10 kts tonight and increase
from the south to between 12 and 17 kts by afternoon with a few
gusts possible. It appears our best chances for scattered TSRA
will be as a cold front moves thru the area just after this
forecast period (00z Wed).

Smith
&&


.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 212152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
452 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY.

MTF

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD.

MTF

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 212152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
452 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY.

MTF

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD.

MTF

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 212032
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
332 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.

HJS

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KILX 212032
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
332 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 332 PM CDT Mon Jul 21 2014

SHORT TERM...Tonight through Thursday

Temperatures and dewpoints are up several degrees across central
and Southeast Illinois since 24 hours ago as high pressure builds
into the region along with southerly low level flow.
Forecast/observed soundings show a strong capping inversion around
4000 feet agl keeping scattered cumulus cloud development shallow.
For Tuesday...the inversion remains strong for most of the day as
low level moisture and temperature peak out with heat index values
around 96 to 100 degrees affect the region. In the evening, a cold
front will approach from the north bringing mid-level cooling and
surface convergence to erode the capping inversion. A line of
thunderstorms is likely to move across the region as a result,
affecting areas mainly north of I-72 in the evening and sweeping
across I-70 and areas southward by Wednesday morning. Timing of
the front overnight will reduce the threat of severe thunderstorms
with the line, however CAPE/shear values associated with the system
as it approaches suggest isolated severe wind gusts and hail can`t
be ruled out yet. Cooler and drier high pressure pushes into the
region behind this system for Wednesday and Thursday for highs
generally around 80.

LONG TERM...Friday through Monday

Cool and dry conditions will continue through Friday before a
stronger low pressure system moves over the top of the
ridge...initially bringing warmer and more humid conditions and a
chance for thunderstorms Saturday. By Sunday, the low will help
carve out a deep low pressure trough over the eastern U.S. late in
the weekend and into next week. Timing of precipitation features
headed for the area next weekend is far from certain at this time,
between potential MCS activity early in the weekend and a cold
front late in the weekend. Have broadbrushed this with chance to
slight chance category PoP`s Friday night through Monday.

Onton

&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.

HJS

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 212007
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 212007
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 212007
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 212007
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
307 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
306 PM CDT

FOR THE NEARSHORE WATERS...WINDS WILL INCREASE TOMORROW AFTERNOON
AND BECOME HAZARDOUS TO SMALL CRAFT OVER THE IL NEARSHORE WATERS. A
COLD FRONT PUSHES DOWN THE LAKE TUESDAY EVENING AND NIGHT...WITH
WINDS INCREASING TO 30 KT OVER ALL OF THE NEARSHORE WATERS AND WAVES
BUILDING TO 9 FT.  ANOTHER SMALL CRAFT WILL BE NEEDED FOR AN
EXTENDED PERIOD...RIGHT NOW EARLY WEDNESDAY MORNING THROUGH AT LEAST
THURSDAY MORNING.

HIGH PRESSURE CONTINUES TO HOLD ON OVER THE EASTERN GREAT LAKES
WHILE LOW PRESSURE IS OVER THE DAKOTAS.  SOUTH WINDS ARE ACROSS THE
LAKE WITH THE HIGHEST GUSTS UP TO 25 KT OVER THE NORTHERN HALF OF
THE LAKE.  THE LOW WILL DEEPEN AS IT MOVES OVER LAKE SUPERIOR
TOMORROW AND EXPECTING SOUTH GUSTS TO INCREASE TO 30 KT OVER THE
NORTHERN TWO THIRDS OF THE LAKE. MAY SEE OCCASIONAL GALES TO 35 KT
OVER THE NORTHERN HALF OF THE LAKE TOMORROW AFTERNOON.  FORECAST
SOUNDINGS HAVE WINDS 40-50 KT JUST 200 FT ABOVE THE SURFACE SO WE
WILL LIKELY SEE OCNL GALE GUSTS. HOWEVER NOT EXPECTING ENOUGH GUSTS
TO JUSTIFY A GALE WARNING.

THE LOWS COLD FRONT PASSES OVER THE LAKE TOMORROW EVENING AND WINDS
WILL TURN NORTH BEHIND THE FRONT. GUSTS WILL INCREASE TO 30 KT OVER
THE SOUTHERN HALF OF THE LAKE THROUGH THE NSH WATERS.  THE LOW
DEEPENS AS IT MOVES NORTHEAST INTO NEWFOUNDLAND...AND NORTH WINDS
SLOWLY DIMINISH OVER THE SOUTHERN HALF OF THE LAKE AS HIGH PRESSURE
SPREADS OVER THE LAKE WEDNESDAY NIGHT. WINDS REMAIN NORTH TO
NORTHEAST THROUGH THURSDAY EVENING AND THEN BECOME VARIABLE UNDER
THE HIGH THURSDAY NIGHT INTO FRIDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM TUESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 212003 AAA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO









000
FXUS63 KLOT 212003 AAA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE.
THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER NOT TO BACK OFF
ON LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 211958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE. THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER TO BACK OFF ON
LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211958
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 PM CDT MON JUL 21 2014

.DISCUSSION...
257 PM CDT

WEATHER HIGHLIGHTS INCLUDE THE HEAT AND HUMIDITY THAT WILL BE ON TAP
THROUGH TOMORROW. A COLD FRONT WILL BRING A CHANCE FOR THUNDERSTORMS
TUESDAY EVENING INTO EARLY WEDNESDAY. COOLER AND DRY CONDITIONS WILL
RETURN FOR THE LATTER HALF OF THE WEEK...FOLLOWED BY A RETURN TO
UNSETTLED THOUGH STILL GENERALLY COOLER WEATHER FOR THE EXTENDED.

IT IS FEELING A BIT MORE SUMMERLIKE THIS AFTERNOON AS DEWPOINTS
ACROSS THE AREA HOVER IN THE MID 60S AND TEMPERATURES INTO THE 80S.
CLOUD COVER OFF THE N IS FADING AS THE STRONG UPPER RIDGE IN THE
NATIONS HEARTLAND EXPANDS NORTH AND EASTWARD INTO NORTHERN
ILLINOIS...AND MUCH LESS IN THE WAY OF DIURNAL CUMULUS CLOUDS.  THE
LAKE BREEZE HAS BEEN HELD LARGELY IN CHECK TODAY DUE TO THE
STRENGTHENING SW WINDS THOUGH IS MAKING AN APPEARANCE ALONG THE
NORTH SHORE.

OUR MAIN FEATURE OF INTEREST IS A SHORTWAVE PUSHING INTO THE DAKOTAS
WORKING ITS WAY ALONG THE PERIPHERY OF THE UPPER RIDGE OUT AHEAD OF
A DIGGING UPPER TROUGH OFF THE PACIFIC NW COAST. THUNDERSTORMS ARE
ONGOING ACROSS THE DAKOTAS AHEAD OF THIS WAVE. THERE IS ADDITIONAL
ACTIVITY SPREADING INTO NEBRASKA WHERE WEAKER FORCING IS IN PLACE. THIS
DISTURBANCE IS FORECAST TO STRENGTHEN AS IT ENTERS MINNESOTA LATE
TONIGHT WHILE THE UPPER RIDGE FLATTENS SOMEWHAT TO OUR WEST.
THUNDERSTORMS LOOK TO BE ONGOING LATE TONIGHT AND LIKELY IN A
DECAYING PHASE AS THEY PASS BY TO THE NORTH AND POSSIBLY DRIFT
TOWARD OUR FAR WESTERN COUNTIES. SOME HI-RES GUIDANCE SUGGESTS
THAT SOME ACTIVITY MAY SNEAK INTO THESE AREAS ESPECIALLY IF THE
ACTIVITY PUSHING INTO NEBRASKA HOLDS TOGETHER...BUT STILL FEEL THAT
MOST/ALL OF THE AREA WILL REMAIN DRY INTO TUESDAY MORNING WITH ALL
SREF/GEFS MEMBERS KEEPING THINGS OUT OF OUR AREA.

ON TUESDAY THIS SHORTWAVE WILL CONTINUE SLIDING SOUTHEAST AND WILL
DRIVE A COLD FRONT AND SURFACE WAVE THROUGH NE IL/NW IN TUESDAY
NIGHT. BEFORE THAT HAPPENS...THE 850H THERMAL RIDGE BUILDS OVERHEAD.
GUSTY SW WINDS AND MOISTURE POOLING ARE EXPECTED AHEAD OF THE COLD
FRONT WITH THE MOST UNCOMFORTABLE DAY OF THE WEEK. HEAT INDEX VALUES
LOOK TO TOP OUT AROUND 100 OR SO DO TO AN UPTICK IN TEMPERATURES AND
A MORE SIGNIFICANT INCREASE IN DEWPOINTS OVER THAT EXPERIENCED TODAY.

