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000
FXUS63 KLOT 251812
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
112 PM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

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

* SOUTH WINDS GUSTING AROUND 20 KT THIS AFTERNOON.

* POTENTIAL FOR A FEW SCATTERED SHRA THIS AFTERNOON.

* CHANCE OF TSRA INCREASES LATE TONIGHT.

* PERIOD OF MVFR CIG/FOG POSSIBLE EARLY SATURDAY.

* WIND DIRECTION SOMEWHAT VARIABLE SAT MORNING.

RATZER

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

LOW PRESSURE WAS OVER EASTERN NEBRASKA AT MIDDAY...WITH A WARM
FRONT EXTENDING SOUTHEAST ACROSS THE LOWER MISSOURI RIVER VALLEY.
CIRCULATION ASSOCIATED WITH A MID-LEVEL DISTURBANCE/REMNANT MCV
OVER SOUTHERN WI WAS PRODUCING SOME RAIN ACROSS WI...BUT ONLY
SPOTTY SHRA INTO NORTHERN FOR THE MOST PART...WHILE A COMPLEX OF
THUNDERSTORMS CONTINUES TO MOVE SOUTHEAST ALONG THE MISSISSIPPI
RIVER INTO WESTERN/SOUTHERN IL. TERMINALS WILL REMAIN IN AN AREA
OF BROAD MOIST ASCENT INTO TONIGHT...WITH NOCTURNAL INCREASE IN
LOW LEVEL JET AND AN APPROACHING MID-LEVEL WAVE EXPECTED TO
EVENTUALLY SHIFT THE ELEVATED WARM FRONTAL ZONE EASTWARD AND
PRODUCE SCATTERED THUNDERSTORM THREAT OVER THE TERMINALS LATER
TONIGHT. PATTERN IS RELATIVELY MESSY HOWEVER...WITH FAIRLY LOW
CONFIDENCE IN TIMING DETAILS BEYOND THE OVERALL TREND AT THIS
TIME. AT THIS TIME HOWEVER...IT APPEARS THAT THE GREATEST
THUNDERSTORM THREAT WILL BE TOWARD/AFTER MIDNIGHT. LOW LEVEL JET
THEN TO BECOME MORE WEST/NORTHWEST BY SATURDAY
MORNING...DECREASING THUNDERSTORM POTENTIAL OVER TERMINALS AFTER
SUNRISE. SOME POTENTIAL WILL EXIST FOR BRIEF PERIOD OF MVFR
CEILING AND SOME GROUND FOG WILL EXIST EARLY SATURDAY MORNING
ESPECIALLY WHERE ORGANIZED RAINS FALL.

SOUTHERLY SURFACE WINDS GUSTING AROUND 20 KT THIS AFTERNOON IN
RESPONSE TO PRESSURE FALLS ACROSS WI/IA...APPARENTLY ENHANCED OVER
WESTERN IL BY WAKE LOW BEHIND MISSISSIPPI VALLEY THUNDERSTORM
COMPLEX. WINDS DIMINISH TONIGHT AFTER SUNSET AS GRADIENT WEAKENS
WITH APPROACH OF SURFACE TROUGH. WINDS SHOULD SHIFT MORE
WEST/NORTHWEST SATURDAY MORNING AS SURFACE TROUGH/COLD FRONT SAGS
SOUTHEAST ACROSS THE AREA...THOUGH GUIDANCE INDICATES SOME
VARIABILITY IN WIND DIRECTION IN WEAK GRADIENT NEAR THE TROUGH.

RATZER


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

* LOW CONFIDENCE IN SHRA THIS AFTN/EVENING. MEDIUM CONFIDENCE IN
  TSRA LATE TONIGHT.

* MEDIUM CONFIDENCE IN WIND TRENDS THIS AFTERNOON/EVENING. LOW
  CONFIDENCE IN WIND DIRECTION DETAILS SATURDAY MORNING.

* LOW CONFIDENCE IN MVFR CIG/VIS DEVELOPMENT LATE TONIGHT/EARLY
  SATURDAY.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251621
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1121 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

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

* SOUTH WINDS GUSTING NEAR 20 KT AT TIMES INTO THIS AFTERNOON.

* SCATTERED LIGHT SHRA THROUGH EARLY AFTERNOON...WITH A BREAK
  EXPECTED LATE AFTERNOON/EARLY EVENING.

* CHANCE OF TSRA...MAINLY TONIGHT.

RATZER


//DISCUSSION...UPDATED 16Z...

MID-LEVEL DISTURBANCE MOVING SOUTHEAST ACROSS SOUTHERN WI/NORTHERN
IL THROUGH MID-AFTERNOON WILL BRING POTENTIAL FOR SCATTERED
SHOWERS FROM VFR MID-DECK CIGS. TIMING OF MID-LEVEL CIRCULATION IN
RADAR APPROACHING KDLL SUGGESTS THIS FEATURE WILL PASS ACROSS
WESTERN LAKE MICHIGAN SHORE AROUND 21Z WITH A DECREASE IN SHRA
COVERAGE AFTER THAT TIME. IT APPEARS LITTLE THREAT OF THUNDER WILL
EXIST AT TERMINALS...WITH BETTER CHANCES REMAINING WEST AND FOCUSED
FROM EASTERN IOWA SOUTH ALONG THE MISSISSIPPI RIVER.

SURFACE PRESSURE FALLS ACROSS WI/NORTHERN IL AT 16Z IN ASSOCIATION
WITH ABOVE MENTIONED DISTURBANCE HELPING TO INCREASE WINDS AND
BACK THEM A BIT MORE SOUTHERLY 190-180 DEG. 1-MIN ASOS DATA
SHOWING SOME GUSTS ALREADY APPROACHING 20 KT AT ORD.

RATZER

PREVIOUS DISCUSSION FROM 12Z...

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.

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

* MEDIUM IN SHRA TRENDS. CIGS/VIS SHOULD REMAIN VFR.

* MEDIUM CONFIDENCE IN WIND TRENDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251621
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1121 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

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

* SOUTH WINDS GUSTING NEAR 20 KT AT TIMES INTO THIS AFTERNOON.

* SCATTERED LIGHT SHRA THROUGH EARLY AFTERNOON...WITH A BREAK
  EXPECTED LATE AFTERNOON/EARLY EVENING.

* CHANCE OF TSRA...MAINLY TONIGHT.

RATZER


//DISCUSSION...UPDATED 16Z...

MID-LEVEL DISTURBANCE MOVING SOUTHEAST ACROSS SOUTHERN WI/NORTHERN
IL THROUGH MID-AFTERNOON WILL BRING POTENTIAL FOR SCATTERED
SHOWERS FROM VFR MID-DECK CIGS. TIMING OF MID-LEVEL CIRCULATION IN
RADAR APPROACHING KDLL SUGGESTS THIS FEATURE WILL PASS ACROSS
WESTERN LAKE MICHIGAN SHORE AROUND 21Z WITH A DECREASE IN SHRA
COVERAGE AFTER THAT TIME. IT APPEARS LITTLE THREAT OF THUNDER WILL
EXIST AT TERMINALS...WITH BETTER CHANCES REMAINING WEST AND FOCUSED
FROM EASTERN IOWA SOUTH ALONG THE MISSISSIPPI RIVER.

SURFACE PRESSURE FALLS ACROSS WI/NORTHERN IL AT 16Z IN ASSOCIATION
WITH ABOVE MENTIONED DISTURBANCE HELPING TO INCREASE WINDS AND
BACK THEM A BIT MORE SOUTHERLY 190-180 DEG. 1-MIN ASOS DATA
SHOWING SOME GUSTS ALREADY APPROACHING 20 KT AT ORD.

RATZER

PREVIOUS DISCUSSION FROM 12Z...

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.

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

* MEDIUM IN SHRA TRENDS. CIGS/VIS SHOULD REMAIN VFR.

* MEDIUM CONFIDENCE IN WIND TRENDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.

RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

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

* CHANCE FOR SCATTERED MAINLY LIGHT SHRA TODAY AND EARLY THIS EVE.

* CHANCE FOR TSRA...MAINLY TONIGHT.

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

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.

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

* LOW IN ANY RAIN AT THE AIRPORTS TODAY...HOWEVER IF IT OCCURS IT
  WOULD BE LIGHT AND VFR.

* MEDIUM IN WINDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.


//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

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

* CHANCE FOR SCATTERED MAINLY LIGHT SHRA TODAY AND EARLY THIS EVE.

* CHANCE FOR TSRA...MAINLY TONIGHT.

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

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.

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

* LOW IN ANY RAIN AT THE AIRPORTS TODAY...HOWEVER IF IT OCCURS IT
  WOULD BE LIGHT AND VFR.

* MEDIUM IN WINDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.


//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* CHANCE FOR SCATTERED MAINLY LIGHT SHRA TODAY AND EARLY THIS EVE.

* CHANCE FOR TSRA...MAINLY TONIGHT.


