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000
FXUS63 KLOT 302205
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
505 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
235 PM CDT

MONDAY NIGHT THROUGH SUNDAY...

WEAK MID-LVL WAVE CONTINUES TO BE ADVERTISED BY A FEW OF THE
OPERATIONAL GUIDANCE SOLUTIONS...WHICH COULD TOUCH OF A FEW
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DIMINISHING
WITH THIS SCENARIO IN THE MON NGT/TUE TIMEFRAME. HAVE TRIMMED BACK
POPS FOR TUE...BUT HELD ONTO A SLIGHT CHANCE TUE AFTERNOON FOR ANY
DIURNALLY DRIVEN PRECIP THAT MAY DEVELOP ALONG THE EASTERN HALF OF
THE CWFA. OTHERWISE WILL MAINTAIN A DRY FORECAST IN THE MON NGT/TUE
TIMEFRAME.

LOW LEVEL RIDGE CENTERED OVER THE MID-ATLANTIC REGION WILL KEEP A
SOUTHERLY TO SLIGHTLY SOUTHWESTERLY FLOW OVER THE FORECAST
AREA...WITH A PLUME OF BETTER MOISTURE STREAMING NORTH FROM THE GULF
OF MEXICO. THIS SHOULD MAINTAIN SLIGHTLY ELEVATED PWAT VALUES. TEMPS
WILL GENERALLY BE IN THE MID/UPR 60S AT NIGHT AND MID/UPR 80S DURING
THE AFTN HOURS.

WEDNESDAY THROUGH SATURDAY... BROAD MID-LVL RIDGE REMAINS CENTERED
OVER THE REGION...WITH THE BEST FORCING REMAINING SHIFTED TO THE
NORTH. THIS SHOULD KEEP THE BULK OF SHOWERS/THUNDERSTORMS IN THE
LONGER TERM NORTH OF THE FORECAST AREA. ENSEMBLES CONTINUE TO
SUPPORT A DRY EXTENDED...ALTHOUGH A DIURNALLY DRIVEN SHOWER/STORM
COULD STILL DEVELOP BUT THE ORGANIZATION OR COVERAGE SHOULD REMAIN
VERY MINIMAL.

WARM THERMAL RIDGE IN THE MID-LVLS CONTINUES TO BE PROGGED
UNDERNEATH...WHICH SHOULD ALLOW TEMPS TO APPROACH THE UPR 80S TO
NEAR 90. THE LIMITING FACTOR COULD BE HOW MUCH CLOUD COVER DEVELOPS
ALONG WITH LLVL MOISTURE. LATER IN THE WEEK HEADING INTO THE LABOR
DAY WEEKEND...ENSEMBLES ARE HINTING AT A PATTERN CHANGE THAT COULD
FEATURE THE STRONG MID-LVL HEIGHTS LOWERING AND BRINGING AN ACTIVE
PATTERN BACK TO THE REGION FOR NEXT SATURDAY.

BEACHLER

&&

.AVIATION...

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

* POTENTIAL FOR FOG OVERNIGHT.

BMD

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

BMD

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
235 PM CDT

RATHER BENIGN PATTERN CONTINUES ACROSS THE WESTERN GREAT
LAKES...WHICH WILL LIKELY ALLOW AREAS OF FOG TO ONCE AGAIN DEVELOP
TONIGHT AND COULD LINGER INTO MONDAY AFTERNOON/EVENING. A WEAK LOW
PRESSURE WILL LIFT NORTHEAST OF LAKE SUPERIOR...WHICH COULD ALLOW
A SLIGHT INCREASE IN THE WINDS FOR THE NORTHERN PORTIONS OF THE
LAKE MON/MON NGT.

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST TOWARDS THE
OHIO VALLEY...THEN REMAIN ANCHORED THROUGH THE END OF THE WEEK. THIS
WILL MAINTAIN A SOUTHERLY FLOW FOR MUCH OF THE LAKE...WITH ONLY A
BRIEF BUMP IN THE GRADIENT AND WINDS MON NGT/TUE.

BEACHLER

&&

.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 302011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
235 PM CDT

MONDAY NIGHT THROUGH SUNDAY...

WEAK MID-LVL WAVE CONTINUES TO BE ADVERTISED BY A FEW OF THE
OPERATIONAL GUIDANCE SOLUTIONS...WHICH COULD TOUCH OF A FEW
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DIMINISHING
WITH THIS SCENARIO IN THE MON NGT/TUE TIMEFRAME. HAVE TRIMMED BACK
POPS FOR TUE...BUT HELD ONTO A SLIGHT CHANCE TUE AFTERNOON FOR ANY
DIURNALLY DRIVEN PRECIP THAT MAY DEVELOP ALONG THE EASTERN HALF OF
THE CWFA. OTHERWISE WILL MAINTAIN A DRY FORECAST IN THE MON NGT/TUE
TIMEFRAME.

LOW LEVEL RIDGE CENTERED OVER THE MID-ATLANTIC REGION WILL KEEP A
SOUTHERLY TO SLIGTHLY SOUTHWESTERLY FLOW OVER THE FORECAST
AREA...WITH A PLUME OF BETTER MOISTURE STREAMING NORTH FROM THE GULF
OF MEXICO. THIS SHOULD MAINTAIN SLIGHTLY ELEVATED PWAT VALUES. TEMPS
WILL GENERALLY BE IN THE MID/UPR 60S AT NIGHT AND MID/UPR 80S DURING
THE AFTN HOURS.