MODELS ARE STILL AT ODDS WITH HOW WIDESPREAD THUNDERSTORM ACTIVITY
WILL BE WITH THE FRONTAL PASSAGE DUE TO A STRONG CAP IN
PLACE...MAKING FOR A CHALLENGING FORECAST. I PREFER TO BACK OFF ON
LIKELY POPS BUT FEEL SLIGHTLY LESS CONFIDENT THAN YESTERDAY ON
MORE THAN SCATTERED COVERAGE. WITH THE GENERAL PATTERN CANNOT
RULE OUT ISOLATED ACTIVITY IN THE AFTERNOON WITH CONVERGENCE AHEAD
OF THE FRONT IN THE MOIST WARM SECTOR. BUT THE MORE ORGANIZED TIME
PERIOD WOULD BE IN THE EVENING HOURS. CONFIDENCE IS MODERATE TO
HIGH THAT THERE BE AT LEAST SCATTERED THUNDERSTORM ACTIVITY.
INSTABILITY AND MOISTURE VALUES ARE VERY HIGH...AND BULK SHEAR HAS
SHOWN SIGNS OF INCREASING IN RECENT MODELS SPC HAS HIGHLIGHTED SE
WISCONSIN AND NE ILLINOIS IN THE SLIGHT RISK CATEGORY FOR SEVERE
STORMS TUESDAY NIGHT IN THE REGION WHERE STRONG INSTABILITY/HIGHER
SHEAR WILL BE THE BEST CO- LOCATED...GENERALLY ALONG AND NORTH OF
INTERSTATE 80. SEVERE WIND GUSTS/LARGE HAIL MAY BE POSSIBLE...BUT
THE GREATEST THREAT WILL BE HEAVY RAINFALL RATES GIVEN PWAT VALUES
ABOVE 2" WHICH MEANS STORMS WILL BE VERY EFFICIENT RAIN MAKERS
WITH 1"/HR TOTALS POSSIBLE. STORMS MAY STILL BE SURFACE BASED EVEN
WITH THE FRONTAL PASSAGE COMING IN THE EVENING AS TEMPERATURES AND
DEWPOINTS REMAIN ON THE HIGH SIDE. NO CLEAR SIGNAL OF ANY TRAINING
GIVEN THE PROGRESSIVE NATURE OF THE FRONT. CAPPING ISSUES DECREASE
CONFIDENCE IN COVERAGE FARTHER SOUTH AND EAST...BUT IRONICALLY AS
THE FRONT AND UPPER FORCING HAVE A LONGER TIME TO ACT ON THE CAP
AREAS SOUTH MAY ACTUALLY HAVE A BETTER CHANCE FOR MORE WIDESPREAD
ELEVATED STORMS...THOUGH CONFIDENCE ON SEVERE IN THESE AREAS IS
LOWER.

850 TEMPERATURES DROP SOME 8-10C ON WEDNESDAY WITH THE LOW LEVEL
FLOW TURNING ONSHORE. HIGH PRESSURE BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL KEEP A MODEST PRESSURE GRADIENT DRAPED OVER THE
AREA WEDNESDAY BEHIND THE DEPARTING SURFACE WAVE. THEREFORE EXPECT
GUSTY N/NE WINDS AND HIGHS IN THE 70S. THE SURFACE HIGH BUILDS
OVERHEAD THURSDAY FOR ANOTHER SEASONABLY COOL AND DRY DAY...THEN THE
HIGH DRIFTS EAST ON FRIDAY BRINGING SOME RECOVERY TO TEMPS CLOSER TO
80 OR SO WITH MORE OF SOUTHERLY COMPONENT TO LOWER LEVEL WINDS.

BEYOND THIS TIME FRAME...AN UPPER TROUGH WILL REMAIN PARKED OVER
EASTERN CANADA WHILE ANOTHER UPPER LOW MIGRATES THROUGH THE CANADIAN
PRAIRIES. WEAK RIPPLES AROUND THE CENTRAL U.S. UPPER RIDGE COMBINED
WITH WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY. THE UPPER AIR
PATTERN EVOLUTION GETS A BIT MESSIER BEYOND THAT...BUT GENERALLY THE
REGION WILL REMAIN UNDER THE INFLUENCE OF THE EASTERN U.S. TROUGH TO
SOME DEGREE CREATING SOMEWHAT COOLER AND UNSETTLED CONDITIONS.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 211745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 211745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 211745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 211745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY SOUTH/SOUTHWEST WINDS TUESDAY. CMS

//DISCUSSION...UPDATED 18Z...

SOUTH/SOUTHWEST WINDS WILL CONTINUE THROUGH THE PERIOD AS THE
GRADIENT SLOWLY TIGHTENS. A LAKE BREEZE IS POSSIBLE RIGHT ALONG
THE IL SHORE THIS AFTERNOON...BUT IS NOT EXPECTED TO REACH ANY OF
THE TERMINALS INCLUDING GYY. PREVAILING SPEEDS WILL REMAIN IN THE
8-12 KT RANGE THROUGH SUNSET WITH SOME HIGHER GUSTS INTO THE
MID/UPPER TEEN KT RANGE ACROSS NORTHWEST IL AND RFD. SPEEDS WILL
DIMINISH UNDER 10 KTS THIS EVENING AND THEN INCREASE AGAIN AFTER
SUNRISE TUESDAY MORNING. HOW STRONG WINDS WILL BECOME TUESDAY
MORNING INTO TUESDAY AFTERNOON IS STILL A BIT UNCERTAIN. FORECAST
SOUNDINGS SHOW LOW LEVELS MIXING SHORTLY AFTER SUNRISE...THUS
EXPECT SPEEDS/GUSTS TO BE STEADILY INCREASE THRU 12Z-14Z. IN
ADDITION...QUITE A BIT OF WIND ALOFT DURING THE MORNING AND
CURRENT SPEEDS/GUSTS MAY END UP BEING TOO LOW. GUSTS INTO THE
LOWER/MID 20KT RANGE WILL BE POSSIBLE FROM MID MORNING THROUGH
EARLY TUESDAY EVENING.

THERE IS A CHANCE OF TSRA ACROSS PORTIONS OF NORTHEAST IA AND
SOUTHWEST WI LATE TONIGHT INTO TUESDAY MORNING. ITS POSSIBLE THAT
SOME OF THIS ACTIVITY COULD DRIFT SOUTHEAST TOWARD RFD BEFORE
DISSIPATING TUESDAY MORNING. WITH MUCH OF THIS ACTIVITY EXPECTED
TO STAY NORTHWEST OF RFD...MAINTAINED DRY CONDITIONS WITH THIS
FORECAST. A COLD FRONT WILL MOVE SOUTH ACROSS THE TERMINALS
TUESDAY NIGHT...SHIFTING WINDS NORTHERLY. THERE IS A CHANCE OF
TSRA ALONG AND AHEAD OF THIS FRONT TUESDAY EVENING INTO TUESDAY
NIGHT AND APPEARS THAT ANY TSRA TUESDAY EVENING WOULD BE AFTER
THE END OF THIS 30 HOUR ORD TAF.

PATCHY/SHALLOW FOG FORMED AGAIN THIS MORNING AND THIS MAY
REDEVELOP OVERNIGHT INTO EARLY TUESDAY MORNING. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM FOR WINDS THROUGH THE PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 211743
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1243 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.



&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.


HJS
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 211743
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1243 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.



&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.


HJS
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 211743
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1243 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.



&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.


HJS
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 211743
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1243 PM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.



&&

.AVIATION...
ISSUED 1240 PM CDT Mon Jul 21 2014
SCT CU field slowly developing on vis sat imagery. Southerly winds
dominating with some variability to the east, closer to the sfc
ridge axis. Skies clearing towards sunset and winds decreasing
somewhat, decoupling, but being countered by a slight increase in
the pressure gradient from the west. Vis reduction before dawn
most likely only to affect far east, with CMI dropping to
predominate MVFR for a few hours, only tempo for DEC.


HJS
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 211614
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1114 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* NONE. CMS

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH FOR ALL ELEMENTS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 211547
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1047 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.

