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000
FXUS63 KLOT 291430
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
930 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI/BEACHLER

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI/BEACHLER

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291430
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
930 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI/BEACHLER

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI/BEACHLER

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
645 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* OCNL SHRA THIS MORNING...ISOLD SHRA AND PERHAPS A TSRA POSSIBLE
  THIS AFTERNOON
* FOG/STRATUS POSSIBLE TONIGHT

IZZI

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

SHRA WILL CONTINUE FOR SEVERAL MORE HOURS ACROSS THE TERMINALS
WITH COVERAGE LIKELY TO DECREASE BY LATE MORNING. OCNL MVFR VSBY
LIKELY IN THE HEAVIER SHRA WITH BRIEF IFR VSBY POSSIBLE. THERE IS
A CHANCE FOR RENEWED SHRA DEVELOPMENT THIS AFTERNOON AND PERHAPS A
THUNDERSTORM NEAR THE VERY WEAK FRONT IN THE AREA. THINKING
INSTABILITY WILL BE WEAK AND CHANCES TOO LOW TO GO WITH ANYTHING
MORE THAN VCSH AT THIS TIME. WEAKENING DIFFUSE FRONT WILL SAG
SOUTH OF THE AREA LATE THIS AFTERNOON AND ALLOW WEAK NE WIND WITH
FOG AND STRATUS POTENTIAL INCREASING TONIGHT TO THE NORTH OF THE
FRONT. DESPITE SOMEWHAT UNFAVORABLE TIME OF YEAR FOR STRATUS/FOG
HAVE OPTED TO TREND TAFS DOWNWARD A BIT FARTHER GIVEN TODAYS RAIN
AND UPSTREAM STRATUS/FOG OVER MN/IA THIS MORNING.

IZZI

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

* HIGH CONFIDENCE IN PRECIP THIS MORNING...LOW CONFIDENCE IN
  PRECIP TRENDS THIS AFTERNOON
* HIGH CONFIDENCE IN WINDS PRIMARILY UNDER 10KT...LOW-MEDIUM
  CONFIDENCE IN DIRECTION
* LOW-MEDIUM CONFIDENCE IN CIGS/VSBY TONIGHT

IZZI

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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:
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  [top]

000
FXUS63 KILX 291135
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
635 AM CDT SAT AUG 29 2015

.SHORT TERM...(TODAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

07Z/2AM SURFACE ANALYSIS SHOWS A WEAK FRONTAL BOUNDARY EXTENDING
FROM WISCONSIN SOUTHWESTWARD TO THE TEXAS PANHANDLE.  A PLUME OF
MAINLY MID-LEVEL MOISTURE AHEAD OF THE FRONT HAS RESULTED IN
SCATTERED LIGHT SHOWERS/SPRINKLES ACROSS THE WESTERN HALF OF THE
KILX CWA EARLY THIS MORNING.  00Z UPPER AIR SOUNDING SHOWED PLENTY
OF DRY AIR BELOW 850MB...SO PRECIP HAS BEEN HAVING A HARD TIME
REACHING THE GROUND IN MANY AREAS.  FORECAST SOUNDINGS SHOW A
GRADUAL MOISTENING OF THE PROFILE TODAY...HOWEVER DEEP-LAYER
MOISTURE REMAINS LACKING.  IN ADDITION...WIDESPREAD CLOUD COVER WILL
LIMIT INSTABILITY...WITH GFS SBCAPE VALUES ONLY REACHING THE 500 TO
1000J/KG RANGE.  END RESULT WILL BE SCATTERED SHOWERS WITH PERHAPS A
RUMBLE OF THUNDER.  THINK AREAL COVERAGE OF PRECIP WILL REMAIN
LOW...SO WILL ONLY CARRY 30-40 POPS.  HIGH TEMPERATURES WILL RANGE
FROM THE UPPER 70S ALONG/NORTHWEST OF THE ILLINOIS RIVER...TO THE
MIDDLE 80S ALONG/SOUTHEAST OF I-70 WHERE CONDITIONS WILL REMAIN DRY
UNTIL A FEW SHOWERS ARRIVE DURING THE AFTERNOON.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

FRONTAL BOUNDARY WILL SLOWLY PUSH EASTWARD LATER TODAY INTO
TONIGHT...WITH MODEL CONSENSUS SHOWING IT REACHING A CHICAGO TO
KIRKSVILLE LINE BY 12Z SUN. SCATTERED SHOWERS WILL BE ONGOING
AHEAD OF THE FRONT ACROSS MUCH OF THE AREA THIS EVENING...THEN
WILL SHIFT TO MAINLY LOCATIONS ALONG/EAST OF I-57 OVERNIGHT. MAIN
WEATHER CONCERN FOR TONIGHT WILL BE THE POTENTIAL FOR FOG ACROSS
THE W/NW CWA. AS THE SLOW-MOVING FRONT ARRIVES...WINDS WILL BECOME
LIGHT/VARIABLE ACROSS THIS AREA. DUE TO THE NEARLY CALM
WINDS...ADDED LOW-LEVEL MOISTURE FROM SHOWERS TODAY...AND PARTIAL
CLEARING LATE TONIGHT...THINK AT LEAST PATCHY FOG WILL FORM. BOTH
FORECAST SOUNDINGS AND NUMERIC GUIDANCE SUGGEST A REDUCTION IN
VISBY OVERNIGHT. CURRENT OBSERVATIONS IN THE VICINITY OF THE FRONT
ACROSS IOWA SHOW WIDESPREAD FOG...WITH A FEW VISBYS DOWN TO AROUND
1/4 MILE. THINK THIS SAME SCENARIO WILL UNFOLD FURTHER EAST
TONIGHT...SO HAVE INCLUDED PATCHY FOG IN THE FORECAST WEST OF I-55
AFTER MIDNIGHT.

THE FRONTAL BOUNDARY WILL SLOWLY DISSIPATE ON SUNDAY...HOWEVER
ENOUGH UPPER-LEVEL SUPPORT WILL PERSIST TO SUPPORT AT LEAST A
MENTION OF A FEW SHOWERS/THUNDERSTORMS.  MOST MODELS PRODUCE LIGHT
QPF ACROSS NEARLY THE ENTIRE CWA AS THE BOUNDARY HAS SLOWED SLIGHTLY
FROM PREVIOUS RUNS.  AS A RESULT...HAVE PULLED POPS FURTHER WEST TO
INCLUDE SLIGHT CHANCES AS FAR WEST AS THE ILLINOIS RIVER SUNDAY
AFTERNOON/EVENING.

AFTER THAT...THE REMAINDER OF THE EXTENDED LOOKS WARM AND DRY AS
UPPER-LEVEL RIDGING DOMINATES THE EASTERN CONUS THROUGH THE END OF
THE COMING WEEK.  A SLIGHT WEAKNESS IN THE RIDGE APPEARS TO DEVELOP
ACROSS ILLINOIS INTO THE OHIO RIVER VALLEY...POTENTIALLY TRIGGERING
ISOLATED AFTERNOON/EVENING CONVECTION TUESDAY THROUGH FRIDAY.
HOWEVER...MID-LEVEL WARMING BENEATH THE RIDGE WILL LIKELY LEAD TO
CAPPING AND AN OVERALL SUPPRESSION OF CONVECTION.  AS A
RESULT...WILL MAINTAIN A DRY FORECAST WITH HIGH TEMPERATURES
CLIMBING INTO THE UPPER 80S TO AROUND 90 DEGREES EACH DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 635 AM CDT SAT AUG 29 2015

GENERALLY QUIET/VFR CONDITIONS EXPECTED ACROSS THE CENTRAL
ILLINOIS TERMINALS THROUGH THE 12Z TAF VALID TIME, DESPITE THE
PRESENCE OF A WEAK WEATHER DISTURBANCE AND SPOTTY
SHOWERS/THUNDERSTORMS. AT THIS POINT, EXPECT THE THUNDER COVERAGE
TO BE TOO SPARSE TO WARRANT A MENTION, AND WILL LIMIT SHOWERS TO
VCSH. THE ADDED LOW LEVEL MOISTURE FROM THE PRECIPITATION IN THE
AREA, AS WELL AS THE SLOW APPROACH OF A FRONTAL BOUNDARY
ASSOCIATED WITH DISTURBANCE, MAY RESULT IN FOG AND/OR STRATUS
DEVELOPMENT BY LATE TONIGHT. KPIA STANDS THE BEST CHANCE OF SEEING
A SIGNIFICANT CIG/VSBY REDUCTION LATER TONIGHT AS THE FRONTAL
BOUNDARY SHOULD BE CLOSEST TO THAT TERMINAL.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...BARNES
AVIATION...BAK



000
FXUS63 KILX 291135
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
635 AM CDT SAT AUG 29 2015

.SHORT TERM...(TODAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

07Z/2AM SURFACE ANALYSIS SHOWS A WEAK FRONTAL BOUNDARY EXTENDING
FROM WISCONSIN SOUTHWESTWARD TO THE TEXAS PANHANDLE.  A PLUME OF
MAINLY MID-LEVEL MOISTURE AHEAD OF THE FRONT HAS RESULTED IN
SCATTERED LIGHT SHOWERS/SPRINKLES ACROSS THE WESTERN HALF OF THE
KILX CWA EARLY THIS MORNING.  00Z UPPER AIR SOUNDING SHOWED PLENTY
OF DRY AIR BELOW 850MB...SO PRECIP HAS BEEN HAVING A HARD TIME
REACHING THE GROUND IN MANY AREAS.  FORECAST SOUNDINGS SHOW A
GRADUAL MOISTENING OF THE PROFILE TODAY...HOWEVER DEEP-LAYER
MOISTURE REMAINS LACKING.  IN ADDITION...WIDESPREAD CLOUD COVER WILL
LIMIT INSTABILITY...WITH GFS SBCAPE VALUES ONLY REACHING THE 500 TO
1000J/KG RANGE.  END RESULT WILL BE SCATTERED SHOWERS WITH PERHAPS A
RUMBLE OF THUNDER.  THINK AREAL COVERAGE OF PRECIP WILL REMAIN
LOW...SO WILL ONLY CARRY 30-40 POPS.  HIGH TEMPERATURES WILL RANGE
FROM THE UPPER 70S ALONG/NORTHWEST OF THE ILLINOIS RIVER...TO THE
MIDDLE 80S ALONG/SOUTHEAST OF I-70 WHERE CONDITIONS WILL REMAIN DRY
UNTIL A FEW SHOWERS ARRIVE DURING THE AFTERNOON.

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

FRONTAL BOUNDARY WILL SLOWLY PUSH EASTWARD LATER TODAY INTO
TONIGHT...WITH MODEL CONSENSUS SHOWING IT REACHING A CHICAGO TO
KIRKSVILLE LINE BY 12Z SUN. SCATTERED SHOWERS WILL BE ONGOING
AHEAD OF THE FRONT ACROSS MUCH OF THE AREA THIS EVENING...THEN
WILL SHIFT TO MAINLY LOCATIONS ALONG/EAST OF I-57 OVERNIGHT. MAIN
WEATHER CONCERN FOR TONIGHT WILL BE THE POTENTIAL FOR FOG ACROSS
THE W/NW CWA. AS THE SLOW-MOVING FRONT ARRIVES...WINDS WILL BECOME
LIGHT/VARIABLE ACROSS THIS AREA. DUE TO THE NEARLY CALM
WINDS...ADDED LOW-LEVEL MOISTURE FROM SHOWERS TODAY...AND PARTIAL
CLEARING LATE TONIGHT...THINK AT LEAST PATCHY FOG WILL FORM. BOTH
FORECAST SOUNDINGS AND NUMERIC GUIDANCE SUGGEST A REDUCTION IN
VISBY OVERNIGHT. CURRENT OBSERVATIONS IN THE VICINITY OF THE FRONT
ACROSS IOWA SHOW WIDESPREAD FOG...WITH A FEW VISBYS DOWN TO AROUND
1/4 MILE. THINK THIS SAME SCENARIO WILL UNFOLD FURTHER EAST
TONIGHT...SO HAVE INCLUDED PATCHY FOG IN THE FORECAST WEST OF I-55
AFTER MIDNIGHT.

THE FRONTAL BOUNDARY WILL SLOWLY DISSIPATE ON SUNDAY...HOWEVER
ENOUGH UPPER-LEVEL SUPPORT WILL PERSIST TO SUPPORT AT LEAST A
MENTION OF A FEW SHOWERS/THUNDERSTORMS.  MOST MODELS PRODUCE LIGHT
QPF ACROSS NEARLY THE ENTIRE CWA AS THE BOUNDARY HAS SLOWED SLIGHTLY
FROM PREVIOUS RUNS.  AS A RESULT...HAVE PULLED POPS FURTHER WEST TO
INCLUDE SLIGHT CHANCES AS FAR WEST AS THE ILLINOIS RIVER SUNDAY
AFTERNOON/EVENING.

AFTER THAT...THE REMAINDER OF THE EXTENDED LOOKS WARM AND DRY AS
UPPER-LEVEL RIDGING DOMINATES THE EASTERN CONUS THROUGH THE END OF
THE COMING WEEK.  A SLIGHT WEAKNESS IN THE RIDGE APPEARS TO DEVELOP
ACROSS ILLINOIS INTO THE OHIO RIVER VALLEY...POTENTIALLY TRIGGERING
ISOLATED AFTERNOON/EVENING CONVECTION TUESDAY THROUGH FRIDAY.
HOWEVER...MID-LEVEL WARMING BENEATH THE RIDGE WILL LIKELY LEAD TO
CAPPING AND AN OVERALL SUPPRESSION OF CONVECTION.  AS A
RESULT...WILL MAINTAIN A DRY FORECAST WITH HIGH TEMPERATURES
CLIMBING INTO THE UPPER 80S TO AROUND 90 DEGREES EACH DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 635 AM CDT SAT AUG 29 2015

GENERALLY QUIET/VFR CONDITIONS EXPECTED ACROSS THE CENTRAL
ILLINOIS TERMINALS THROUGH THE 12Z TAF VALID TIME, DESPITE THE
PRESENCE OF A WEAK WEATHER DISTURBANCE AND SPOTTY
SHOWERS/THUNDERSTORMS. AT THIS POINT, EXPECT THE THUNDER COVERAGE
TO BE TOO SPARSE TO WARRANT A MENTION, AND WILL LIMIT SHOWERS TO
VCSH. THE ADDED LOW LEVEL MOISTURE FROM THE PRECIPITATION IN THE
AREA, AS WELL AS THE SLOW APPROACH OF A FRONTAL BOUNDARY
ASSOCIATED WITH DISTURBANCE, MAY RESULT IN FOG AND/OR STRATUS
DEVELOPMENT BY LATE TONIGHT. KPIA STANDS THE BEST CHANCE OF SEEING
A SIGNIFICANT CIG/VSBY REDUCTION LATER TONIGHT AS THE FRONTAL
BOUNDARY SHOULD BE CLOSEST TO THAT TERMINAL.