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

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* LOW IN ANY RAIN AT THE AIRPORTS TODAY...HOWEVER IF IT OCCURS IT
  WOULD BE LIGHT AND VFR.

* MEDIUM IN WINDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.


//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 251129
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* CHANCE FOR SCATTERED MAINLY LIGHT SHRA TODAY AND EARLY THIS EVE.

* CHANCE FOR TSRA...MAINLY TONIGHT.


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

MOIST ADVECTION ALOFT ACROSS IA/NW IL/WI CONTINUES TO SPRING
SCATTERED SHOWERS WITH A FEW STORMS EARLY THIS MORNING. THE MAIN
DRIVING UPPER DISTURBANCE IS IN CENTRAL IA AND WILL CONTINUE TO
MOVE SOUTHEAST. IMMEDIATELY EAST OF THIS SHOULD BE THE MORE
WIDESPREAD SHOWER/STORM ACTIVITY...WITH ONLY ISOLATED/SCATTERED
FURTHER NORTHEAST NEAR THE CHICAGOLAND TAF SITES.

WHILE THE UPPER DISTURBANCE MOVES BEYOND THE AREA IN THE
AFTERNOON...THERE WILL STILL BE MOIST ADVECTION ALONG WITH THE
APPROACH OF A SURFACE TROUGH...SO CANNOT RULE OUT SOME SHRA/TSRA
ACTIVITY. HOWEVER OVERALL SUPPORT IS LOW AND THUS HAVE TAFS MAINLY
DRY IN THE AFTERNOON. THE MORE FAVORABLE CHANCES FOR PRECIP WILL
ARRIVE AFTER DARK AS THE NEXT UPPER DISTURBANCE MOVES ACROSS THE
AREA AND INTO A VERY MOIST ENVIRONMENT. CONTINUE TO MENTION
PROB30S FOR TSRA DURING THE MID/LATE EVE INTO EARLY OVERNIGHT.
SOME GUIDANCE DOES INDICATE MVFR CONDITIONS IN THE IMMEDIATE WAKE
OF THIS AND BELIEVE IF IT DOES RAIN WITH DIMINISHING FLOW LATE
TONIGHT THEN THERE COULD VERY WELL BE SOME LOWERED VISBYS/CIGS
INTO EARLY SATURDAY MORNING.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* LOW IN ANY RAIN AT THE AIRPORTS TODAY...HOWEVER IF IT OCCURS IT
  WOULD BE LIGHT AND VFR.

* MEDIUM IN WINDS.

* LOW IN TSRA OCCURRING TONIGHT. MEDIUM IN TIMING IF IT WERE TO
  OCCUR.


//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...SMALL CHANCE OF TSRA.
SUNDAY...CHANCE OF TSRA.
MONDAY...VFR LIKELY. STRONG NORTH-NORTHEAST WINDS.
TUESDAY...VFR.
WEDNESDAY-THURSDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
403 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCES FOR MAINLY LIGHT SHRA TODAY.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
403 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* CHANCES FOR MAINLY LIGHT SHRA TODAY.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
324 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.


JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
324 AM CDT FRI JUL 25 2014

.DISCUSSION...
324 AM CDT

SYNOPSIS...A TRICKY UNSETTLED FORECAST IS EXPECTED TODAY THROUGH
SUNDAY. THEN THINGS QUIET DOWN FOR THE BEGINNING OF THE WORK WEEK.
SATURDAY WILL BE THE WARMEST DAY IN THE FORECAST WITH HIGHS NEAR
90.  TEMPS THEN FALL TO BELOW NORMAL SUNDAY AND SLOWLY BEGIN TO
CLIMB BACK TO NEAR 80 BY LATE NEXT WEEK.

TODAY AND TONIGHT...
AN UPPER LEVEL HIGH IS OVER THE SOUTHWEST U.S. AND SOUTHERN PLAINS
WHILE LOW PRESSURE IS OVER THE ALBERTA/SASKATCHEWAN BORDER.  THE
HIGH WILL SLOWLY RETROGRADE THROUGH MONDAY AFTERNOON TO OVER THE SW
U.S. WHILE THE LOW PASSES OVER LAKE MICHIGAN SUNDAY EVENING.  AT THE
SURFACE HIGH PRESSURE IS OVER THE OHIO RIVER VALLEY AND IT WILL MOVE
OFF THE ATLANTIC COAST TONIGHT.  THERE ARE TWO SURFACE LOWS...ONE
OVER THE NORTHERN PLAINS AND THE SECOND CO-LOCATED WITH THE UPPER
LEVEL LOW OVER THE ALBERTA/SASKATCHEWAN BORDER.

CONVECTION IS ONGOING OVER WEST CENTRAL MINNESOTA AND IOWA VERY
EARLY THIS MORNING. THE STORMS WILL BE MOVING INTO A MORE STABLE
ENVIRONMENT AND THE LOW LEVEL JET WILL ALSO BE WEAKENING AS IT
PUSHES EAST. THERE IS HIGH CONFIDENCE THAT THE STORMS OVER IOWA WILL
WEAKEN AS THEY APPROACH THE CWA...BUT EXPECTING SHOWERS AND A COUPLE
OF STORMS TO REACH THE I-39 CORRIDOR BY MID MORNING. SOME GUIDANCE
MEMBERS SUGGEST SHOWERS AND STORMS COULD LINGER INTO THE MID
AFTERNOON HOURS BUT THINKING THEY WILL DISSIPATE BY THE EARLY
AFTERNOON.

HIGH CLOUDS WILL BE OVERHEAD AND MAY LIMIT HEATING A BIT...AS SUCH
LEFT HIGH TEMPS TODAY IN THE UPPER 70S.

MULTIPLE ROUNDS OF STORMS ARE EXPECTED WITH THE SECOND ROUND
SPREADING SOUTH THIS EVENING. THE LOW OVER THE PLAINS WILL WEAKEN AS
IT PUSHES EAST AND FORM AN OPEN TROUGH. THE LOWS WARM FRONT WILL
APPROACH THE REGION TONIGHT AND EXPECTING STORMS AHEAD OF IT. THE
NOSE OF THE LOW LEVEL JET WILL ALSO BE OVER NORTHWEST IL THIS
EVENING PROVIDING ADDITIONAL LIFT.  CAPE WILL BE LIMITED WITH
MODEL SOUNDINGS SHOWING SHALLOW AREAS OF CAPE AT 1000 J/KG OR LESS.
PWAT VALUES WILL BE AROUND 1.9 INCHES SO TORRENTIAL DOWNPOURS ARE
THE MOST LIKELY HAZARD.

SATURDAY...
THE PLAINS LOW/TROUGH MOVES OVER THE MIDWEST WITH SATURDAY
HAVING THE BEST CHANCE FOR SEVERE WEATHER ESPECIALLY SOUTH OF I-88.
PWAT VALUES REMAIN HIGH AROUND 1.8 INCHES IN THE MORNING AND THEN
INCREASE TO 2-2.3 INCHES SOUTH OF I-80 SATURDAY AFTERNOON.  CAPE
VALUES WILL BE MUCH MORE HEALTHY IN THE 3000 J/KG RANGE ESPECIALLY
ALONG AND SOUTH OF THE I-80 CORRIDOR.  EXPECTING STORMS TO FIRE
ALONG THE LOWS COLD FRONT SATURDAY AFTERNOON AND EVENING WITH THE
CHANCES OF SHOWERS AND STORMS INCREASING AS YOU HEAD SOUTH.  SOME OF
THESE STORMS MAY BE SEVERE WITH TORRENTIAL DOWNPOURS.  HAIL AND WIND
LOOK TO BE THE MAIN SEVERE THREATS.

SATURDAY WILL FEEL UNPLEASANT TO MANY WITH HIGHS IN THE UPPER 80S
AND HIGH DEWPOINTS.  MAX HEAT INDICES WILL BE IN THE 90S...WITH MID
TO UPPER 90 HEAT INDICES EXPECTED SOUTH OF I-80.

SUNDAY...
THE LOW OVER CANADA DRIFTS SOUTHEAST MOVING OVER WISCONSIN SUNDAY.
ADDITIONAL THUNDERSTORMS ARE POSSIBLE NORTH OF THE I-80
CORRIDOR...WITH THE BEST CHANCES ALONG THE IL/WI STATE LINE. THE
STORMS PUSH EAST OF THE CWA IN THE EVENING. COOLER AIR ASSOCIATED
WITH THE LOW ALSO SPREAD SOUTH WITH HIGHS ON SUNDAY ONLY EXPECTED TO
GET INTO THE LOW TO MID 80S.  OVERNIGHT LOWS WILL BE AROUND
60...EXCEPT FOR DOWNTOWN WHICH WILL BE IN THE LOW 60S.