WEDNESDAY THROUGH SATURDAY... BROAD MID-LVL RIDGE REMAINS CENTERED
OVER THE REGION...WITH THE BEST FORCING REMAINING SHIFTED TO THE
NORTH. THIS SHOULD KEEP THE BULK OF SHOWERS/THUNDERSTORMS IN THE
LONGER TERM NORTH OF THE FORECAST AREA. ENSEMBLES CONTINUE TO
SUPPORT A DRY EXTENDED...ALTHOUGH A DIURNALLY DRIVEN SHOWER/STORM
COULD STILL DEVELOP BUT THE ORGANIZATION OR COVERAGE SHOULD REMAIN
VERY MINIMAL.

WARM THERMAL RIDGE IN THE MID-LVLS CONTINUES TO BE PROGGED
UNDERNEATH...WHICH SHOULD ALLOW TEMPS TO APPROACH THE UPR 80S TO
NEAR 90. THE LIMITING FACTOR COULD BE HOW MUCH CLOUD COVER DEVELOPS
ALONG WITH LLVL MOISTURE. LATER IN THE WEEK HEADING INTO THE LABOR
DAY WEEKEND...ENSEMBLES ARE HINTING AT A PATTERN CHANGE THAT COULD
FEATURE THE STRONG MID-LVL HEIGHTS LOWERING AND BRINGING AN ACTIVE
PATTERN BACK TO THE REGION FOR NEXT SATURDAY.

BEACHLER

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN/BEACH

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/BEACH

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
235 PM CDT

RATHERN BENIGN PATTERN CONTINUES ACROSS THE WESTERN GREAT
LAKES...WHICH WILL LIKELY ALLOW AREAS OF FOG TO ONCE AGAIN DEVELOP
TONIGHT AND COULD LINGER INTO MONDAY AFTERNOON/EVENING. A WEAK LOW
PRESSURE WILL LIFT NORTHEAST OF LAKE SUPERIOR...WHICH COULD ALLOW A
SLIGHT INCREASE IN THE WINDS FOR THE NORTHERN PORTIONS OF THE LAKE
MON/MON NGT.

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST TOWARDS THE
OHIO VALLEY...THEN REMAIN ANCHORED THROUGH THE END OF THE WEEK. THIS
WILL MAINTAIN A SOUTHERLY FLOW FOR MUCH OF THE LAKE...WITH ONLY A
BRIEF BUMP IN THE GRADIENT AND WINDS MON NGT/TUE.

BEACHLER

&&

.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 302011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
235 PM CDT

MONDAY NIGHT THROUGH SUNDAY...

WEAK MID-LVL WAVE CONTINUES TO BE ADVERTISED BY A FEW OF THE
OPERATIONAL GUIDANCE SOLUTIONS...WHICH COULD TOUCH OF A FEW
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DIMINISHING
WITH THIS SCENARIO IN THE MON NGT/TUE TIMEFRAME. HAVE TRIMMED BACK
POPS FOR TUE...BUT HELD ONTO A SLIGHT CHANCE TUE AFTERNOON FOR ANY
DIURNALLY DRIVEN PRECIP THAT MAY DEVELOP ALONG THE EASTERN HALF OF
THE CWFA. OTHERWISE WILL MAINTAIN A DRY FORECAST IN THE MON NGT/TUE
TIMEFRAME.

LOW LEVEL RIDGE CENTERED OVER THE MID-ATLANTIC REGION WILL KEEP A
SOUTHERLY TO SLIGTHLY SOUTHWESTERLY FLOW OVER THE FORECAST
AREA...WITH A PLUME OF BETTER MOISTURE STREAMING NORTH FROM THE GULF
OF MEXICO. THIS SHOULD MAINTAIN SLIGHTLY ELEVATED PWAT VALUES. TEMPS
WILL GENERALLY BE IN THE MID/UPR 60S AT NIGHT AND MID/UPR 80S DURING
THE AFTN HOURS.

WEDNESDAY THROUGH SATURDAY... BROAD MID-LVL RIDGE REMAINS CENTERED
OVER THE REGION...WITH THE BEST FORCING REMAINING SHIFTED TO THE
NORTH. THIS SHOULD KEEP THE BULK OF SHOWERS/THUNDERSTORMS IN THE
LONGER TERM NORTH OF THE FORECAST AREA. ENSEMBLES CONTINUE TO
SUPPORT A DRY EXTENDED...ALTHOUGH A DIURNALLY DRIVEN SHOWER/STORM
COULD STILL DEVELOP BUT THE ORGANIZATION OR COVERAGE SHOULD REMAIN
VERY MINIMAL.

WARM THERMAL RIDGE IN THE MID-LVLS CONTINUES TO BE PROGGED
UNDERNEATH...WHICH SHOULD ALLOW TEMPS TO APPROACH THE UPR 80S TO
NEAR 90. THE LIMITING FACTOR COULD BE HOW MUCH CLOUD COVER DEVELOPS
ALONG WITH LLVL MOISTURE. LATER IN THE WEEK HEADING INTO THE LABOR
DAY WEEKEND...ENSEMBLES ARE HINTING AT A PATTERN CHANGE THAT COULD
FEATURE THE STRONG MID-LVL HEIGHTS LOWERING AND BRINGING AN ACTIVE
PATTERN BACK TO THE REGION FOR NEXT SATURDAY.