&&

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

$$

SHORT TERM...BARNES
LONG TERM...BARNES
AVIATION...BAK




000
FXUS63 KLOT 290902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290830
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
330 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290830
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
330 AM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 290812
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
312 AM CDT SAT AUG 29 2015

.SHORT TERM...(TODAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

07Z/2AM SURFACE ANALYSIS SHOWS A WEAK FRONTAL BOUNDARY EXTENDING
FROM WISCONSIN SOUTHWESTWARD TO THE TEXAS PANHANDLE.  A PLUME OF
MAINLY MID-LEVEL MOISTURE AHEAD OF THE FRONT HAS RESULTED IN
SCATTERED LIGHT SHOWERS/SPRINKLES ACROSS THE WESTERN HALF OF THE
KILX CWA EARLY THIS MORNING.  00Z UPPER AIR SOUNDING SHOWED PLENTY
OF DRY AIR BELOW 850MB...SO PRECIP HAS BEEN HAVING A HARD TIME
REACHING THE GROUND IN MANY AREAS.  FORECAST SOUNDINGS SHOW A
GRADUAL MOISTENING OF THE PROFILE TODAY...HOWEVER DEEP-LAYER
MOISTURE REMAINS LACKING.  IN ADDITION...WIDESPREAD CLOUD COVER WILL
LIMIT INSTABILITY...WITH GFS SBCAPE VALUES ONLY REACHING THE 500 TO
1000J/KG RANGE.  END RESULT WILL BE SCATTERED SHOWERS WITH PERHAPS A
RUMBLE OF THUNDER.  THINK AREAL COVERAGE OF PRECIP WILL REMAIN
LOW...SO WILL ONLY CARRY 30-40 POPS.  HIGH TEMPERATURES WILL RANGE
FROM THE UPPER 70S ALONG/NORTHWEST OF THE ILLINOIS RIVER...TO THE
MIDDLE 80S ALONG/SOUTHEAST OF I-70 WHERE CONDITIONS WILL REMAIN DRY
UNTIL A FEW SHOWERS ARRIVE DURING THE AFTERNOON.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 312 AM CDT SAT AUG 29 2015

FRONTAL BOUNDARY WILL SLOWLY PUSH EASTWARD LATER TODAY INTO
TONIGHT...WITH MODEL CONSENSUS SHOWING IT REACHING A CHICAGO TO
KIRKSVILLE LINE BY 12Z SUN. SCATTERED SHOWERS WILL BE ONGOING
AHEAD OF THE FRONT ACROSS MUCH OF THE AREA THIS EVENING...THEN
WILL SHIFT TO MAINLY LOCATIONS ALONG/EAST OF I-57 OVERNIGHT. MAIN
WEATHER CONCERN FOR TONIGHT WILL BE THE POTENTIAL FOR FOG ACROSS
THE W/NW CWA. AS THE SLOW-MOVING FRONT ARRIVES...WINDS WILL BECOME
LIGHT/VARIABLE ACROSS THIS AREA. DUE TO THE NEARLY CALM
WINDS...ADDED LOW-LEVEL MOISTURE FROM SHOWERS TODAY...AND PARTIAL
CLEARING LATE TONIGHT...THINK AT LEAST PATCHY FOG WILL FORM. BOTH
FORECAST SOUNDINGS AND NUMERIC GUIDANCE SUGGEST A REDUCTION IN
VISBY OVERNIGHT. CURRENT OBSERVATIONS IN THE VICINITY OF THE FRONT
ACROSS IOWA SHOW WIDESPREAD FOG...WITH A FEW VISBYS DOWN TO AROUND
1/4 MILE. THINK THIS SAME SCENARIO WILL UNFOLD FURTHER EAST
TONIGHT...SO HAVE INCLUDED PATCHY FOG IN THE FORECAST WEST OF I-55
AFTER MIDNIGHT.

THE FRONTAL BOUNDARY WILL SLOWLY DISSIPATE ON SUNDAY...HOWEVER
ENOUGH UPPER-LEVEL SUPPORT WILL PERSIST TO SUPPORT AT LEAST A
MENTION OF A FEW SHOWERS/THUNDERSTORMS.  MOST MODELS PRODUCE LIGHT
QPF ACROSS NEARLY THE ENTIRE CWA AS THE BOUNDARY HAS SLOWED SLIGHTLY
FROM PREVIOUS RUNS.  AS A RESULT...HAVE PULLED POPS FURTHER WEST TO
INCLUDE SLIGHT CHANCES AS FAR WEST AS THE ILLINOIS RIVER SUNDAY
AFTERNOON/EVENING.

AFTER THAT...THE REMAINDER OF THE EXTENDED LOOKS WARM AND DRY AS
UPPER-LEVEL RIDGING DOMINATES THE EASTERN CONUS THROUGH THE END OF
THE COMING WEEK.  A SLIGHT WEAKNESS IN THE RIDGE APPEARS TO DEVELOP
ACROSS ILLINOIS INTO THE OHIO RIVER VALLEY...POTENTIALLY TRIGGERING
ISOLATED AFTERNOON/EVENING CONVECTION TUESDAY THROUGH FRIDAY.
HOWEVER...MID-LEVEL WARMING BENEATH THE RIDGE WILL LIKELY LEAD TO
CAPPING AND AN OVERALL SUPPRESSION OF CONVECTION.  AS A
RESULT...WILL MAINTAIN A DRY FORECAST WITH HIGH TEMPERATURES
CLIMBING INTO THE UPPER 80S TO AROUND 90 DEGREES EACH DAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...BARNES
AVIATION...SHIMON



000
FXUS63 KLOT 290707
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
207 AM CDT SAT AUG 29 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290707
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
207 AM CDT SAT AUG 29 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
108 AM CDT SAT AUG 29 2015

.UPDATE...

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* PERIOD OF RAIN OVERNIGHT INTO SATURDAY MORNING
* MVFR OR LOWER CIGS AND VSBY POSSIBLE SAT NIGHT

IZZI

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

WEAKENING STORM SYSTEM WILL BRING A PERIOD OF RAIN WITH POSSIBLE
PERIODIC MVFR VSBY LATE TONIGHT INTO SAT MORNING BEFORE RAIN
TAPERS OFF AND ENDS BY MIDDAY. SMALL CHANCE EXISTS FOR SOME ISOLD
SHRA OR PERHAPS A TSRA DURING THE LATE AFTERNOON AS WHAT IS LEFT
OF THE STORM SYSTEM FESTERS...BUT CHANCES LOOK TOO LOW TO INCLUDE
PRECIP IN TAFS AT THIS TIME. LIGHT EAST TO SOUTHEAST WINDS COULD
TURN MORE SOUTHERLY SAT MORNING BEFORE PROBABLY TURNING FAIRLY
LIGHT AND VARIABLE DURING THE AFTERNOON. SHOULD SEE A TENDENCY FOR
WINDS TO BECOME LIGHT NORTHEAST SAT NIGHT AND WITH AMPLE LOW LEVEL
MOISTURE AND RECENT RAINS COULD SEE SOME LIGHT FOG AND/OR STRATUS
DEVELOP.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN RAIN LATE TONIGHT/SAT MORNING
* HIGH CONFIDENCE IN WINDS BELOW 10KT...BUT LOW CONFIDENCE IN
  DIRECTION.
* LOW CONFIDENCE IN CIGS/VSBY SAT NIGHT

IZZI

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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000
FXUS63 KILX 290442
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290442
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290442
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290442
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1142 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1142 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA WILL CONTINUE TO DRIFT EAST
TONIGHT. IT WILL GRADUALLY DISSIPATE NEAR WESTERN ILLINOIS
SATURDAY AFTERNOON/EVE. SHOWERS HAVE EXPANDED IN COVERAGE BETWEEN
04Z-05Z, AND RAIN IS STARTING TO REACH THE GROUND FROM CLOUD
BASES AT 8K FT OR HIGHER. SCATTERED RAIN SHOWERS WILL PERIODICALLY
AFFECT THE TERMINAL SITES OVER THE NEXT 18 HOURS, BEFORE
DISSIPATING SATURDAY EVENING. THE CHANCES ONLY WARRANTED A VCSH
AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS FROM HRRR AND
RAP/NAM OUTPUT. USED ONLY VCSH IN ALL TAFS TO ACCOUNT FOR PRECIP,
AS TIMING WILL BE HIGHLY VARIABLE IN TERMS OF TIMING AND LOCATION.
ENDED ALL MENTION OF PRECIP BEFORE 00Z/30. WINDS ARE EXPECTED TO
REMAIN SOUTH THROUGH AT LEAST 18Z, THEN BEGIN TO SHIFT TO THE
SOUTHWEST AS THE LOW AND COLD FRONT APPROACH WESTERN ILLINOIS.
PREVAILING WIND SPEEDS SHOULD REMAIN 10KT OR LESS THROUGH TOMORROW
AFTERNOON.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KLOT 290306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1006 PM CDT FRI AUG 28 2015

.UPDATE...626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE PERIOD.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1006 PM CDT FRI AUG 28 2015

.UPDATE...626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE PERIOD.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1006 PM CDT FRI AUG 28 2015

.UPDATE...626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE PERIOD.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1006 PM CDT FRI AUG 28 2015

.UPDATE...626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE PERIOD.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 290209
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
909 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290209
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
909 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290209
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
909 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 903 PM CDT FRI AUG 28 2015

THE DRY AIR IN PLACE ACROSS CENTRAL IL HAS CAUSED THE LEADING PUSH
OF SHOWERS TO DISSIPATE BEFORE REACHING THE ILLINOIS RIVER. THAT
SHOULD CONTINUE TO BE THE CASE UNTIL AT LEAST 06Z/1AM. WE EXPECT
BETTER POTENTIAL FOR RAIN TOMORROW AS THE LOW AND COLD FRONT
REACH WESTERN IL. THE WEAKENING OF THE ENTIRE LOW PRESSURE SYSTEM
AS IT REACHES ILLINOIS WILL SUPPORT KEEPING THE POPS IN THE LOW
CHANCE CATEGORY. WILL DIMINISH THE SOUTHERN EXTENT OF CHANCE POPS
BETWEEN 06Z AND 12Z, BASED ON TRENDS THIS EVENING. A VEIL OF HIGH
CLOUDS WILL KEEP LOW TEMPS WARMER THAN LAST NIGHT, WITH READINGS
MAINLY IN THE MID 60S. UPDATES THIS EVENING WILL BE MAINLY IN THE
WEATHER/POP AREA, AS THE REMAINDER OF THE FORECAST IS GENERALLY ON
TRACK.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON



000
FXUS63 KILX 290003
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
703 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.

&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON



000
FXUS63 KILX 290003
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
703 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.

&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KILX 290003
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
703 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.

&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON



000
FXUS63 KILX 290003
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
703 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 700 PM CDT FRI AUG 28 2015

LOW PRESSURE CENTERED IN WESTERN IOWA IS PROJECTED TO DRIFT EAST
AS IT GRADUALLY DISSIPATES NEAR WESTERN ILLINOIS SATURDAY
AFTERNOON/EVE. SHOWERS ARE DRIFTING INTO A RELATIVELY DRY AIRMASS,
AS CONFIRMED BY THE ILX 00Z SOUNDING. SPOTTY RAIN WILL EVENTUALLY
MOVE ACROSS CENTRAL ILLINOIS, AHEAD OF THE LOW. THE CHANCES ONLY
WARRANTED A VCSH AND VFR CLOUD COVER, BASED ON FORECAST SOUNDINGS
FROM HRRR AND RAP/NAM OUTPUT. WE STARTED VCSH AT PIA THE SOONEST,
AT 03Z, WHILE DELAYING AT BMI UNTIL 12Z AND THE SOUTHERN TAF SITES
AFTER 18Z. WINDS ARE EXPECTED TO REMAIN SOUTH THROUGH AT LEAST
18Z, THEN BEGIN TO SHIFT TO THE SOUTHWEST AS THE LOW AND COLD
FRONT APPROACH WESTERN ILLINOIS. PREVAILING WIND SPEEDS SHOULD
REMAIN 10KT OR LESS THROUGH TOMORROW AFTERNOON.

&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...SHIMON




000
FXUS63 KLOT 282332
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE DAY TOMORROW.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282332
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE DAY TOMORROW.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282332
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE DAY TOMORROW.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282332
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* UNCERTAINTY IN WIND DIRECTION THROUGH MUCH OF THE DAY TOMORROW.
* CHANCES FOR RAIN LATE OVERNIGHT THROUGH MID MORNING...THEN
  CHANCES FOR SHOWERS AND THUNDERSTORMS TOMORROW AFTERNOON.

BMD

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

WEAK LOW PRESSURE OVER IOWA THIS EVENING IS PROGGED TO LIFT ENE
AND FILL OVERNIGHT. SHOWERS ARE A FEW EMBEDDED THUNDERSTORMS ARE
ONGOING ACROSS WISCONSIN AND IOWA THIS EVENING AHEAD OF THE LOW
AND WILL GRADUALLY TRANSLATE EAST OVERNIGHT...REACHING RFD JUST
AFTER MIDNIGHT TONIGHT AND THEN THE CHICAGO TERMINALS EARLY ON
SATURDAY. A SECONDARY WAVE DIGGING ACROSS THE REGION TOMORROW IS
EXPECTED TO KICK OFF ADDITIONAL SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON. CONFIDENCE IN THE WIND
DIRECTION IS LOW WITH LARGE DIFFERENCES BETWEEN MODELS.