MONDAY THROUGH THURSDAY...
WE REMAIN UNDER THE UPPER LEVEL TROUGH THROUGH NEXT WEEK WITH A
SURFACE HIGH MOVING OVER THE REGION BY MID WEEK.  THERE ARE
OCCASIONAL CHANCES OF SHOWERS AND STORMS BUT NONE OF THOSE CHANCES
LOOK ALL THAT IMPRESSIVE AT THIS POINT.  THE BIGGER STORY WILL BE
ANOTHER EXTENDED PERIOD OF BELOW NORMAL TEMPS...ALTHOUGH
TEMPERATURES WILL BE SLOWLY RISING THROUGH THE END OF THE FORECAST
PERIOD.


JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250729
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 AM CDT FRI JUL 25 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250729
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 AM CDT FRI JUL 25 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.

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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
228 AM CDT

SOUTHERLY FLOW WILL INCREASE OVER THE LAKE TODAY AS HIGH PRESSURE
SCOOTS EASTWARD FROM THE OHIO RIVER VALLEY. THE SURFACE TROUGH
LEADING TO THE INCREASE IN WINDS WILL ARRIVE EARLY
SATURDAY...HOWEVER WEAKEN TO THE POINT WHERE IT WILL NOT SHIFT THE
WINDS MUCH IF ANY FROM THE SOUTH-SOUTHWEST. THE LOW PRESSURE
DRIVING THIS TROUGH WILL EVOLVE OVER THE LAKE ON SUNDAY TURNING
WINDS NORTHERLY AND DRIVING A SHARP INCREASE IN SPEEDS SUNDAY
NIGHT AND PERSISTING INTO MONDAY. FOR JULY STANDARDS THESE WIND
SPEEDS ONCE AGAIN WILL BE QUITE STRONG WITH EVEN POSSIBLY SOME
GALE FORCE NORTHERLY GUSTS LATE SUNDAY NIGHT INTO MONDAY MORNING.
WITH ONCE AGAIN A LONG FETCH WAVES SHOULD REACH HEIGHTS OF OVER 6
FT OVER MUCH OF THE LAKE WITH EVEN POSSIBLY UP TO 10 FT AGAIN
ACROSS THE FAR SOUTH...PRIMARILY NEAR THE INDIANA SHORE.

MTF

&&

.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 250551
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1251 AM CDT FRI JUL 25 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.


//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.


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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 250551
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1251 AM CDT FRI JUL 25 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* CHANCES FOR MAINLY LIGHT SHRA MID-LATE AFTERNOON.

* CHANCES FOR TSRA AFTER 00Z.


//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE ACROSS THE OHIO RIVER VALLEY WILL CONTINUE TO DEPART
TO THE EAST WHILE A TROUGH OF LOW PRESSURE INCHES EASTWARD FROM
THE DAKOTAS TODAY. SOUTHERLY FLOW WILL INCREASE TODAY AND WITH
THAT WILL COME MORE MOISTURE. REMNANT SHOWERS AND POSSIBLY A FEW
STORMS ARE LIKELY TO MAKE IT INTO NORTHWEST IL LATE THIS MORNING
INTO EARLY AFTERNOON. THE FOCUS FOR THESE SHOULD WANE INTO THE
AFTERNOON...HOWEVER OVERALL INSTABILITY ALOFT WILL BE ON THE
INCREASE...SO IT IS DIFFICULT TO SAY HOW SHOWERS WILL BEHAVE
FURTHER EASTWARD TOWARD CHICAGO. THUNDER POTENTIAL LOOKS TO BE
GREATER DURING THE EVENING INTO EARLY OVERNIGHT AS ANOTHER UPPER
DISTURBANCE MOVES OVER THE AREA. HOWEVER...WITH THE ATMOSPHERE
BEING MOIST AND UNSTABLE CANNOT RULE OUT A TSRA AT ANYTIME
TONIGHT.


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* LOW IN PRECIPITATION COVERAGE AND TIMING THIS AFTERNOON AND
  TONIGHT. ALTHOUGH HIGH THAT ANY PRECIP PRIOR TO 00Z WOULD BE
  MAINLY LIGHT AND VFR.


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

SATURDAY-SUNDAY...CHANCE OF TSRA.
MONDAY-TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE OF TSRA.

MTF

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 250317
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1017 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* SOUTH SOUTHEAST WINDS TONIGHT...THEN SOUTH SOUTHWEST EARLY
  FRIDAY.

* LOW CHANCE FOR SHRA FRIDAY MORNING.

* POSSIBILITY FOR TSRA FRIDAY AFTERNOON...WITH CHANCES
  INCREASING FOR SHRA/TSRA ONCE AGAIN FRIDAY NIGHT.

RODRIGUEZ

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

ACTIVITY ACROSS THE TERMINALS POSSIBLY INCREASING ON FRIDAY AS
CURRENT HIGH PRESSURE OVERHEAD SHIFTS EAST OF THE AREA...AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. IN THE NEAR TERM
AND INTO TONIGHT...ANY ACTIVITY WILL REMAIN WELL WEST OF THE
TERMINALS WITH CURRENT PRECIP OVER IOWA DROPPING TO THE SOUTH
WHILE DISSIPATING...AND WITH VFR CONDITIONS EXPECTED TONIGHT.
INCREASING MID/UPPER LEVEL SUPPORT FOR PRECIP WILL BEGIN TO
INCREASE LATE TONIGHT INTO EARLY FRIDAY MORNING AS A MID LEVEL
DISTURBANCE APPROACHES BUT WITH THE BULK OF ANY PRECIP STILL TO
REMAIN TO THE WEST. GUIDANCE IS HINTING AT THE POSSIBILITY FOR A
STRAY SHOWER OR TWO TO DEVELOP OUT AHEAD OF THE MAIN PRECIP EARLY
FRIDAY MORNING...BUT WITH THESE CHANCES REMAINING LOW AND WITHOUT
ANY THUNDER EXPECTED DID LEAVE OUT OF THE TAFS AT THIS TIME.
BETTER FORCING WITH PRECIP AND VFR CEILINGS SHOULD PUSH EAST BY
MID DAY INTO THE AFTERNOON TIME FRAME...BUT WITH SOME GUIDANCE
INDICATING THIS PRECIP COULD REMAIN WEST OF THE TERMINALS.
ALTHOUGH WITH THE LIKELIHOOD FOR ANY SHRA/TSRA WEST OF THE
TERMINALS TO DRIFT EAST TOWARDS THE TERMINALS INCREASING DURING
THIS TIME...HAVE MAINTAINED CURRENT THUNDER MENTION BUT DID
SHORTEN UP THE DURATION. CHANCES FOR SHRA/TSRA WILL DIMINISH
TOWARDS EARLY EVENING...BUT INCREASE ONCE AGAIN BY LATE EVENING AS
BEST FORCING TO MOVE OVERHEAD.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.

* LOW CONFIDENCE WITH SHRA CHANCES FRIDAY MORNING.

* LOW MEDIUM CONFIDENCE WITH TSRA ACROSS THE TERMINALS FRIDAY
  AFTERNOON AND FRIDAY NIGHT...LOW MEDIUM CONFIDENCE WITH
  TIMING/DURATION.

RODRIGUEZ

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

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 250317
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1017 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* SOUTH SOUTHEAST WINDS TONIGHT...THEN SOUTH SOUTHWEST EARLY
  FRIDAY.

* LOW CHANCE FOR SHRA FRIDAY MORNING.

* POSSIBILITY FOR TSRA FRIDAY AFTERNOON...WITH CHANCES
  INCREASING FOR SHRA/TSRA ONCE AGAIN FRIDAY NIGHT.

RODRIGUEZ

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

ACTIVITY ACROSS THE TERMINALS POSSIBLY INCREASING ON FRIDAY AS
CURRENT HIGH PRESSURE OVERHEAD SHIFTS EAST OF THE AREA...AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. IN THE NEAR TERM
AND INTO TONIGHT...ANY ACTIVITY WILL REMAIN WELL WEST OF THE
TERMINALS WITH CURRENT PRECIP OVER IOWA DROPPING TO THE SOUTH
WHILE DISSIPATING...AND WITH VFR CONDITIONS EXPECTED TONIGHT.
INCREASING MID/UPPER LEVEL SUPPORT FOR PRECIP WILL BEGIN TO
INCREASE LATE TONIGHT INTO EARLY FRIDAY MORNING AS A MID LEVEL
DISTURBANCE APPROACHES BUT WITH THE BULK OF ANY PRECIP STILL TO
REMAIN TO THE WEST. GUIDANCE IS HINTING AT THE POSSIBILITY FOR A
STRAY SHOWER OR TWO TO DEVELOP OUT AHEAD OF THE MAIN PRECIP EARLY
FRIDAY MORNING...BUT WITH THESE CHANCES REMAINING LOW AND WITHOUT
ANY THUNDER EXPECTED DID LEAVE OUT OF THE TAFS AT THIS TIME.
BETTER FORCING WITH PRECIP AND VFR CEILINGS SHOULD PUSH EAST BY
MID DAY INTO THE AFTERNOON TIME FRAME...BUT WITH SOME GUIDANCE
INDICATING THIS PRECIP COULD REMAIN WEST OF THE TERMINALS.
ALTHOUGH WITH THE LIKELIHOOD FOR ANY SHRA/TSRA WEST OF THE
TERMINALS TO DRIFT EAST TOWARDS THE TERMINALS INCREASING DURING
THIS TIME...HAVE MAINTAINED CURRENT THUNDER MENTION BUT DID
SHORTEN UP THE DURATION. CHANCES FOR SHRA/TSRA WILL DIMINISH
TOWARDS EARLY EVENING...BUT INCREASE ONCE AGAIN BY LATE EVENING AS
BEST FORCING TO MOVE OVERHEAD.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.