HJS
&&

.AVIATION...
ISSUED 700 AM CDT Mon Jul 21 2014

MVFR fog will linger around CMI through 13z then dissipate to VFR
vis. Any other vis reductions for the other TAF sites should
remain VFR at 6SM BR. The surface ridge axis in the Ohio River
Valley will slowly move east today, allowing more southerly flow
to develop across central IL. South winds will increase to around
10kt at the terminal sites, then decrease again by evening.

Cloud development today will be mainly in the 4-5K ft layer, with
very few periods of ceilings becoming BKN.

MVFR light fog could develop again late tonight around CMI,
possibly down to 4SM BR after 10z/5am.

Shimon
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KILX 211547
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1047 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 1043 AM CDT Mon Jul 21 2014
High pressure ridge axis slipping eastward and increasingly
southerly return flow pushing warmer and more humid air into the
region. Wind speeds picking up a bit as the pressure gradient
begins to increase...with lighter and slightly more variable winds
in the east. Expecting some cu to develop yet again today, but
will not do much for the warming trend and forecast is on track
for the mid to upper 80s for the max temps. No update anticipated
at this time.

HJS
&&

.AVIATION...
ISSUED 700 AM CDT Mon Jul 21 2014

MVFR fog will linger around CMI through 13z then dissipate to VFR
vis. Any other vis reductions for the other TAF sites should
remain VFR at 6SM BR. The surface ridge axis in the Ohio River
Valley will slowly move east today, allowing more southerly flow
to develop across central IL. South winds will increase to around
10kt at the terminal sites, then decrease again by evening.

Cloud development today will be mainly in the 4-5K ft layer, with
very few periods of ceilings becoming BKN.

MVFR light fog could develop again late tonight around CMI,
possibly down to 4SM BR after 10z/5am.

Shimon
&&

.PREV DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KLOT 211403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NONE. CMS

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR ALL ELEMENTS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NONE. CMS

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR ALL ELEMENTS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NONE. CMS

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR ALL ELEMENTS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* NONE. CMS

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH FOR ALL ELEMENTS. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 211202
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
702 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.AVIATION...
ISSUED 700 AM CDT Mon Jul 21 2014

MVFR fog will linger around CMI through 13z then dissipate to VFR
vis. Any other vis reductions for the other TAF sites should
remain VFR at 6SM BR. The surface ridge axis in the Ohio River
Valley will slowly move east today, allowing more southerly flow
to develop across central IL. South winds will increase to around
10kt at the terminal sites, then decrease again by evening.

Cloud development today will be mainly in the 4-5K ft layer, with
very few periods of ceilings becoming BKN.

MVFR light fog could develop again late tonight around CMI,
possibly down to 4SM BR after 10z/5am.

Shimon
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 211202
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
702 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.

SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.

LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart


&&

.AVIATION...
ISSUED 700 AM CDT Mon Jul 21 2014

MVFR fog will linger around CMI through 13z then dissipate to VFR
vis. Any other vis reductions for the other TAF sites should
remain VFR at 6SM BR. The surface ridge axis in the Ohio River
Valley will slowly move east today, allowing more southerly flow
to develop across central IL. South winds will increase to around
10kt at the terminal sites, then decrease again by evening.

Cloud development today will be mainly in the 4-5K ft layer, with
very few periods of ceilings becoming BKN.

MVFR light fog could develop again late tonight around CMI,
possibly down to 4SM BR after 10z/5am.

Shimon
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$







000
FXUS63 KLOT 211129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 211129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

//DISCUSSION...UPDATED 12Z...

LOW PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL INCH TOWARDS
THE UPPER MIDWEST THROUGH THE NEXT 24 HOURS ALLOWING THE GRADIENT TO
INCREASE SOME. SOUTH TO SOUTH-SOUTHWEST WINDS TODAY WILL INCREASE TO
AROUND 10 KT OR SO BY MID TO LATE THIS MORNING WITH A FEW GUSTS INTO
THE MID TEENS POSSIBLE AT RFD. WINDS WILL TAPER SOME OVERNIGHT...BUT
THEN RESUME AGAIN MID MORNING TUESDAY WITH GUSTS INTO THE HIGH TEENS
AND LOW 20 KT RANGE POSSIBLE INCLUDING AT THE CHICAGO TERMINALS
TUESDAY AFTERNOON. OUTSIDE OF SOME PATCHY EARLY MORNING FOG MAINLY
IMPACTING DPA AND GYY THIS MORNING...VFR CONDITIONS WILL PREVAIL.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...THUNDERSTORMS LIKELY.
WEDNESDAY THROUGH FRIDAY...VFR.
SATURDAY THROUGH SUNDAY...CHANCES FOR THUNDERSTORMS.

BMD

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210900
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
400 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 210900
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
400 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 210756
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
256 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.


SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.


LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$





000
FXUS63 KILX 210756
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
256 AM CDT Mon Jul 21 2014

.DISCUSSION...
ISSUED 255 AM CDT Mon Jul 21 2014

Stagnant weather pattern continues across the area, with just some
cirrus dropping southward early this morning. Had a rather
pronounced smoke layer also moving southward through the state
yesterday, but latest status is unknown as it was only tracked
via visible satellite imagery which is currently dark. Similar to
this time yesterday, have had some shallow dense fog across mainly
the far eastern CWA, closer to the lingering ridge axis. Aloft,
high pressure over New Mexico continues to build northward through
the central Plains, tracking any shortwaves well to our north
along the periphery of the ridge.

The main forecast concern remains with rain chances Tuesday night
and Wednesday with the passage of a cold front.


SHORT TERM...Today through Wednesday:

Beginnings of our cold front is taking shape to our west, with low
pressure over central South Dakota and a trailing cold front
extending into Colorado. The front is expected to cross the
forecast area late Tuesday night and early Wednesday. The
atmosphere ahead of this front should be rather capped on Tuesday,
as 700 mb temperatures rise to around 14C northwest of I-55, and
there is some question as to how fast it will break during the
evening. Have removed the slight chance PoP`s during the day
northwest of the Illinois River, and kept a narrow axis of likely
PoP`s Tuesday night to about I-55. Am hesitant to introduce it
further east for now due to the uncertainty as to whether the cap
fully breaks. Severe weather threat looks marginal, with very weak
shear ahead of the front and the aforementioned cap issues. Much
of the rain should be out of northwest half of the forecast area
by midday Wednesday, but will likely linger for a time into the
afternoon across the southeast half.

Temperature-wise, the heat and humidity will continue to slowly
build through Tuesday. Lower 90s will be common on Tuesday, with
the highest heat index values west, around 100-102. Cooler air
will start to plunge southward on Wednesday as an upper trough
deepens overhead, and highs may struggle to reach 80 north of
I-74.


LONG TERM...Thursday through Sunday:

The strong upper high should flatten some late week, as a closed
low deepens over the Pacific Northwest and rides along the top of
the ridge. Will see a day or two of more pleasant conditions with
highs near 80 and lower humidity, before slightly warmer and more
humid conditions return for the weekend. However, this will be
short lived, as the pattern for next week returns to cooler than
normal temperatures again.

High pressure to dominate Thursday and Friday with fair
conditions, then concern shifts to potential MCS activity as a
weak shortwave tracks in from the Dakotas. Not much model
agreement in the details that far out, with the GEM mainly to our
southwest, the ECMWF splitting it around us, and the GFS affecting
us most. Have not made a lot of changes to the PoP`s yet as a
result, but there will probably be a period of drier weather on
Sunday as weak high pressure moves in temporarily.