BMD

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

* MEDIUM IN PRECIP TIMING EARLY SATURDAY...LOW-MEDIUM IN TSRA
  TIMING/COVERAGE SATURDAY AFTERNOON.
* LOW CONFIDENCE IN WIND DIRECTION SATURDAY.

BMD

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

SUNDAY...VFR. EAST WIND.
MONDAY...VFR. SOUTHEAST WIND.
TUESDAY...VFR. SOUTH WIND.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WIND.
THURSDAY...VFR. SOUTH WIND.

BMD

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282326
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282326
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 282326
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 282326
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
626 PM CDT FRI AUG 28 2015

.UPDATE...
626 PM CDT

HAVE ADJUSTED POPS DOWNWARD THROUGH THE MID EVENING HOURS TO
ACCOUNT FOR RADAR AND NEAR-TERM GUIDANCE TRENDS. LEADING EDGE OF
SHORTWAVE TROUGH AND VORTICITY MAXIMA WILL MOVE EAST FROM
WISCONSIN THIS EVENING...KEEPING BEST FORCING FOR PRECIP NORTH OF
THE STATE LINE. THUS...JUST HAVE GENERALLY ISOLATED
SHRA/INTERMITTENT SPRINKLE MENTION THROUGH MID EVENING IN FAR
NORTHERN ILLINOIS. VERY DRY AIR NOTED AROUND 800 MB ON A RECENT
AMDAR SOUNDING FROM MDW WILL MAKE IT TOUGH FOR ANY STEADY PRECIP
UNTIL DRY AIR GETS ERODED. UPPER TROUGH/SHORTWAVE AXIS AND
SHEARED VORT MAX ALONG TROUGH AXIS WILL SLOWLY PROGRESS FROM IA TO
NORTHERN IL LATE THIS EVENING AND OVERNIGHT...BRINGING GRADUALLY
INCREASING SHRA/RAIN COVERAGE FROM NORTHWEST TO SOUTHEAST...BUT
MANY AREAS ALONG AND EAST OF AN EVANSTON TO PONTIAC LINE COULD
VERY WELL REMAIN DRY THROUGH DAYBREAK. VERY LITTLE IF ANY
INSTABILITY OVER AREA THROUGH THE NIGHT AND POOR MIDLEVEL LAPSE
RATES SUPPORT KEEPING SLIGHT CHANCE TSRA AT BEST. THE REST OF THE
FORECAST LOOKS TO BE ON TRACK.

RC

&&

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282200
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
500 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282200
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
500 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB/BMD

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB/BMD

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 282010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 282010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
307 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

THE LATEST LONGER TERM GUIDANCE IS INDICATING SOME CHANGES POSSIBLE
FOR THE LONGER RANGE TRENDS FOR TEMPERATURES AND PCPN...BUT THE
EARLIER PORTION OF THE LONG TERM FORECAST IS RELATIVELY CONSISTENT
WITH PREVIOUS RUNS.

THE GENERAL TREND FOR TEMPERATURES IS STILL FOR A WARMING TREND FOR
NEXT WEEK...BUT TEMPERATURES SHOULD STILL BE SLIGHTLY BELOW NORMAL
THROUGH SUNDAY.  FOR SATURDAY NIGHT AND INTO EARLY SUNDAY...THERE
SHOULD STILL BE A CHANCE OF SOME LINGERING SHOWERS OR A FEW
THUNDERSTORMS...ESPECIALLY FOR NWRN INDIANA AS THE UPPER LEVEL
SHORTWAVE RESPONSIBLE FOR FOCUSING THE CONVECTIVE ACTIVITY LIFTS
OFF TO THE EAST AND WEAKENS. BY SUNDAY...LEE TROUGHING WILL DEVELOP
OVER THE WRN PLAINS AS A NORTHERN STREAM SHORTWAVE AND AN ASSOCIATED
SFC REFLECTION DROPS OUT OF THE CANADIAN ROCKIES AND INTO THE
PRAIRIES.  THE OVERALL PATTERN WILL BECOME NEARLY STATIONARY THROUGH
MUCH OF NEXT WEEK AS THE SFC HIGH REMAINS PARKED OVER THE MID
ATLANTIC REGION WHILE THE TROUGH REMAINS OVER THE PLAINS.  THIS WILL
HELP AID THE WARMING TREND AS SLY WINDS TRY TO DRAW MOISTURE NWD
FROM THE GLFMEX...THOUGH WEAK SFC RIDGING THROUGH THE NRN GULF COAST
MAY CAUSE SOME DELAY IN THE MOISTURE RETURN.

THE MAIN CHANGE TO THE EXTENDED FORECAST IS RELATED TO HOW THE
MODELS NOW HANDLE THE REMNANTS OF TS ERIKA.  PREVIOUS RUNS OF THE
LONGER RANGE GUIDANCE HAD PREVIOUSLY LIMITED THE WESTWARD
PROGRESSION OF THE TROPICAL SYSTEM...WHILE THE LATEST RUNS ARE
HINTING THAT ERIKA COULD TRACK FARTHER WEST.  SO...WHILE THERE IS
STILL A FAIR AMOUNT OF UNCERTAINTY IN HOW FAR WEST THE PERIPHERAL
EFFECT OF THE TROPICAL SYSTEM WILL EXTEND...AND WE ARE NOT TALKING
ABOUT THE TROPICAL SYSTEM ACTUALLY MOVING ANYWHERE CLOSE TO NRN
IL/IN...RATHER THE IDEA IS THAT IF THE TROPICAL SYSTEM CAN TRACK A
LITTLE FURTHER WEST...THEN THERE WILL BE GREATER MOISTURE TRANSPORT
INTO THE MIDWEST...AND AS A RESULT...GREATER CHANCES FOR SHRA/TSRA
AND MORE CLOUD COVER THAN PREVIOUSLY ANTICIPATED.  SO HAVE BACKED
OFF A COUPLE DEGREES ON MAX TEMPS THROUGH THE EXTENDED PERIOD AS
WELL AS INTRODUCING PERIODIC SLIGHT CHANCE POPS AND A BIT MORE CLOUD
COVER.

KREIN

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
310 PM CDT

HIGH PRESSURE OVER THE MID ATLANTIC REGION WILL MOVE VERY LITTLE
THROUGH THE MIDDLE OF NEXT WEEK. WEAK LOW PRESSURE OVER WESTERN
IOWA WILL WEAKEN AS IT MOVES INTO THE MIDDLE MISSISSIPPI VALLEY
AND DISSIPATES SATURDAY EVENING. ANOTHER AREA OF LOW PRESSURE IS
EXPECTED TO DROP OUT OF THE CANADIAN ROCKIES SUNDAY NIGHT WHILE A
TROUGH OF LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. THIS
TROUGH AND THE HIGH OVER THE MID ATLANTIC REGION WILL MOVE LITTLE
OVER THE NEXT SEVERAL DAYS...KEEPING MODEST SOUTH TO SOUTHWEST
WINDS OVER THE LAKE FOR THE NEXT SEVERAL DAYS.

KREIN

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 281950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 281950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT FRI AUG 28 2015

.SHORT TERM...

TONIGHT AND SATURDAY...

250 PM...FORECAST CONCERNS INCLUDE PRECIP COVERAGE/TIMING AND
RAINFALL AMOUNTS.

LOW PRESSURE OVER WESTERN IOWA WILL SLOWLY MOVE EAST TONIGHT AND
EVENTUALLY DISSIPATE OVER NORTHERN ILLINOIS SATURDAY. FIRST WAVE OF
PRECIP IS GENERALLY LIFTING NORTHEAST INTO SOUTHERN WISCONSIN AND
THE MODELS SEEM TO HAVE THIS HANDLED FAIRLY WELL WITH THE HRRR ALSO
SHOWING JUST ISOLATED SHOWERS/SPRINKLES INTO EARLY THIS EVENING AND
MAINLY ACROSS NORTHWEST AND NORTHERN IL. ADDITIONAL PRECIP IS
EXPECTED TO DEVELOP LATER THIS EVENING AND SPREAD NORTHEAST
OVERNIGHT INTO SATURDAY MORNING. THIS PRECIP WILL ALSO BE FOCUSED
ACROSS NORTHWEST/NORTHERN IL...INTO SOUTHERN WI. MODEL QPF AMOUNTS
NEAR THE IL/WI STATE LINE ARE IN THE 1 TO 1.5 INCH RANGE. THESE
AMOUNTS HAVE BEEN CONSISTENT BETWEEN RUNS AND VARIOUS MODELS SO IT
IS LIKELY SOME AREAS WILL SEE OVER AN INCH OF RAIN. HOWEVER...THESE
AMOUNTS APPEAR TO DROP OFF QUICKLY BETWEEN I-88 AND I-80 WITH MUCH
OF THE SOUTHEAST THIRD OR HALF OF THE CWA POSSIBLY STAYING DRY INTO
SATURDAY MORNING. INSTABILITY IS LIMITED AND LIGHTNING HAS BEEN
CONFINED TO THE STRONGEST STORMS/CONVECTION. THUNDER IS CERTAINLY
POSSIBLE TONIGHT BUT OVERALL COVERAGE SHOULD BE LIMITED AND HELD
SLIGHT CHANCE MENTION OF THUNDER TO HIGHER POP AREAS.

AFTER THE MAIN AREA OF RAIN MOVES NORTHEAST SATURDAY MORNING...
PRECIP ACROSS THE REST OF THE CWA WILL BE MORE SCATTERED...OR
ISOLATED...INTO THE LATE MORNING/EARLY AFTERNOON. APPEARS THERE
COULD BE NEW DEVELOPMENT IN THE EARLY/MID AFTERNOON BUT COVERAGE
POSSIBLY STILL JUST SCATTERED. THUS DIDN/T MAKE TOO MANY CHANGES
FROM CURRENT POPS IN THE 40-50 PERCENT RANGE.

TEMPS WILL ONLY SLOWLY FALL INTO THE LOWER/MID 60S TONIGHT AND HIGHS
ON SATURDAY WILL BE DEPENDENT ON PRECIP COVERAGE AND CLOUD COVER.
CURRENT FORECAST OF MID 70S NORTH TO LOWER 80S SOUTHEAST WILL
NEED SOME SUN TO OCCUR. SOUTHEASTERLY WINDS WILL KEEP THE IL SHORE
A BIT COOLER. CMS

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB

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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 281943
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
243 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.


&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...GEELHART



000
FXUS63 KILX 281943
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
243 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.


&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...GEELHART




000
FXUS63 KILX 281943
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
243 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.


&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...GEELHART




000
FXUS63 KILX 281943
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
243 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.


&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...GEELHART




000
FXUS63 KILX 281943
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
243 PM CDT FRI AUG 28 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 243 PM CDT FRI AUG 28 2015

AFTERNOON SURFACE MAP SHOWING LOW PRESSURE CENTERED NEAR OMAHA, WITH
A WARM FRONT EXTENDING NORTHEAST ACROSS IOWA AND A COLD FRONT INTO
CENTRAL KANSAS. MAIN ACTIVITY OF SHOWERS AND THUNDERSTORMS HAS BEEN
CLOSER TO THE WARM FRONT AND TRACKING NORTH OF OUR FORECAST AREA. A
GENERAL EASTWARD PROGRESSION OF THE BOUNDARIES IS EXPECTED OVER THE
NEXT SEVERAL HOURS, WITH THE COLD FRONT APPROACHING THE
ILLINOIS/IOWA BORDER TOWARD 3-4 AM. FORECAST SOUNDINGS ARE RATHER
DRY BELOW 12,000 FEET FROM ABOUT PEORIA EAST AND SOUTH, AND AM
STARTING TO GET CONCERNED THAT THERE WILL BE LITTLE MORE THAN
ISOLATED SHOWERS BETWEEN I-55 AND THE ILLINOIS RIVER TONIGHT.
HOWEVER, THE HRRR AND ARW MODELS ARE A BIT MORE AGGRESSIVE WITH
SHOWERS MOVING INTO THIS AREA AFTER 3 AM, SO WILL MAINTAIN CHANCE
POP`S ACROSS THE ILLINOIS RIVER VALLEY MAINLY FROM LATE EVENING
THROUGH OVERNIGHT. INSTABILITY IS A LITTLE MORE SPARSE THOUGH, WITH
THE CURRENT THUNDER ACTIVITY MAINLY NEAR THE UPPER LEVEL DISTURBANCE
TRACKING ACROSS CENTRAL IOWA, AND HAVE TRIMMED BACK THE THUNDER
POTENTIAL TO MAINLY WEST OF THE RIVER. OTHERWISE, HAVE MAINLY GONE
DRY EAST OF I-55. MILDER CONDITIONS EXPECTED OVERNIGHT WITH CLOUD
COVER MUCH MORE EXTENSIVE AND A SOUTHERLY FLOW, WITH MOST AREAS
DIPPING INTO THE MID 60S.

&&

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 243 PM CDT FRI AUG 28 2015

LOW PRESSURE AREA AND ASSOCIATED FRONT WEST OF THE AREA WILL
CONTINUE TO SLOWLY MOVE EAST AND INTO THE CWA DURING THE WEEKEND.
HOWEVER...VERY LITTLE SUPPORT FOR THIS SYSTEM AS IT MOVES EAST SO
ALL MODELS HAVE THIS SYSTEM WEAKENING AS IT MOVES INTO THE AREA.
THEREFORE...WILL ONLY HAVE CHANCE POPS FOR SAT MORNING WEST OF I-55
AND THEN MOVE POPS EAST DURING THE AFTERNOON BUT REMAINING MAINLY
NORTH OF I-70 AS FRONT CONTINUES TO WEAKEN AND BECOME SOMEWHAT
PARALLEL TO THE FLOW AND VERY LACKING ON CONVERGENCE/SUPPORT. CHANCE
POPS FOR SAT NIGHT WILL CONTINUE AS THE UPPER LEVEL WAVE SHIFTS EAST
ACROSS THE AREA. PCPN WILL BE MAINLY SHOWERS AND ISOLATED
THUNDERSTORMS...DUE TO LACK OF FORCING AND INSTABILITY. BY
SUNDAY...THE WAVE SHOULD BE VERY WEAK AND EAST OF THE CWA...SO WILL
ONLY HAVE SLIGHT CHANCE POPS. FOR REMAINDER OF THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK...DRY CONDITIONS CAN BE EXPECTED AS HIGH
PRESSURE BEGINS TO BUILD IN THE WEST AND PUSH INTO THE NORTHERN PART
OF THE AREA.