* LOW CONFIDENCE WITH SHRA CHANCES FRIDAY MORNING.

* LOW MEDIUM CONFIDENCE WITH TSRA ACROSS THE TERMINALS FRIDAY
  AFTERNOON AND FRIDAY NIGHT...LOW MEDIUM CONFIDENCE WITH
  TIMING/DURATION.

RODRIGUEZ

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

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 250015
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
715 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* EAST NORTHEAST WIND BECOMING SOUTHEAST TONIGHT...THEN SOUTH
  SOUTHWEST EARLY FRIDAY.

* LOW CHANCE FOR SHRA FRIDAY MORNING.

* POSSIBILITY FOR TSRA FRIDAY AFTERNOON...WITH CHANCES
  INCREASING FOR SHRA/TSRA ONCE AGAIN FRIDAY NIGHT.

RODRIGUEZ

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

ACTIVITY ACROSS THE TERMINALS POSSIBLY INCREASING ON FRIDAY AS
CURRENT HIGH PRESSURE OVERHEAD SHIFTS EAST OF THE AREA...AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. IN THE NEAR TERM
AND INTO TONIGHT...ANY ACTIVITY WILL REMAIN WELL WEST OF THE
TERMINALS WITH CURRENT PRECIP OVER IOWA DROPPING TO THE SOUTH
WHILE DISSIPATING...AND WITH VFR CONDITIONS EXPECTED TONIGHT.
INCREASING MID/UPPER LEVEL SUPPORT FOR PRECIP WILL BEGIN TO
INCREASE LATE TONIGHT INTO EARLY FRIDAY MORNING AS A MID LEVEL
DISTURBANCE APPROACHES BUT WITH THE BULK OF ANY PRECIP STILL TO
REMAIN TO THE WEST. GUIDANCE IS HINTING AT THE POSSIBILITY FOR A
STRAY SHOWER OR TWO TO DEVELOP OUT AHEAD OF THE MAIN PRECIP EARLY
FRIDAY MORNING...BUT WITH THESE CHANCES REMAINING LOW AND WITHOUT
ANY THUNDER EXPECTED DID LEAVE OUT OF THE TAFS AT THIS TIME.
BETTER FORCING WITH PRECIP AND VFR CEILINGS SHOULD PUSH EAST BY
MID DAY INTO THE AFTERNOON TIME FRAME...BUT WITH SOME GUIDANCE
INDICATING THIS PRECIP COULD REMAIN WEST OF THE TERMINALS.
ALTHOUGH WITH THE LIKELIHOOD FOR ANY SHRA/TSRA WEST OF THE
TERMINALS TO DRIFT EAST TOWARDS THE TERMINALS INCREASING DURING
THIS TIME...HAVE MAINTAINED CURRENT THUNDER MENTION BUT DID
SHORTEN UP THE DURATION. CHANCES FOR SHRA/TSRA WILL DIMINISH
TOWARDS EARLY EVENING...BUT INCREASE ONCE AGAIN BY LATE EVENING AS
BEST FORCING TO MOVE OVERHEAD.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.

* LOW CONFIDENCE WITH SHRA CHANCES FRIDAY MORNING.

* LOW MEDIUM CONFIDENCE WITH TSRA ACROSS THE TERMINALS FRIDAY
  AFTERNOON AND FRIDAY NIGHT...LOW MEDIUM CONFIDENCE WITH
  TIMING/DURATION.

RODRIGUEZ

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

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 250015
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
715 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* EAST NORTHEAST WIND BECOMING SOUTHEAST TONIGHT...THEN SOUTH
  SOUTHWEST EARLY FRIDAY.

* LOW CHANCE FOR SHRA FRIDAY MORNING.

* POSSIBILITY FOR TSRA FRIDAY AFTERNOON...WITH CHANCES
  INCREASING FOR SHRA/TSRA ONCE AGAIN FRIDAY NIGHT.

RODRIGUEZ

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

ACTIVITY ACROSS THE TERMINALS POSSIBLY INCREASING ON FRIDAY AS
CURRENT HIGH PRESSURE OVERHEAD SHIFTS EAST OF THE AREA...AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. IN THE NEAR TERM
AND INTO TONIGHT...ANY ACTIVITY WILL REMAIN WELL WEST OF THE
TERMINALS WITH CURRENT PRECIP OVER IOWA DROPPING TO THE SOUTH
WHILE DISSIPATING...AND WITH VFR CONDITIONS EXPECTED TONIGHT.
INCREASING MID/UPPER LEVEL SUPPORT FOR PRECIP WILL BEGIN TO
INCREASE LATE TONIGHT INTO EARLY FRIDAY MORNING AS A MID LEVEL
DISTURBANCE APPROACHES BUT WITH THE BULK OF ANY PRECIP STILL TO
REMAIN TO THE WEST. GUIDANCE IS HINTING AT THE POSSIBILITY FOR A
STRAY SHOWER OR TWO TO DEVELOP OUT AHEAD OF THE MAIN PRECIP EARLY
FRIDAY MORNING...BUT WITH THESE CHANCES REMAINING LOW AND WITHOUT
ANY THUNDER EXPECTED DID LEAVE OUT OF THE TAFS AT THIS TIME.
BETTER FORCING WITH PRECIP AND VFR CEILINGS SHOULD PUSH EAST BY
MID DAY INTO THE AFTERNOON TIME FRAME...BUT WITH SOME GUIDANCE
INDICATING THIS PRECIP COULD REMAIN WEST OF THE TERMINALS.
ALTHOUGH WITH THE LIKELIHOOD FOR ANY SHRA/TSRA WEST OF THE
TERMINALS TO DRIFT EAST TOWARDS THE TERMINALS INCREASING DURING
THIS TIME...HAVE MAINTAINED CURRENT THUNDER MENTION BUT DID
SHORTEN UP THE DURATION. CHANCES FOR SHRA/TSRA WILL DIMINISH
TOWARDS EARLY EVENING...BUT INCREASE ONCE AGAIN BY LATE EVENING AS
BEST FORCING TO MOVE OVERHEAD.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.

* LOW CONFIDENCE WITH SHRA CHANCES FRIDAY MORNING.

* LOW MEDIUM CONFIDENCE WITH TSRA ACROSS THE TERMINALS FRIDAY
  AFTERNOON AND FRIDAY NIGHT...LOW MEDIUM CONFIDENCE WITH
  TIMING/DURATION.

RODRIGUEZ

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

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242208
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
508 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242208
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
508 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242044
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
344 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH LATE AFTERNOON.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242044
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
344 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH LATE AFTERNOON.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242023
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
323 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 242023
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
323 PM CDT THU JUL 24 2014

.DISCUSSION...
323 PM CDT

THE MAIN WEATHER CONCERNS DURING THE PERIOD WILL FOCUS ON THE SHOWER
AND THUNDERSTORM CHANGES LATE FRIDAY THROUGH SATURDAY NIGHT...ALONG
WITH THE THREAT FOR SEVERE STORMS AND EXTREMELY HEAVY RAINFALL ACROSS
PORTIONS OF THE AREA SATURDAY NIGHT.

SURFACE HIGH PRESSURE IS CURRENTLY MOVING OVERHEAD THIS
AFTERNOON...AND IT IS RESULTING IN ANOTHER GREAT WEATHER DAY ACROSS
THE REGION. THIS HIGH WILL CONTINUE TO SHIFT EASTWARD ACROSS THE
OHIO VALLEY AND THE EASTERN SEABOARD DURING THE DAY FRIDAY. AS THIS
OCCURS...THE LOWER LEVEL FLOW WILL VEER SOUTHERLY...ALLOWING
MOISTURE TO BEGIN RETURNING TO THE AREA INTO SATURDAY.
MEANWHILE...IN THE MID AND UPPER LEVELS...A SIGNIFICANT DISTURBANCE
AND ASSOCIATED SPEED MAX...CURRENTLY NOTED IN WATER VAPOR IMAGERY
ACROSS THE PACIFIC NORTHWEST...IS EXPECTED TO SHIFT EASTWARD ALONG
THE INTERNATIONAL BOARDER INTO SATURDAY ATOP A STOUT RIDGE ACROSS
THE SOUTHWESTERN CONUS. THIS SHOULD SET UP AN ENHANCED BELT OF 85+
KT WESTERLIES IN THE UPPER LEVELS FROM THE NORTHERN HIGH
PLAINS...EASTWARD ACROSS THE UPPER MIDWEST AND INTO THE GREAT LAKES
REGION DURING MUCH OF THE WEEKEND. ULTIMATELY...THIS PATTERN WILL
SET UP ANOTHER SHORT PERIOD OF VERY WARM AND HUMID WEATHER...ALONG
WITH A COUPLE PERIODS FOR CONVECTION THROUGH MUCH OF THE WEEKEND.