Geelhart

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$






000
FXUS63 KLOT 210748
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210748
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
247 AM CDT

HIGH PRESSURE SPANS FROM NEW ENGLAND INTO THE MID MISSISSIPPI VALLEY
WHILE A COUPLE AREAS OF LOW PRESSURE LIE OVER HUDSON BAY AND THE
NORTHERN PLAINS. A MODEST GRADIENT HAS DEVELOPED OVER NORTHERN LAKE
MICHIGAN THIS MORNING AND WILL SPREAD ACROSS THE REMAINDER OF THE
LAKE TODAY WITH SOUTH WINDS FRESHENING UP INTO THE 15 TO 25 KT RANGE
ACROSS PARTICULARLY THE NORTHERN PORTIONS OF LAKE MICHIGAN. THE AREA
OF LOW PRESSURE OVER THE NORTHERN PLAINS WILL TRACK ACROSS THE
NORTHERN GREAT LAKES REGION TUESDAY NIGHT INTO WEDNESDAY DRAGGING A
COLD FRONT ACROSS LAKE MICHIGAN. WINDS TURN NORTHERLY BEHIND THE
FRONT AND A QUICKLY TIGHTENING GRADIENT AND MODERATE PRESSURE RISES
OVERSPREADING THE LAKE WILL RESULT IN NORTH/NORTHWEST WINDS TO
AROUND 30 KT AT TIMES. HIGH PRESSURE WILL BUILD BACK OVER THE LAKE
DURING THE LATTER HALF OF THE WEEK RESULTING IN TAPERING WINDS AND
WAVES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 210710
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210710
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210710
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210710
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
210 AM CDT MON JUL 21 2014

.DISCUSSION...
205 AM CDT

TODAY THROUGH TONIGHT...
MAIN CONCERNS FOR TODAY WILL BE ON HOW WARM SFC TEMPS BECOME...AS
BROAD SFC RIDGE CONTINUES TO PROVIDE A DRY INFLUENCE. THE STRETCH OF
DRY WEATHER OVER THE PAST SEVERAL DAYS...AND DEW PTS NOT POISED TO
START CLIMBING BACK INTO THE UPR 60S TO LOW 70S UNTIL LATE
TONIGHT...THIS WILL ALLOW PARCELS TO EASILY WARM GIVEN THE DRY
ENVIRONMENT...FORTUNATELY GUIDANCE HAS PICKED UP ON THIS AND TEMPS
ARE GENERALLY IN THE MID/UPR 80S. THE SOUTHERLY FLOW SHUD HELP PUSH
TEMPS TO NEAR 90 FOR DOWNTOWN CHICAGO.

THE SFC RIDGE WILL CONTINUE TO DRIFT EAST...WHICH WILL ALLOW THE
FLOW TO SLOWLY TURN SOUTHWESTERLY LATE TONIGHT. ENOUGH SFC RIDGING
WILL LINGER INTO TONIGHT TO HOLD-OFF PRECIP...HOWEVER THE ATMOS
RIVER THAT HAS BEEN PARKED OVER THE CENTRAL PLAINS WILL ARRIVE LATE
THIS EVENING. THIS WILL PUMP DEW POINTS BACK INTO THE UPR 60S OVER
THE REGION...AND HELP HOLD OVERNIGHT LOWS UP IN THE UPR 60S TO PSBLY
THE LOW 70S CLOSER TO DOWNTOWN CHICAGO. GUIDANCE HAS CONTINUED TO
SUGGEST THAT ANY COMPLEX OF THUNDERSTORMS THAT DEVELOP OVER THE
UPPER MIDWEST WITH A VORT MAXIMA TO REMAIN WELL NORTHWEST OF THE
FORECAST AREA TONIGHT...SO HAVE HELD ONTO DRY FORECAST OVERNIGHT.

TUESDAY...
SHORTWAVE WILL BE SLIDING EAST ACROSS LAKE SUPERIOR SHORTLY AFT
DAYBREAK...WITH EXPECTED ONGOING CONVECTION. HI-RES LCL ARW8KM
SUGGESTS A FRONTAL BOUNDARY WILL EXTEND SOUTH FROM THIS FEATURE INTO
SOUTHERN WISC...WHICH COULD ACT AS A TRIGGER TO PRODUCE AN AREA OF
SHOWERS/THUNDERSTORMS EARLY TUE. FORTUNATELY TEMPS ALOFT WILL BE
RISING...NEARING 20-23 DEG C...WHICH WILL PRODUCE A DECENT CAPPED
ENVIRONMENT THRU THE AFTN HOURS TUE. THIS SHUD LIMIT CONVECTIVE
DEVELOPMENT UNTIL LATE IN THE DAY...SO MOST OF TUE COULD END UP
BEING DRY. UNFORTUNATELY THE ATMOS RIVER WILL BE ARRIVING OVERHEAD
WITH DEW PTS PUSHING INTO THE LOW 70S...WITH PWAT VALUES HOVERING
ARND 2" BY TUE AFTN/EVE. SFC TEMPS SHUD BE ABLE TO REALIZE THE WARM
AIR ALOFT...COUPLED WITH THE STRETCH OF DRY DAYS PRECEDING
TUE...THAT SFC TEMPS WILL PUSH TO ARND 90 PSBLY THE LOW 90S. WITH
THE HIGH VOLUME OF MOISTURE IN THE ATMOS...AND TEMPS NEARING THE LOW
90S...HEAT INDEX VALUES WILL BE HOVERING ARND 100 DEG BY MID-AFTN
TUE.

THEN BY LATE AFTN/EVE THE FOCUS WILL TURN TOWARDS A VORT/WAVE THAT
WILL PUSH INTO WESTCENTRAL WISC. BY EARLY EVE THE CAPPED ENVIRONMENT
SHUD BE STARTING TO WEAKEN...HOWEVER THE LCL ARW8KM IS LEANING
TOWARDS THE CAP LINGERING INTO THE EVENING HOURS. THERE WILL BE AN
APPROACHING WAVE APPROACHING TO THE NORTH/NORTHWEST OF THE
FORECAST AREA...WHICH COULD BECOME A FOCAL POINT FOR ANY
CONVECTIVE GROWTH. FORTUNATELY FOR THE FORECAST AREA THERE
REMAINS MARGINAL SHEAR. THE BEST TIMING APPEARS TO BE LATE IN THE
EVENING...BUT THE LACK OF FORCING OVER THE AREA COULD RESULT IN
JUST SOME ISOLATED STORMS. IT WILL ALL HINGE ON THE LONGEVITY OF
THE CAP.

CONFIDENCE IN TEMPS/HEAT INDEX VALUES...HIGH.
CONFIDENCE IN STORMS...MEDIUM.

WEDNESDAY THROUGH THURSDAY...
MID-LVL RIDGE WILL BE BUILDING OVER THE CENTRAL ROCKIES WED WITH A
DOWNSTREAM TROUGH ARRIVING IN THE GREAT LAKES. A SFC RIDGE WILL ALSO
BE ASSOCIATED WITH THE GREAT LAKES TROUGH...WITH TEMPS WED LIKELY
HOLDING IN THE 70S FOR MOST LOCATIONS AND DRY WEATHER RETURNING FOR
WED/THUR. THE ONSHORE FLOW FOR BOTH DAYS COULD HOLD TEMPS ARND 70
FOR ADJACENT LAKE MICHIGAN LOCATIONS. OVERNIGHT LOWS WILL DIP INTO
THE LOW/MID 50S...TO ARND 60 FOR AREAS ADJACENT TO LAKE MICHIGAN.

CONFIDENCE...HIGH.

FRIDAY THROUGH THE WEEKEND...
ENSEMBLES MEMBERS HAVE CONTINUE TO DEMONSTRATE A HIGH CONFIDENCE IN
THE EXTENDED PERIODS...WITH THE LATE WEEK SFC RIDGE HOLDING THRU
MOST OF THE DAY FRI. THIS WILL MAINTAIN DRY WEATHER THRU FRI...ALONG
WITH TEMPS TRYING TO RETURN TO NEAR 80 DEG. THE BROAD MID-LVL RIDGE
OVER CENTRAL ROCKIES APPEARS TO FLATTEN SLIGHTLY FRI...WHICH COULD
RELAX ENOUGH FRI EVENING TO NUDGE THE GREAT LAKES SFC RIDGE FURTHER
EAST. CURRENT EXTENDED OPER GUIDANCE IS INDICATING A SHORTWAVE
SLIDING ALONG THE NORTHERN PERIPHERY OF THE MID-LVL RIDGE FRI
NGT...WITH POP CHANCES RETURNING LATE FRI THRU THE WEEKEND.

ENSEMBLES AND OPER SOLUTIONS HAVE BEEN CONSISTENT IN RETURNING A
HIGH AMPLITUDE RIDGE TO THE WESTERN CONUS EARLY NEXT WEEK...WITH A
HIGH LATITUDE BLOCK OVER THE NORTH ATLANTIC. THIS COULD BRING
TROUGHING AND UNSEASONABLY COOL WEATHER BACK TO THE GREAT LAKES
REGION.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210520
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1220 AM CDT MON JUL 21 2014

.DISCUSSION...
210 PM CDT

FORECAST CONCERNS REMAIN CENTERED ON INCREASING HEAT AND HUMIDITY
FOR MONDAY AND TUESDAY...FOLLOWED BY CHANCES FOR THUNDERSTORMS AND
POTENTIALLY HEAVY RAINFALL TUESDAY NIGHT. AFTER A COLD FRONT BRINGS
A RETURN TO DRIER AND COOLER WEATHER...A MORE ACTIVE PATTERN LOOKS
TO SET UP FOR THE WEEKEND.