BEGINNING TUE AND THROUGH MOST OF THE WEEK...A COUPLE OF MODELS
BRING REMNANTS OF TS ERIKA INTO THE AREA. HOWEVER...THIS IS
DEPENDENT ON WHERE THE TS GOES. AND IT IS FAR ENOUGH AWAY IN TIME
THAT WILL JUST KEEP CLOSE TO WHAT THE CRINT HAS...AND THAT IS JUST
SLIGHT CHANCE POPS IN SOME AREAS FOR WED THROUGH THUR. SLIGHT CHANCE
POPS WILL BE IN THE GRIDS BUT NOT MENTIONED IN THE WORDED FORECAST.

TEMPS THROUGH THE WEEKEND WILL BE TEMPERED DUE TO CLOUD COVER AND
SCATTERED PCPN...BUT STILL EXPECTING THEM TO RISE INTO THE 80S FOR
THE WEEKEND. BY NEXT WEEK...WITH UPPER LEVEL RIDGING BUILDING INTO
THE AREA AND DEWPOINTS BEING DRIER...EXPECTING TEMPS TO RISE INTO
THE UPPER 80S TO AROUND 90 FOR THE ENTIRE WEEK. THIS WILL BE MUCH
ABOVE NORMAL FOR THE BEGINNING OF SEPT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.


&&

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

$$

SHORT TERM...GEELHART
LONG TERM...AUTEN
AVIATION...GEELHART




000
FXUS63 KILX 281727
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1227 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 1034 AM CDT FRI AUG 28 2015

EXTENSIVE MID/HIGH CLOUD SHIELD HAS OVERSPREAD THE FORECAST AREA
IN CONJUNCTION WITH THE STORM SYSTEM TO OUR WEST. MUCH OF THE
RAIN IN IOWA WAS TRACKING TO THE EAST-NORTHEAST ON A TRAJECTORY
THAT WOULD PASS NORTH OF OUR FORECAST AREA. CONVECTION FURTHER
SOUTHWEST ALONG THE BOUNDARY, ACROSS NORTHWEST MISSOURI, IS MORE
LIKELY TO GET HERE LATER THIS EVENING. THEREFORE, HAVE NOT CHANGED
POP`S TOO MUCH, WHICH ORIGINALLY WERE CONFINED TO MAINLY SLIGHT
CHANCES. HOWEVER, HAVE BUMPED THEM UP A TAD AROUND GALESBURG, AS
THE SOUTHERN FLANK OF THE RAIN SHIELD IN SOUTHEAST IOWA MAY CLIP
THAT AREA IN A COUPLE HOURS. HAVE ALSO LOWERED TEMPERATURES BY A
DEGREE OR TWO MOST AREAS, BUT WILL HAVE TO MONITOR THE NORTHWEST
CWA CLOSELY AS THE THICKER CLOUD COVER WILL PERSIST THERE THROUGH
THE DAY, AND TEMPERATURES THERE HAVE ONLY REACHED THE MID 60S AS
OF 10 AM.

&&

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDITIONS TO PERSIST
ACROSS THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A
SLIGHT CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF
THE FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS
ARE CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL
AIRMASS WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY
FLOW, BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT
THESE CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.

&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...HJS
AVIATION...GEELHART



000
FXUS63 KILX 281727
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1227 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 1034 AM CDT FRI AUG 28 2015

EXTENSIVE MID/HIGH CLOUD SHIELD HAS OVERSPREAD THE FORECAST AREA
IN CONJUNCTION WITH THE STORM SYSTEM TO OUR WEST. MUCH OF THE
RAIN IN IOWA WAS TRACKING TO THE EAST-NORTHEAST ON A TRAJECTORY
THAT WOULD PASS NORTH OF OUR FORECAST AREA. CONVECTION FURTHER
SOUTHWEST ALONG THE BOUNDARY, ACROSS NORTHWEST MISSOURI, IS MORE
LIKELY TO GET HERE LATER THIS EVENING. THEREFORE, HAVE NOT CHANGED
POP`S TOO MUCH, WHICH ORIGINALLY WERE CONFINED TO MAINLY SLIGHT
CHANCES. HOWEVER, HAVE BUMPED THEM UP A TAD AROUND GALESBURG, AS
THE SOUTHERN FLANK OF THE RAIN SHIELD IN SOUTHEAST IOWA MAY CLIP
THAT AREA IN A COUPLE HOURS. HAVE ALSO LOWERED TEMPERATURES BY A
DEGREE OR TWO MOST AREAS, BUT WILL HAVE TO MONITOR THE NORTHWEST
CWA CLOSELY AS THE THICKER CLOUD COVER WILL PERSIST THERE THROUGH
THE DAY, AND TEMPERATURES THERE HAVE ONLY REACHED THE MID 60S AS
OF 10 AM.

&&

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDITIONS TO PERSIST
ACROSS THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A
SLIGHT CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF
THE FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS
ARE CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL
AIRMASS WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY
FLOW, BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT
THESE CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.

&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...HJS
AVIATION...GEELHART




000
FXUS63 KLOT 281724
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1224 PM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB


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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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:
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000
FXUS63 KLOT 281724
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1224 PM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB


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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 281724
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1224 PM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB


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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 281724
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1224 PM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EAST-SOUTHEASTERLY LIKELY EARLY THIS EVENING.
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING.
  SLIGHTLY BETTER CHANCE OF THUNDER SATURDAY AFTERNOON.

KJB

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

AN ATMOSPHERIC DISTURBANCE...CURRENTLY DRIVING AN AREA OF SHOWERS
AND EMBEDDED STORMS OVER IOWA...WILL GRADUALLY SHIFT EASTWARD
TONIGHT. HOWEVER...IT APPEARS THE MAIN FOCUS FOR SHOWERS AND ANY
STORMS MAY LARGELY REMAIN NORTH OF THE EASTERN TERMINALS...ACROSS
FAR NORTHERN ILLINOIS AND INTO WISCONSIN. BETTER CHANCES OF MORE
SUBSTANTIAL SHOWERS LOOKS TO ENTER THE PICTURE AFTER DAYBREAK
SATURDAY...AND CONTINUING AT TIMES INTO THE AFTERNOON. IT APPEARS
THE THUNDER THREAT WILL BE LOW WITH MUCH OF THIS ACTIVITY.
HOWEVER...THERE WILL BE A SLIGHT BETTER CHANCE OF THUNDER SUNDAY
AFTERNOON AS A FRONTAL ZONE SAGS SOUTHEASTWARD OVER THE AREA.
GIVEN THIS...I HAVE OPTED TO ADD A PROB30 FOR A PERIOD OF THUNDER
LATER SATURDAY AFTERNOON AT THE END OF THE 30 HOUR ORD TAF.

KJB


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

* HIGH WITH WIND SHIFT TO SOUTHEAST THIS EVENING...LOW WITH PRECISE
  SPEEDS AND TIMING.
* MEDIUM WITH PRECIP CHANCES/TIMING...ESPECIALLY SATURDAY
  MORNING/EARLY AFTERNOON.
* LOW WITH THREAT OF THUNDER DURING THE PERIOD.
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS.

KJB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 281602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1102 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI/KB

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW-MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 281534
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1034 AM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 1034 AM CDT FRI AUG 28 2015

EXTENSIVE MID/HIGH CLOUD SHIELD HAS OVERSPREAD THE FORECAST AREA
IN CONJUNCTION WITH THE STORM SYSTEM TO OUR WEST. MUCH OF THE
RAIN IN IOWA WAS TRACKING TO THE EAST-NORTHEAST ON A TRAJECTORY
THAT WOULD PASS NORTH OF OUR FORECAST AREA. CONVECTION FURTHER
SOUTHWEST ALONG THE BOUNDARY, ACROSS NORTHWEST MISSOURI, IS MORE
LIKELY TO GET HERE LATER THIS EVENING. THEREFORE, HAVE NOT CHANGED
POP`S TOO MUCH, WHICH ORIGINALLY WERE CONFINED TO MAINLY SLIGHT
CHANCES. HOWEVER, HAVE BUMPED THEM UP A TAD AROUND GALESBURG, AS
THE SOUTHERN FLANK OF THE RAIN SHIELD IN SOUTHEAST IOWA MAY CLIP
THAT AREA IN A COUPLE HOURS. HAVE ALSO LOWERED TEMPERATURES BY A
DEGREE OR TWO MOST AREAS, BUT WILL HAVE TO MONITOR THE NORTHWEST
CWA CLOSELY AS THE THICKER CLOUD COVER WILL PERSIST THERE THROUGH
THE DAY, AND TEMPERATURES THERE HAVE ONLY REACHED THE MID 60S AS
OF 10 AM.

&&

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDITIONS TO PERSIST
ACROSS THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A
SLIGHT CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF
THE FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS
ARE CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL
AIRMASS WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY
FLOW, BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT
THESE CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.


&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK




000
FXUS63 KILX 281534
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1034 AM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 1034 AM CDT FRI AUG 28 2015

EXTENSIVE MID/HIGH CLOUD SHIELD HAS OVERSPREAD THE FORECAST AREA
IN CONJUNCTION WITH THE STORM SYSTEM TO OUR WEST. MUCH OF THE
RAIN IN IOWA WAS TRACKING TO THE EAST-NORTHEAST ON A TRAJECTORY
THAT WOULD PASS NORTH OF OUR FORECAST AREA. CONVECTION FURTHER
SOUTHWEST ALONG THE BOUNDARY, ACROSS NORTHWEST MISSOURI, IS MORE
LIKELY TO GET HERE LATER THIS EVENING. THEREFORE, HAVE NOT CHANGED
POP`S TOO MUCH, WHICH ORIGINALLY WERE CONFINED TO MAINLY SLIGHT
CHANCES. HOWEVER, HAVE BUMPED THEM UP A TAD AROUND GALESBURG, AS
THE SOUTHERN FLANK OF THE RAIN SHIELD IN SOUTHEAST IOWA MAY CLIP
THAT AREA IN A COUPLE HOURS. HAVE ALSO LOWERED TEMPERATURES BY A
DEGREE OR TWO MOST AREAS, BUT WILL HAVE TO MONITOR THE NORTHWEST
CWA CLOSELY AS THE THICKER CLOUD COVER WILL PERSIST THERE THROUGH
THE DAY, AND TEMPERATURES THERE HAVE ONLY REACHED THE MID 60S AS
OF 10 AM.

&&

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDITIONS TO PERSIST
ACROSS THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A
SLIGHT CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF
THE FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS
ARE CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL
AIRMASS WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY
FLOW, BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT
THESE CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.


&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK



000
FXUS63 KLOT 281400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI/KB

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW-MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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:
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000
FXUS63 KLOT 281400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI/KB

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW-MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 281400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI/KB

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW-MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KB

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 281144
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
644 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.

&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK



000
FXUS63 KILX 281144
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
644 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.

&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK




000
FXUS63 KILX 281144
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
644 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.

&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK



000
FXUS63 KILX 281144
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
644 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 644 AM CDT FRI AUG 28 2015

A SLOW MOVING WEATHER SYSTEM WILL APPROACH THE CENTRAL ILLINOIS
TERMINALS FROM THE WEST DURING THE 12Z TAF VALID TIME. WHILE
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED, A GRADUAL THICKENING
AND LOWERING OF THE CLOUD DECK IS ANTICIPATED. MOST LOCAL
TERMINALS SHOULD REMAIN DRY, BUT A FEW SHOWERS OR STORMS CAN`T BE
RULED OUT AT KPIA BEFORE THE END OF THE PERIOD. WINDS WILL
GENERALLY BE SOUTH TO SOUTHEAST AHEAD OF THE APPROACHING SYSTEM,
WITH A FEW GUSTS INTO THE TEENS DURING PEAK DIURNAL HEATING.

&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...BAK




000
FXUS63 KLOT 281139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW- MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 281139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW- MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 281139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE THIS AFTERNOON
* CHANCE OF SHRA/SLIGHT CHANCE OF TS TONIGHT INTO SAT MORNING

IZZI

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

A SLOW MOVING STORM SYSTEM OVER IOWA WILL WEAKEN AS IT MOVES
CLOSER TO THE REGION TONIGHT INTO SATURDAY. AREA OF SHOWERS AND
ISOLD TSRA OVER IOWA WILL CONTINUE TO INCH EASTWARD BUT PROGRESS
SHOULD BE SLOW AND LEADING EDGE COULD ERODE SOME IN DRIER AIR MASS
OVER OUR REGION WITH FOCUS INITIALLY LIKELY MORE INTO WISCONSIN.
WITH TIME THE SHOWERS AND PERHAPS A TS OR TWO WILL SAG SOUTH INTO
N IL TONIGHT (MAINLY LATE) INTO SAT MORNING. SOME GUIDANCE
SUGGESTS PRECIP WILL BE DECREASING IN COVERAGE/INTENSITY BY THIS
TIME...LENDING TO SOME UNCERTAINTIES IN HOW TO BEST CONVEY THREAT
IN TAFS. OTHER THAN PRECIP...WHICH COULD POSSIBLY RESULT IN SOME
MVFR CIGS BY SAT MORNING...ONLY OTHER CONCERN WILL BE WINDS THIS
AFTERNOON AND EVENING. INITIALLY LIGHT SOUTHERLY WINDS WILL LIKELY
SHIFT TO EASTERLY LATE THIS AFTERNOON...POSSIBLY ENHANCED BY LAKE
IN CHGO TERMINALS. COULD SEE A BRIEF PERIOD OF 10-12KT WINDS BUT
SUSPECT WINDS WILL LARGELY END UP JUST BELOW 10KT FROM EASTERLY
DIRECTION THROUGH TONIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATER THIS
  AFTERNOON...LOW- MEDIUM CONFIDENCE IN PRECISE SPEEDS AND TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...VFR. NORTHEAST WINDS.