AN IMPRESSIVE THERMAL RIDGE...ASSOCIATED WITH THE STOUT 994+ DAM
UPPER RIDGE OVER THE SOUTHWEST...IS CURRENTLY IN PLACE ACROSS THE
PLAINS AND INTER-MOUNTAIN REGION. IN FACT...MORNING RAOBS INDICATE
IN EXCESS OF 24 DEGREE CELSIUS TEMPERATURES AT 850 MB FROM EASTERN
MONTANA AND ACROSS THE PLAINS STATES. THIS THERMAL RIDGE WILL BE
ADVECTED EASTERLY TONIGHT THROUGH SATURDAY IN RESPONSE TO THE
DEVELOPMENT OF A 30+ KT SOUTHWESTERLY LOW LEVEL JET OUT AHEAD OF A
EAST-SOUTHEASTWARD MOVING LOWER LEVEL AREA OF LOW
PRESSURE...CURRENTLY OVER THE NORTHERN HIGH PLAINS. THIS WILL SET UP
ANOTHER WARMING TREND FRIDAY INTO SATURDAY...WITH SATURDAY LIKELY TO
BE A ANOTHER VERY WARM AND HUMID DAY ACROSS THE AREA.

ALSO...WITH THE INCREASING HEAT AND HUMIDITY...SO TO WILL OUR
CHANCES FOR THUNDERSTORMS. SHOWER AND THUNDERSTORM ACTIVITY IS
CURRENTLY ONGOING ACROSS THE EASTERN DAKOTAS...SOUTHWESTERN
MINNESOTA AND INTO NORTHWESTERN SECTIONS OF IOWA ALONG THE
NORTHEASTERN PERIPHERY OF THE SOUTHWESTERN UPPER RIDGE. THIS ACTIVITY
SHOULD CONTINUE TO DEVELOP ACROSS IOWA TONIGHT AS STRONG THETA E
ADVECTION SETS UP ACROSS THE CORN BELT ALONG THE NOSE OF A 40 KT
SOUTHWESTERLY JET. IT APPEARS THAT THE REMNANTS OF THIS ACTIVITY
WILL MOVE ACROSS NORTHERN ILLINOIS AND NORTHWESTERN INDIANA DURING
THE DAY FRIDAY AS THE BETTER MOISTURE SHIFTS EASTWARD. SHOWERS AND A
FEW ELEVATED THUNDERSTORMS WILL BE POSSIBLE AS A RESULT OF THIS ON
FRIDAY.

ADDITIONAL ELEVATED SHOWERS AND STORMS ARE EXPECTED DEVELOP ACROSS
THE AREA FRIDAY NIGHT AS THE LOW LEVEL JET NOSES UP ACROSS THE AREA.
MID LEVEL LAPSE RATES ARE EXPECTED TO STEEPEN ACROSS THE AREA INTO
FRIDAY NIGHT AS THE WARMER AIR GETS ADVECTED OVER THE AREA FROM THE
HIGH PLAINS. AS A RESULT OF THIS...IT APPEARS THERE COULD BE A SMALL
THREAT FOR HAIL WITH SOME OF THESE STORMS. HOWEVER...IT ALSO APPEARS
THAT THERE COULD BE A HEAVY RAIN THREAT WITH THIS ACTIVITY AS WELL.
THE SOUTHWESTERLY JET IS EXPECTED TO PUMP IN DEEPER
MOISTURE...RESULTING IN UPWARDS OF 1.75 PWATS ACROSS THE AREA FRIDAY
NIGHT. HOWEVER...ALTHOUGH THESE STORMS COULD PRODUCE TORRENTIAL
DOWNPOURS FOR A PERIOD...IT APPEARS THAT A QUICK STORM MOTION WILL
KEEP THE THREAT FOR SIGNIFICANT FLASH FLOODING LOW.

DURING THE DAY SUNDAY IT APPEARS THAT AN EML WILL SET UP ACROSS THE
AREA. THEREFORE...IN SPITE OF THE FACT THAT VERY HIGH THETA E AIR
WILL BECOME JUXTAPOSED BENEATH A CORRIDOR OF STEEP MID LEVEL LAPSE
RATES...RESULTING IN A MODERATELY TO STRONGLY UNSTABLE
ENVIRONMENT...IT APPEARS THE AREA MAY REMAIN CAPPED FOR MUCH OF THE
DAY LIMITING THE THREAT OF CONVECTIVE ACTIVITY. CONDITIONS ACROSS THE
AREA WILL LIKELY BECOME UNCOMFORTABLE AGAIN AS TEMPERATURES TOP OUT
IN THE MID TO UPPER 80S...WITH SOME AREAS AROUND 90 CERTAINLY
POSSIBLE. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOW TO
MID 70S WILL RESULT IN HEAT INDICIES FROM 95 TO NEAR 100.

CONVECTION LOOKS TO DEVELOP BY SATURDAY EVENING ACROSS PORTIONS OF
THE AREA AS BETTER MOISTURE CONVERGENCE SETS UP ALONG THE LOW LEVEL
JET AND MODEST HEIGHT FALLS ALOFT HELP WEAKEN THE CAP. CURRENTLY
THERE APPEARS TO BE SOME UNCERTAINTIES ON THE EXACT AREAS THAT WILL
BE UNDER THE THREAT FOR THESE STORMS SATURDAY NIGHT...WITH THE
NUMERICAL GUIDANCE SLOWING A BIT DISAGREEMENT. BUT WITH THE A
SURFACE BOUNDARY EXPECTED TO BE IN PLACE ACROSS CENTRAL ILLINOIS BY
SATURDAY NIGHT...IT APPEARS THE MAIN THREAT FOR THIS ACTIVITY WILL
BE MAINLY ACROSS MY SOUTHERN CWA. THEREFORE...I HAVE FOCUSED THE
HIGHEST POPS SOUTH OF INTERSTATE 80. THIS THUNDERSTORM ACTIVITY
COULD ALSO BE A SEVERE THREAT WITH A POSSIBLE FORWARD PROPAGATING MCS
GIVEN THE MAGNITUDE OF THE DEEP LAYER SHEAR AND THE INSTABILITY.
VERY HEAVY RAINFALL WILL AGAIN BE A THREAT WITH THESE
STORMS.

IT APPEARS CONDITIONS WILL REMAIN IN THE 80S AGAIN ON SUNDAY...WITH
A COLD FRONT EXPECTED TO MOVE ACROSS THE REGION DURING THE AFTERNOON
AND EARLY EVENING. ADDITIONAL SHOWERS AND STORMS COULD DEVELOP ACROSS
PORTIONS OF THE AREA IN THE AFTERNOON AS THE MAIN MID LEVEL IMPULSE
DROPS ACROSS SOUTHERN WISCONSIN.

IN THE EXTENDED PERIOD MONDAY THROUGH THURSDAY A UPPER LEVEL TROUGH
IS EXPECTED TO DIG ACROSS THE EASTERN HALF OF THE COUNTRY WITH THE
RIDGING...AND HENCE THE HEAT...RETROGRESSING BACK ACROSS THE WESTERN
CONUS. COOL AND PLEASANT CONDITIONS ARE EXPECTED THROUGH NEXT WEEK.
TEMPERATURES ARE EXPECTED TO ONLY BE IN THE 70S AGAIN...WITH ONLY A
SLOW WARMING TREND EXPECTED BY LATE WEEK.

KJB

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 241937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 241937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
235 PM CDT

A BROAD AREA OF HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST
AND WESTERN GREAT LAKES REGION THIS AFTERNOON. THE PRESSURE GRADIENT
OVER THE SOUTHERN TIP OF THE LAKE IS WEAKENING AS THE HIGH MOVES
OVERHEAD BUT ENOUGH OF A GRADIENT TO KEEP WINDS AND WAVES A BIT
ELEVATED THROUGH SUNSET.  A LAKE BREEZE HAS DEVELOPED WITH
ONSHORE FLOW EXPECTED THROUGH THE EVENING. AS THE HIGH DRIFTS TO
SOUTHEAST TONIGHT...A SERIES OF LOW PRESSURE SYSTEMS WILL BEGIN TO
EMERGE FROM THE NORTHERN ROCKIES AND CANADIAN PRAIRIES THROUGH THE
NEXT FEW DAYS. SOUTH TO SOUTHWEST FLOW WILL DEVELOP AHEAD OF THESE
SYSTEMS THAT WILL EASE THE NORTH SWELL CURRENTLY OVER THE LAKE

THE FIRST LOW MOVING OUT OF THE NORTHERN ROCKIES IS PROGGED TO
WEAKEN AND DISSIPATE AS IT MOVES THROUGH ON SATURDAY. THE NORTHERN
LOW IS SLIGHTLY DEEPER AND WILL MOVE ACROSS THE GREAT LAKES SUNDAY
DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN. BEHIND THE FRONT STRONG
NORTH/NORTHWEST WINDS APPROACHING 30 KT ARE EXPECTED ONCE AGAIN
SUNDAY NIGHT INTO MONDAY. THIS WILL BRING ANOTHER PERIOD OF LARGER
WAVES...ESPECIALLY OVER THE SOUTHERN HALF OF THE LAKE.