THE OVERALL WEATHER PATTERN ACROSS THE MIDWEST HAS CHANGED SLIGHTLY
OVER THE LAST 24 HOURS. BROAD UPPER LEVEL TROUGHING REMAINS IN PLACE
ACROSS THE EASTERN THIRD OF THE COUNTRY. A FEW WEAK WAVES ON THE
BACK SIDE OF THIS TROUGH ARE MOVING SOUTHWEST THROUGH THE AREA. A
STRONG UPPER LEVEL RIDGE CONTINUES TO STRENGTHEN IN THE SOUTHERN
PLAINS AND EXTENDING INTO THE ROCKY MOUNTAIN REGION. THE UPPER LEVEL
JET IS FOCUSED NORTH OF THE CANADIAN BORDER AND A STRONGER WAVE IS
PASSING THROUGH THE CENTRAL AND NORTHERN MANITOBA...LEAVING FAIRLY
ZONAL FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY. AT THE
SURFACE...WIDESPREAD HIGH PRESSURE EXTENDS FROM THE ATLANTIC AND
THROUGH THE EASTERN GREAT LAKES. A TROUGH AXIS EXTENDS THROUGH THE
NATIONS HEARTLAND. THIS LEAVES A PRESSURE GRADIENT DRAPED TO OUR
NORTH AND WEST.

THE LEADING EDGE OF THE THERMAL RIDGE IS STILL LARGELY WEST OF THE
AREA THIS AFTERNOON...SO TEMPERATURES HAVE WARMED JUST SLIGHTLY INTO
THE 80S WITH JUST A SLIGHT INCREASE IN HUMIDITY LEVELS FROM
SATURDAY. DIURNAL CUMULUS AND THE LAKE BREEZE IS AGAIN KEEPING
THINGS IN CHECK TODAY. A FEW WEAK WAVES ARE TRAVERSING THE UPPER
FLOW ON THE BACK SIDE OF THE EASTERN U.S. TROUGH BRINGING VARIABLE
CLOUDINESS AT TIMES...BUT GENERALLY UPPER LEVEL HEIGHTS CONTINUE TO
BUILD KEEPING CLOUD COVER SOMEWHAT LIMITED OUTSIDE OF THE DAYTIME
CUMULUS DEVELOPMENT. THAT SAID...A FAIRLY EXTENSIVE AREA OF HAZE FROM
FIRES IN THE WESTERN UNITED STATES EXTENDS BACK TO THE IOWA BORDER
THIS AFTERNOON...AND THUS EXPECT THE HAZY CONDITIONS TO PERSIST
THROUGH THE EVENING HOURS AND POSSIBLY INTO TOMORROW. DEWPOINTS REMAIN IN
THE UPPER 50S TO LOW 60S TONIGHT...SO EXPECT LOWS TO REMAIN IN THE
60S. ANY POTENTIAL CONVECTION TONIGHT INTO MONDAY MORNING WOULD
REMAIN WELL NORTH AND WEST CLOSER TO THE LOW LEVEL JET AXIS AND
UPPER FORCING.

ON MONDAY THE UPPER RIDGE IN THE CENTER OF THE COUNTRY STRENGTHENS
AND EXPANDS EXPANDS EASTWARD OVER THE AREA. IT ALSO AMPLIFIES IN
RESPONSE TO A DIGGING TROUGH OFF THE PACIFIC COAST. AS THIS OCCURS
THE THERMAL RIDGE AXIS EXPANDS EASTWARD WITH A MORE NOTICEABLE
INCREASE IN TEMPERATURES AND HUMIDITY VALUES. 850 TEMPS REACH FROM
18-21C ON MONDAY...POSSIBLY COOLER EAST INTO NW INDIANA. LOCAL
CLIMATOLOGY WOULD SUPPORT AROUND 90 IN SPOTS...BUT MOS GUIDANCE HAS
BEEN PERFORMING WELL THE PAST FEW DAYS. STILL EXPECTING TEMPS
GENERALLY IN THE MID TO UPPER 80S.

MONDAY NIGHT INTO TUESDAY SEVERAL WAVES WILL BE RIDING ALONG THE
NORTHERN SIDE OF THE STRONG UPPER LEVEL HIGH. MODELS ARE IN GOOD
AGREEMENT IN CONVECTION BREAKING OUT IN THE NORTHERN PLAINS EARLIER
IN THE DAY WHICH MAY POTENTIALLY MORPH INTO A FORWARD PROPAGATING MCS
OVERNIGHT. THE LOW LEVEL JET AXIS AND INSTABILITY AXIS AGAIN REMAINS
FOCUSED NORTH AND WEST OF THE AREA. STILL SOMETHING TO KEEP AN EYE
ON. BY TUESDAY MORNING SOME OF THE SHORTWAVE ENERGY GETS MERGED WITH
THE NORTHERN STREAM UPPER LOW IN NORTHERN CANADA. THE CONVECTION
MONDAY NIGHT INTO TUESDAY WILL GET MUCH CLOSER...THOUGH MOST OF OUR
AREA REMAINS LARGELY CAPPED EVEN INTO TUESDAY. OVERNIGHT LOWS WILL
BE IN THE MID TO UPPER 60S...TO THE LOW 70S DOWNTOWN.

TUESDAY THE HEAT AND CERTAINLY HUMIDITY WILL BE IN FULL EFFECT. ONCE
ANY MORNING DEBRIS CLOUDS CLEAR SW WINDS. LOCAL 925/850 CLIMATOLOGY
AND CURRENT GRIDS ARE IN LINE IN SHOOTING FOR THE LOW 90S...WHICH IS
CERTAINLY PLAUSIBLE GIVEN THAT THE THERMAL RIDGE AXIS WILL BE RIGHT
OVER US AND SW FLOW REMAINS IN PLACE AHEAD OF THE SOUTHWARD MOVING
COLD FRONT. CONCERNS ARE ANY LINGERING DEBRIS CLOUDS AND THE HIGH
END OF SREF/GEFS ENSEMBLE GUIDANCE TOPPING OUT NEAR 90...FEEL WITH
THE SW WINDS THAT THE POTENTIAL IS STILL THERE. REGARDLESS IT WILL
FEEL QUITE UNCOMFORTABLE WITH DEWPOINTS INTO THE 70S RESULTING IN
HEAT INDICES AROUND 100. SW WINDS WILL PUSH THE MUGGY CONDITIONS ALL
THE WAY TO THE LAKEFRONT. THERE IS A FAIRLY STRONG CAP IN PLACE THAT
LOOKS TO REMAIN IN PLACE ACROSS MOST OF THE AREA...BUT KEPT A CHANCE
POP IN FOR THE NORTHERN TIER SHOULD THE WAVE GET CLOSER SOUTH.

THE POSITIVELY TILTED SHORTWAVE WILL PUSH SE THROUGH THE AREA
SOMETIME TUESDAY EVENING/NIGHT...BUT SOME DISAGREEMENTS AS TO HOW
STRONG THE WAVE WILL BE. THE ASSOCIATED SURFACE COLD FRONT WILL BE
PUSHING INTO THE UPPER MIDWEST BY EARLY AFTERNOON/EVENING AND
APPEARS ENOUGH COMBINATION OF UPPER LEVEL DYNAMICS AND LOW LEVEL
CONVERGENCE FOR SHOWERS AND THUNDERSTORMS.  ISOLATED SEVERE
WIND/HAIL REMAINS POSSIBLE WITH THE THREAT FOR HEAVY RAINFALL/FLASH
FLOODING BEING THE MOST LIKELY HAZARD AS FORECAST SOUNDINGS SUGGEST
PRECIPITABLE WATER VALUES IN EXCESS OF 2 INCHES. MODELS GENERALLY
KEEP THE HEAVIEST PRECIPITATION NORTH BUT A LOT DEPENDS ON THE TIMING
AND HOW INTACT THE FRONT/WAVE REMAINS AS IT SLIDES THROUGH OUR AREA.
SEEMS THERE WOULD BE ENOUGH FORCING/CONVERGENCE TO WARRANT LIKELY
POPS FOR A GOOD PORTION OF THE AREA.