MONDAY THROUGH THURSDAY...VFR. SOUTHERLY WINDS...POSSIBLE
AFTERNOON WIND SHIFTS TO EASTERLY WITH LAKE BREEZES EACH
AFTERNOON.

IZZI

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280943
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
443 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

A FEW SPRINKLES BRIEF LIGHT SHRA COULD IMPACT MAINLY RFD DURING
PREDAWN HOURS.

IZZI

UPDATED 06Z...

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280943
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
443 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

A FEW SPRINKLES BRIEF LIGHT SHRA COULD IMPACT MAINLY RFD DURING
PREDAWN HOURS.

IZZI

UPDATED 06Z...

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 280845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280845
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
345 AM CDT FRI AUG 28 2015

.SHORT TERM...
344 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PRECIP TRENDS LATER
TODAY INTO TONIGHT...AND INTO THE WEEKEND.

LATEST SATELLITE IMAGERY DEPICTING UPPER LEVEL WITH SEVERAL VORT
LOBES ROUNDING THE BASE...PROGRESSING EAST THROUGH THE NORTHERN
PLAINS EARLY THIS MORNING. ALTHOUGH ASSOCIATED PRECIP REMAINS WELL
WEST OF THE CWA AT THIS TIME...FAIRLY DENSE MID/HIGH LEVEL CLOUD
COVER ALREADY STRETCHING EAST INTO NORTHERN ILLINOIS. RADAR
IMAGERY SHOWING SOME WEAK RETURNS AT THIS TIME...HOWEVER...THIS IS
PICKING UP THESE CLOUDS WITH ANY PRECIP LIKELY NOT MAKING IT TO
THE SURFACE. HAVE MAINTAINED A DRY FORECAST EARLY THIS MORNING
THROUGH MIDDAY FOR THE ENTIRE CWA AS STRONGEST FORCING WITH THE
FIRST WAVE LIFTING EAST/NORTHEAST STAYING TO THE WEST/NORTHWEST.
SOME GUIDANCE IS TRYING TO HINT AT SOME STRAY LIGHT SHOWERS OVER
PORTIONS OF NORTHERN ILLINOIS THIS MORNING BUT WITH RATHER DRY LOW
LEVELS IN PLACE THIS MORNING...PER 00Z OBSERVED SOUNDINGS AND
LATEST FORECAST SOUNDINGS...THINK ANY FORCING OWING TO WEAK WAA
WILL NOT BE ABLE TO OVERCOME THIS DRIER AIR. DO BRING SLIGHT
CHANCE TO CHANCE POPS OVER FAR NORTHERN ILLINOIS BY MID TO LATE
AFTERNOON TODAY AS THIS MID/UPPER LEVEL TROUGH AND ASSOCIATED
ENERGY MOVE CLOSER TO THE CWA...BUT ONCE AGAIN FEEL THAT THE BEST
FORCING WILL STILL BE TO THE NORTH AND NORTHWEST. HAVE MAINTAINED
SHOWERS AND DID NOT INCLUDE THUNDER...WITH INSTABILITY STAYING TO
THE WEST OF THE CWA. HIGH TEMPERATURES WILL BE LIMITED TODAY DUE
TO THE MID/HIGH CLOUDS IN THE 70S...AND DID LOWER THEM SLIGHTLY TO
THE LOW/MID 70S ACROSS NORTHERN ILLINOIS WHERE MORE DENSE CLOUDS
AND PRECIP WILL LIKELY BE LOCATED.

HIGHER CHANCES FOR PRECIP WILL ARRIVE LATER THIS EVENING AND
ESPECIALLY OVERNIGHT TONIGHT FOR MOST OF NORTHERN ILLINOIS...AS
SHORTWAVE ENERGY ON THE BACKSIDE OF THIS TROUGH AND ATTENDANT
SURFACE REFLECTION WILL PUSH INTO NORTHERN ILLINOIS. DID MAINTAIN
SLIGHT CHANCE FOR THUNDER WITH THE LIKELY/CAT POPS OVER NORTHERN
ILLINOIS TONIGHT...DESPITE LACKING INSTABILITY. STRENGTHENING LLJ
AND STRONGER FORCING COULD OFFSET THIS LACKING INSTABILITY AND
ALLOW THUNDER...SIMILAR TO WHAT IS OCCURRING NOW OVER IOWA. EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA WONT OBSERVE THE HIGHER
CHANCES FOR SHOWERS/THUNDER UNTIL SATURDAY MORNING AND SATURDAY AS
THIS TROUGH PUSHES THROUGH. CONFIDENCE WITH OVERALL PRECIP TRENDS
ON SATURDAY AND SATURDAY NIGHT DOES LOWER WITH GUIDANCE VARYING TO
THE EXTENT AND LOCATION OF BEST FORCING. DID MAINTAIN HIGH CHANCE
POPS FOR SHOWERS ACROSS MUCH OF THE CWA SATURDAY AND THEN TOOK
THESE CHANCE POPS EASTWARD THROUGH TIME DURING SATURDAY NIGHT.
INSTABILITY WILL TRY TO INCREASE ON SATURDAY...BUT STILL THINK IT
WONT BE HIGH ENOUGH TO WARRANT ANY WORDING OTHER THAN SLIGHT
CHANCE.

RODRIGUEZ

&&

.LONG TERM...
344 AM CDT

SUNDAY THROUGH THURSDAY...

END OF THE WEEKEND INTO THE START OF NEXT WEEK WILL SEE THIS
MID/UPPER TROUGH SLOWLY EXITING TO THE EAST...WITH CLOUDS AND
PRECIP CHANCES LIKEWISE EXITING DURING THE DAY SUNDAY. GUIDANCE
VARIES TO THE EVOLUTION OF THIS EXITING SYSTEM BUT LIKELY SCENARIO
FOR OUR AREA WILL BE FOR UPPER LEVEL RIDGING WITH WEAKER FLOW
ALOFT. CONDITIONS WILL LIKELY BE ON THE DRY SIDE THROUGH EARLY
NEXT WEEK...OUTSIDE OF SOME POSSIBLE AFTERNOON THUNDERSTORMS ON
TUESDAY DUE TO INCREASING MOISTURE/INSTABILITY...WHILE A WARMING
TREND CONTINUES.

RODRIGUEZ

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 280828
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
328 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHTS TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.


&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...SHIMON



000
FXUS63 KILX 280828
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
328 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHTS TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.


&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...SHIMON




000
FXUS63 KILX 280828
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
328 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHTS TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.


&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...SHIMON



000
FXUS63 KILX 280828
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
328 AM CDT FRI AUG 28 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDTIONS TO PERSIST ACROSS
THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A SLIGHT
CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF THE
FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS ARE
CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL AIRMASS
WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY FLOW,
BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT THESE
CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

&&

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHTS TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.


&&

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

$$

SHORT TERM...BAK
LONG TERM...HJS
AVIATION...SHIMON




000
FXUS63 KLOT 280657
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
157 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTURBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. SATURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIRONMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPECIALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGGRESSIVE MODEL WITH REGARDS TO THE
LOWER LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR
AN EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW
90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280657
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
157 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTURBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. SATURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIRONMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPECIALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGGRESSIVE MODEL WITH REGARDS TO THE
LOWER LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR
AN EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW
90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 280657
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
157 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTURBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. SATURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIRONMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPECIALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGGRESSIVE MODEL WITH REGARDS TO THE
LOWER LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR
AN EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW
90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 280657
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
157 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTURBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. SATURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIRONMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPECIALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGGRESSIVE MODEL WITH REGARDS TO THE
LOWER LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR
AN EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW
90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
157 AM CDT

FAIRLY TYPICAL SUMMER PATTERN LIKELY TO PERSIST THROUGH THE
UPCOMING WEEK WITH GENERALLY NO SIGNIFICANT WINDS/WAVES
ANTICIPATED. WEAK SURFACE LOW OVER THE CORN BELT WILL TRACK SLOWLY
EAST INTO NORTHERN ILLINOIS/SOUTHERN WISCONSIN THROUGH SATURDAY
BEFORE DISSIPATING. THE MAIN RESULT WILL BE A BACKING OF WINDS TO
EASTERLY OVER SOUTHERN PORTIONS OF THE LAKE LATER TODAY INTO THIS
EVENING BEFORE VEERING SOUTHERLY AGAIN LATE TONIGHT AND FRESHENING
UP JUST A BIT...BUT LIKELY LESS THAN 20KT.

IZZI

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280543
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1243 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 280543
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1243 AM CDT FRI AUG 28 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO EASTERLY LIKELY LATE FRIDAY AFTERNOON
* CHANCE OF -SHRA/SLIGHT CHANCE OF TS FRIDAY NIGHT

IZZI

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

VFR WITH LIGHT WINDS THROUGH FRIDAY MORNING AS SLOW MOVING STORM
SYSTEM OVER NEBRASKA/WESTERN IOWA SLOWLY MOVES TOWARD REGION.
PRESSURE FALLS IN ADVANCE OF THIS SYSTEM SHOULD CAUSE INITIALLY
SOUTH-SOUTHWEST WINDS FRIDAY TO BACK MORE EASTERLY WITH LAKE
INFLUENCE LIKELY RESULTING IN A MORE DRAMATIC SHIFT TO EASTERLY
FOR CHICAGO TERMINALS. CERTAINLY PLAUSIBLE THAT THERE COULD BE A
PERIOD OF 10-12KT EASTERLY WINDS...PARTICULARLY WITHIN AN HOUR OR
SO OF THE WIND SHIFT...BUT CLOUD COVER AND WEAKER THERMAL GRADIENT
LEAD ME TO BELIEVE THAT IF EASTERLY WINDS REACH PREVAILING 10KT IT
WON`T LAST LONG OR MORE LIKELY JUST A PERIOD OF A COUPLE HOURS OF
OCNL 10KT WINDS. THREAT OF SHOWERS AND PERHAPS ISOLATED TSRA WILL
SLOWLY INCREASE FROM THE WEST/NORTHWEST FRIDAY NIGHT.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO EAST LATE FRIDAY...LOW-MEDIUM
  CONFIDENCE IN SPEEDS AND PRECISE TIMING
* MEDIUM CONFIDENCE IN PRECIP CHANCES/TIMING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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:
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000
FXUS63 KILX 280447
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1147 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON




000
FXUS63 KILX 280447
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1147 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1147 PM CDT THU AUG 27 2015

VFR CONDITIONS SHOULD PREVAIL FOR THE MAJORITY OF THIS VALID TAF
PERIOD THROUGH 06Z SAT. HIGH PRESSURE IS DEPARTING SLOWLY TO THE
EAST, WHILE A LOW PRESSURE SYSTEM OVER EASTERN NEBRASKA
APPROACHES. THE LOW IS EXPECTED TO REACH NORTHEAST IOWA BY FRIDAY
EVENING. LIGHT EAST-SOUTHEAST WIND THE REST OF TONIGHT WILL BECOME
MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO TIGHTEN
AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 16KT OR HIGHER FRIDAY AFTERNOON.

AS FOR CLOUDS, SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT OVERNIGHT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND
FOG LATE TONIGHT INTO FRIDAY MORNING BUT OVERALL EFFECTS WILL BE
MINIMAL AT ANY TAF LOCATION.

RAIN CHANCES WILL HOLD OFF TOMORROW, AS MID AND HIGH CLOUDS
CONTINUE TO THICKEN DURING THE AFTERNOON. A VCSH WAS INCLUDED AT
PIA AFTER 04Z, BASED ON FORECAST SOUNDINGS IN THE SHORT TERM
MODELS. BETTER CHANCES OF RAIN SHOULD COME AFTER THIS TAF VALID
PERIOD.

&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON



000
FXUS63 KILX 280359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1059 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON




000
FXUS63 KILX 280359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1059 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON



000
FXUS63 KILX 280359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1059 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON




000
FXUS63 KILX 280359
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1059 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1051 PM CDT THU AUG 27 2015

HIGH PRESSURE WILL KEEP QUIET WEATHER THROUGH THE NIGHT. HIGH
CLOUDS WILL DRIFT INTO ILLINOIS, BUT SKIES SHOULD REMAIN MOSTLY
CLEAR THROUGH SUNRISE. LIGHT FOG WILL BE POSSIBLE IN AREAS THAT
REMAIN CLEAR ALL NIGHT, UNDER LIGHT WINDS. HOWEVER, FOG SHOULD NOT
BE A MAJOR CONCERN FOR TRAVEL. LOW TEMPS LOOK ON TRACK, AS DOES
THE REST OF THE OVERNIGHT FORECAST. UPDATED INFO IS ALREADY
AVAILABLE.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.


&&

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

$$

UPDATE...SHIMON
SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON



000
FXUS63 KLOT 280304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST AROUND 10 KT FRIDAY
  AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC

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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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:
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000
FXUS63 KLOT 280304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST AROUND 10 KT FRIDAY
  AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC

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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 280304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST AROUND 10 KT FRIDAY
  AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC

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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 280304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST AROUND 10 KT FRIDAY
  AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC

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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 280018
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
717 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON



000
FXUS63 KILX 280018
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
717 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON




000
FXUS63 KILX 280018
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
717 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON



000
FXUS63 KILX 280018
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
717 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 717 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. LIGHT
SOUTHEAST WINDS EARLY THIS EVENING WILL BECOME LIGHT OVERNIGHT, THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE TO
10-14KTS BY 16Z, THEN GUST TO 18KT OR HIGHER FRIDAY AFTERNOON.

SCT CU IN THE 3-4KFT RANGE WILL LINGER FOR A COUPLE HOURS THIS
EVENING, THEN SCT MID-HIGH CLOUDS WILL FILTER INTO IL ON NW FLOW
ALOFT. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME DUE TO QUESTIONS ON HOW MUCH HIGH CLOUDS
WILL BE ACROSS THE AREA LATE TONIGHT, SO NO MENTION WITH THIS
FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...SHIMON




000
FXUS63 KLOT 272348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT DIMINISHING THIS HOUR.

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST FRIDAY AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC


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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 272348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT DIMINISHING THIS HOUR.