KMD

&&

.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 241742
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1242 PM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

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 241742
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1242 PM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT THROUGH EARLY EVENING.

* SLY-SWLY WINDS TO ARND 10KT TOMORROW.

* CHANCE TSRA TOMORROW AFTERNOON.

KREIN

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

THE CENTER OF A LARGE AREA OF HIGH PRESSURE HAS MOVED OVER NRN IL
AND THE HIGH EXTENDS FROM LAKE MICHIGAN THROUGH THE MIDDLE
MISSISSIPPI VALLEY. WITH THE EXCEPTION OF SOME DIURNAL CU
DEVELOPMENT...SKIES REMAIN MOSTLY CLEAR WITH WX NIL. THE MAIN
CONCERN FOR THE REMAINDER OF THE AFTERNOON WILL BE WIND
DIRECTION/SPEED. WITH THE CENTER OF THE HIGH TO THE NORTHWEST OF
THE TERMINALS...A WEAK NELY GRADIENT HAS SET UP AND SOME LAKE
ENHANCEMENT/EFFECT IS ALLOWING WINDS TO REACH 10-12KT WITH AN
OCCASIONAL HIGHER GUST. AS THE CENTER OF THE HIGH MOVES ACROSS THE
TERMINALS TONIGHT...WINDS WILL BECOME LGT/VRBL...BEFORE BECMG SLY-
SWLY TOMORROW AS THE CENTER OF THE HIGH SETTLES TO THE SOUTHEAST
OF THE TERMINALS. THE GRADIENT WILL REMAIN WEAK...WITH SPEEDS ARND
10KT LIKELY AGAIN TOMORROW. THE OTHER CONCERN FOR TOMORROW WILL BE
THE CHANCE FOR THUNDERSTORMS FROM THE LATE MORNING THROUGH THE
AFTERNOON HOURS. THE MODELS CONTINUE TO SUGGEST THAT A CLUSTER OF
THUNDERSTORMS MAY DEVELOP FORM OVER THE UPPER MIDWEST LATE TONIGHT
OR EARLY TOMORROW MORNING AND ON THE NOSE OF THE LOW LEVEL
JET AND THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOES NOT QUITE REACH AS FAR EAST AS THE CHICAGO METRO
TERMINALS WITH RFD THE MORE LIKELY SITE IN THE PATH OF THE TS.
HOWEVER...WILL GO WITH A PROB30 FOR THE END OF THE TAF PERIOD AT
THIS TIME IN DEFERENCE TO THE CHANCES THAT THE TRACK OF THE TS
CLUSTER COULD BE A LITTLE FARTHER EAST THAN CURRENTLY ANTICIPATED.

KREIN

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

* LOW CONFIDENCE IN CHANCES FOR TS TO DIRECTLY IMPACT THE
  TERMINALS TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

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 241622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1122 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT.

KREIN

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

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 241622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1122 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT.

KREIN

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

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 241412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT.

KREIN

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 241412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NELY WINDS ARND 10KT.

KREIN

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 241123
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
623 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH.

BMD

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 241123
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
623 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* NONE.

BMD

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

HIGH PRESSURE IS CENTERED ACROSS THE UPPER MIDWEST AND WESTERN GREAT
LAKES REGION THIS MORNING RESULTING IN LIGHT NORTHERLY FLOW ACROSS
THE TERMINALS AND VFR CONDITIONS WHICH ARE EXPECTED TO PERSIST
THROUGH THE DAY. WINDS WILL VEER TO THE NORTHEAST TODAY THEN TO THE
SOUTH THIS EVENING AS THE HIGH MOVES ACROSS THE AREA. TONIGHT MID
AND HIGH CLOUDS WILL BEGIN TO INCREASE AS MID LEVEL WARM ADVECTION
WING LIFTS ACROSS THE REGION. MODELS SUGGEST THAT A CONVECTIVE
COMPLEX MAY FORM TO OUR NORTHWEST ON THE NOSE OF THE LOW LEVEL
JET...THEN MOVE SOUTHEAST ALONG THE INSTABILITY GRADIENT. THE
INSTABILITY DOESNT QUITE REACH AS FAR EAST AS THE TERMINALS THOUGH
AND DRY LOW/MID LEVELS SHOULD MAKE IT DIFFICULT FOR PRECIP TO
PERSIST INTO THE AREA.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH.

BMD

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

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

BMD

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 240902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 240902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 240808
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
308 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 240808
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
308 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
307 AM CDT

CONDITIONS WILL CONTINUE TO GRADUALLY IMPROVE ACROSS LAKE MICHIGAN
AS HIGH PRESSURE BUILDS OVER THE AREA TODAY. WINDS HAVE ALREADY
ABATED ACROSS MUCH OF THE LAKE WITH SOME LINGERING WINDS AND WAVES
MAINLY CONFINED TO THE FAR SOUTH END OF THE LAKE EARLY THIS MORNING.
AS WINDS CONTINUE TO DISSIPATE TODAY...EXPECT LAKE BREEZES TO
DEVELOP WITH ONSHORE FLOW THIS AFTERNOON AND EVENING. SOUTHWEST FLOW
WILL FRESHEN UP ACROSS THE LAKE TONIGHT THROUGH THE WEEKEND AS A
PAIR OF LOW PRESSURE SYSTEMS DEVELOP TO OUR WEST. WHILE THE SOUTHERN
LOW IS PROGGED TO WEAKEN AND DISSIPATE...A SLIGHTLY DEEPER LOW OVER
CANADA WILL MOVE ACROSS THE GREAT LAKES SUNDAY DRAGGING A COLD FRONT
ACROSS LAKE MICHIGAN WITH NORTH/NORTHWEST WINDS ONCE AGAIN
APPROACHING 30 KT SUNDAY NIGHT INTO MONDAY BEHIND THE FRONT.

BMD

&&

.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 240709
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
209 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 240709
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
209 AM CDT THU JUL 24 2014

.DISCUSSION...
207 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR...WITH ONLY A FEW
HIGH BASED CLOUDS. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK A FEW POINTS COULD DIP TO THE UPR
40S.

BROAD ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION
TODAY...PROVIDING ABUNDANT SUNSHINE AND UNSEASONABLY COOL/DRY AIR
FOR A SECOND DAY. TEMPS SHUD BE ABLE TO HOLD GENERALLY IN THE MID
70S...HOWEVER WITH A NORTHEAST FLOW OFF OF LAKE MICHIGAN THE COOLER
MARINE AIR MAY KEEP TEMPS ALONG THE SHORELINE IN THE UPR 60S.

BY THIS AFTN THE SFC RIDGE AXIS WILL BE DRIFTING EAST ACROSS THE
OHIO VALLEY...WITH FLOW SLOWLY TURNING SOUTHERLY BY LATE TONIGHT.
DEPENDING ON THE TIMING...TEMPS COULD RADIATE IN THE LATE EVENING
BEFORE HOLDING STEADY OVERNIGHT IN THE MID/UPR 50S. A WEAK WAVE WILL
BE SLIDING EAST FROM THE DAKOTAS LATE TONIGHT...WITH SOME ISENTROPIC
MOISTENING ON THE LEE-SIDE ALLOWING FOR SOME SPOTTY SHOWERS AND
PERHAPS AN ISO TSRA JUST BEFORE DAYBREAK FRI IN THE WESTERN CWFA.

CONFIDENCE THRU TODAY...HIGH.
CONFIDENCE IN PRECIP OVERNIGHT/TEMPS...MEDIUM.

FRIDAY THROUGH SUNDAY...
500MB RIDGE OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN...ALLOWING A QUASI-ZONAL FLOW ALONG THE NORTHERN PERIPHERY
WITH A SERIES OF WEAK MID-LVL VORTS SLIDING EAST INTO THE UPPER
MIDWEST/GREAT LAKES. GUIDANCE HAS A WEAK SFC WAVE MOVING EAST FROM
THE CENTRAL PLAINS INTO THE GREAT LAKES FRI BEFORE WEAKENING. THE
STRONGER MID-LVL VORTICITY MAXIMA REMAINS CONFINED ALONG THE HIGH
PLAINS/CANADIAN PRAIRIES FRI/SAT...WHICH WILL ALLOW A FEW ROUNDS OF
SHOWERS/THUNDERSTORMS TO PUSH ACROSS THE FORECAST AREA STARTING
FRI-SUN. AT THIS TIME THOUGH IT DOES APPEAR THE BEST CHANCE FOR
PRECIP FRI WILL BE IN THE EVENING HOURS.