THE WARM UP WILL BE SHORT LIVED AS WEDNESDAY WE WILL BE BACK INTO
THE COOLER AND DRIER REGIME AS A COLD FRONT BRINGS THE RETURN TO DRY
AND COOL NORTHERLY TO ONSHORE FLOW. EXPECT GENERALLY CLEAR SKIES FOR
SEVERAL DAYS BEHIND THE FRONT WITH READINGS BACK INTO THE 70S TO
AROUND 80 WITH COOLER CONDITIONS AT THE LAKEFRONT. THE NEXT CHANCES
FOR PRECIP DOES NOT LOOK TO BE UNTIL FRIDAY NIGHT OR POSSIBLY
SATURDAY AS AN UPPER LOW ALONG THE CANADIAN PRAIRIES APPROACHES FROM
THE NORTHWEST WITH ACTIVE AND COOLER THAN NORMAL CONDITIONS REMAINING IN
PLACE AS THE LOW CUTS OFF AND SLIDES THROUGH WISCONSIN ON SUNDAY.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 210520
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1220 AM CDT MON JUL 21 2014

.DISCUSSION...
210 PM CDT

FORECAST CONCERNS REMAIN CENTERED ON INCREASING HEAT AND HUMIDITY
FOR MONDAY AND TUESDAY...FOLLOWED BY CHANCES FOR THUNDERSTORMS AND
POTENTIALLY HEAVY RAINFALL TUESDAY NIGHT. AFTER A COLD FRONT BRINGS
A RETURN TO DRIER AND COOLER WEATHER...A MORE ACTIVE PATTERN LOOKS
TO SET UP FOR THE WEEKEND.

THE OVERALL WEATHER PATTERN ACROSS THE MIDWEST HAS CHANGED SLIGHTLY
OVER THE LAST 24 HOURS. BROAD UPPER LEVEL TROUGHING REMAINS IN PLACE
ACROSS THE EASTERN THIRD OF THE COUNTRY. A FEW WEAK WAVES ON THE
BACK SIDE OF THIS TROUGH ARE MOVING SOUTHWEST THROUGH THE AREA. A
STRONG UPPER LEVEL RIDGE CONTINUES TO STRENGTHEN IN THE SOUTHERN
PLAINS AND EXTENDING INTO THE ROCKY MOUNTAIN REGION. THE UPPER LEVEL
JET IS FOCUSED NORTH OF THE CANADIAN BORDER AND A STRONGER WAVE IS
PASSING THROUGH THE CENTRAL AND NORTHERN MANITOBA...LEAVING FAIRLY
ZONAL FLOW ACROSS THE NORTHERN TIER OF THE COUNTRY. AT THE
SURFACE...WIDESPREAD HIGH PRESSURE EXTENDS FROM THE ATLANTIC AND
THROUGH THE EASTERN GREAT LAKES. A TROUGH AXIS EXTENDS THROUGH THE
NATIONS HEARTLAND. THIS LEAVES A PRESSURE GRADIENT DRAPED TO OUR
NORTH AND WEST.

THE LEADING EDGE OF THE THERMAL RIDGE IS STILL LARGELY WEST OF THE
AREA THIS AFTERNOON...SO TEMPERATURES HAVE WARMED JUST SLIGHTLY INTO
THE 80S WITH JUST A SLIGHT INCREASE IN HUMIDITY LEVELS FROM
SATURDAY. DIURNAL CUMULUS AND THE LAKE BREEZE IS AGAIN KEEPING
THINGS IN CHECK TODAY. A FEW WEAK WAVES ARE TRAVERSING THE UPPER
FLOW ON THE BACK SIDE OF THE EASTERN U.S. TROUGH BRINGING VARIABLE
CLOUDINESS AT TIMES...BUT GENERALLY UPPER LEVEL HEIGHTS CONTINUE TO
BUILD KEEPING CLOUD COVER SOMEWHAT LIMITED OUTSIDE OF THE DAYTIME
CUMULUS DEVELOPMENT. THAT SAID...A FAIRLY EXTENSIVE AREA OF HAZE FROM
FIRES IN THE WESTERN UNITED STATES EXTENDS BACK TO THE IOWA BORDER
THIS AFTERNOON...AND THUS EXPECT THE HAZY CONDITIONS TO PERSIST
THROUGH THE EVENING HOURS AND POSSIBLY INTO TOMORROW. DEWPOINTS REMAIN IN
THE UPPER 50S TO LOW 60S TONIGHT...SO EXPECT LOWS TO REMAIN IN THE
60S. ANY POTENTIAL CONVECTION TONIGHT INTO MONDAY MORNING WOULD
REMAIN WELL NORTH AND WEST CLOSER TO THE LOW LEVEL JET AXIS AND
UPPER FORCING.

ON MONDAY THE UPPER RIDGE IN THE CENTER OF THE COUNTRY STRENGTHENS
AND EXPANDS EXPANDS EASTWARD OVER THE AREA. IT ALSO AMPLIFIES IN
RESPONSE TO A DIGGING TROUGH OFF THE PACIFIC COAST. AS THIS OCCURS
THE THERMAL RIDGE AXIS EXPANDS EASTWARD WITH A MORE NOTICEABLE
INCREASE IN TEMPERATURES AND HUMIDITY VALUES. 850 TEMPS REACH FROM
18-21C ON MONDAY...POSSIBLY COOLER EAST INTO NW INDIANA. LOCAL
CLIMATOLOGY WOULD SUPPORT AROUND 90 IN SPOTS...BUT MOS GUIDANCE HAS
BEEN PERFORMING WELL THE PAST FEW DAYS. STILL EXPECTING TEMPS
GENERALLY IN THE MID TO UPPER 80S.

MONDAY NIGHT INTO TUESDAY SEVERAL WAVES WILL BE RIDING ALONG THE
NORTHERN SIDE OF THE STRONG UPPER LEVEL HIGH. MODELS ARE IN GOOD
AGREEMENT IN CONVECTION BREAKING OUT IN THE NORTHERN PLAINS EARLIER
IN THE DAY WHICH MAY POTENTIALLY MORPH INTO A FORWARD PROPAGATING MCS
OVERNIGHT. THE LOW LEVEL JET AXIS AND INSTABILITY AXIS AGAIN REMAINS
FOCUSED NORTH AND WEST OF THE AREA. STILL SOMETHING TO KEEP AN EYE
ON. BY TUESDAY MORNING SOME OF THE SHORTWAVE ENERGY GETS MERGED WITH
THE NORTHERN STREAM UPPER LOW IN NORTHERN CANADA. THE CONVECTION
MONDAY NIGHT INTO TUESDAY WILL GET MUCH CLOSER...THOUGH MOST OF OUR
AREA REMAINS LARGELY CAPPED EVEN INTO TUESDAY. OVERNIGHT LOWS WILL
BE IN THE MID TO UPPER 60S...TO THE LOW 70S DOWNTOWN.

TUESDAY THE HEAT AND CERTAINLY HUMIDITY WILL BE IN FULL EFFECT. ONCE
ANY MORNING DEBRIS CLOUDS CLEAR SW WINDS. LOCAL 925/850 CLIMATOLOGY
AND CURRENT GRIDS ARE IN LINE IN SHOOTING FOR THE LOW 90S...WHICH IS
CERTAINLY PLAUSIBLE GIVEN THAT THE THERMAL RIDGE AXIS WILL BE RIGHT
OVER US AND SW FLOW REMAINS IN PLACE AHEAD OF THE SOUTHWARD MOVING
COLD FRONT. CONCERNS ARE ANY LINGERING DEBRIS CLOUDS AND THE HIGH
END OF SREF/GEFS ENSEMBLE GUIDANCE TOPPING OUT NEAR 90...FEEL WITH
THE SW WINDS THAT THE POTENTIAL IS STILL THERE. REGARDLESS IT WILL
FEEL QUITE UNCOMFORTABLE WITH DEWPOINTS INTO THE 70S RESULTING IN
HEAT INDICES AROUND 100. SW WINDS WILL PUSH THE MUGGY CONDITIONS ALL
THE WAY TO THE LAKEFRONT. THERE IS A FAIRLY STRONG CAP IN PLACE THAT
LOOKS TO REMAIN IN PLACE ACROSS MOST OF THE AREA...BUT KEPT A CHANCE
POP IN FOR THE NORTHERN TIER SHOULD THE WAVE GET CLOSER SOUTH.