BEACHLER

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN/BEACH

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/BEACH

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
235 PM CDT

RATHERN BENIGN PATTERN CONTINUES ACROSS THE WESTERN GREAT
LAKES...WHICH WILL LIKELY ALLOW AREAS OF FOG TO ONCE AGAIN DEVELOP
TONIGHT AND COULD LINGER INTO MONDAY AFTERNOON/EVENING. A WEAK LOW
PRESSURE WILL LIFT NORTHEAST OF LAKE SUPERIOR...WHICH COULD ALLOW A
SLIGHT INCREASE IN THE WINDS FOR THE NORTHERN PORTIONS OF THE LAKE
MON/MON NGT.

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST TOWARDS THE
OHIO VALLEY...THEN REMAIN ANCHORED THROUGH THE END OF THE WEEK. THIS
WILL MAINTAIN A SOUTHERLY FLOW FOR MUCH OF THE LAKE...WITH ONLY A
BRIEF BUMP IN THE GRADIENT AND WINDS MON NGT/TUE.

BEACHLER

&&

.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 301936
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
235 PM CDT

MONDAY NIGHT THROUGH SUNDAY...

WEAK MID-LVL WAVE CONTINUES TO BE ADVERTISED BY A FEW OF THE
OPERATIONAL GUIDANCE SOLUTIONS...WHICH COULD TOUCH OF A FEW
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DIMINISHING
WITH THIS SCENARIO IN THE MON NGT/TUE TIMEFRAME. HAVE TRIMMED BACK
POPS FOR TUE...BUT HELD ONTO A SLIGHT CHANCE TUE AFTERNOON FOR ANY
DIURNALLY DRIVEN PRECIP THAT MAY DEVELOP ALONG THE EASTERN HALF OF
THE CWFA. OTHERWISE WILL MAINTAIN A DRY FORECAST IN THE MON NGT/TUE
TIMEFRAME.

LOW LEVEL RIDGE CENTERED OVER THE MID-ATLANTIC REGION WILL KEEP A
SOUTHERLY TO SLIGTHLY SOUTHWESTERLY FLOW OVER THE FORECAST
AREA...WITH A PLUME OF BETTER MOISTURE STREAMING NORTH FROM THE GULF
OF MEXICO. THIS SHOULD MAINTAIN SLIGHTLY ELEVATED PWAT VALUES. TEMPS
WILL GENERALLY BE IN THE MID/UPR 60S AT NIGHT AND MID/UPR 80S DURING
THE AFTN HOURS.

WEDNESDAY THROUGH SATURDAY... BROAD MID-LVL RIDGE REMAINS CENTERED
OVER THE REGION...WITH THE BEST FORCING REMAINING SHIFTED TO THE
NORTH. THIS SHOULD KEEP THE BULK OF SHOWERS/THUNDERSTORMS IN THE
LONGER TERM NORTH OF THE FORECAST AREA. ENSEMBLES CONTINUE TO
SUPPORT A DRY EXTENDED...ALTHOUGH A DIURNALLY DRIVEN SHOWER/STORM
COULD STILL DEVELOP BUT THE ORGANIZATION OR COVERAGE SHOULD REMAIN
VERY MINIMAL.

WARM THERMAL RIDGE IN THE MID-LVLS CONTINUES TO BE PROGGED
UNDERNEATH...WHICH SHOULD ALLOW TEMPS TO APPROACH THE UPR 80S TO
NEAR 90. THE LIMITING FACTOR COULD BE HOW MUCH CLOUD COVER DEVELOPS
ALONG WITH LLVL MOISTURE. LATER IN THE WEEK HEADING INTO THE LABOR
DAY WEEKEND...ENSEMBLES ARE HINTING AT A PATTERN CHANGE THAT COULD
FEATURE THE STRONG MID-LVL HEIGHTS LOWERING AND BRINGING AN ACTIVE
PATTERN BACK TO THE REGION FOR NEXT SATURDAY.

BEACHLER

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
235 PM CDT

RATHERN BENIGN PATTERN CONTINUES ACROSS THE WESTERN GREAT
LAKES...WHICH WILL LIKELY ALLOW AREAS OF FOG TO ONCE AGAIN DEVELOP
TONIGHT AND COULD LINGER INTO MONDAY AFTERNOON/EVENING. A WEAK LOW
PRESSURE WILL LIFT NORTHEAST OF LAKE SUPERIOR...WHICH COULD ALLOW A
SLIGHT INCREASE IN THE WINDS FOR THE NORTHERN PORTIONS OF THE LAKE
MON/MON NGT.

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST TOWARDS THE
OHIO VALLEY...THEN REMAIN ANCHORED THROUGH THE END OF THE WEEK. THIS
WILL MAINTAIN A SOUTHERLY FLOW FOR MUCH OF THE LAKE...WITH ONLY A
BRIEF BUMP IN THE GRADIENT AND WINDS MON NGT/TUE.