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST FRIDAY AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC


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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 272348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
648 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* EAST WINDS AROUND 10 KT DIMINISHING THIS HOUR.

* SOUTH WINDS SHIFTING TO EAST-SOUTHEAST FRIDAY AFTERNOON.

* CHANCE OF SHRA LATE FRIDAY AFTERNOON THROUGH FRIDAY EVENING.

RC

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

AREA REMAINS INFLUENCED BY HIGH PRESSURE CENTERED OVER CENTRAL AND
EASTERN GREAT LAKES. THE HIGH PRESSURE WILL SLIDE EAST ON FRIDAY
AS WEAKENING LOW PRESSURE SLOWLY MOVES ACROSS IOWA. EAST WINDS
BEHIND LAKE BREEZE WILL DIMINISH QUICKLY THIS EVENING AND TURN
LIGHT SOUTH OVERNIGHT. SOUTH WINDS WILL TURN SOUTHEAST TO EAST-
SOUTHEAST DURING FRIDAY AFTERNOON...POSSIBLY WITH SOME LAKE
INFLUENCE AND SPEEDS ARE EXPECTED TO BE AROUND OR SLIGHTLY OVER 10
KT.

PRIMARILY VFR CIGS ARE EXPECTED THROUGH THE PERIOD...THOUGH SOME
GUIDANCE INDICATES A PERIOD OF HIGH END MVFR CIGS FRIDAY MORNING.
ALSO MVFR BR IS POSSIBLE MAINLY AT DPA LATE TONIGHT INTO EARLY
FRIDAY. AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOW
PRESSURE WILL FOCUS BEST FORCING FOR PRECIP INTO SOUTHERN
WISCONSIN FRIDAY AFTERNOON. A FEW ISOLATED OR SCATTERED SHRA
CANNOT BE RULED OUT...ESPECIALLY AT RFD...BUT HAVE MAINTAINED A
DRY TAF THERE DUE TO LOW CONFIDENCE. BETTER CHANCE FOR SHRA AT ORD
LOOKS TO ARRIVE MAINLY AFTER 06Z TOMORROW NIGHT INTO SATURDAY AT
ORD...SO ALSO HAVE A DRY FORECAST IN ORD 30-HR TAF. THE CHANCE FOR
ANY THUNDER WITH THIS SYSTEM APPEARS TO BE LOW.

RC


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

* HIGH IN WIND TRENDS THROUGH FRIDAY MORNING...MEDIUM FRIDAY
  AFTERNOON AND EVENING.

* LOW IN SHRA AT TERMINALS FRIDAY AFTERNOON AND EVENING.

RC

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

SATURDAY...A FEW PERIODS OF SHRA PROBABLE AND ASSOCIATED VSBY
IMPACTS. SLIGHT CHANCE OF TSRA. VFR CIGS LIKELY.

SUNDAY...PRIMARILY VFR...SLIGHT CHANCE OF SHRA. NORTH TO NORTHEAST
WINDS.

MONDAY THROUGH WEDNESDAY...VFR. AFTERNOON WIND SHIFTS TO EAST-
SOUTHEAST POSSIBLE.

RC

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 272154
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
454 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* EAST WINDS OF 10-12 KT THROUGH EARLY EVENING.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON.

RC

//DISCUSSION...UPDATED 22Z...

WINDS INCREASED TO OVER 10 KT OUT OF THE EAST AT ORD/MDW BEHIND
THE LAKE BREEZE. BASED OFF AIRCRAFT SOUNDINGS AND MODEL
SOUNDINGS...EXPECT THE PREVAILING 10+ KT SPEEDS TO END BY 00-01Z.

RC

FROM 18Z...

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM IN END TIME OF PREVAILING 10+ WINDS THIS EVENING...AND
  MEDIUM IN FORECAST THROUGH THE REST OF THE PERIOD.

RC

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 272154
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
454 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* EAST WINDS OF 10-12 KT THROUGH EARLY EVENING.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON.

RC

//DISCUSSION...UPDATED 22Z...

WINDS INCREASED TO OVER 10 KT OUT OF THE EAST AT ORD/MDW BEHIND
THE LAKE BREEZE. BASED OFF AIRCRAFT SOUNDINGS AND MODEL
SOUNDINGS...EXPECT THE PREVAILING 10+ KT SPEEDS TO END BY 00-01Z.

RC

FROM 18Z...

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM IN END TIME OF PREVAILING 10+ WINDS THIS EVENING...AND
  MEDIUM IN FORECAST THROUGH THE REST OF THE PERIOD.

RC

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 272005
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 272005
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
256 PM CDT

SATURDAY NIGHT THROUGH THURSDAY...

FOCUS ON THE EXTENDED IS FOR WEEKEND PRECIPITATION CHANCES/LINGERING
CLOUD COVER AND IMPACT ON TEMPERATURES...THEN SHIFTING TO AN
EXTENDED PERIOD OF WARM AND DRY CONDITIONS.

AT THE START OF THE PERIOD...THE LEADING UPPER
DISTURBANCE...EMANATING FROM COLORADO...WILL HAVE LIFTED NORTH AND
EAST OF THE AREA. TRAILING ENERGY FROM WYOMING WILL STILL CREATE
SOME LIFT IN THE MORNING...IN ADDITION TO A NORTHERN STREAM PACIFIC
SHORTWAVE ENERGY MOVING INTO THE BACK SIDE OF THE SLOW MOVING UPPER
LOW WHICH WILL KEEP PRECIPITATION CHANCES IN THE FORECAST FOR
SATURDAY AFTERNOON. CONFIDENCE ON THE DETAILS IS A BIT LIMITED AT
THIS POINT AS THERE IS STILL QUITE A BIT OF MODEL UNCERTAINTY AS TO
WHAT DEGREE THESE DISTURBANCES INTERACT AND THEIR TIMING. THE
INTERACTION OF THESE DISTUBBANCES ARE ALSO PLAYING HAVOC ON HOW
QUICKLY THE ASSOCIATED SURFACE LOW MOVES THROUGH...AND MORE
SPECIFICALLY PRECIPITATION CHANCES DURING THE AFTERNOON
SATURDAY...AS IF THE SURFACE BOUNDARY LINGERS...LOW LEVEL
CONVERGENCE AND MOIST UNSTABLE ENVIRONMENT MAY PROMOTE THE
REDEVELOPMENT OF THUNDERSTORMS SATURDAY AFTERNOON AFTER THE MAIN
UPPER FORCING DEPARTS.

EITHER WAY...MOST GUIDANCE SUGGEST SOME DEGREE OF UPPER LEVEL
TROUGHING SATURDAY NIGHT INTO SUNDAY..THOUGH MUCH WEAKER THEN ON
SATURDAY. STURDAY NIGHT INTO SUNDAY MORNING LOOKS TO BE A QUIET
PERIOD. THERE COULD BE SOME LINGERING CLOUDINESS OR MAY SOME LIGHT
RAIN SHOWERS...ESPECIALLY CLOSER TO LAKE MICHIGAN. WE WILL STILL
HAVE A FAIRLY MOIST ENVIORNMENT IN THE WARM SECTOR AHEAD OF THE
SURFACE LOW WHERE SOME SHOWERS AND THUNDERSTORMS REMAIN
POSSIBLE...ESPEICALLY GIVEN THE WPC PREFERENCE FOR A SOLUTION
PROGRESSION OF THE LOW. LOW CONFIDENCE EXISTS NONETHELESS...WITH
AREAS SOUTH AND EAST FAVORED FOR ANY ADDITIONAL PRECIPITATION.

MODELS ARE IN VERY GOOD AGREEMENT WITH REGARDS TO THE EXPANSION OF
THE UPPER RIDGE IN THE WEST OVER MUCH OF THE EASTERN TWO THIRDS OF
THE COUNTY. THIS WILL BE ESPECIALLY TRUE FOR MUCH OF THE NATIONS
HEARTLAND...WHILE THE SOUTH AND THE EAST COAST MAY FEEL SOME IMPACTS
FROM TROPICAL STORM ERIKA AND AN ADDITIONAL CUT OFF LOW IN THE GULF
OF MEXICO.

THE ECMWF REMAINS THE MORE AGREESIVE MODEL WITH REGARDS TO THE LOWER
LEVEL WARMING...BUT BOTH MODELS IN VERY GOOD AGREEMENT FOR AN
EXTENDED PERIOD OF HIGH TEMPERATURES IN THE UPPER 80S TO LOW 90S
...AND IF THE WARMER ECMWF VERIFIES...BEGINNING TUESDAY...AFTER A
TRANSITION DAY OF MID 80S ON MONDAY. ENSEMBLE TEMPERATURE
ANOMALIES ARE STILL ONLY IN THE 2 STANDARD DEVIATION ABOVE NORMAL
CATEGORY...BASED ON THE MORE TEMPERED GFS...AND FORTUNATELY
DEWPOINTS LOOK TO PEAK IN THE MID 60S...RESULTING IN HEAT INDICES
IN THE UPPER 80S TO LOW 90S. WITH A WEAK LOW LEVEL WIND COMPONENT
AND THE SURFACE HIGH FOCUSED TO OUR EAST...ONSHORE FLOW AT TIMES
WILL KEEP AFTERNOON CONDITIONS COOLER AT THE LAKEFRONT.

KMD

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
256 PM CDT

HIGH PRESSURE EAST OF LAKE MICHIGAN WILL CONTINUE EAST TONIGHT...AS
LOW PRESSURE OVER THE CNETRAL PLAINS DEEPENS AND MOVES INTO IOWA
FRIDAY AFTERNOON. THE LOW WILL SLOW ITS EASTWARD PROGRESS AS THE
RIDGE AXIS ASSOCAITED WITH THE DEPARTING HIGH EXTENDS BACK
NORTHWESTWARD TO THE NORTHERN LAKES.  AS THE LOW APPROACHES FRIDAY
NIGHT...A PERIOD OF GUSTY EAST THEN SOUTHEAST WINDS WILL SETUP
ACROSS THE SOUTHERN HALF OF THE LAKE...POSSIBLY APPROACHING 25 KT.
THE LOW WILL PASS OVER THE SOUTHERN TIP OF LAKE MICHIGAN LATER
SATURDAY INTO EARLY SUNDAY AND WEAKEN. HIGH PRESSURE WILL THEN TAKE
CONTROL OF THE EASTERN THIRD OF THE COUNTRY FOR MOST OF THE UPCOMING
WEEK...WITH LOW PRESSURE REMAINING IN THE CENTRAL HIGH PLAINS.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 271952
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
252 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...CMS



000
FXUS63 KILX 271952
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
252 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...CMS



000
FXUS63 KILX 271952
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
252 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...CMS



000
FXUS63 KILX 271952
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
252 PM CDT THU AUG 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 220 PM CDT THU AUG 27 2015

FOR TONIGHT...WEATHER WILL REMAIN QUIET ACROSS THE REGION AS A
LARGE AREA OF HIGH PRESSURE CENTERED OVER THE EASTERN GREAT LAKES
SLOWLY MOVES OFF TO THE EAST AND LOW PRESSURE DEEPENS OVER THE
CENTRAL PLAINS. THE DIURNAL CUMULUS SHOULD LARGELY DISSIPATE AT
SUNSET...BUT SOME MID AND HIGH CLOUD FROM ONGOING THUNDERSTORM
ACTIVITY OVER THE CENTRAL PLAINS WILL BEGIN TO OVERSPREAD THE
REGION TONIGHT. AS THE SURFACE PATTERN PROGRESSES...LOW LEVEL
FLOW WILL BECOME MORE SOUTHERLY...ALLOWING DEWPOINTS TO INCH A
LITTLE HIGHER OVERNIGHT. THE INCREASING MID AND HIGH CLOUD...
COMBINED WITH WINDS REMAINING AROUND 5 MPH OR SO OVERNIGHT SHOULD
PREVENT TEMPERATURES FROM DROPPING QUITE AS LOW AS LAST NIGHT DUE
TO REDUCED RADIATIONAL COOLING. OVERNIGHT LOWS SHOULD BE IN THE
MIDDLE TO UPPER 50S. HIGHER DEWPOINT DEPRESSIONS AND SOME
BREEZINESS SHOULD PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...
EXPECT PERHAPS IN SOME ISOLATED...SHELTERED AREAS.

.LONG TERM...(FRIDAY THROUGH THURSDAY)
ISSUED AT 220 PM CDT THU AUG 27 2015

THE TREND THROUGH THE LONGER TERM FORECAST PERIOD WILL BE FOR
INCREASING TEMPERATURES AND THE ONLY SIGNIFICANT CHANCE FOR PCPN
WILL BEGIN BY FRIDAY AFTERNOON OR EVENING AS THE SHORTWAVE
RESPONSIBLE FOR THE ONGOING CONVECTION OVER THE CENTRAL PLAINS
TRACKS ACROSS IOWA AND THROUGH THE UPPER MISSISSIPPI VALLEY AND
INTO SWRN WISCONSIN BY FRIDAY EVENING. INCREASING MOISTURE AND
INSTABILITY IN THE AIRMASS AHEAD OF A TRAILING COLD FRONT WILL AID
THE DEVELOPMENT OF SHOWERS AND SCATTERED THUNDERSTORMS AS THE
BOUNDARY SLOWLY SAGS THROUGH NWRN IL BY SATURDAY MORNING. THE
PROGRESSION OF THE MID LEVEL SHORTWAVE IS EXPECTED TO SLOW AND
BECOME ALMOST STATIONARY OVER THE WESTERN GREAT LAKES REGION AS
ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY PHASES WITH THE
INITIAL WAVE...ALLOWING THE FRONTAL BOUNDARY TO BECOME A MORE
EAST-WEST ORIENTED QUASI-STATIONARY FRONT ACROSS CNTRL IL. THE
LATEST GUIDANCE SUGGESTS THAT THE BOUNDARY WILL BE RELATIVELY
DIFFUSE...LIMITING SFC FORCING ACROSS CNTRL IL WHILE THE GREATEST
UPPER LEVEL FORCING REMAINS WELL TO THE NORTH OVER NRN IL/SRN
WI/SRN LAKE MICHIGAN. SO...WHILE THERE IS RELATIVELY HIGH
CONFIDENCE IN AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE WEEKEND...FEEL THAT THE LACK OF WELL DEFINED FORCING
MECHANISMS SHOULD KEEP ACTIVITY ILL-DEFINED AND GENERALLY
SCATTERED.