THE POSITIVELY TILTED SHORTWAVE WILL PUSH SE THROUGH THE AREA
SOMETIME TUESDAY EVENING/NIGHT...BUT SOME DISAGREEMENTS AS TO HOW
STRONG THE WAVE WILL BE. THE ASSOCIATED SURFACE COLD FRONT WILL BE
PUSHING INTO THE UPPER MIDWEST BY EARLY AFTERNOON/EVENING AND
APPEARS ENOUGH COMBINATION OF UPPER LEVEL DYNAMICS AND LOW LEVEL
CONVERGENCE FOR SHOWERS AND THUNDERSTORMS.  ISOLATED SEVERE
WIND/HAIL REMAINS POSSIBLE WITH THE THREAT FOR HEAVY RAINFALL/FLASH
FLOODING BEING THE MOST LIKELY HAZARD AS FORECAST SOUNDINGS SUGGEST
PRECIPITABLE WATER VALUES IN EXCESS OF 2 INCHES. MODELS GENERALLY
KEEP THE HEAVIEST PRECIPITATION NORTH BUT A LOT DEPENDS ON THE TIMING
AND HOW INTACT THE FRONT/WAVE REMAINS AS IT SLIDES THROUGH OUR AREA.
SEEMS THERE WOULD BE ENOUGH FORCING/CONVERGENCE TO WARRANT LIKELY
POPS FOR A GOOD PORTION OF THE AREA.

THE WARM UP WILL BE SHORT LIVED AS WEDNESDAY WE WILL BE BACK INTO
THE COOLER AND DRIER REGIME AS A COLD FRONT BRINGS THE RETURN TO DRY
AND COOL NORTHERLY TO ONSHORE FLOW. EXPECT GENERALLY CLEAR SKIES FOR
SEVERAL DAYS BEHIND THE FRONT WITH READINGS BACK INTO THE 70S TO
AROUND 80 WITH COOLER CONDITIONS AT THE LAKEFRONT. THE NEXT CHANCES
FOR PRECIP DOES NOT LOOK TO BE UNTIL FRIDAY NIGHT OR POSSIBLY
SATURDAY AS AN UPPER LOW ALONG THE CANADIAN PRAIRIES APPROACHES FROM
THE NORTHWEST WITH ACTIVE AND COOLER THAN NORMAL CONDITIONS REMAINING IN
PLACE AS THE LOW CUTS OFF AND SLIDES THROUGH WISCONSIN ON SUNDAY.

KMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE REMAINS EAST OF THE TERMINALS WITH A WEAK GRADIENT
MAINLY OVER NORTH CENTRAL ILLINOIS PROVIDING LIGHT SOUTHERLY WINDS.
PATCHY FOG IS ALREADY STARTING TO DEVELOP...MAINLY ACROSS PORTIONS
OF EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA THIS EVENING WHERE
THE GRADIENT IS WEAKER. AS SOME LINGERING CIRRUS CLEARS OUT OVER THE
NEXT COUPLE HOURS...EXPECT FOG TO EXPAND BUT FOR NOW EXPECT IT TO BE
CONFINED TO GYY. SOUTH WINDS WILL PICK UP SOME MONDAY MORNING TO
AROUND 10 KT OR SO AND SHOULD KEEP ANY LAKE BREEZE FROM PUSHING
ACROSS THE TERMINALS. OUTSIDE OF THE FOG POTENTIAL
OVERNIGHT...EXPECT VFR CONDITIONS TO PREVAIL THROUGH THE REMAINDER
OF THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...TSRA LIKELY DURING THE NIGHT.
WEDNESDAY...CHC OF TSRA EARLY THEN INCREASING GUSTY NE WINDS.
THURSDAY...VFR. NORTHEAST WINDS.
FRIDAY...SLGT CHC OF TSRA LATE.
SATURDAY...CHC OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

LOW PRESSURE MOVING OUT OF SASKATCHEWAN INTO ONTARIO WILL PUSH A
COLD FRONT DOWN THE LAKE TUESDAY NIGHT.  FROM TONIGHT THROUGH LATE
TUESDAY THE LAKE WILL INCREASINGLY BECOME INFLUENCED BY THE
SOUTHERLY FLOW AHEAD OF THIS FRONT AS IT WORKS ITS WAY TOWARD THE
AREA.  THE RELATIVELY LIGHT PRESSURE GRADIENT TODAY IS STILL
ALLOWING SOME PRONOUNCED ONSHORE FLOW TO DEVELOP AROUND THE
PERIMETER OF THE LAKE.  THIS CAN BE SEEN AS POCKETS OF CLEARING
EVIDENT IN VISIBLE SATELLITE IMAGERY...AND OF COURSE IN THE WIND
OBSERVATIONS AT THE COASTAL PLATFORMS.  WINDS WILL TURN QUICKLY TO
THE NORTH TUESDAY NIGHT AND INCREASE AS THE FRONT MOVES THROUGH.
WINDS MAINTAIN A NORTHERLY COMPONENT THROUGH LATE IN THE WEEK BUT
GRADUALLY RELAX.

DEPENDING ON THE STRENGTH OF THE PRESSURE GRADIENT AND THE COOLNESS
OF THE POST FRONTAL AIRMASS...GUSTS COULD APPROACH LOW END GALES FOR
A WHILE ON WEDNESDAY.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 210406
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1106 PM CDT Sun Jul 20 2014

.DISCUSSION...
ISSUED 830 PM CDT Sun Jul 20 2014

Our quiet weather is expected to continue over the next 36 hours
as high pressure off to our east will be slow to move away. The
southerly winds associated with the departing high will increase
over the next day or so allowing warmer temperatures to filter
into our area along with increasing humidity levels. Already seeing
dew points about 3 to 5 degrees higher than what was observed at
this time yesterday with most areas in the low to mid 60s early
this evening. This will allow for warmer overnight lows and bring
the threat for at least some patchy fog again, especially across the
east by dawn Monday. Latest surface analysis showing the real surge
of 70 to 75 degree dew points still well west of our area this
evening with that type of oppressive humidity pushing into the
region just ahead of a cold front late Tuesday. Forecast in good
shape this evening, so no ZFP update will be needed.

Smith

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith
&&


.PREV DISCUSSION...
ISSUED 327 PM CDT Sun Jul 20 2014

SHORT TERM...Tonight through Wednesday

Scattered cumulus covers much of Illinois again this afternoon,
generally based around 4000 to 6000 feet. 24 hour change in
temperatures and dewpoint generally up a few degrees since
yesterday as expected with a warm high pressure ridge building
into the region. Overnight, some fog is possible again as clear
skies combine with increased low-level moisture. West of I-57
pressure gradients start to increase overnight indicating some
light wind which will likely prevent any substantial fog, however
from around I-57 east have placed patchy fog in the forecast
again from around midnight to 7 a.m.

Monday into Tuesday a strong 500 mb ridge will continue to develop
over the West and extend into the Midwest. This will bring a warm
and stable air mass over Illinois. Southerly low level flow will
bring an increase in moisture yielding dewpoints over 70 by Monday
and Tuesday and heat index values approaching 100 by Tuesday
afternoon.

An upper level trough will move over the top of the ridge and
southeastward through the Midwest Tuesday night, along with a
surface cold front. Most model solutions feature fairly similar
timing of a progressive system moving into northwest Illinois
Tuesday evening and exiting Illinois Wednesday afternoon. Have
only slightly increased probability of precipitation with this
feature to bring likely category (60% or greater) to most of the
central IL forecast area at some point as the feature moves
through. Not expecting a significant severe threat given the
arrival time at night, but don`t think the possibility can be
ruled out at this point given uncertainty with the timing and
CAPE/shear values expected to accompany the system. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north will likely be dry by
afternoon as high pressure begins to build from the north.

LONG TERM...Thursday through Sunday

Cooler conditions are expected Thursday and Friday as cool dry
northerly flow pushes into the region following the Tuesday night
shortwave. Past there, focus shifts to potential MCS activity
Friday night sliding down the upper ridge, which will be re-
establishing itself along and west of the Rockies. For Sunday, a
deep trough is progged by both the GFS and European models over
the Midwest, hence cooler than climatological temperatures and a
chance for precipitation are in the forecast.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 210406
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1106 PM CDT Sun Jul 20 2014

.DISCUSSION...
ISSUED 830 PM CDT Sun Jul 20 2014

Our quiet weather is expected to continue over the next 36 hours
as high pressure off to our east will be slow to move away. The
southerly winds associated with the departing high will increase
over the next day or so allowing warmer temperatures to filter
into our area along with increasing humidity levels. Already seeing
dew points about 3 to 5 degrees higher than what was observed at
this time yesterday with most areas in the low to mid 60s early
this evening. This will allow for warmer overnight lows and bring
the threat for at least some patchy fog again, especially across the
east by dawn Monday. Latest surface analysis showing the real surge
of 70 to 75 degree dew points still well west of our area this
evening with that type of oppressive humidity pushing into the
region just ahead of a cold front late Tuesday. Forecast in good
shape this evening, so no ZFP update will be needed.