BEACHLER

&&

.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 301936
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
235 PM CDT

MONDAY NIGHT THROUGH SUNDAY...

WEAK MID-LVL WAVE CONTINUES TO BE ADVERTISED BY A FEW OF THE
OPERATIONAL GUIDANCE SOLUTIONS...WHICH COULD TOUCH OF A FEW
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DIMINISHING
WITH THIS SCENARIO IN THE MON NGT/TUE TIMEFRAME. HAVE TRIMMED BACK
POPS FOR TUE...BUT HELD ONTO A SLIGHT CHANCE TUE AFTERNOON FOR ANY
DIURNALLY DRIVEN PRECIP THAT MAY DEVELOP ALONG THE EASTERN HALF OF
THE CWFA. OTHERWISE WILL MAINTAIN A DRY FORECAST IN THE MON NGT/TUE
TIMEFRAME.

LOW LEVEL RIDGE CENTERED OVER THE MID-ATLANTIC REGION WILL KEEP A
SOUTHERLY TO SLIGTHLY SOUTHWESTERLY FLOW OVER THE FORECAST
AREA...WITH A PLUME OF BETTER MOISTURE STREAMING NORTH FROM THE GULF
OF MEXICO. THIS SHOULD MAINTAIN SLIGHTLY ELEVATED PWAT VALUES. TEMPS
WILL GENERALLY BE IN THE MID/UPR 60S AT NIGHT AND MID/UPR 80S DURING
THE AFTN HOURS.

WEDNESDAY THROUGH SATURDAY... BROAD MID-LVL RIDGE REMAINS CENTERED
OVER THE REGION...WITH THE BEST FORCING REMAINING SHIFTED TO THE
NORTH. THIS SHOULD KEEP THE BULK OF SHOWERS/THUNDERSTORMS IN THE
LONGER TERM NORTH OF THE FORECAST AREA. ENSEMBLES CONTINUE TO
SUPPORT A DRY EXTENDED...ALTHOUGH A DIURNALLY DRIVEN SHOWER/STORM
COULD STILL DEVELOP BUT THE ORGANIZATION OR COVERAGE SHOULD REMAIN
VERY MINIMAL.

WARM THERMAL RIDGE IN THE MID-LVLS CONTINUES TO BE PROGGED
UNDERNEATH...WHICH SHOULD ALLOW TEMPS TO APPROACH THE UPR 80S TO
NEAR 90. THE LIMITING FACTOR COULD BE HOW MUCH CLOUD COVER DEVELOPS
ALONG WITH LLVL MOISTURE. LATER IN THE WEEK HEADING INTO THE LABOR
DAY WEEKEND...ENSEMBLES ARE HINTING AT A PATTERN CHANGE THAT COULD
FEATURE THE STRONG MID-LVL HEIGHTS LOWERING AND BRINGING AN ACTIVE
PATTERN BACK TO THE REGION FOR NEXT SATURDAY.

BEACHLER

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
235 PM CDT

RATHERN BENIGN PATTERN CONTINUES ACROSS THE WESTERN GREAT
LAKES...WHICH WILL LIKELY ALLOW AREAS OF FOG TO ONCE AGAIN DEVELOP
TONIGHT AND COULD LINGER INTO MONDAY AFTERNOON/EVENING. A WEAK LOW
PRESSURE WILL LIFT NORTHEAST OF LAKE SUPERIOR...WHICH COULD ALLOW A
SLIGHT INCREASE IN THE WINDS FOR THE NORTHERN PORTIONS OF THE LAKE
MON/MON NGT.

HIGH PRESSURE OVER THE CENTRAL PLAINS WILL SLIDE EAST TOWARDS THE
OHIO VALLEY...THEN REMAIN ANCHORED THROUGH THE END OF THE WEEK. THIS
WILL MAINTAIN A SOUTHERLY FLOW FOR MUCH OF THE LAKE...WITH ONLY A
BRIEF BUMP IN THE GRADIENT AND WINDS MON NGT/TUE.

BEACHLER

&&

.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 301930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

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 301737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

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 301737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

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 301603
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1103 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY ARND NOON.

* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT.

KREIN

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL NOON SUNDAY.

&&

$$

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 301603
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1103 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY ARND NOON.

* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT.

KREIN

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL NOON SUNDAY.

&&

$$

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 301603
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1103 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY ARND NOON.

* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT.

KREIN

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL NOON SUNDAY.

&&

$$

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 301400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR LATE MORNING. A BIT LONGER THAN PREVIOUSLY
  ANTICIPATED.

* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT.

KREIN

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO MVFR AND
  THEN VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL NOON SUNDAY.

&&

$$

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 301400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR LATE MORNING. A BIT LONGER THAN PREVIOUSLY
  ANTICIPATED.

* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT.

KREIN

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO MVFR AND
  THEN VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL NOON SUNDAY.

&&

$$

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 301108
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
608 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR THIS MORNING
* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT

IZZI

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* HIGH CONFIDENCE IN VSBY/CIG TRENDS THIS MORNING
* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 301108
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
608 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR THIS MORNING
* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT

IZZI

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* HIGH CONFIDENCE IN VSBY/CIG TRENDS THIS MORNING
* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 301108
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
608 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR THIS MORNING
* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT

IZZI

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* HIGH CONFIDENCE IN VSBY/CIG TRENDS THIS MORNING
* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 301108
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
608 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR LIFTING TO MVFR THIS MORNING
* MVFR/IFR VSBY IN FOG POSSIBLE TONIGHT

IZZI

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

BANK OF STRATUS AND LIGHT FOG OVER THE TERMINALS EARLY THIS
MORNING SHOULD LIFT THIS MORNING THEN LIKELY SCATTER OUT THIS
AFTERNOON. LINGERING LOW LEVEL COULD ALLOW SOME GROUND FOG TO
REDEVELOP TONIGHT AS WINDS REMAIN LIGHT AND SKIES LIKELY MOSTLY
CLEAR.

IZZI

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

* HIGH CONFIDENCE IN VSBY/CIG TRENDS THIS MORNING
* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

VSBY HAVE LARGELY HELD STEADY AT THE TERMINALS THE LAST SEVERAL
HOURS AND WITH CIGS ACTUALLY TRENDING UPWARD A BIT THINKING THE
THREAT OF DENSE FOG IS DIMINISHING. HAVE TRENDED CIG/VSBY TRENDS
HIGHER IN THE TAFS...THOUGH STILL A CHANCE THAT VSBY COULD BRIEFLY
DROP AROUND SUNRISE.

IZZI

UPDATED 06Z...

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM CONFIDENCE IN GENERAL VSBY/CIG TRENDS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY MID-LATE MORNING
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

VSBY HAVE LARGELY HELD STEADY AT THE TERMINALS THE LAST SEVERAL
HOURS AND WITH CIGS ACTUALLY TRENDING UPWARD A BIT THINKING THE
THREAT OF DENSE FOG IS DIMINISHING. HAVE TRENDED CIG/VSBY TRENDS
HIGHER IN THE TAFS...THOUGH STILL A CHANCE THAT VSBY COULD BRIEFLY
DROP AROUND SUNRISE.

IZZI

UPDATED 06Z...

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM CONFIDENCE IN GENERAL VSBY/CIG TRENDS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY MID-LATE MORNING
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

VSBY HAVE LARGELY HELD STEADY AT THE TERMINALS THE LAST SEVERAL
HOURS AND WITH CIGS ACTUALLY TRENDING UPWARD A BIT THINKING THE
THREAT OF DENSE FOG IS DIMINISHING. HAVE TRENDED CIG/VSBY TRENDS
HIGHER IN THE TAFS...THOUGH STILL A CHANCE THAT VSBY COULD BRIEFLY
DROP AROUND SUNRISE.

IZZI

UPDATED 06Z...

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM CONFIDENCE IN GENERAL VSBY/CIG TRENDS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY MID-LATE MORNING
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

VSBY HAVE LARGELY HELD STEADY AT THE TERMINALS THE LAST SEVERAL
HOURS AND WITH CIGS ACTUALLY TRENDING UPWARD A BIT THINKING THE
THREAT OF DENSE FOG IS DIMINISHING. HAVE TRENDED CIG/VSBY TRENDS
HIGHER IN THE TAFS...THOUGH STILL A CHANCE THAT VSBY COULD BRIEFLY
DROP AROUND SUNRISE.

IZZI

UPDATED 06Z...

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM CONFIDENCE IN GENERAL VSBY/CIG TRENDS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY MID-LATE MORNING
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300831
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300831
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300721
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 AM CDT SUN AUG 30 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300721
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 AM CDT SUN AUG 30 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300721
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
221 AM CDT SUN AUG 30 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300556
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 AM CDT SUN AUG 30 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300556
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 AM CDT SUN AUG 30 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* IFR/LIFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

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

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

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

* MEDIUM-HIGH CONFIDENCE IN GENERAL VSBY/CIG TRENDS...BUT LOW
  CONFIDENCE IN PRECISE FLIGHT CATS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY AFTERNOON
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT SAT AUG 29 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* MEDIUM CONFIDENCE IN GENERAL CIG/VSBY TRENDS AND TIMING
  OVERNIGHT. LOW-MEDIUM CONFIDENCE IN TIMING IMPROVEMENT
  TOMORROW.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT SAT AUG 29 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* MEDIUM CONFIDENCE IN GENERAL CIG/VSBY TRENDS AND TIMING
  OVERNIGHT. LOW-MEDIUM CONFIDENCE IN TIMING IMPROVEMENT
  TOMORROW.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300323
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1023 PM CDT SAT AUG 29 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNIBLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* MEDIUM CONFIDENCE IN GENERAL CIG/VSBY TRENDS AND TIMING
  OVERNIGHT. LOW-MEDIUM CONFIDENCE IN TIMING IMPROVEMENT
  TOMORROW.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
859 PM CDT SAT AUG 29 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNABLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* A FEW LINGERING SHOWERS THIS EVENING.
* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* HIGH CONFIDENCE IN SHRA ENDING BY AROUND 01-02Z AT THE
  TERMINALS.
* MEDIUM-HIGH CONFIDENCE IN GENERAL CIG/VSBY TRENDS
  OVERNIGHT...BUT LOW-MEDIUM IN TIMING OF IFR AT 04Z. CONFIDENCE
  IN IFR INCREASES THRU AND AFTER 07Z.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 300159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
859 PM CDT SAT AUG 29 2015

.UPDATE...
859 PM CDT

MAIN FORECAST CONCERN OVERNIGHT CONTINUES TO BE THE POTENTIAL FOR
AREAS OF DENSE FOG TO DEVELOP. WITH WEAK LOW PRESSURE THAT WAS
OVER MID MS VALLEY DISSIPATING TO A TROUGH...WARM FRONT EXTENDING
NORTHWEST FROM THE LOW HAS BECOME BARELY DISCERNABLE. THIS FRONT
SERVED AS A MOISTURE CONVERGENCE AXIS COMBINED WITH FORCING FROM
THE UPPER TROUGH AXIS PIVOTING GRADUALLY SOUTHEAST ACROSS THE
REGION TO YIELD THE PERSISTENT SHOWER ACTIVITY INTO THIS
EVENING...BUT THE FORCING IS WEAKENING AS THE TROUGH SHIFTS
EAST...SO SHOWER ACTIVITY WILL FINALLY TAPER OFF...LATEST IN FAR
SOUTHEAST. AS OF THIS WRITING...THERE WAS A LOW TOPPED SUPERCELL
IN JASPER COUNTY WHERE BETTER INSTABILITY RESIDED AND ABOUT 20 KT
OF 0-1 KM SHEAR ACCORDING TO SPC MESOANALYSIS. THUNDER THREAT
SHOULD QUICKLY WANE IN EAST CENTRAL IL AND SOUTH OF KANKAKEE RIVER
IN INDIANA OVER NEXT FEW HOURS.

TURNING TO THE FOG POTENTIAL...THE WEAKENING OF THE LOW AND
EXTENSIVE HIGH PRESSURE COVERING THE EASTERN THIRD OF THE CONUS
HAS SET UP A VERY WEAK PRESSURE GRADIENT. DESPITE PLENTY OF
STRATUS...VERY MOIST LOW LEVELS AND LOW DEWPOINT DEPRESSIONS
SHOULD STILL SUPPORT FOG. BASED OFF OBS AND WEBCAMS ALONG
WISCONSIN SHORE TO THE ILLINOIS SHORE...VISIBILITY HAS BEEN ON A
DOWNWARD TREND THIS EVENING. HRRR-X SEEMS TO HAVE A GOOD HANDLE ON
FOG PROGRESSION...WHICH WOULD MEAN AREAS OF DENSE FOG ALONG THE
SHORE WOULD THEN SPREAD INLAND OVERNIGHT. DO NOT YET HAVE ENOUGH
CONFIDENCE TO ISSUE A DENSE FOG ADVISORY...BUT WILL ISSUE AN SPS
FOR THE LAKESHORE COUNTIES AND A GRAPHICAST TO HIT THE FOG
POTENTIAL ON OUR WEBSITE AND SOCIAL MEDIA. HAVE HIGHER CONFIDENCE
IN AREAS OF DENSE FOG FOCUSING ON COUNTIES ALONG AND NORTH OF
I-80...BUT WOULDNT BE SURPRISED TO SEE DENSE FOG ACROSS THE CWA IN
THE PREDAWN HOURS. UPDATED ZONES WILL BE SENT SHORTLY.

RC

&&

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* A FEW LINGERING SHOWERS THIS EVENING.
* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* HIGH CONFIDENCE IN SHRA ENDING BY AROUND 01-02Z AT THE
  TERMINALS.
* MEDIUM-HIGH CONFIDENCE IN GENERAL CIG/VSBY TRENDS
  OVERNIGHT...BUT LOW-MEDIUM IN TIMING OF IFR AT 04Z. CONFIDENCE
  IN IFR INCREASES THRU AND AFTER 07Z.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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 292336
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
636 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* A FEW LINGERING SHOWERS THIS EVENING.
* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* HIGH CONFIDENCE IN SHRA ENDING BY AROUND 01-02Z AT THE
  TERMINALS.
* MEDIUM-HIGH CONFIDENCE IN GENERAL CIG/VSBY TRENDS
  OVERNIGHT...BUT LOW-MEDIUM IN TIMING OF IFR AT 04Z. CONFIDENCE
  IN IFR INCREASES THRU AND AFTER 07Z.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292336
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
636 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* A FEW LINGERING SHOWERS THIS EVENING.
* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* HIGH CONFIDENCE IN SHRA ENDING BY AROUND 01-02Z AT THE
  TERMINALS.
* MEDIUM-HIGH CONFIDENCE IN GENERAL CIG/VSBY TRENDS
  OVERNIGHT...BUT LOW-MEDIUM IN TIMING OF IFR AT 04Z. CONFIDENCE
  IN IFR INCREASES THRU AND AFTER 07Z.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292336
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
636 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* A FEW LINGERING SHOWERS THIS EVENING.
* LOWERING CIGS/VSBY OVERNIGHT.

BMD

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

A TROUGH IS DRAPED FROM NORTHEASTERN ILLINOIS INTO WEST CENTRAL
ILLINOIS THIS EVENING SERVING THE FOCUS FOR SCATTERED SHOWERS.
THESE SHOWERS ARE EXPECTED TO CONTINUE TO DIMINISH WITH PRIMARILY
DRY CONDITIONS EXPECTED OVERNIGHT AND THE REMAINDER OF THE TAF
PERIOD. THE TROUGH AXIS WILL SLOWLY SAG SOUTH OVERNIGHT WITH LIGHT
NORTHERLY WINDS OVERSPREADING THE TERMINALS. WIDESPREAD MVFR
STRATUS IS NOTED UPSTREAM WITH AN AREA OF IFR/LIFR CIGS OVER FAR
SOUTHEASTERN WISCONSIN. CIGS ARE EXPECTED TO LOWER AT THE
TERMINALS OVERNIGHT ALONG WITH VISIBILITY DROPPING WITH THE
DEVELOPMENT OF FOG. CONDITIONS SHOULD BE SLOW TO IMPROVE TOMORROW.
LIGHT WINDS WILL CONTINUE THROUGH THE DAY TOMORROW.

BMD

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

* HIGH CONFIDENCE IN SHRA ENDING BY AROUND 01-02Z AT THE
  TERMINALS.
* MEDIUM-HIGH CONFIDENCE IN GENERAL CIG/VSBY TRENDS
  OVERNIGHT...BUT LOW-MEDIUM IN TIMING OF IFR AT 04Z. CONFIDENCE
  IN IFR INCREASES THRU AND AFTER 07Z.

BMD

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

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.MARINE...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
510 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* ISO SHOWERS THROUGH 00Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER/BMD

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...LOW-MEDIUM
  CONFIDENCE IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 00Z.

* MEDIUM/HIGH CONFIDENCE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

BEACHLER/BMD

//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...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
510 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* ISO SHOWERS THROUGH 00Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER/BMD

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...LOW-MEDIUM
  CONFIDENCE IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 00Z.

* MEDIUM/HIGH CONFIDENCE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

BEACHLER/BMD

//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...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292002
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
302 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* ISO SHOWERS THROUGH 22Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 292002
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
302 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.LONG TERM...
301 PM CDT

SUNDAY NIGHT THROUGH SATURDAY...

FOR THE LONGER TERM FORECAST PERIOD...A RATHER STAGNANT PATTERN IS
SETTING UP WITH HIGH PRESSURE SITTING OVER THE ERN CONUS AND A
TROUGH OF LOW PRESSURE REMAINING NEARLY STATIONARY OVER THE WESTERN
PLAINS.  THE UPPER LEVEL PATTERN WILL BE A LITTLE MORE
PROGRESSIVE...BUT THE PROGRESSION WILL LARGELY BE CONFINED TO NORTH
OF THE CANADIAN BORDER...WITH LITTLE EFFECT ON THE LOCAL AREA.

THE GENERAL TREND FOR THE LONG TERM FORECAST PERIOD WILL BE FOR A
WARMING TREND...BEGINNING ON SUNDAY AND PERSISTING THROUGH THE
REMAINDER OF THE WEEK.  BY MONDAY...A POSITIVE TILT UPPER LEVEL
RIDGE WILL EXTEND FROM THE DESERT SOUTHWEST THROUGH THE WESTERN
GREAT LAKES REGION...WITH GENERAL UPPER RIDGING PERSISTING OVER THE
REGION THROUGH THE WEEK.  BY MONDAY...TEMPERATURES SHOULD REACH THE
MIDDLE 80S ACROSS THE REGION...BUT A SOUTHEAST COMPONENT TO SFC
WINDS IS EXPECTED TO DEVELOP THROUGH THE DAY...WHICH COULD LIMIT
WARMING ALONG THE ILLINOIS LAKE MICHIGAN SHORE TO ARND 80F OR
POSSIBLE A LITTLE LESS.  THE REMNANTS OF WEAK TROPICAL SYSTEMS ARE
EXPECTED TO UNDERCUT THE UPPER RIDGE...TRACKING ACROSS THE SRN
MISSISSIPPI VALLEY...SETTING UP SLY-SWLY FLOW THROUGH THE LOWER
LEVELS...DRAWING SOME GULF MOISTURE INTO THE REGION.  THIS WOULD AID
IN THE DEVELOPMENT OF DIURNAL CU...WITH PERIODIC CHANCES FOR ISOLD-
SCT SHRA/TSRA...GENERALLY DURG THE DAYTIME HOURS.  THE LATEST LONG
RANGE MODEL RUNS CONTINUE THE TREND BEGUN YESTERDAY IN LIMITING
DAYTIME WARMING TO THE MIDDLE TO UPPER 80S THROUGH MUCH OF NEXT WEEK
WITH DEWPOINTS IN THE UPPER 60S TO LOWER 70S.  SO...WITH THE ABSENCE
OF ANY SIGNIFICANT FOCUSING MECHANISM...DO NOT EXPECT ANY
WIDESPREAD ORGANIZED PCPN THROUGH THE PERIOD WITH GENERALLY WARM AND
HUMID CONDITIONS.

KREIN

&&

.AVIATION...

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

* ISO SHOWERS THROUGH 22Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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...
301 PM CDT

A WEAK TROUGH OF LOW PRESSURE EXTENDS FROM THE MIDDLE MISSISSIPPI
VALLEY THROUGH SOUTHERN LAKE MICHIGAN AS HIGH PRESSURE SITS OVER
THE ERN CONUS AND A SLIGHTLY DEEPER TROUGH OF LOW PRESSURE
DEVELOPS OVER THE WESTERN PLAINS. THE WEAK TROUGH OVER SRN LAKE
MICHIGAN WILL PERSIST LONG ENOUGH INTO THIS EVENING FOR ELY WINDS
OVER THE SRN PORTIONS OF THE LAKE WHILE LOW PRESSURE MOVING
THROUGH THE CANADIAN PRAIRIES WILL KEEP WINDS OVER THE NORTHERN
PORTIONS OF THE LAKE MORE SLY TO SWLY. WEAK HIGH PRESSURE WILL BE
OVER THE SOUTH HALF OF THE LAKE SUNDAY...LEADING TO LAKE BREEZE
DEVELOPMENT AND ONSHORE WINDS OVER THE NEARSHORE WATERS AND LIGHT
AND VARIABLE WINDS OVER THE OPEN WATERS OF THE SOUTH HALF OF THE
LAKE. BY MONDAY...SLY-SWLY WINDS WILL COVER THE WHOLE LAKE BY
MONDAY AS A MODEST PRESSURE GRADIENT DEVELOPS OVER LAKE MICHIGAN
AS THE HIGH OVER THE ERN CONUS AND THE TROUGH OVER THE WRN PLAINS
REMAIN STATIONARY.

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 291959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.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 20Z...

* ISO SHOWERS THROUGH 22Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.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 20Z...

* ISO SHOWERS THROUGH 22Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.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 18Z...

* SCATTERED SHOWERS ISOLATED THUNDER NEAR ORD/MDW THRU 19Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT SAT AUG 29 2015

.SHORT TERM...

TONIGHT AND SUNDAY...

248 PM...FORECAST CONCERNS ARE DENSE FOG POTENTIAL TONIGHT...
LINGERING PRECIP TONIGHT AND ISOLATED THUNDERSTORMS SUNDAY
AFTERNOON.

WHILE MUCH OF THE PRECIP HAS ENDED THIS AFTERNOON WITH JUST SOME
SCATTERED SHOWERS ACROSS NORTHEAST IL AND NORTHWEST INDIANA...THERE
REMAINS THE POTENTIAL FOR SHOWERS INTO THIS EVENING MAINLY ACROSS
THE EASTERN HALF OR SO OF THE CWA. MAINTAINED CHANCE POPS SLOWLY
DROPPING OFF INTO THIS EVENING THOUGH OVERALL COVERAGE OF PRECIP
TRENDS IS A BIT UNCERTAIN. ANY LINGERING SHOWERS OVERNIGHT INTO
EARLY SUNDAY MORNING SHOULD BE CONFINED TO THE FAR SOUTHEAST CWA.

AS THE LOW NOW OVER WESTERN IL CONTINUES TO DISSIPATE...THE GRADIENT
WILL BECOME QUITE WEAK TONIGHT WITH WINDS ALREADY SHIFTING TO LIGHT
EAST/NORTHEAST ACROSS SOUTHEAST WI AND FAR NORTHEAST IL WHERE LOWER
CLOUDS AND SOME LIGHT FOG HAS DEVELOPED. MODEL FOG/VIS GUIDANCE ALL
SHOW FOG DEVELOPING IN THESE AREAS THIS EVENING THEN SPREADING TO
THE WEST/SOUTHWEST OVERNIGHT INTO SUNDAY MORNING. WITH MOS GUIDANCE
SHOWING MANY LOCATIONS TANKING OVERNIGHT. WITH THE LOW LEVELS
ALREADY SATURATED...THIS TREND SEEMS REASONABLE AND ADDED DENSE FOG
OVER NORTHWEST IL...MAINLY NORTHWEST OF AN ORD TO VYS LINE. WITH
LATE AUGUST SUNSHINE...EXPECT THIS TO BURN OFF BY MID MORNING
SUNDAY WITH CLOUDS SCATTERING OUT BY AFTERNOON. ASSUMING THIS
OCCURS...TEMPS SHOULD BE ABLE TO WARM INTO THE LOWER 80S. THOUGH A
LAKE BREEZE WILL LIKELY KEEP THE LAKESHORE AREAS COOLER.

AS TEMPS WARM...ESPECIALLY IN THE SOUTHEAST WHERE LESS FOG IS
EXPECTED...ENOUGH INSTABILITY IS PRESENT FOR ISOLATED SHOWERS AND
POSSIBLY A THUNDERSTORM. THIS SHOULD BE MAINLY DIURNALLY DRIVEN
FROM EARLY AFTERNOON TO EARLY EVENING THOUGH WITH MINIMAL
FORCING...PRECIP MAY END UP QUITE SPARSE. CMS

&&

.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 18Z...

* SCATTERED SHOWERS ISOLATED THUNDER NEAR ORD/MDW THRU 19Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM 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 18Z...

* SCATTERED SHOWERS ISOLATED THUNDER NEAR ORD/MDW THRU 19Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER


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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM 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 18Z...

* SCATTERED SHOWERS ISOLATED THUNDER NEAR ORD/MDW THRU 19Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER


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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

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 291614
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1114 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 16Z...

* 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 16Z...

* 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 291614
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1114 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 16Z...

* 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 16Z...

* 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 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 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 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 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 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 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 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 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 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 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 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:
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 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 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.
&&

$$

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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




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