BY EARLY NEXT WEEK...THE NRN STREAM SHORTWAVE SHOULD MOVE OFF TO
THE EAST WHILE THE SOUTHERN PORTION OF THE UPPER LEVEL WAVE LAGS
BACK OVER SRN MO/IL/IN...PERHAPS KEEPING A SLIGHT CHANCE FOR
LINGERING SHOWERS OVER FAR SOUTHERN ILLINOIS. UPPER RIDGING
BUILDING ACROSS THE MIDWEST WILL HELP CONTINUE THE WARMING TREND
THROUGH NEXT WEEK WHILE ENDING ANY SGFNT PCPN CHANCES. EXPECT THAT
TEMPS COULD REACH THE UPPER 80S BY MONDAY AND LOWER 90S FOR
TUESDAY THROUGH THURSDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

SHORT TERM...KREIN
LONG TERM...KREIN
AVIATION...CMS



000
FXUS63 KLOT 271950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
225 AM CDT

SATURDAY THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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:
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WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 271950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT THU AUG 27 2015

.SHORT TERM...
246 PM CDT

THROUGH FRIDAY NIGHT...

TONIGHT...
VISIBLE IMAGERY THIS AFTERNOON SHOWS SOME FAIR WEATHER CUMULUS
CLOUDS ACROSS NORTHERN IL/NORTHWEST IN...WITH A CIRRUS SHIELD
ARRIVING OVERHEAD. THIS CIRRUS SHIELD WAS FROM THE AREA OF
SHOWERS/THUNDERSTORMS OVER THE CENTRAL PLAINS. WITH HIGH PRESSURE
CENTERED OVER THE REGION...THE EASTERN PROGRESSION OF PRECIP AND THE
LOW OVER THE CENTRAL PLAINS WILL BE SLOW TO MOVE. THIS WILL ALLOW
QUIET CONDITIONS TO LINGER TONIGHT...SO HAVE MAINTAIN A DRY
FORECAST. SKIES WILL STEADILY THICKEN OVERNIGHT AS THE LOW DRIFTS
EAST. EXPECT OVERNIGHT LOWS TO FALL INTO THE MID/UPR 50S ACROSS THE
BULK OF THE FORECAST AREA...WITH SOME AREAS CLOSER TO LAKE MICHIGAN
SEEING A LIGHT ONSHORE FLOW AND KEEPING TEMPS IN THE LOW 60S.

FRIDAY THROUGH FRIDAY NIGHT... DIFFERENCES AMONGST OPERATIONAL
SOLUTIONS LINGERS INTO FRI MORNING...WITH SOME OF THE HI-RES
SIMULATIONS ANTICIPATING AN AREA OF STORMS/RAIN TO PUSH EAST INTO
EASTERN IOWA THEN QUICKLY DECAY SHORTLY AFTER DAYBREAK FRI. GIVEN A
RATHER STABLE ENVIRONMENT OVER NORTHERN IL/NORTHWEST IN WITH
CONSIDERABLE CLOUD COVER...THIS APPEARS FAVORABLE TO OCCUR.
INSTABILITY DOES NOT LOOK TO EXPAND MUCH DURING THE LATE
MORNING/AFTERNOON HOURS...HOWEVER WITH SOME BETTER FORCING ARRIVING
IN THE MID-LVLS LATE MORNING/AFTERNOON...THIS MAY ALLOW FOR SOME
EMBEDDED THUNDER TO DEVELOP WITH THE SHORTWAVE AS IT APPROACHES THE
REGION. HAVE ONLY MADE MINOR ADJUSTMENTS TO THE PRECIP COVERAGE AND
TIMING.

ONE ITEM THAT MAY NEED FURTHER ADJUSTMENTS WILL BE HIGH TEMPS FOR
FRI...GIVEN THE THICKENING SOLAR SHIELDING. HAVE NUDGED TEMPS DOWN A
DEGREES INTO THE LOW/MID 70S FOR CENTRAL/NORTH AND UPR 70S ACROSS
THE FAR SOUTH. THERE MAY BE ENOUGH CLOUD COVER TO LIMIT
HEATING...AND KEEP TEMPS SEVERAL DEGREES COOLER IN THE UPR 60S TO
LOWER 70S.

PRECIP CHANCES WILL CONTINUE THRU FRI NIGHT...BUT WITH THE SHORTWAVE
LIFTING NORTHEAST ACROSS WISC...THE BEST PROBS FOR PRECIP WILL BE
FOCUSED TO OUR NORTH. HAVE REFLECTED THIS WITHIN THE CURRENT PRECIP
FORECAST WITH LOWER POPS FURTHER SOUTH. TEMPS FRI NIGHT WILL LIKELY
REMAIN MILD GIVEN THE THICK CLOUD COVER...WITH LOWS IN THE MID 60S.

BEACHLER

&&

.LONG TERM...
225 AM CDT

SATURDAY THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 271745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 271745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 271745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 271745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1245 PM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON.
* POSSIBLE LAKE BREEZE AND EASTERLY WINDS FRIDAY AFTERNOON. CMS

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

MAIN FORECAST CONCERN AND CHALLENGE WILL BE WIND DIRECTIONS THRU
THE PERIOD. WINDS ARE GENERALLY LIGHT SOUTHEASTERLY ACROSS THE
AREA EARLY THIS AFTERNOON WITH SPEEDS UNDER 10KTS THOUGH THERE IS
SOME VARIABILITY TO THE WIND DIRECTIONS. A LAKE BREEZE HAS FORMED
ACROSS FAR NORTHEAST IL. THIS LAKE BREEZE MAY TURN WINDS A BIT
MORE EASTERLY...IF IT MAKES IT TO ORD/MDW...BUT SPEEDS SHOULD
REMAIN UNDER 10KTS. SPEEDS WILL DIMINISH A BIT THIS EVENING WITH
SOUTHERLY WINDS EXPECTED FRIDAY MORNING. LOW PRESSURE OVER THE
PLAINS WILL MOVE TO NORTHEAST IA BY FRIDAY EVENING. THE GRADIENT
WILL TIGHTEN FRIDAY AFTERNOON WITH SOUTH/SOUTHEASTERLY WINDS
AROUND 10KTS FRIDAY AFTERNOON. ITS POSSIBLE A LAKE BREEZE WILL
REACH ORD/MDW MID/LATE FRIDAY AFTERNOON TURNING WINDS MORE TO THE
EAST/SOUTHEAST WITH THE POTENTIAL FOR 10KTS WITH THIS LAKE BREEZE.

ANY PRECIPITATION FROM THE APPROACHING LOW PRESSURE SHOULD BE
AFTER THE 30 HR ORD TAF AND PERHAPS EVEN AFTER 00Z AT RFD. SOME
LIGHT/SHALLOW GROUND FOG IS POSSIBLE OVERNIGHT INTO FRIDAY
MORNING. NOT EXPECTING ANYTHING TOO WIDESPREAD AND CONFIDENCE IS
LOW SO NO MENTION WITH THIS FORECAST.

CU/STRATOCU MAY BE SLOW TO SCATTER OUT ACROSS FAR NORTHEAST IL AND
NORTHWEST INDIANA THIS AFTERNOON BUT CIGS SHOULD REMAIN AT OR JUST
ABOVE 3KFT. CMS.

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 271724
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
1224 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...CMS




000
FXUS63 KILX 271724
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
1224 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...CMS



000
FXUS63 KILX 271724
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
1224 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...CMS




000
FXUS63 KILX 271724
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
1224 PM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1224 PM CDT THU AUG 27 2015

HIGH PRESSURE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY WILL
MOVE EAST TONIGHT AND FRIDAY AS LOW PRESSURE CURRENTLY OVER THE
CENTRAL PLAINS MOVES TO NORTHEAST IOWA BY FRIDAY EVENING. EAST/
SOUTHEAST WINDS THIS AFTERNOON WILL BECOME LIGHT TONIGHT THEN
BECOME MORE SOUTHERLY FRIDAY MORNING AS THE GRADIENT BEGINS TO
TIGHTEN AHEAD OF THE APPROACHING LOW. SPEEDS WILL LIKELY INCREASE
TO 10KTS OR HIGHER BY THE END OF THE PERIOD WITH 10-15KTS ALONG
WITH SOME HIGHER GUSTS LIKELY FRIDAY AFTERNOON.

SCT/BKN CU IN THE 2-3KFT RANGE ACROSS EAST CENTRAL IL WILL
CONTINUE TO LIFT AS IT SCATTERS WITH INCREASING HIGH CLOUDS THIS
AFTERNOON. THERE IS SOME POTENTIAL FOR LIGHT/SHALLOW GROUND FOG
OVERNIGHT INTO FRIDAY MORNING BUT CONFIDENCE REGARDING HOW
WIDESPREAD IT MAY BECOME IS LOW SO NO MENTION WITH THIS FORECAST.

&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...CMS



000
FXUS63 KLOT 271604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1104 AM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON. CMS

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

WITH HIGH PRESSURE OVERHEAD...FOG AND LOW END VFR STRATUS WERE
ABLE TO FORM. LUCKILY THE PATCHY FOG ONLY IMPACTED DPA FOR A SHORT
PERIOD AND NOT EXPECTING ANY OTHER FOG DEVELOPMENT. THE STRATUS
SHOULD ALSO DISSIPATE THIS MORNING. VRB WINDS WILL BECOME
SOUTHEAST BY THE LATE MORNING AND REMAIN LESS THAN 10 KT. A SCT
VFR CUMULUS DECK IS ALSO EXPECTED THIS AFTERNOON. WINDS THEN
BECOME MORE SOUTH-SOUTHEAST THIS EVENING AS THE HIGH SHIFTS EAST.
HIGH LEVEL CLOUDS WILL BE INCREASING OVERNIGHT IN COVERAGE AS THE
NEXT LOW PRESSURE SYSTEM APPROACHES.

JEE

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 271604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1104 AM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON. CMS

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

WITH HIGH PRESSURE OVERHEAD...FOG AND LOW END VFR STRATUS WERE
ABLE TO FORM. LUCKILY THE PATCHY FOG ONLY IMPACTED DPA FOR A SHORT
PERIOD AND NOT EXPECTING ANY OTHER FOG DEVELOPMENT. THE STRATUS
SHOULD ALSO DISSIPATE THIS MORNING. VRB WINDS WILL BECOME
SOUTHEAST BY THE LATE MORNING AND REMAIN LESS THAN 10 KT. A SCT
VFR CUMULUS DECK IS ALSO EXPECTED THIS AFTERNOON. WINDS THEN
BECOME MORE SOUTH-SOUTHEAST THIS EVENING AS THE HIGH SHIFTS EAST.
HIGH LEVEL CLOUDS WILL BE INCREASING OVERNIGHT IN COVERAGE AS THE
NEXT LOW PRESSURE SYSTEM APPROACHES.

JEE

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 271604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1104 AM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON. CMS

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

WITH HIGH PRESSURE OVERHEAD...FOG AND LOW END VFR STRATUS WERE
ABLE TO FORM. LUCKILY THE PATCHY FOG ONLY IMPACTED DPA FOR A SHORT
PERIOD AND NOT EXPECTING ANY OTHER FOG DEVELOPMENT. THE STRATUS
SHOULD ALSO DISSIPATE THIS MORNING. VRB WINDS WILL BECOME
SOUTHEAST BY THE LATE MORNING AND REMAIN LESS THAN 10 KT. A SCT
VFR CUMULUS DECK IS ALSO EXPECTED THIS AFTERNOON. WINDS THEN
BECOME MORE SOUTH-SOUTHEAST THIS EVENING AS THE HIGH SHIFTS EAST.
HIGH LEVEL CLOUDS WILL BE INCREASING OVERNIGHT IN COVERAGE AS THE
NEXT LOW PRESSURE SYSTEM APPROACHES.

JEE

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 271604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1104 AM CDT THU AUG 27 2015

.SHORT TERM...
225 AM CDT

THROUGH FRIDAY...

CANADIAN HIGH PRESSURE IS CENTERED FROM DIRECTLY OVER THE FORECAST
AREA NORTHWARD THROUGH LAKE SUPERIOR THIS MORNING. A FEW UPPER 40S
BEING OBSERVED IN OUTLYING LOCATIONS UNDER A CLEAR SKY OUTSIDE OF
A FEW LINGERING STRATUS PATCHES IN NORTHWEST INDIANA. EXPECT THAT
SOME DIURNAL CUMULUS WILL FORM TODAY AWAY FROM THE LAKE
SHADOW...AND LIKELY A LITTLE MORE PREVALENT EAST OF THE I-55
CORRIDOR INTO NORTHWEST INDIANA. ALL IN ALL THOUGH MORE SUNSHINE
THAN THE PAST COUPLE DAYS. LIGHT ONSHORE FLOW WILL DEVELOP AND
POSSIBLY IN THE FORM OF A TRADITIONAL LAKE BREEZE ACROSS NORTHEAST
ILLINOIS AND FAR NORTHWEST INDIANA THIS AFTERNOON. THIS WILL
PROBABLY DROP TEMPERATURES INTO THE 60S IN AREAS NEAR THE SHORE.
AFTERNOON HIGHS ELSEWHERE LOOK TO BE IN THE MID 70S AS THE AIR
MASS BEGINS TO MODIFY. MORE CLOUDS ON FRIDAY WILL LIKELY LEVEL OUT
THE MODIFYING...WITH HIGHS MID TO UPPER 70S FORECAST FROM NORTH TO
SOUTH.

MTF

&&

.LONG TERM...
225 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

A BROAD AREA OF INCREASED SUBTROPICAL MOISTURE IS SEEN ON MORNING
WATER VAPOR IMAGERY OVER THE INTERMOUNTAIN WEST AND WESTERN
PLAINS. WITHIN THIS ARE A FEW EMBEDDED SHORT WAVES...WITH TWO KEY
ONES ACCORDING TO NUMERICAL MODEL GUIDANCE BEING OVER NORTHERN
WYOMING AND SOUTHWEST COLORADO AS OF 230 AM. MODEL SOLUTIONS ARE
SPLIT ON WHICH OF THESE...IF EITHER...BECOME MORE DOMINANT ON
FRIDAY AS THEY TRACK EAST. A DEEPENING OF A LOW AMPLITUDE
SHORTWAVE TROUGH FROM THESE WAVES IS EXPECTED...WHICH SHOULD HELP
RAIN COVERAGE AND FOCUS WITHIN THE UPPER MIDWEST BY FRIDAY
EVENING. THE QUESTION IS AT WHAT LATITUDE WILL THIS BE AND THE
FURTHER SOUTH THE GREATER LIKELIHOOD FOR SHOWER POTENTIAL AND
DURATION IN THE CWA.

AT THIS TIME HAVE LEANED TOWARD A SLIGHTLY NORTH OF A MEAN
SOLUTION...CLOSER TO THE NAM AND EC. SUCH AN EVOLUTION WOULD STILL
APPEAR CLOSE ENOUGH FOR LIKELY RAIN SHOWERS WITHIN QG FORCING
FIELDS...ESPECIALLY NORTH OF INTERSTATE 80...FOR A PERIOD SOMETIME
FRIDAY NIGHT INTO SATURDAY MORNING. A 27.03 SREF MEAN FOR
ROCKFORD PROVIDES AROUND 0.40 OF AN INCH OF RAIN WITH AMOUNTS
DROPPING SOUTH AND EAST...ALTHOUGH QUITE A BIT OF SPREAD. HAVE
LEANED CLOSE TO A COLLABORATED WPC QPF WITH NO SIGNS OF ANY STRONG
MESOSCALE FORCING.

GUIDANCE ALSO DISAGREES ON HOW QUICKLY THE SURFACE TROUGH ASSOCIATED
WITH THIS SYSTEM MOVES EASTWARD. SOME MODELS SUCH AS THE EC HAVE IT
EAST OF THE AREA SATURDAY NIGHT...WHILE OTHER GLOBAL GUIDANCE LIKE
THE GFS AND GEM WEAKEN THE TROUGH JUST WEST OR OVER THE AREA GOING
INTO SUNDAY. BASICALLY CONTINUE TO GRADUALLY SHIFT RAIN CHANCES
EASTWARD THROUGH SATURDAY AFTERNOON AND NIGHT. MARGINAL INSTABILITY
MAY BE ENOUGH FOR ISOLATED TO SCATTERED THUNDER IN THE REGION
LATE FRIDAY NIGHT INTO SATURDAY...BUT SEVERE WEATHER IS UNLIKELY
BASED ON THE INSTABILITY AND MOISTURE SPECTRUM FORECAST.

WITH THE WEAKENING OF THE SURFACE LOW...LOOKS LIKE LINGERING CLOUDS
FROM THIS SYSTEM COULD BE A PROBLEM...ESPECIALLY IF A SLOWER
SOLUTION PANS OUT. CONCEIVABLY CLOUDS COULD LAST INTO THE DAY SUNDAY
AND LIMIT WARMTH. FOR NOW...HAVE KEPT SATURDAY HIGHS SEVERAL DEGREES
BELOW A SMART GUIDANCE BLEND.

INTO NEXT WEEK THE PATTERN CONTINUES TO LOOK SLOW-MOVING WITH THE
PRIMARY JET STREAM WELL NORTH INTO CANADA AND UPPER/MID-LEVEL
HEIGHTS ABOVE NORMAL ON THE SUITE OF LONG RANGE GUIDANCE. THE
PATTERN IS ONE THAT LOOKS MAINLY SUNNY FROM MONDAY ONWARD. THE EC
HAS QUICKER WARMING IN THE LOW-LEVELS THAN THE GFS...WITH 850MB
TEMPERATURES AT 19-20C BY MONDAY NIGHT INTO TUESDAY. HAVE GONE
WITH THE GUIDANCE BLEND AND A LITTLE WARMER BY WEDNESDAY. FLOW
STRENGTH LOOKS LIGHT ENOUGH THAT LAKE BREEZES COULD DEVELOP AND
WILL HAVE TO REFINE THOSE DETAILS IN TIME.

MTF

&&

.AVIATION...

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

* SOUTHEAST WINDS JUST UNDER 10KTS THIS AFTERNOON. CMS

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

WITH HIGH PRESSURE OVERHEAD...FOG AND LOW END VFR STRATUS WERE
ABLE TO FORM. LUCKILY THE PATCHY FOG ONLY IMPACTED DPA FOR A SHORT
PERIOD AND NOT EXPECTING ANY OTHER FOG DEVELOPMENT. THE STRATUS
SHOULD ALSO DISSIPATE THIS MORNING. VRB WINDS WILL BECOME
SOUTHEAST BY THE LATE MORNING AND REMAIN LESS THAN 10 KT. A SCT
VFR CUMULUS DECK IS ALSO EXPECTED THIS AFTERNOON. WINDS THEN
BECOME MORE SOUTH-SOUTHEAST THIS EVENING AS THE HIGH SHIFTS EAST.
HIGH LEVEL CLOUDS WILL BE INCREASING OVERNIGHT IN COVERAGE AS THE
NEXT LOW PRESSURE SYSTEM APPROACHES.

JEE

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

* MEDIUM FOR WINDS THRU THE PERIOD. CMS

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

FRIDAY NIGHT...SHRA AND CHC TSRA. MAINLY VFR. SOUTHEAST WINDS.

SATURDAY...SHRA AND SCHC TSRA. MVFR OR LOWER PSBL. SOUTH WINDS
BCMG NORTHWEST OVERNIGHT.

SUNDAY...VFR. NORTH WINDS BCMG SOUTH OVERNIGHT.

MONDAY AND TUESDAY...VFR. SOUTH WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

JEE

&&

.MARINE...
225 AM CDT

HIGH PRESSURE IS OVER THE LAKE THIS MORNING AND IT WILL SLOWLY DRIFT
EAST THROUGH FRIDAY AFTERNOON.  VARIABLE WIND DIRECTIONS ACROSS THE
LAKE WILL BECOME MAINLY SOUTH BY THIS EVENING AS THE HIGH SHIFTS
EAST.  THE NEXT LOW IS OVER THE CENTRAL PLAINS...AND WHILE GUIDANCE
STILL DIFFERS ON THE EXACT PATH OF THIS LOW...SIDING WITH THE
MAJORITY OF GUIDANCE MEMBERS THAT TAKE THE LOW OVER THE CENTRAL
PORTION OF THE LAKE SATURDAY.  SOUTHEAST WINDS INCREASE TO 20 KT
OVER THE SOUTHERN TWO THIRDS OF THE LAKE FRIDAY NIGHT AND SPREAD TO
THE WHOLE LAKE BY SATURDAY MORNING. AS THE LOW MOVES OVER THE
LAKE...WIND DIRECTION WILL VARY FROM EAST OVER THE NORTHERN END TO
WEST OVER THE SOUTHERN END.  THE LOW DISSIPATES OVER THE EASTERN
GREAT LAKES SUNDAY WITH A BROAD HIGH PRESSURE SYSTEM REMAINING OVER
THE LAKE THROUGH NEXT WEEK. LIGHT WINDS BECOME SOUTH MONDAY THROUGH
AT LEAST MID WEEK.

JEE

&&

.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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 271529
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1029 AM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

KREIN

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 615 AM CDT THU AUG 27 2015

EXCEPT FOR A BRIEF PERIOD OF MVFR VSBYS IN FOG AT KBMI...KDEC AND
KCMI...LOOK FOR VFR CONDITIONS FOR THE REST OF THIS FORECAST
PERIOD. SOME LIGHT FOG HAS DEVELOPED OVER PARTS OF EAST CENTRAL
IL THIS MORNING BUT THAT SHOULD QUICKLY DISSIPATE AS TEMPERATURES
WARM UP OVER THE NEXT FEW HOURS. FORECAST SOUNDINGS SUGGEST SOME
SCATTERED CUMULUS WILL DEVELOP LATER THIS MORNING WITH CLOUD
BASES FROM 3500 TO 4500 FEET. WITH HIGH PRESSURE SITUATED OVER
THE AREA TODAY...WINDS WILL BE A NON-FACTOR FOR AVIATION INTERESTS
WITH AN EAST TO SOUTHEAST FLOW EXPECTED TO REMAIN AT OR BELOW
10 KTS.


&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...SMITH




000
FXUS63 KILX 271529
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1029 AM CDT THU AUG 27 2015

.UPDATE...
ISSUED AT 1028 AM CDT THU AUG 27 2015

THE FORECAST IS PRETTY MUCH ON TRACK FOR TODAY. WITH DAYTIME
WARMING AND AMPLE SUNSHINE...ANY RESIDUAL PATCHY FOG HAS BURNED
OFF.  UNDER MOSTLY CLEAR SKIES...TEMPERATURES ARE ALREADY IN THE
UPPER 60S ACROSS THE AREA. WHILE THERE MAY BE SOME SCATTERED
FAIR WEATHER CUMULUS DEVELOPMENT THROUGH THE DAY...TEMPERATURES
SHOULD HAVE NO TROUBLE REACHING THE UPPER 70S TO AROUND 80 DEGREES
THIS AFTERNOON.

KREIN

&&

.SHORT TERM...(TODAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

EARLY MORNING SURFACE MAP INDICATES HIGH PRESSURE OVER NORTH CENTRAL
ILLINOIS RESULTING IN A MOSTLY CLEAR SKY AND RATHER COOL
TEMPERATURES. IDEAL RADIATIONAL CONDITIONS UNDERNEATH THE LARGE FAIR
WEATHER SYSTEM THIS MORNING WITH THE MERCURY ALREADY DOWN TO 48
DEGREES HERE AT THE OFFICE IN LINCOLN WITH A FEW OTHER LOCATIONS
APPROACHING 50 DEGREES. TEMP-DEW POINT SPREADS DECREASING AS WELL
SO SOME PATCHY FOG WILL BE POSSIBLE EARLY THIS MORNING WITH ANY
FOG DISSIPATING QUICKLY AS TEMPERATURES WARM RAPIDLY THRU THE
MORNING HOURS. FORECAST SOUNDINGS SUGGEST SOME CLOUDS DEVELOPING
AGAIN LATE THIS MORNING INTO THIS AFTERNOON, ESPECIALLY OVER THE
EASTERN HALF OF THE FORECAST AREA. HOWEVER, WE ARE NOT EXPECTING AS
MUCH CLOUDINESS AS WE SAW YESTERDAY WHICH SHOULD KEEP TEMPERATURES
MORE UNIFORM OVER CENTRAL ILLINOIS WITH HIGHS RANGING FROM THE
MID 70S FAR EAST TO AROUND 80 ACROSS THE REMAINDER OF THE FORECAST
AREA.

.LONG TERM...(TONIGHT THROUGH WEDNESDAY)
ISSUED AT 326 AM CDT THU AUG 27 2015

TEMPERATURES CLOSE TO CLIMATOLOGICAL NORMS TONIGHT AND TOMORROW AS
STORM SYSTEM TAKES SHAPE AND MOVES INTO THE REGION.  WAVE IS
CURRENTLY OVER THE NORTHERN ROCKIES AND IS SLIDING THROUGH THE
PLAINS AND INTO THE MIDWEST TO BRING INCREASING CHANCES FOR PRECIP
FOR FRI NIGHT AND SATURDAY.  ALTHOUGH THE MODELS ARE DOING BETTER
WITH THE TIMING OF THE WAVE, THE SOUTHERN EXTENT OF THE BETTER
PRECIP COVERAGE IS STILL BEING CALLED INTO QUESTION. A DRY AIRMASS
OVERALL ON ILX SOUNDINGS IS PART OF THE PROBLEM.  ALTHOUGH THE SFC
WINDS BECOME MORE SOUTHERLY THROUGH THE DAY ON FRIDAY, THE MOISTURE
ADVECTION IS LIMITED BY LIGHTER WINDS TO THE SOUTH.  THE MODELS HAVE
BEEN TRENDING THE WAVE A LITTLE FURTHER NORTH IN THE LATEST RUNS AS
WELL.  STILL CONCERNED THAT THE PRECIP WILL STILL BE MORE
INTERMITTENT THAN WIDESPREAD ALONG THE FRONTAL PASSAGE...WITH WEAKER
CONVERGENCE ALONG THE BOUNDARY.  GFS AND NAM STARTING TO TREND THAT
WAY, LINGERING THE PRECIP INTO SAT NIGHT AND IN THE EAST FOR EARLY
SUNDAY MORNING.

WAVE MOVING THROUGH EFFECTIVELY SHIFTS THE NORTHWESTERLY FLOW TO A
MORE SOUTHWESTERLY FROM THE SOUTHERN PAC COAST INTO THE HUDSON BAY
REGION...AND RATHER WEAK FLOW ALOFT FOR MOST OF THE EASTERN HALF
OF THE COUNTRY AFTER THE WEEKEND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 615 AM CDT THU AUG 27 2015

EXCEPT FOR A BRIEF PERIOD OF MVFR VSBYS IN FOG AT KBMI...KDEC AND
KCMI...LOOK FOR VFR CONDITIONS FOR THE REST OF THIS FORECAST
PERIOD. SOME LIGHT FOG HAS DEVELOPED OVER PARTS OF EAST CENTRAL
IL THIS MORNING BUT THAT SHOULD QUICKLY DISSIPATE AS TEMPERATURES
WARM UP OVER THE NEXT FEW HOURS. FORECAST SOUNDINGS SUGGEST SOME
SCATTERED CUMULUS WILL DEVELOP LATER THIS MORNING WITH CLOUD
BASES FROM 3500 TO 4500 FEET. WITH HIGH PRESSURE SITUATED OVER
THE AREA TODAY...WINDS WILL BE A NON-FACTOR FOR AVIATION INTERESTS
WITH AN EAST TO SOUTHEAST FLOW EXPECTED TO REMAIN AT OR BELOW
10 KTS.


&&

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

$$

UPDATE...KREIN
SHORT TERM...SMITH
LONG TERM...HJS
AVIATION...SMITH



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