A BOUNDARY LAYS OUT OVER THE MID-MISSOURI VALLEY STRETCHING EAST
THRU OHIO SAT AFTN/EVE. FOR THE SECOND HALF OF THE WEEKEND THE
PATTERN WILL ONCE AGAIN BE STARTING TO CHANGE TOWARDS A WESTERN
RIDGE AND GREAT LAKES TROUGH. THE SEMI-STATIONARY MID-LVL VORT OVER
THE HIGH PLAINS WILL SLIDE EAST EARLY SUN INTO THE NORTHERN GREAT
LAKES...WITH A SERIES OF WEAK SFC WAVES CONSOLIDATING OVER LOWER
MICHIGAN SUN MORNING.

TEMPS WILL START TO MODERATE OVER THE WEEKEND INTO THE UPR 70S/LOW
80S...AND WITH THE INCREASED LLVL MOISTURE DEW PTS WILL CREEP BACK
INTO THE MID/UPR 60S SAT EVE. THE FAR WEST/SOUTHWEST FORECAST AREA
COULD SEE DEW PTS BACK INTO THE LOW 70S.

THEN FOR SUN A FRONTAL BOUNDARY WILL BE SLIDING SOUTHEAST ACROSS THE
CWFA...HOWEVER TEMPS SHUD STILL BE ABLE TO REACH 80 TO THE LOW 80S.

CONFIDENCE...MEDIUM/HIGH.

MONDAY THROUGH THURSDAY...
ENSEMBLES FOR SEVERAL CYCLES HAVE PROGGED A NORTH ATLANTIC RIDGE
COUPLED WITH A HIGH AMPLITUDE RIDGE DEVELOPING ACROSS WESTERN
CANADA. THE RESULTING FEATURE WILL LIKELY BE A TROUGH DIGGING SOUTH
ACROSS THE GREAT LAKES/HUDSON BAY EARLY NEXT WEEK AND LIKELY
PERSISTING THRU LATE NEXT WEEK. UNSEASONABLY COOL AIR WILL BLEED
SOUTH WITH ENSEMBLES DEMONSTRATING A HIGH CONFIDENCE IN THE 850MB
ISOTHERMS OVER THE FORECAST AREA GENERALLY BETWEEN 8-10 DEG C FOR
MON/TUE...THEN VERY SLOW TO MODERATE BACK TO A 10-12 DEG C RANGE
LATE WEEK. SO TO KICK-OFF NEXT WEEK TEMPS IN THE LOW 70S LOOK LIKELY
WITH A NORTHWEST FLOW AND BROAD SFC RIDGE. AS THE WEEK PROGRESSES
TEMPS SHUD PUSH BACK INTO THE MID/UPR 70S...BUT CURRENTLY THE
NORTHWEST FLOW WOULD SUGGEST DRY CONDITIONS TO PERSIST.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 240532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT THU JUL 24 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 240532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT THU JUL 24 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NONE.

BMD

//DISCUSSION...UPDATED 06Z...

WEATHER WILL REMAIN FAIRLY BENIGN OVER THE NEXT TAF PERIOD AS HIGH
PRESSURE BUILDS ACROSS THE REGION. NORTH WINDS TONIGHT WILL VEER
TO THE NORTHEAST MID MORNING THURSDAY WITH SPEEDS APPROACHING 10
KT THROUGH THE DAY. WINDS WILL CONTINUE TO VEER EVENTUALLY COMING
AROUND TO THE SOUTH THURSDAY EVENING AS THE RIDGE AXIS SLIDES EAST
OF THE AREA. VFR CONDITIONS ARE EXPECTED TO PREVAIL WITH
INCREASING HIGH THEN MID CLOUDS MAINLY LATE IN THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH.

BMD

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 240307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1007 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* NORTHEAST WINDS THROUGH THE FORECAST PERIOD.

* SPEEDS INCREASING TO OR AROUND 10 KT THURSDAY MORNING.

RODRIGUEZ

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

LINGERING SCT CLOUDS WILL FURTHER ERODE THIS EVENING AS HIGH
PRESSURE SPANS THE REGION. QUIET AND VFR CONDITIONS WILL PERSIST
THROUGH THE FORECAST PERIOD WITH THIS HIGH REMAINING OVERHEAD ON
THURSDAY. AS NORTHEAST WINDS REMAIN IN PLACE THROUGH THE FORECAST
PERIOD...GUSTS THIS EVENING WILL DIMINISH BUT INCREASE BACK TO
AROUND THE 10 KT MARK THURSDAY MORNING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND DIRECTION...MEDIUM HIGH CONFIDENCE
  WITH SPEEDS.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 232352
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* NORTHEAST WINDS THROUGH THE FORECAST PERIOD.

* GUSTS DIMINISHING THIS EVENING...WITH SPEEDS INCREASING AT OR
  AROUND 10 KT THURSDAY MORNING.

RODRIGUEZ

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

LINGERING SCT CLOUDS WILL FURTHER ERODE THIS EVENING AS HIGH
PRESSURE SPANS THE REGION. QUIET AND VFR CONDITIONS WILL PERSIST
THROUGH THE FORECAST PERIOD WITH THIS HIGH REMAINING OVERHEAD ON
THURSDAY. AS NORTHEAST WINDS REMAIN IN PLACE THROUGH THE FORECAST
PERIOD...GUSTS THIS EVENING WILL DIMINISH BUT INCREASE BACK TO
AROUND THE 10 KT MARK THURSDAY MORNING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND DIRECTION...MEDIUM HIGH CONFIDENCE
  WITH SPEEDS.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 232352
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
652 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* NORTHEAST WINDS THROUGH THE FORECAST PERIOD.

* GUSTS DIMINISHING THIS EVENING...WITH SPEEDS INCREASING AT OR
  AROUND 10 KT THURSDAY MORNING.

RODRIGUEZ

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

LINGERING SCT CLOUDS WILL FURTHER ERODE THIS EVENING AS HIGH
PRESSURE SPANS THE REGION. QUIET AND VFR CONDITIONS WILL PERSIST
THROUGH THE FORECAST PERIOD WITH THIS HIGH REMAINING OVERHEAD ON
THURSDAY. AS NORTHEAST WINDS REMAIN IN PLACE THROUGH THE FORECAST
PERIOD...GUSTS THIS EVENING WILL DIMINISH BUT INCREASE BACK TO
AROUND THE 10 KT MARK THURSDAY MORNING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND DIRECTION...MEDIUM HIGH CONFIDENCE
  WITH SPEEDS.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 12Z FRIDAY-12Z WEDNESDAY...UPDATED 00Z...

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

MONDAY...VFR.

TUESDAY...SLIGHT CHANCE OF SHRA LATE.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 232210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
510 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 232210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
510 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 232017
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
317 PM CDT WED JUL 23 2014

.DISCUSSION...
315 PM CDT

SUMMER STRUGGLES TO MAINTAIN A GRIP ON THE REGION.  COOL WEATHER
TOMORROW AND FRIDAY WILL ONLY BRIEFLY YIELD TO TYPICAL TEMPERATURES
AND INCREASED TSRA CHANCES FOR THE WEEKEND BEFORE MOVING RIGHT BACK
INTO THE AREA TO START NEXT WEEK.

BEHIND THE PASSAGE OF A COLD FRONT LAST NIGHT...COOL AND DRY
NORTHEASTERLY FLOW TODAY HAS BEEN KEEPING HIGHS ABOUT 10 TO 15
DEGREES BELOW AVERAGE FOR THIS TIME OF THE YEAR.  THIS FLOW AHEAD OF
A SURFACE RIDGE CENTERED WEST OF THE AREA TODAY WILL GRADUALLY
TRANSITION TO SOUTHERLY WARM AND MOIST FLOW BY LATE FRIDAY AS THE
RIDGE SLIDES OVERHEAD TOMORROW AND THEN MOVES OFF TO THE EAST.
SHOWER AND THUNDERSTORM CHANCES INCREASE BY LATE FRIDAY AND REMAIN
ELEVATED THROUGH THE WEEKEND AS THE WARM AND MOIST AIRMASS SETTLES
INTO PLACE.  BY SUNDAY NIGHT THE COOLER AND DRIER AIR RETURNS WITH
THE PASSAGE OF YET ANOTHER COLD FRONT.  SO THE FIRST HALF OF NEXT
WEEK IS SETTING UP MUCH LIKE THE LAST HALF OF THIS ONE.  THE MAIN
QUESTIONS FOR THE NEXT SEVERAL DAYS INVOLVE THE TIMING AND EXTENT OF
SHRA/TSRA THROUGH THE WEEKEND.

NEAR TERM...TONIGHT THROUGH SATURDAY

TONIGHT AND THURSDAY WILL REMAIN DRY AND COOL UNDERNEATH A BROAD
AREA OF HIGH PRESSURE.  THURSDAY NIGHT AN UPPER SHORTWAVE AND
PRONOUNCED MOISTURE FLUX SUPPORTED BY THE LOW LEVEL JET ACROSS IOWA
INCREASE TSRA CHANCES IN OUR WESTERN COUNTIES EARLY FRIDAY.  OFTEN
THIS SUMMER THE SURFACE RIDGE HAS BEEN TOO DOMINANT LOCALLY AND THE
LOW LEVEL MOISTURE OVER THE AREA HAS BEEN TOO LIMITED TO MAINTAIN
TSRA ACTIVITY AS IT MOVES OUT OF IOWA INTO NORTHWEST ILLINOIS.
GIVEN THESE TRENDS...WILL ELECT NOT TO INCREASE POPS ABOVE THE
CHANCE CATEGORY THURSDAY NIGHT AND FRIDAY...WITH THE HIGHEST VALUES
FOCUSED WEST OF I-39 DURING THE FRIDAY MORNING PERIOD.

BY FRIDAY NIGHT THE GULF MOISTURE HAS RETURNED AND THE SURFACE HIGH
HAS MOVED WELL OFF TO THE EAST.  MODELS DEPICT AN UPPER LEVEL
SHORTWAVE EMBEDDED IN FAIRLY STRONG ZONAL FLOW ACROSS THE NORTHERN
CONUS...WITH ITS ASSOCIATED SURFACE LOW MOVING ACROSS IOWA INTO THE
LOCAL AREA ALONG WITH A FRONTAL ZONE.  WHILE THE DIURNAL TIMING MAY
NOT BE GREAT...THE COMBINATION OF LOW LEVEL CONVERGENCE...MODERATE
MID LEVEL LAPSE RATES...AND A SHORTWAVE ALOFT ALL WOULD SUGGEST
INCREASED TSRA CHANCES AGAIN FRIDAY NIGHT INTO EARLY SATURDAY.

MODELS SHOW THE FRONT PUSHING THROUGH SATURDAY MORNING AND STALLING
OUT SOUTH OF THE AREA FOR THE REMAINDER OF THE WEEKEND.  THIS WOULD
KEEP THE WARMER AND MORE HUMID AIR OVER THE AREA BUT FOCUS THE
BETTER TSRA CHANCES TO OUR SOUTHERN COUNTIES TOWARD CENTRAL ILLINOIS.

EXTENDED PERIOD...SUNDAY INTO WEDNESDAY

THE ZONAL FLOW WHICH DEVELOPS BRIEFLY ON SATURDAY BEGINS TO AMPLIFY
AGAIN ON SUNDAY.  AT 500 MB...THE GFS AND EURO BOTH POINT TO A
VORTICITY MAXIMUM MOVING FROM SOUTH-CENTRAL CANADA INTO THE GREAT
LAKES REGION BY SUNDAY MORNING...DEEPENING AN UPPER TROUGH OVER THE
EASTERN CONUS. AT THE SURFACE...SOUTHERLY TO SOUTHWESTERLY FLOW
SATURDAY INTO EARLY SUNDAY HELPS MAINTAIN MODERATE DEWPOINTS IN
THE MID TO UPPER 60S DURING THE DAY ON SUNDAY. NORTH OF THE
FRONTAL BOUNDARY...WITH WINDS FROM THE WEST OR NORTHWEST DURING
THE DAY ON SUNDAY...WAA IS LIMITED. THE UPPER LEVEL DISTURBANCE
COMBINED WITH MODERATE MOISTURE AND WARMTH LEADS TO A CONTINUED
CHANCE OF STORMS ON SUNDAY IN THE MID MORNING TO AFTERNOON
TIMEFRAME...HOWEVER...DUE TO A LACK OF CLEAR FORCING DUE TO THE
POSITION OF THE FRONT...NOT EXPECTING COVERAGE TO BE WIDESPREAD.

MEANWHILE...SATURDAY NIGHT INTO SUNDAY MORNING...A PRONOUNCED RIDGE
BEGINS BUILDING OVER THE WESTERN US.  AS MENTIONED ABOVE...THE
DOWNSTREAM RESPONSE TO THIS RIDGE IS A TROUGH DEEPENING OVER THE
EASTERN HALF OF THE CONUS SUNDAY NIGHT INTO MONDAY. THIS AMPLIFIED
TROUGH OVER THE EASTERN HALF OF THE US REMAINS IN PLACE THROUGH THE
END OF THE FORECAST PERIOD. THUS...AFTER THE FRONT SOUTH OF OUR AREA
FINALLY PUSHES OUT OF THE REGION SUNDAY NIGHT...BELOW AVERAGE
TEMPERATURES ARE LIKELY FOR THE FIRST HALF OF NEXT WEEK.

NEAR TERM...LENNING
EXTENDED PERIOD...FOWLER/HILGENBRINK/SOELLE/LENNING

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 231935
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 231935
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.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 231921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD


&&

.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 231736
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1236 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN


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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231736
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1236 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN


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

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231559
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1059 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD

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

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231559
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1059 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD

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

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231401
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
901 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD

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

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231401
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
901 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD

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

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231125
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
625 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

BMD

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN VFR CONDITIONS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 231125
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
625 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

BMD

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH THUNDERSTORMS NOW
PRIMARILY IN CENTRAL INDIANA AND DOWNSTATE ILLINOIS WITH HIGH
PRESSURE BUILDING IN FROM THE NORTHWEST TODAY. A MODERATE PRESSURE
GRADIENT REMAINS IN PLACE WITH EFFICIENT MIXING TODAY RESULTING
IN GUSTY WINDS OUT OF THE NNE/NE. WINDS LIKELY WILL REMAIN FAIRLY
STEADY THROUGH THE DAY THEN BEGIN TO TAPER THIS EVENING AND
TONIGHT. VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH CONFIDENCE IN VFR CONDITIONS.

BMD

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 230904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* GUSTY NNE/NE WINDS THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 230904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* GUSTY NNE/NE WINDS THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* HIGH IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 230817
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
317 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 230817
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
317 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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...
316 AM CDT

WINDS AND WAVES HAVE ALREADY INCREASED ACROSS LAKE MICHIGAN...NOW
BLOWING OUT OF THE NORTH AT AROUND 30 KT ESPECIALLY OVER THE SOUTH
HALF OF THE LAKE WHERE A FEW GALE FORCE GUSTS ARE POSSIBLE BEHIND
A DEPARTING COLD FRONT. A SMALL CRAFT ADVISORY IS IN EFFECT TODAY
FOR THE INDIANA AND ILLINOIS NEARSHORE WATERS DUE TO THE ELEVATED
WINDS AND WAVES. HIGH PRESSURE CURRENTLY OVER THE CANADIAN
PRAIRIES WILL BEGIN TO BUILD ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY.

BMD

&&

.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 230749
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
249 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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 230749
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
249 AM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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 230525
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1225 AM CDT WED JUL 23 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 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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 230525
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1225 AM CDT WED JUL 23 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 06Z...

* POTENTIAL FOR MVFR CIGS OVERNIGHT.
* GUSTY NNE/NE WINDS TONIGHT THROUGH WEDNESDAY EVENING.

BMD

//DISCUSSION...UPDATED 06Z...

A COLD FRONT IS DROPPING SOUTH ACROSS THE REGION TONIGHT WITH A
BROKEN LINE OF THUNDERSTORMS ALREADY MOVING SOUTH OF THE TERMINALS.
BEHIND THE FRONT WINDS HAVE TURNED NORTHEAST WITH GUSTS INTO THE LOW
TO MID 20 KT RANGE. SOME STRATUS IS ALSO EVIDENT ON SPLIT CHANNEL IR
IMAGERY HUGGING THE LAKE MICHIGAN SHORES WITH CEILINGS BETWEEN
ROUGHLY 025 AND 035. FARTHER UPSTREAM VFR CONDITIONS PREVAIL WITH
JUST SOME PATCHY MID AND HIGH CLOUDS. WITH COLD ADVECTION INTO THE
AREA...MODERATE WINDS TO AROUND 30 KT ARE EVIDENT IN SOUNDINGS AS
LOW AS AROUND 010 AND MAY BE ABLE TO MIX DOWN TO THE SURFACE AT
TIMES OVERNIGHT RESULTING IN CONTINUED GUSTINESS THROUGH THE
OVERNIGHT HOURS. IN FACT...WINDS MAY NOT BEGIN TO TAPER UNTIL CLOSER
TO SUNSET WEDNESDAY EVENING.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION...MEDIUM IN WIND GUSTS SPEEDS.
* LOW CONFIDENCE IN PREVAILING MVFR CIGS OVERNIGHT.
* HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE DAY WEDNESDAY.

BMD

//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






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 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 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 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







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