Smith

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith
&&


.PREV DISCUSSION...
ISSUED 327 PM CDT Sun Jul 20 2014

SHORT TERM...Tonight through Wednesday

Scattered cumulus covers much of Illinois again this afternoon,
generally based around 4000 to 6000 feet. 24 hour change in
temperatures and dewpoint generally up a few degrees since
yesterday as expected with a warm high pressure ridge building
into the region. Overnight, some fog is possible again as clear
skies combine with increased low-level moisture. West of I-57
pressure gradients start to increase overnight indicating some
light wind which will likely prevent any substantial fog, however
from around I-57 east have placed patchy fog in the forecast
again from around midnight to 7 a.m.

Monday into Tuesday a strong 500 mb ridge will continue to develop
over the West and extend into the Midwest. This will bring a warm
and stable air mass over Illinois. Southerly low level flow will
bring an increase in moisture yielding dewpoints over 70 by Monday
and Tuesday and heat index values approaching 100 by Tuesday
afternoon.

An upper level trough will move over the top of the ridge and
southeastward through the Midwest Tuesday night, along with a
surface cold front. Most model solutions feature fairly similar
timing of a progressive system moving into northwest Illinois
Tuesday evening and exiting Illinois Wednesday afternoon. Have
only slightly increased probability of precipitation with this
feature to bring likely category (60% or greater) to most of the
central IL forecast area at some point as the feature moves
through. Not expecting a significant severe threat given the
arrival time at night, but don`t think the possibility can be
ruled out at this point given uncertainty with the timing and
CAPE/shear values expected to accompany the system. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north will likely be dry by
afternoon as high pressure begins to build from the north.

LONG TERM...Thursday through Sunday

Cooler conditions are expected Thursday and Friday as cool dry
northerly flow pushes into the region following the Tuesday night
shortwave. Past there, focus shifts to potential MCS activity
Friday night sliding down the upper ridge, which will be re-
establishing itself along and west of the Rockies. For Sunday, a
deep trough is progged by both the GFS and European models over
the Midwest, hence cooler than climatological temperatures and a
chance for precipitation are in the forecast.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 210406
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1106 PM CDT Sun Jul 20 2014

.DISCUSSION...
ISSUED 830 PM CDT Sun Jul 20 2014

Our quiet weather is expected to continue over the next 36 hours
as high pressure off to our east will be slow to move away. The
southerly winds associated with the departing high will increase
over the next day or so allowing warmer temperatures to filter
into our area along with increasing humidity levels. Already seeing
dew points about 3 to 5 degrees higher than what was observed at
this time yesterday with most areas in the low to mid 60s early
this evening. This will allow for warmer overnight lows and bring
the threat for at least some patchy fog again, especially across the
east by dawn Monday. Latest surface analysis showing the real surge
of 70 to 75 degree dew points still well west of our area this
evening with that type of oppressive humidity pushing into the
region just ahead of a cold front late Tuesday. Forecast in good
shape this evening, so no ZFP update will be needed.

Smith

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith
&&


.PREV DISCUSSION...
ISSUED 327 PM CDT Sun Jul 20 2014

SHORT TERM...Tonight through Wednesday

Scattered cumulus covers much of Illinois again this afternoon,
generally based around 4000 to 6000 feet. 24 hour change in
temperatures and dewpoint generally up a few degrees since
yesterday as expected with a warm high pressure ridge building
into the region. Overnight, some fog is possible again as clear
skies combine with increased low-level moisture. West of I-57
pressure gradients start to increase overnight indicating some
light wind which will likely prevent any substantial fog, however
from around I-57 east have placed patchy fog in the forecast
again from around midnight to 7 a.m.

Monday into Tuesday a strong 500 mb ridge will continue to develop
over the West and extend into the Midwest. This will bring a warm
and stable air mass over Illinois. Southerly low level flow will
bring an increase in moisture yielding dewpoints over 70 by Monday
and Tuesday and heat index values approaching 100 by Tuesday
afternoon.

An upper level trough will move over the top of the ridge and
southeastward through the Midwest Tuesday night, along with a
surface cold front. Most model solutions feature fairly similar
timing of a progressive system moving into northwest Illinois
Tuesday evening and exiting Illinois Wednesday afternoon. Have
only slightly increased probability of precipitation with this
feature to bring likely category (60% or greater) to most of the
central IL forecast area at some point as the feature moves
through. Not expecting a significant severe threat given the
arrival time at night, but don`t think the possibility can be
ruled out at this point given uncertainty with the timing and
CAPE/shear values expected to accompany the system. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north will likely be dry by
afternoon as high pressure begins to build from the north.

LONG TERM...Thursday through Sunday

Cooler conditions are expected Thursday and Friday as cool dry
northerly flow pushes into the region following the Tuesday night
shortwave. Past there, focus shifts to potential MCS activity
Friday night sliding down the upper ridge, which will be re-
establishing itself along and west of the Rockies. For Sunday, a
deep trough is progged by both the GFS and European models over
the Midwest, hence cooler than climatological temperatures and a
chance for precipitation are in the forecast.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








000
FXUS63 KILX 210406
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1106 PM CDT Sun Jul 20 2014

.DISCUSSION...
ISSUED 830 PM CDT Sun Jul 20 2014

Our quiet weather is expected to continue over the next 36 hours
as high pressure off to our east will be slow to move away. The
southerly winds associated with the departing high will increase
over the next day or so allowing warmer temperatures to filter
into our area along with increasing humidity levels. Already seeing
dew points about 3 to 5 degrees higher than what was observed at
this time yesterday with most areas in the low to mid 60s early
this evening. This will allow for warmer overnight lows and bring
the threat for at least some patchy fog again, especially across the
east by dawn Monday. Latest surface analysis showing the real surge
of 70 to 75 degree dew points still well west of our area this
evening with that type of oppressive humidity pushing into the
region just ahead of a cold front late Tuesday. Forecast in good
shape this evening, so no ZFP update will be needed.

Smith

&&

.AVIATION...
ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.

Smith
&&


.PREV DISCUSSION...
ISSUED 327 PM CDT Sun Jul 20 2014

SHORT TERM...Tonight through Wednesday

Scattered cumulus covers much of Illinois again this afternoon,
generally based around 4000 to 6000 feet. 24 hour change in
temperatures and dewpoint generally up a few degrees since
yesterday as expected with a warm high pressure ridge building
into the region. Overnight, some fog is possible again as clear
skies combine with increased low-level moisture. West of I-57
pressure gradients start to increase overnight indicating some
light wind which will likely prevent any substantial fog, however
from around I-57 east have placed patchy fog in the forecast
again from around midnight to 7 a.m.

Monday into Tuesday a strong 500 mb ridge will continue to develop
over the West and extend into the Midwest. This will bring a warm
and stable air mass over Illinois. Southerly low level flow will
bring an increase in moisture yielding dewpoints over 70 by Monday
and Tuesday and heat index values approaching 100 by Tuesday
afternoon.

An upper level trough will move over the top of the ridge and
southeastward through the Midwest Tuesday night, along with a
surface cold front. Most model solutions feature fairly similar
timing of a progressive system moving into northwest Illinois
Tuesday evening and exiting Illinois Wednesday afternoon. Have
only slightly increased probability of precipitation with this
feature to bring likely category (60% or greater) to most of the
central IL forecast area at some point as the feature moves
through. Not expecting a significant severe threat given the
arrival time at night, but don`t think the possibility can be
ruled out at this point given uncertainty with the timing and
CAPE/shear values expected to accompany the system. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north will likely be dry by
afternoon as high pressure begins to build from the north.

LONG TERM...Thursday through Sunday

Cooler conditions are expected Thursday and Friday as cool dry
northerly flow pushes into the region following the Tuesday night
shortwave. Past there, focus shifts to potential MCS activity
Friday night sliding down the upper ridge, which will be re-
establishing itself along and west of the Rockies. For Sunday, a
deep trough is progged by both the GFS and European models over
the Midwest, hence cooler than climatological temperatures and a
chance for precipitation are in the forecast.

Onton


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$








    US Dept of Commerce
    National Oceanic and Atmospheric Administration
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910
    Page Author: NWS Internet Services Team
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities