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000
FXUS63 KLOT 272346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT EARLY THIS EVENING...AND ONCE
  AGAIN ON TUESDAY.

RODRIGUEZ

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

SHOWER/THUNDERSTORM ACTIVITY CONTINUES TO REMAIN WELL WEST OF THE
TERMINALS THIS EVENING...AND WILL CONTINUE TO DO SO THROUGHOUT
MUCH OF THE ENTIRE FORECAST. HOWEVER...DENSE HIGH LEVEL CLOUDS
FROM THESE STORMS HAVE MADE IT ACROSS THE TERMINALS...AND WILL
REMAIN IN PLACE THROUGH THE EVENING. EAST/NORTHEST WINDS CONTINUE
AT SPEEDS AROUND 10 KT...BUT WILL OBSERVE A DIMINISHING TREND OVER
THE NEXT COUPLE OF HOURS. LIGHTER EAST/SOUTHEAST WINDS WILL
INITIALLY BE IN PLACE ON TUESDAY...BUT EXPECT LAKE COMPONENT TO
TAKE THEM MORE EASTERLY WHILE ALSO INCREASING INTO THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

WEDNESDAY...CHANCE OF TSRA IN THE MORNING.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 272346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT EARLY THIS EVENING...AND ONCE
  AGAIN ON TUESDAY.

RODRIGUEZ

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

SHOWER/THUNDERSTORM ACTIVITY CONTINUES TO REMAIN WELL WEST OF THE
TERMINALS THIS EVENING...AND WILL CONTINUE TO DO SO THROUGHOUT
MUCH OF THE ENTIRE FORECAST. HOWEVER...DENSE HIGH LEVEL CLOUDS
FROM THESE STORMS HAVE MADE IT ACROSS THE TERMINALS...AND WILL
REMAIN IN PLACE THROUGH THE EVENING. EAST/NORTHEST WINDS CONTINUE
AT SPEEDS AROUND 10 KT...BUT WILL OBSERVE A DIMINISHING TREND OVER
THE NEXT COUPLE OF HOURS. LIGHTER EAST/SOUTHEAST WINDS WILL
INITIALLY BE IN PLACE ON TUESDAY...BUT EXPECT LAKE COMPONENT TO
TAKE THEM MORE EASTERLY WHILE ALSO INCREASING INTO THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

WEDNESDAY...CHANCE OF TSRA IN THE MORNING.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 272346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT EARLY THIS EVENING...AND ONCE
  AGAIN ON TUESDAY.

RODRIGUEZ

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

SHOWER/THUNDERSTORM ACTIVITY CONTINUES TO REMAIN WELL WEST OF THE
TERMINALS THIS EVENING...AND WILL CONTINUE TO DO SO THROUGHOUT
MUCH OF THE ENTIRE FORECAST. HOWEVER...DENSE HIGH LEVEL CLOUDS
FROM THESE STORMS HAVE MADE IT ACROSS THE TERMINALS...AND WILL
REMAIN IN PLACE THROUGH THE EVENING. EAST/NORTHEST WINDS CONTINUE
AT SPEEDS AROUND 10 KT...BUT WILL OBSERVE A DIMINISHING TREND OVER
THE NEXT COUPLE OF HOURS. LIGHTER EAST/SOUTHEAST WINDS WILL
INITIALLY BE IN PLACE ON TUESDAY...BUT EXPECT LAKE COMPONENT TO
TAKE THEM MORE EASTERLY WHILE ALSO INCREASING INTO THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

WEDNESDAY...CHANCE OF TSRA IN THE MORNING.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 272346
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
646 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT EARLY THIS EVENING...AND ONCE
  AGAIN ON TUESDAY.

RODRIGUEZ

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

SHOWER/THUNDERSTORM ACTIVITY CONTINUES TO REMAIN WELL WEST OF THE
TERMINALS THIS EVENING...AND WILL CONTINUE TO DO SO THROUGHOUT
MUCH OF THE ENTIRE FORECAST. HOWEVER...DENSE HIGH LEVEL CLOUDS
FROM THESE STORMS HAVE MADE IT ACROSS THE TERMINALS...AND WILL
REMAIN IN PLACE THROUGH THE EVENING. EAST/NORTHEST WINDS CONTINUE
AT SPEEDS AROUND 10 KT...BUT WILL OBSERVE A DIMINISHING TREND OVER
THE NEXT COUPLE OF HOURS. LIGHTER EAST/SOUTHEAST WINDS WILL
INITIALLY BE IN PLACE ON TUESDAY...BUT EXPECT LAKE COMPONENT TO
TAKE THEM MORE EASTERLY WHILE ALSO INCREASING INTO THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

WEDNESDAY...CHANCE OF TSRA IN THE MORNING.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 272206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
506 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* E WINDS...TURNING SE FOR TONIGHT AND TOMORROW.

LENNING/RODRIGUEZ

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING/RODRIGUEZ

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* E TO SSE WINDS TODAY...TURNING SE FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* E TO SSE WINDS TODAY...TURNING SE FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* E TO SSE WINDS TODAY...TURNING SE FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
240 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...
240 PM CDT

SURFACE HIGH PRESSURE OVER THE GREAT LAKES THIS AFTERNOON WILL
SLIDE SLOWLY OFF TO THE EASTERN LAKES TUESDAY...AND ACROSS NEW
ENGLAND BY WEDNESDAY AS AN AREA OF LOW PRESSURE LIFTS NORTHEAST
INTO NORTHERN ONTARIO. A COLD FRONT TRAILING FROM THIS LOW WILL
PUSH SOUTHEAST ACROSS LAKE MICHIGAN WEDNESDAY MORNING THROUGH
EARLY AFTERNOON. LIGHT WINDS DOMINATED BY AFTERNOON LAKE BREEZE
CIRCULATIONS THIS AFTERNOON WILL BECOME MORE SOUTH-SOUTHEAST
TUESDAY...BEFORE SHIFTING TO THE WEST BEHIND THE FRONT WEDNESDAY.
A BRIEF PERIOD OF SOUTHWEST 15-20 KT IS POSSIBLE JUST AHEAD OF THE
FRONT EARLY WEDNESDAY...WITH WEST WINDS GENERALLY 15-20 KTS BEHIND
THE FRONT THROUGH WEDNESDAY NIGHT. OTHERWISE...A PROLONGED PERIOD
OF MODEST WEST-SOUTHWEST WINDS APPEARS LIKELY THROUGH THE END OF
THE WEEK AS THE LAKES SIT BEHIND LOW PRESSURE OVER HUDSON
BAY...AND WEAK HIGH PRESSURE THROUGH THE OHIO VALLEY.

RATZER

&&

.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 271922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
222 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
222 PM CDT MON JUL 27 2015

.SHORT TERM...
222 PM CDT

SHORT TERM...

TONIGHT THROUGH WEDNESDAY...

MAIN CONCERN IN THE SHORT TERM IS TIMING THE POTENTIAL FOR
THUNDERSTORMS FROM TUESDAY AFTERNOON THROUGH WEDNESDAY...AS WELL
AS VERY WARM AND HUMID WEATHER UNTIL COLD FRONT PASSES.

SURFACE HIGH PRESSURE ACROSS THE GREAT LAKES REGION WILL ONLY
SLOWLY DRIFT OFF TO THE EAST TUESDAY...AS DEEP LOW PRESSURE
DEVELOPS OVER THE NORTHERN PLAINS AND LIFTS NORTHEAST INTO
NORTHERN ONTARIO THROUGH WEDNESDAY IN RESPONSE TO A STRONG UPPER
TROUGH AND CLOSED LOW WHICH EJECTS FROM THE NORTHERN ROCKIES. IN
THE PROCESS...A DIFFUSE WARM FRONTAL ZONE CURRENTLY DRAPED ACROSS
THE LOWER MISSOURI VALLEY AND SOUTHERN IL/IN WILL LIFT NORTH
ACROSS THE FORECAST AREA LATE TUESDAY AND TUESDAY NIGHT...AHEAD OF
A COLD FRONT TRAILING THE CANADIAN LOW. WARM/HUMID AIR IN PLACE
ACROSS THE WARM FRONTAL ZONE WILL SPREAD INTO NORTHERN
IL/IN...INCREASING HUMIDITY AS WELL AS THE POTENTIAL FOR
THUNDERSTORMS...ESPECIALLY LATE TUESDAY NIGHT AND WEDNESDAY AHEAD
OF THE COLD FRONT.

SEVERAL CONVECTION ALLOWING MODELS DEPICT STORMS DEVELOPING
ACROSS THE CENTRAL PLAINS AND MID-MISSOURI RIVER VALLEY TO OUR
WEST TONIGHT...WITH DECAYING CONVECTION PERHAPS REACHING OUR
WESTERN CWA COUNTIES MIDDAY TUESDAY BEFORE DISSIPATING. HAVE
INDICATED SOME SLIGHT CHANCE POPS ACROSS PARTS OF NORTH CENTRAL
ILLINOIS TUESDAY AFTERNOON WITH THIS SCENARIO IN MIND. GREATER
POTENTIAL FOR THUNDERSTORMS LOOKS TO SPREAD IN AHEAD OF THE COLD
FRONT TUESDAY NIGHT AS INDICATED ABOVE. LATEST GUIDANCE RUNS ARE
SLIGHTLY FASTER WITH THE COLD FRONT THAN PREVIOUS...WITH THE FRONT
ALONG ROUGHLY A CHICAGO-ST LOUIS LINE WEDNESDAY MORNING.
THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE SOUTHEAST HALF OF
THE CWA ALONG/AHEAD OF THE FRONT INTO THE AFTERNOON BEFORE THE
FRONT CLEARS THE FA.

IN ADVANCE OF THE FRONT AND THE SOUTHERN PERIPHERY OF THE UPPER
TROUGH AXIS...RIDGING CONTINUES TO STRENGTHEN ALOFT EARLY TUESDAY.
925 MB TEMPS IN THE +24/26 RANGE WOULD SUPPORT UPPER 80S TO LOWER
90S MAX TEMPS. CONSIDERING POSSIBLE HIGH CLOUD COVER FROM STORMS
TO OUR WEST...HAVE GONE MORE IN THE 87-90 RANGE ALONG THE LINES OF
A MAV/MET BLEND FOR TUESDAY HIGH TEMPS. SOUTH-SOUTHEAST SYNOPTIC
FLOW SHOULD PRODUCE A SOUTHEAST LAKE BREEZE ALONG THE IL SHORE
TUESDAY...WHERE TEMPS WILL BE HELD TO AROUND 80 DEGREES. AFTER A
WARM/HUMID NIGHT IN THE LOW-MID 70S TUESDAY NIGHT...COOLING TEMPS
FROM THE NORTHWEST BEHIND THE COLD FRONT WEDNESDAY SUPPORT HIGHS
FROM THE LOW-MID 80S NORTHWEST TO THE UPPER 80S SOUTHEAST. SURFACE
DEW POINTS IN THE MID-70S IN MOIST AXIS AHEAD OF THE FRONT
COMBINED WITH THESE WARM AIR TEMPS YIELD PEAK HEAT INDICIES AROUND
100 DEGREES. DEW POINTS AND HUMIDITY FALL OFF BEHIND THE FRONT
WEDNESDAY AFTERNOON.

RATZER

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
206 PM CDT MON JUL 27 2015

.UPDATE...1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
206 PM CDT MON JUL 27 2015

.UPDATE...1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
206 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

FIRST PORTION OF THE EXTENDED PERIOD WILL FEATURE A BROAD SFC
RIDGE THAT STRETCHES FROM THE ROCKIES EAST THROUGH THE OHIO
VALLEY. THIS COUPLED WITH BROAD 500MB RIDGE COVERING MUCH OF THE
CENTRAL CONUS WILL HELP TO STEER WAVES FURTHER NORTH INTO THE
NORTHERN PLAINS/SOUTHERN CANADA. OPERATIONAL SOLUTIONS HAVE
DEMONSTRATED SOME VARIABILITY WITH RESPECT TO PLACEMENT OF THE
RIDGE AXIS.

THROUGH THE WEEKEND ENSEMBLES MAINTAIN A HIGH CONFIDENCE/MINIMAL
SPREAD PROG OF THE 500MB HEIGHTS...WITH SOME TROUGHING DEVELOPING
ACROSS THE GREAT LAKES LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

OPERATIONAL SOLUTIONS BRING A FRONTAL BOUNDARY NEAR THE REGION
FRI...HOWEVER MOISTURE DOES NOT APPEAR TO BE ABUNDANCE WITH THIS
BOUNDARY AND MAY END UP BEING JUST A WIND SHIFT WITH SOME CLOUDS.
HAVE HELD ONTO A DRY FORECAST FRI/FRI NGT...THEN IT APPEARS A
SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS RETURNS SAT AND
COULD BE MORE DIURNALLY DRIVEN. THEN THE TROUGH BEGINS TO TAKE SHAPE
AND SAGS A BOUNDARY OVER THE REGION NEXT WEEKEND...WITH PERIODIC
CHANCES FOR SHOWERS AND THUNDERSTORMS.

TEMPERATURES THROUGHOUT THE EXTENDED PERIODS WILL REMAIN WITHIN
SEASONAL CONDITIONS...POSSIBLY NEARING THE UPR 80S SAT PRIOR TO THE
ARRIVAL OF THE FRONTAL BOUNDARY. OTHERWISE TEMPS WILL MAINLY BE IN
TEH MID 80S...WITH OVERNIGHT LOWS IN THE MID/UPR 60S.

BEACHLER

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271854
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
154 PM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING


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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271854
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
154 PM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY...TURNING SOUTHEAST FOR TONIGHT AND TOMORROW.

LENNING

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

A DOME OF HIGH PRESSURE SITTING OVER THE GREAT LAKES WILL SHIFT
EAST AND ALLOW WINDS TO TURN SOUTHEAST OVERNIGHT. UPSTREAM OF THE
AREA OVER IOWA A COMPLEX OF THUNDERSTORMS HAS INCREASED IN
COVERAGE TODAY BUT IS EXPECTED TO FOLLOW THE UPPER LEVEL STEERING
FLOW AND DROP SOUTHWEST OF THE LOCAL AREA THIS EVENING AND
TONIGHT.

TOMORROW AGAIN LOOKS QUIET UNDER THE CONTINUED INFLUENCE OF THE
HIGH...BUT A DISTURBANCE MOVING IN LATE TOMORROW COULD BRING
STORMS TO THE LOCAL AREA TUESDAY NIGHT.

LENNING


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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271630
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1130 AM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271630
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1130 AM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271630
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1130 AM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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
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000
FXUS63 KLOT 271630
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1130 AM CDT MON JUL 27 2015

.UPDATE...
1130 AM CDT

FOR MORNING UPDATE...

NO REAL CHANGES TO GOING FORECAST...OTHER THAN USUAL TWEAKS TO
HOURLY SKY COVER AND DEW POINT GRIDS.

SURFACE HIGH PRESSURE REMAINS ACROSS THE GREAT LAKES REGION THIS
MORNING...WITH A RATHER DIFFUSE WARM FRONT TO THE SOUTH ACROSS
SOUTHERN IL AND IND. TEMPERATURES ALREADY CLIMBING THROUGH THE LOWER
80S IN MANY AREAS...WITH FORECAST HIGHS IN THE MID-UPPER 80S LOOKING
ON TRACK BASED ON HIGH-RES GUIDANCE AND MORNING RAOB ANALYSIS.
SOUTHERN COUNTIES OF CWA...WHERE MOIST LOW LEVEL CONDITIONS FROM
YESTERDAYS RAIN RESULTED IN SOME MORNING FOG/LOW CLOUDS WILL LIKELY
BE LIMITED TO THE MID-80S WHERE MIXING IS MORE SHALLOW THIS
AFTERNOON...WHILE AREAS NEAR LAKE MICHIGAN WILL SEE SYNOPTIC
ENHANCED EASTERLY LAKE BREEZE WINDS AND TEMPS IN THE UPPER 70S.
INTERIOR AREAS OF NORTHERN ILLINOIS LIKELY TO TAG UPPER 80S...WITH
925 MB TEMPS OF +23/24 C. CU FIELD...AND HIGH CLOUDS OFF STORMS IN
WESTERN IOWA...WILL PRODUCE PARTLY CLOUDY SKIES FOR THE MOST PART
EXCEPT NEAR THE LAKE WHERE THE COOLER/MORE STABLE MARINE AIR WILL
NOT SUPPORT MUCH CU.

RATZER

&&

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271415
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
915 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT LATE MORNING THRU EARLY EVENING.

CMS/LENNING

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR WINDS THRU THE PERIOD.

CMS/LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT LATE MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT LATE MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT LATE MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 271130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
630 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT LATE MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270913
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
413 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

AREAS OF FOG HAVE DEVELOPED ACROSS CENTRAL IL INTO NORTHWEST
INDIANA...INCLUDING AT GYY. THIS SHOULD QUICKLY DISSIPATE AFTER
SUNRISE. DEWPOINTS ARE A BIT LOWER AT RFD AND WHILE FOG IS STILL
POSSIBLE...REMOVED MENTION WITH THIS UPDATE. CMS

PREVIOUS 06Z DISCUSSION...

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270913
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
413 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

AREAS OF FOG HAVE DEVELOPED ACROSS CENTRAL IL INTO NORTHWEST
INDIANA...INCLUDING AT GYY. THIS SHOULD QUICKLY DISSIPATE AFTER
SUNRISE. DEWPOINTS ARE A BIT LOWER AT RFD AND WHILE FOG IS STILL
POSSIBLE...REMOVED MENTION WITH THIS UPDATE. CMS

PREVIOUS 06Z DISCUSSION...

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270750
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270750
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270711
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
211 AM CDT MON JUL 27 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270711
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
211 AM CDT MON JUL 27 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

.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 270522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1222 AM CDT MON JUL 27 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1222 AM CDT MON JUL 27 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AROUND 10KT TODAY. CMS

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

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY AND
SLOWLY SHIFT TO THE EASTERN LAKES ON TUESDAY. THIS WILL MAINTAIN
EASTERLY WINDS THRU THE PERIOD WHICH ARE EXPECTED TO INCREASE TO
10KT THIS MORNING AND PERSIST THRU SUNSET...WHEN SPEEDS WILL
DIMINISH TO 5KTS OR LESS.

MID/HIGH LEVEL CLOUDS WILL CONTINUE TO SPREAD ACROSS THE REGION
THRU THIS MORNING BUT SHOULD BEGIN TO THIN OUT LATER TODAY WITH
SOME CU POSSIBLE TODAY.

DRY WEATHER IS EXPECTED AT THE TERMINALS WITH JUST A SLIGHT CHANCE
OF SHRA/TSRA ACROSS WESTERN AND CENTRAL IL THIS AFTERNOON. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT SUN JUL 26 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270309
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1009 PM CDT SUN JUL 26 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270150
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
850 PM CDT SUN JUL 26 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270150
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
850 PM CDT SUN JUL 26 2015

.UPDATE...
850 PM CDT

RAINFALL IS MOVING OUT OF MY SOUTHERN COUNTIES...SO I HAVE
UPDATED THE FORECAST TO REMOVE THE MENTION OF
SHOWERS/THUNDERSTORMS FOR THE REST OF THE NIGHT AREA-WIDE.
OTHERWISE...THE ONLY OTHER CHANGE TO THE FORECAST WAS TO ADD
FOG...ESPECIALLY IN AREAS THAT RECEIVED A GOOD DOSE OF RAIN TODAY.
OVERALL...IT WOULD APPEAR THAT THE BEST THREAT OF FOG WOULD BE
ACROSS MY SOUTH...IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY AND
HIGHER DEW POINTS. DEW POINT DEPRESSIONS ARE ALREADY VERY
LOW...ESPECIALLY ACROSS MY SOUTH. THEREFORE...FOG DEVELOPMENT
APPEARS LIKELY EITHER LATER THIS EVENING OR OVERNIGHT. SOME PATCHY
DENSE FOG CANNOT BE RULED OUT.

KJB

&&

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
704 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 270004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
704 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EASTERLY WINDS AT OR ABOVE 10 KT ON MONDAY.

RODRIGUEZ

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

AS AN UPPER LEVEL SYSTEM EXITS THE AREA EARLY THIS
EVENING...ISOLATED/BRIEF LIGHT SHOWERS CONTINUE TO MOVE THROUGH
THE AREA WHILE BETTER SHOWER/THUNDERSTORM DEVELOPMENT STAYS WELL
TO THE SOUTH OF THE TERMINALS. DONT ANTICIPATE MUCH FROM THESE
LIGHT SHOWERS...AS THEY DIMINISH OVER THE NEXT COUPLE OF HOURS.
EXPECT VFR CONDITIONS TO PERSIST TONIGHT INTO MONDAY...WITH
ADDITIONAL SCATTERED SHOWER/THUNDERSTORM DEVELOPMENT POSSIBLE ON
MONDAY. HOWEVER...THE BEST DEVELOPMENT WILL ONCE AGAIN REMAIN TO
THE WEST OF THE TERMINALS WITH RFD POSSIBLY OBSERVING THIS PRECIP
IN THE AFTERNOON. WITH CONFIDENCE LOW AT THIS TIME...HAVE EXCLUDED
ANY MENTION OF PRECIP FOR RFD. AFTER LIGHTER WIND SPEEDS
TONIGHT...EASTERLY WINDS WILL INCREASE TO AROUND 10KT BY MID TO
LATE MORNING ON MONDAY AND CONTINUE INTO THE EARLY EVENING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...SLIGHT CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

SATURDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262219
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
519 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EAST NORTHEAST WINDS BELOW 10 KT THIS EVENING. BETTER CHANCE
  FOR SPEEDS ABOVE 10 KT TOMORROW.

KMD/RODRIGUEZ

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* HIGH THAT WINDS WILL REMAIN BELOW 10 KT. MEDIUM IN WIND SPEED
  TOMORROW.

KMD/RODRIGUEZ

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262219
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
519 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* EAST NORTHEAST WINDS BELOW 10 KT THIS EVENING. BETTER CHANCE
  FOR SPEEDS ABOVE 10 KT TOMORROW.

KMD/RODRIGUEZ

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* HIGH THAT WINDS WILL REMAIN BELOW 10 KT. MEDIUM IN WIND SPEED
  TOMORROW.

KMD/RODRIGUEZ

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* SCHC -RA THIS AFTERNOON.

* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS AFTERNOON
  AT TIMES. BETTER CHANCE TOMORROW.

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH POSSIBLY SOME SPRINKLES THIS AFTERNOON.

* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW TODAY. MEDIUM IN WIND SPEED
  TOMORROW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...
310 PM CDT

TUESDAY THROUGH SUNDAY...

MAIN FOCUS IS HOT/HUMID WEATHER TUESDAY...AS WELL AS THUNDERSTORM
CHANCES AND TIMING INTO WEDNESDAY. LATE WEEK PERIOD LOOKS TO BE
DRY AND SEASONABLY WARM...WITH A RETURN OF WARMER/MORE HUMID
WEATHER BY NEXT WEEKEND.

UPPER LEVEL RIDGE AXIS STRETCHES FROM THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY NORTHEAST INTO THE GREAT LAKES REGION TUESDAY
MORNING...WHILE AN UPPER LEVEL LOW EJECTS FROM THE NORTHERN
ROCKIES ACROSS THE NORTHERN PLAINS AND SOUTHERN CANADIAN PRAIRIES.
WITH SURFACE LOW PRESSURE ACROSS THE PLAINS...LOW LEVEL SOUTH-
SOUTHEAST RETURN FLOW DEVELOPS WITH DIFFUSE WARM FRONT SLOWLY
LIFTING THROUGH THE CWA. WARMING ALOFT BENEATH BUILDING RIDGE
(+19/20C AT 850 MB AND +25/26C AT 925 MB)WOULD SUPPORT SURFACE
TEMPS WARMING INTO THE 90-95 DEGREE RANGE TUESDAY
AFTERNOON...COMBINED WITH SURFACE DEW POINT TEMPS RISING INTO THE
MID-70S. THIS COULD SET THE STAGE FOR RATHER HOT AND HUMID DAY
WITH PEAK HEAT INDEX VALUES IN THE 100-105 DEGREE RANGE. THE MAIN
QUESTION IS HOW MUCH CONVECTIVE DEBRIS AND CLOUD COVER THERE MAY
BE FROM STORMS NORTHWEST OF THE AREA LATE MONDAY NIGHT...AND
WHETHER OR NOT ANY ISOLATED STORMS WOULD FORM WITHIN THE DIFFUSE
WARM FRONTAL ZONE NEAR/IN THE CWA. WITH THE UPPER RIDGE BUILDING
OVERHEAD...AND LARGE SCALE HEIGHT FALLS WELL TO THE NORTH AND
NORTHWEST OF THE FORECAST AREA INTO EARLY WEDNESDAY WITH THE
TROUGH ALONG THE U.S. CANADIAN BORDER...THINKING IS THAT
THUNDERSTORM ACTIVITY IMMEDIATELY ADJACENT/IN THE LOCAL CWA SHOULD
BE RATHER ISOLATED AT BEST. NCEP HIGH-RES 4 KM WRF SEEMS TO DEPICT
A REASONABLE SCENARIO WITH A FEW ISOLATED STORMS SOUTHWEST OF US
ALONG THE WARM FRONT MONDAY NIGHT...THEN MAINLY FARTHER NORTH INTO
WI ALONG WARM FRONTAL ZONE TUES AND TO THE WEST ALONG THE
APPROACHING COLD FRONT. BASED ON THIS HAVE MAINTAINED ONLY A
SLIGHT CHANCE POP FOR TSRA ACROSS IL COUNTIES TUES...AND TEMPS
AROUND 90 PER VERY CLOSE MAV/MET NUMBERS. SHOULD CLOUD COVER FROM
UPSTREAM OR NEARBY STORMS TURN OUT TO NOT BE A FACTOR...IT COULD
TURN OUT A COUPLE OF DEGREES WARMER WITH AN EXCESSIVE HEAT
ADVISORY LIKELY BEING NEEDED FOR AT LEAST A PORTION OF THE CWA.

UPPER LOW/TROUGH CONTINUE TO LIFT NORTHEAST INTO NORTHWESTERN
ONTARIO THROUGH EARLY WEDNESDAY...WITH SURFACE COLD FRONT TRAILING
INTO NORTHERN IL BY WEDNESDAY MORNING. AS INDICATED ABOVE...LARGE
SCALE FORCING REMAINS GREATEST ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN LAKES REGION. IN ADDITION...700 MB TEMPS APPROACHING
+12 C DEPICT POTENTIAL CAPPING FARTHER SOUTH/SOUTHWEST ALONG THE
FRONT INTO CENTRAL/WESTERN IL AND THUS HAVE CARRIED RELATIVELY LOW
CHANCE POPS MAINLY ACROSS THE NORTHERN 2/3 OF THE CWA TUESDAY
NIGHT. BETTER CHANCE APPEARS TO BE ACROSS THE SOUTHEAST 1/2 OF THE
FORECAST AREA DURING THE DAY...ESPECIALLY THE AFTERNOON HOURS OF
WEDNESDAY AS THE FRONT COMPLETES ITS TRANSIT OF THE CWA DURING A
MORE DIURNALLY FAVORED TIME FOR BREAKING THE CAP. WIDESPREAD
SEVERE THREAT APPEARS LOW WITH 0-6 KM BULK SHEAR GENERALLY 20 KT
OR LESS PER FORECAST SOUNDINGS...THOUGH PWATS VARYING FROM 1.6-2.3
INCHES AND POTENTIAL FOR SLOW STORM MOVEMENT DOES SUGGEST A HEAVY
RAIN THREAT. STORMS SHOULD END BY EVENING AS FRONT CLEARS THE
FORECAST AREA TO THE SOUTHEAST. SLIGHTLY COOLER/DRIER AIR WORKS IN
FROM THE NORTHWEST BY AFTERNOON FOR AREAS LIKE ROCKFORD...WITH
HIGHS RANGING FROM THE MID 80S THERE TO NEAR 90 WITH CONTINUED
HUMID CONDITIONS STILL IN THE SOUTHEAST.

THURSDAY AND FRIDAY SHOULD BE RELATIVELY QUIET AS WEAK SURFACE
HIGH PRESSURE BUILDS FROM THE CENTRAL PLAINS EASTWARD ACROSS
CENTRAL IL/IN AND EVENTUALLY ACROSS THE OHIO VALLEY. SEASONABLY
WARM...WITH LOW LEVEL THERMAL PROGS SUPPORTING MID-80S FOR THE
MOST PART AND LOWER DEW POINTS IN THE UPPER 50S TO LOWER 60S.

BY NEXT WEEKEND...UPPER PATTERN EVOLVES TO A WESTERN
RIDGE/EASTERN TROUGH WITH NORTHWEST FLOW ALOFT ACROSS OUR REGION.
LONGER RANGE GUIDANCE DEPICTS A FEW SHORT WAVES PROPAGATING
THROUGH THE NORTHWEST FLOW WITH INDICATION OF A WEAK SURFACE
TROUGH/COLD FRONT SATURDAY INTO SUNDAY...WITH AN UPTICK IN DEW
POINTS/HUMIDITY AHEAD OF THE BOUNDARY AND AT LEAST MODESTLY
INCREASING THUNDERSTORM CHANCES.

RATZER

&&

.AVIATION...

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

* SCHC -RA THIS AFTERNOON.

* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS AFTERNOON
  AT TIMES. BETTER CHANCE TOMORROW.

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH POSSIBLY SOME SPRINKLES THIS AFTERNOON.

* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW TODAY. MEDIUM IN WIND SPEED
  TOMORROW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SCHC -RA THIS AFTERNOON.

* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS AFTERNOON
  AT TIMES. BETTER CHANCE TOMORROW.

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH POSSIBLY SOME SPRINKLES THIS AFTERNOON.

* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW TODAY. MEDIUM IN WIND SPEED
  TOMORROW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 262000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SCHC -RA THIS AFTERNOON.

* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS AFTERNOON
  AT TIMES. BETTER CHANCE TOMORROW.

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH POSSIBLY SOME SPRINKLES THIS AFTERNOON.

* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW TODAY. MEDIUM IN WIND SPEED
  TOMORROW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 261930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* OCCASIONAL -RA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS
  AFTERNOON AT TIMES

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME SPRINKLES THIS AFTERNOON
* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 261930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT SUN JUL 26 2015

.SHORT TERM...
224 PM CDT

THROUGH MONDAY NIGHT...

CLOUDS CONTINUED TO THICKEN FROM WEST TO EAST THIS MORNING...AND HAS
PERSISTED THROUGH THIS AFTERNOON FOR MUCH OF THE FORECAST AREA. A
WEAKENING COMPLEX OF THUNDERSTORMS HAD INITIALLY BECOME FOCUSED
ACROSS NORTHERN MISSOURI THIS MORNING...HOWEVER A FEW STRONGER
POCKETS OF CONVECTION REMAINED OVER FAR EASTERN IOWA. THIS ALLOWED
AN AREA OF MODERATE TO AT TIMES HEAVY RAIN AND A FEW EMBEDDED
THUNDERSTORMS TO PERSIST...AND DRIFT EAST INTO LEE/OGLE COUNTIES
EARLY THIS AFTERNOON. DUAL-POL PRECIP ESTIMATES INDICATED A FEW
LOCATIONS IN LEE COUNTY HAVE RECEIVED BETWEEN 2 AND 3 INCHES OF
RAIN. THE LOOP OF REFLECTIVITY SUGGESTS THIS LINE WAS BEGINNING TO
DRIFT NORTHEAST INTO A SLIGHTLY MORE STABLE ENVIRONMENT. WEAK SFC
RIDGE REMAINED CENTERED OVER LOWER MICHIGAN...FEEDING EASTERLY WINDS
BACK FROM NORTHEAST IL/NORTHWEST IN. THIS HAS ALLOWED DEW POINTS FOR
MUCH OF THE FORECAST AREA TO REMAIN IN THE MID/UPR 60S. MEANWHILE
FURTHER WEST/SOUTH AND CLOSER TO THE QUASI-STATIONARY BOUNDARY
MOISTURE CONTINUES TO POOL ALONG THIS FEATURE WITH DEW POINTS IN THE
LOW/MID 70S. VISIBLE IMAGERY INDICATES SOME VERTICAL GROWTH ALONG
THE STALLED FRONTAL BOUNDARY...WHERE GREATER INSTABILITY REMAINS
THIS AFTERNOON. FORTUNATELY A RELATIVELY THICK SOLAR SHIELD REMAINS
AND HAS KEPT TEMPS FROM WARMING TOO MUCH...MAINLY IN THE LOW 80S.

LATE THIS AFTERNOON SOME EROSION TO THE CLOUD COVER SHOULD OCCUR
ACROSS THE WEST/SOUTH CWFA...WHICH SHOULD ALLOW SOME UPTICK IN THE
SHOWERS AND THUNDERSTORMS. ALTHOUGH THE DEEP LAYER SHEAR...AND MU-
CAPE PARAMETERS ARE NOT SUGGESTIVE OF SEVERE WEATHER. THAT BEING
SAID...ANY STRONGER CORES THAT COULD DEVELOP AND QUICKLY DISSIPATE
MAY GENERATE ENOUGH WIND TO PRODUCE A GUST IN EXCESS OF 40MPH.
WHATEVER CONVECTION DOES DEVELOP...THE LARGER CONCERN WOULD BE FOR
BRIEF HEAVY DOWNPOURS...GIVEN SUCH A MOIST LLVL AND LACK OF STEERING
WINDS. THUS CONVECTION WOULD BE SLOW MOVING. EXPECT AS THE EVENING
PROGRESSES...THE MID-LVL VORT MAX WILL PIVOT SOUTHEAST ALONG THE
QUASI-STATIONARY BOUNDARY AND SHOULD PULL THE BEST CHANCE FOR
CONVECTION FURTHER SOUTH/SOUTHEAST. AT THIS TIME FAR NORTHEAST IL
CONTINUES TO REMAIN ON THE DRY SIDE OF GUIDANCE...AND WILL CONTINUE
TO KEEP A DRY FORECAST TONIGHT. CLOUDS WILL LIKELY LINGER
TONIGHT...WHICH SHOULD HELP KEEP TEMPS MILD IN THE UPR 60S TO ARND
70.

MONDAY THROUGH MONDAY NIGHT... GUIDANCE HAS CONTINUED TO INDICATE
MID-LVL HEIGHTS STEADILY INCREASING FROM WEST TO EAST EARLY MON.
THIS SHOULD HELP PROVIDE SOME DIFFLUENCE IN THE MID-LVLS AND PARTLY
CLOUDY SKIES FOR AT LEAST THE FIRST HALF OF MON. BY LATE IN THE
AFTERNOON 500MB HEIGHTS BEGIN TO FLATTEN...WITH A WEAK LLVL WAVE
OVER THE SOUTHERN PLAINS DRIFTING NORTH AND MAY ALLOW THE QUASI-
STATIONARY BOUNDARY TO LIFT NORTH ACROSS THE WEST/SOUTHWEST CWFA.
GIVEN THE CONTINUED ABUNDANCE OF LLVL MOISTURE MON...IT APPEARS
FAVORABLE THAT THE BEST CHANCE FOR ANY CONVECTION/PRECIP COULD BE
THE WESTERN CWFA.

850MB THERMAL RIDGE AXIS BEGINS TO PIVOT EAST MON...HOWEVER THE
WARMEST AIR CONTINUES TO BE FOCUSED WELL WEST OF THE CWFA IN
IOWA/MISSOURI. HAVE HELD ONTO TEMPS IN THE MID/UPR 80S...ALTHOUGH
COULD SEE A FEW AREAS TOUCHING 90 DEGREES DEPENDING ON CLOUD COVER
AND COVERAGE OF PRECIP. ONSHORE FLOW SHOULD LOCK TEMPS ALONG THE
ILLINOIS NEARSHORE IN THE UPR 70S/ARND 80.

MID-LVL TROUGH WILL BEGIN TO NUDGE EAST FROM THE ROCKIES MON
NGT...PUSHING THE MOIST/WARM CHANNEL ACROSS THE PLAINS FURTHER EAST
MON NGT ACROSS THE FORECAST AREA. THIS SHOULD ALLOW FOR A GREATER
CHANCE FOR SHOWERS/THUNDERSTORMS TO FINALLY ARRIVE OVER NORTHEAST
IL/NORTHWEST IN WITH SOUTHERLY FLOW DEVELOPING AS WELL. OVERNIGHT
LOWS WILL REMAIN MILD ARND 70 TO THE LOW 70S.

BEACHLER

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* OCCASIONAL -RA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS
  AFTERNOON AT TIMES

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD

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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME SPRINKLES THIS AFTERNOON
* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
225 PM CDT

WEAK HIGH PRESSURE REMAINS ACROSS THE EASTERN GREAT LAKES...WITH A
MINIMAL GRADIENT STRETCHING OVER LAKE MICHIGAN. THE WINDS CONTINUE
TO BE GENERALLY FROM THE EAST...BUT AT TIMES VARIABLE. WINDS WILL
BEGIN TO TURN SOUTHEASTERLY MONDAY NIGHT INTO TUESDAY...AS A COLD
FRONT WILL APPROACH THE LAKE WEDNESDAY. THIS WILL ALLOW WINDS TO
INCREASE ALONG A TIGHT GRADIENT...BEFORE TURNING NORTHWEST. THEN
ANOTHER WEAK RIDGE OF HIGH PRESSURE ARRIVES LATER IN THE WEEK.

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 261759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 PM CDT SUN JUL 26 2015

.UPDATE...

MINOR ADJUSTMENTS TO THE GOING FORECAST. CLOUDS HAVE STREAMED EAST
ACROSS MUCH OF NORTHERN IL THIS MORNING...AND EVENTUALLY PUSHING
INTO NORTHWEST INDIANA BY LATE MORNING. A DECAYING LINE OF SHOWERS
EMBEDDED THUNDERSTORMS WAS SLOWLY SLIDING EAST ACROSS THE
MISSISSIPPII RIVER...AND WILL OVERSPREAD SOME RAIN INTO FAR
WESTERN CWFA LATE MORNING/EARLY THIS AFTERNOON. DUE TO THE
ABUNDANT CLOUD COVER...TEMPERATURES MAY BE SLOWER TO
WARM...ALTHOUGH BY MID-AFTERNOON TIMING WOULD INDICATE THE CLOUDS
DEPARTING TO THE EAST WITH PARTLY CLOUDY SKIES REDEVELOPING. THIS
SHOULD ONLY TEMPORARILY DELAY THE WARMING AT THE SFC...SO HAVE
TWEAKED DIURNAL TEMPS TO REFLECT THIS.

THE MAIN FOCUS CONTINUES TO BE THE FRONTAL BOUNDARY WHICH REMAINS
ORIENTED ACROSS NORTHERN MISSOURI EAST THROUGH CENTRAL IL...AND IS
NOT EXPECTED TO MOVE MUCH TODAY GIVEN THE LACK OF FORCING/WINDS.
THUS THE BEST CHANCE FOR ANY AFTERNOON SHOWERS/THUNDERSTORMS WILL
BE CENTERED ALONG AND SOUTH OF I-80...HOWEVER BY LATE AFTERNOON A
STRAY AREA OF CONVECTION CANNOT BE RULED OUT FURTHER NORTH AS SOME
BETTER VERTICAL STRUCTURE TO CUMULUS MAY OCCUR. BEST TIMING
CONTINUES TO BE AFTER 2PM.

BEACHLER

&&

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* OCCASIONAL -RA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS
  AFTERNOON AT TIMES

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD


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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME SPRINKLES THIS AFTERNOON
* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 PM CDT SUN JUL 26 2015

.UPDATE...

MINOR ADJUSTMENTS TO THE GOING FORECAST. CLOUDS HAVE STREAMED EAST
ACROSS MUCH OF NORTHERN IL THIS MORNING...AND EVENTUALLY PUSHING
INTO NORTHWEST INDIANA BY LATE MORNING. A DECAYING LINE OF SHOWERS
EMBEDDED THUNDERSTORMS WAS SLOWLY SLIDING EAST ACROSS THE
MISSISSIPPII RIVER...AND WILL OVERSPREAD SOME RAIN INTO FAR
WESTERN CWFA LATE MORNING/EARLY THIS AFTERNOON. DUE TO THE
ABUNDANT CLOUD COVER...TEMPERATURES MAY BE SLOWER TO
WARM...ALTHOUGH BY MID-AFTERNOON TIMING WOULD INDICATE THE CLOUDS
DEPARTING TO THE EAST WITH PARTLY CLOUDY SKIES REDEVELOPING. THIS
SHOULD ONLY TEMPORARILY DELAY THE WARMING AT THE SFC...SO HAVE
TWEAKED DIURNAL TEMPS TO REFLECT THIS.

THE MAIN FOCUS CONTINUES TO BE THE FRONTAL BOUNDARY WHICH REMAINS
ORIENTED ACROSS NORTHERN MISSOURI EAST THROUGH CENTRAL IL...AND IS
NOT EXPECTED TO MOVE MUCH TODAY GIVEN THE LACK OF FORCING/WINDS.
THUS THE BEST CHANCE FOR ANY AFTERNOON SHOWERS/THUNDERSTORMS WILL
BE CENTERED ALONG AND SOUTH OF I-80...HOWEVER BY LATE AFTERNOON A
STRAY AREA OF CONVECTION CANNOT BE RULED OUT FURTHER NORTH AS SOME
BETTER VERTICAL STRUCTURE TO CUMULUS MAY OCCUR. BEST TIMING
CONTINUES TO BE AFTER 2PM.

BEACHLER

&&

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* OCCASIONAL -RA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10 KT THIS
  AFTERNOON AT TIMES

KMD

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

THE UPPER LEVEL WAVE PRODUCING THE COMPLEX OF THUNDERSTORMS IN
WESTERN ILLINOIS WILL CONTINUE TO WEAKEN AND DIVE SOUTHEAST ALONG
THE BETTER INSTABILITY GRADIENT SOUTH AND EAST OF THE MAIN
CHICAGOLAND TERMINALS. EXPECT CONVECTIVE ACTIVITY TO CONTINUE TO
BUBBLE TO THE SOUTHWEST THROUGH THIS AFTERNOON. EXPECT AS A
PORTION OF THE WAVE MARCHES RIGHT ON THROUGH THE AREA THAT A
PERIOD OF LIGHT RAIN/LARGELY SPRINKLES DUE TO THE HIGH CLOUD
BASES WILL IMPACT THE REMAINDER OF THE AREA IN THE COMING HOURS.

MEANWHILE...EAST WINDS CONTINUE TO LARGELY HOLD IN THE 6-9 KT
RANGE...AND NO CHANGE IN THIS IS EXPECTED OTHER THAN SOME
INFREQUENT 10 KT WINDS OWING TO THE CLOUD COVER...WEAKER THERMAL
CONTRAST BETWEEN LAND/LAKE.

KMD


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

* MEDIUM-HIGH IN ACCUMULATING RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME SPRINKLES THIS AFTERNOON
* HIGH THAT WINDS WILL LARGELY REMAIN IN THE 7-9 KT RANGE AND THAT
  THE 10+ KT FREQUENCY WILL BE LOW.

KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261625
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1125 AM CDT SUN JUL 26 2015

.UPDATE...957 AM CDT

MINOR ADJUSTMENTS TO THE GOING FORECAST. CLOUDS HAVE STREAMED EAST
ACROSS MUCH OF NORTHERN IL THIS MORNING...AND EVENTUALLY PUSHING
INTO NORTHWEST INDIANA BY LATE MORNING. A DECAYING LINE OF SHOWERS
EMBEDDED THUNDERSTORMS WAS SLOWLY SLIDING EAST ACROSS THE
MISSISSIPPII RIVER...AND WILL OVERSPREAD SOME RAIN INTO FAR
WESTERN CWFA LATE MORNING/EARLY THIS AFTERNOON. DUE TO THE
ABUNDANT CLOUD COVER...TEMPERATURES MAY BE SLOWER TO
WARM...ALTHOUGH BY MID-AFTERNOON TIMING WOULD INDICATE THE CLOUDS
DEPARTING TO THE EAST WITH PARTLY CLOUDY SKIES REDEVELOPING. THIS
SHOULD ONLY TEMPORARILY DELAY THE WARMING AT THE SFC...SO HAVE
TWEAKED DIURNAL TEMPS TO REFLECT THIS.

THE MAIN FOCUS CONTINUES TO BE THE FRONTAL BOUNDARY WHICH REMAINS
ORIENTED ACROSS NORTHERN MISSOURI EAST THROUGH CENTRAL IL...AND IS
NOT EXPECTED TO MOVE MUCH TODAY GIVEN THE LACK OF FORCING/WINDS.
THUS THE BEST CHANCE FOR ANY AFTERNOON SHOWERS/THUNDERSTORMS WILL
BE CENTERED ALONG AND SOUTH OF I-80...HOWEVER BY LATE AFTERNOON A
STRAY AREA OF CONVECTION CANNOT BE RULED OUT FURTHER NORTH AS SOME
BETTER VERTICAL STRUCTURE TO CUMULUS MAY OCCUR. BEST TIMING
CONTINUES TO BE AFTER 2PM.

BEACHLER

&&

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI/KMD

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI

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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME OCCASIONAL SPRINKLES AT ORD
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261625
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1125 AM CDT SUN JUL 26 2015

.UPDATE...957 AM CDT

MINOR ADJUSTMENTS TO THE GOING FORECAST. CLOUDS HAVE STREAMED EAST
ACROSS MUCH OF NORTHERN IL THIS MORNING...AND EVENTUALLY PUSHING
INTO NORTHWEST INDIANA BY LATE MORNING. A DECAYING LINE OF SHOWERS
EMBEDDED THUNDERSTORMS WAS SLOWLY SLIDING EAST ACROSS THE
MISSISSIPPII RIVER...AND WILL OVERSPREAD SOME RAIN INTO FAR
WESTERN CWFA LATE MORNING/EARLY THIS AFTERNOON. DUE TO THE
ABUNDANT CLOUD COVER...TEMPERATURES MAY BE SLOWER TO
WARM...ALTHOUGH BY MID-AFTERNOON TIMING WOULD INDICATE THE CLOUDS
DEPARTING TO THE EAST WITH PARTLY CLOUDY SKIES REDEVELOPING. THIS
SHOULD ONLY TEMPORARILY DELAY THE WARMING AT THE SFC...SO HAVE
TWEAKED DIURNAL TEMPS TO REFLECT THIS.

THE MAIN FOCUS CONTINUES TO BE THE FRONTAL BOUNDARY WHICH REMAINS
ORIENTED ACROSS NORTHERN MISSOURI EAST THROUGH CENTRAL IL...AND IS
NOT EXPECTED TO MOVE MUCH TODAY GIVEN THE LACK OF FORCING/WINDS.
THUS THE BEST CHANCE FOR ANY AFTERNOON SHOWERS/THUNDERSTORMS WILL
BE CENTERED ALONG AND SOUTH OF I-80...HOWEVER BY LATE AFTERNOON A
STRAY AREA OF CONVECTION CANNOT BE RULED OUT FURTHER NORTH AS SOME
BETTER VERTICAL STRUCTURE TO CUMULUS MAY OCCUR. BEST TIMING
CONTINUES TO BE AFTER 2PM.

BEACHLER

&&

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI/KMD

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI

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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING
  TERMINALS...THOUGH LIKELY SOME OCCASIONAL SPRINKLES AT ORD
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261502
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1002 AM CDT SUN JUL 26 2015

.UPDATE...
957 AM CDT

MINOR ADJUSTMENTS TO THE GOING FORECAST. CLOUDS HAVE STREAMED EAST
ACROSS MUCH OF NORTHERN IL THIS MORNING...AND EVENTUALLY PUSHING
INTO NORTHWEST INDIANA BY LATE MORNING. A DECAYING LINE OF SHOWERS
EMBEDDED THUNDERSTORMS WAS SLOWLY SLIDING EAST ACROSS THE
MISSISSIPPII RIVER...AND WILL OVERSPREAD SOME RAIN INTO FAR
WESTERN CWFA LATE MORNING/EARLY THIS AFTERNOON. DUE TO THE
ABUNDANT CLOUD COVER...TEMPERATURES MAY BE SLOWER TO
WARM...ALTHOUGH BY MID-AFTERNOON TIMING WOULD INDICATE THE CLOUDS
DEPARTING TO THE EAST WITH PARTLY CLOUDY SKIES REDEVELOPING. THIS
SHOULD ONLY TEMPORARILY DELAY THE WARMING AT THE SFC...SO HAVE
TWEAKED DIURNAL TEMPS TO REFLECT THIS.

THE MAIN FOCUS CONTINUES TO BE THE FRONTAL BOUNDARY WHICH REMAINS
ORIENTED ACROSS NORTHERN MISSOURI EAST THROUGH CENTRAL IL...AND IS
NOT EXPECTED TO MOVE MUCH TODAY GIVEN THE LACK OF FORCING/WINDS.
THUS THE BEST CHANCE FOR ANY AFTERNOON SHOWERS/THUNDERSTORMS WILL
BE CENTERED ALONG AND SOUTH OF I-80...HOWEVER BY LATE AFTERNOON A
STRAY AREA OF CONVECTION CANNOT BE RULED OUT FURTHER NORTH AS SOME
BETTER VERTICAL STRUCTURE TO CUMULUS MAY OCCUR. BEST TIMING
CONTINUES TO BE AFTER 2PM.

BEACHLER

&&

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI/KMD

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI

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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261411
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
911 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI/KMD

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI

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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261411
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
911 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI/KMD

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI

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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI/KMD

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261143
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
643 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI


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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261143
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
643 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI


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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261143
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
643 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI


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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 261143
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
643 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* SLIGHT CHANCE OF SHRA THIS AFTERNOON
* EAST TO NORTHEAST WINDS POTENTIALLY NEARING 10KT THIS AFTERNOON
  AT TIMES

IZZI

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

COMPLEX OF SHRA/TSRA MOVING EAST INTO EASTERN IOWA EARLY THIS
MORNING IS NOT BEING HANDLED WELL BY AVAILABLE FORECAST MODEL
GUIDANCE...BUT GUIDANCE THERE IS SUGGESTS THAT THE NORTHERN
PORTIONS APPROACHING NORTHERN ILLINOIS WILL QUICKLY WEAKEN THIS
MORNING. OBJECTIVE ANALYSIS DATA WOULD ALSO SUPPORT WEAKENING WITH
BETTER MOISTURE AND INSTABILITY SOUTH AND WEST OF THE TERMINALS.
GIVEN ITS CLOSER PROXIMITY TO ONGOING ACTIVITY HAVE ADDED A VCSH
LATE THIS MORNING/EARLY THIS AFTERNOON TO RFD...BUT KEPT TAFS DRY
IN IMMEDIATE CHICAGO AREA. DAY SHIFT WILL NEED TO CLOSELY MONITOR
PROGRESS OF THIS ACTIVITY AND IF WEAKENING IS SLOW TO OCCUR MAY
NEED TO ENTERTAIN THE IDEA OF INTRODUCING SOME PRECIP INTO CHICAGO
AREA TERMINALS. WEAKER PUSH AND MORE CLOUD COVER WILL LIKELY MEAN
A SLIGHTLY WEAKER LAKE BREEZE...SO WHILE A COUPLE BRIEF OBS
NEARING 10KT ARE POSSIBLE AT ORD/MDW THINK THE PREVAILING WINDS
WILL LIKELY REMAIN MAINLY BELOW 10KT.

IZZI


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

* MEDIUM CONFIDENCE IN RAIN DIMINISHING BEFORE REACHING TERMINALS
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

MONDAY NIGHT AND TUESDAY...VFR.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY THROUGH SATURDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260900
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
400 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260900
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
400 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
328 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
328 AM CDT SUN JUL 26 2015

.SHORT TERM...

THROUGH MONDAY NIGHT...

328 AM...FORECAST CONCERNS REMAIN CONVECTIVE CHANCES...LAKE
BREEZES AND EARLY AM FOG.

PATCHY FOG HAS DEVELOPED ACROSS PARTS OF THE AREA...WITH LOWER
VISIBILITIES INTO NORTHERN INDIANA CURRENTLY. MID/HIGH CLOUDS
MOVING ACROSS THE AREA WILL LIKELY LIMIT FOG BUT SOME FOG...
PERHAPS WITH SHALLOW DENSE FOG WILL BE POSSIBLE THRU SUNRISE.
LITTLE CHANGE TO THE AIRMASS TONIGHT INTO MONDAY MORNING AND
SOME FOG WILL ONCE AGAIN BE POSSIBLE.

ONE COMPLEX OF THUNDERSTORMS IS MOVING SOUTHEAST ACROSS EASTERN
MISSOURI AND INTO WESTERN ILLINOIS EARLY THIS MORNING AND WILL
REMAIN SOUTHWEST OF THE CWA. A SECOND COMPLEX IS MOVING SOUTH
INTO NORTHERN IOWA AND WILL CONTINUE SOUTHEAST AS IT WEAKENS
THRU MID/LATE MORNING. POSSIBLE THERE COULD BE SOME ISOLATED
SHOWERS...POSSIBLY WITH THUNDER ACROSS THE FAR WEST/SOUTHWEST
CWA THIS MORNING. BETTER...BUT STILL RATHER LOW...CHANCE FOR
THUNDERSTORMS WILL BE THIS AFTERNOON INTO THIS EVENING...MAINLY
SOUTHWEST HALF OF THE CWA WHICH WILL BE IN THE VICINITY OF THE
SURFACE BOUNDARY AND WHERE DEWPOINTS LOOK TO POOL IN THE LOWER
TO MID 70S. THIS ACTIVITY WILL LIKELY BE MOSTLY DIURNALLY DRIVEN
AND EXPECT A DECREASE IN COVERAGE LATER THIS EVENING WITH THE
OVERNIGHT HOURS POSSIBLY BEING DRY.

FURTHER NORTHEAST...APPEARS MORE STABLE CONDITIONS WILL PERSIST
WITH A LAKE BREEZE MOVING INLAND THIS AFTERNOON AS HIGH PRESSURE
SLIDES EAST ACROSS THE SOUTHERN LAKES REGION. HIGHS INLAND SHOULD
REACH MID 80S...WITH THE EXPECTATION DEBRIS CLOUD SCATTERS OUT BY
LATE MORNING. A FEW LOCATIONS COULD TAG UPPER 80S BUT TEMPS RIGHT
AT THE BEACHES WILL LIKELY STAY IN THE 70S.

THE BOUNDARY TO THE SOUTHWEST TODAY WILL LIFT NORTH AS A WARM
FRONT ON MONDAY. THIS WILL TURN WINDS SOUTHERLY MOST LOCATIONS
BUT ANOTHER LAKE BREEZE IS POSSIBLE MAINLY ACROSS THE ILLINOIS
SHORE. THERE IS LITTLE TO FOCUS/ORGANIZE THUNDERSTORM DEVELOPMENT
MONDAY OR MONDAY NIGHT WITH PERHAPS JUST AN ISOLATED SHOWER OR
STORM MONDAY AFTERNOON/EVENING WITH PEAK HEATING. MAINTAINED
CURRENT SLIGHT CHANCE MENTION ACROSS MAINLY THE WESTERN CWA BUT
ITS POSSIBLE THIS TIME PERIOD WILL END UP BEING DRY.

HIGH TEMPS ON MONDAY WILL REACH THE UPPER 80S WITH A FEW
LOCATIONS POSSIBLY TAGGING 90. DEWPOINTS BACK INTO THE LOWER/MID
70S ACROSS MUCH OF THE AREA WILL PUSH PEAK HEAT INDICES INTO THE
MID 90S NORTH TO UPPER 90S SOUTH. ASSUMING A LAKE BREEZE DOES FORM
AND MOVES INLAND ACROSS PARTS OF NORTHEAST IL...THIS WILL KEEP
TEMPS/HEAT INDICES A BIT LOWER. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

328 AM...MAIN FORECAST CONCERNS ARE HIGH TEMPS/HEAT INDICES
TUESDAY AND THUNDERSTORM CHANCES WITH A COLD FRONT LATE TUESDAY
NIGHT AND WEDNESDAY.

SIMILAR TO MONDAY...IT IS DIFFICULT TO FIND MUCH TO FOCUS
THUNDERSTORM DEVELOPMENT ON TUESDAY. BUT FROM THIS DISTANCE...
ITS POSSIBLE UPSTREAM CONVECTION OR OUTFLOWS COULD BECOME AN
ISSUE. BUT AT THE MOMENT...WHILE MAINTAINING SLIGHT CHANCE
POPS...TUESDAY COULD BE QUITE WARM/HOT AND CONTINUED VERY HUMID
WITH DEWPOINTS WELL INTO THE 70S. CURRENT HIGHS AROUND 90 WOULD
PUSH PEAK HEAT INDICES TO MID/UPPER 90S NORTH AND INTO THE 100-
105 RANGE SOUTH. THIS TIME PERIOD WILL NEED TO BE MONITORED AS
HEAT INDICES APPROACH ADVISORY CRITERIA ACROSS THE SOUTHERN CWA
TUESDAY AFTERNOON.

TUESDAY NIGHT COULD END UP VERY WARM PERHAPS WITH TEMPS ONLY IN
THE MID 70S...UPPER 70S IN URBAN AREAS. BUT DIDN/T GO THIS WARM
FOR ACTUAL LOW TEMPS JUST YET...AS CONVECTION OR CONVECTIVE
OUTFLOWS MAY BE APPROACHING THE NORTHERN CWA OVERNIGHT OR BY
WEDNESDAY MORNING AS BOTH THE GFS/ECMWF HAVE SPED UP THE FRONTAL
TIMING. THIS INCREASES THE UNCERTAINTY FOR WEDNESDAY BOTH FOR
HIGH TEMPS AND CONVECTIVE TRENDS/TIMING. BUT THIS DOES APPEAR TO
BE THE BEST CHANCE FOR THUNDERSTORMS FOR THE ENTIRE AREA OVER THE
NEXT SEVERAL DAYS. WITH THE FRONT NOW PUSHING THRU BY WEDNESDAY
EVENING...HAVE GONE DRY WEDNESDAY NIGHT.

SLIGHTLY COOLER AND LESS HUMID AIR WILL THEN ARRIVE THURSDAY.
THERE NOW APPEARS TO BE ONE OR TWO WEAK WAVES MOVING SOUTHEAST
ACROSS THE MIDWEST/LAKES REGION FRIDAY NIGHT AND AGAIN NEXT
WEEKEND...AT LEAST AS SHOWN BY THE GFS...WHICH MAY BRING THE
CHANCE OF PRECIP BACK INTO THE FORECAST FRIDAY NIGHT INTO NEXT
WEEKEND. CMS

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260629
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
129 AM CDT SUN JUL 26 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
129 AM CDT

NO SIGNIFICANT WINDS/WAVES FORECAST ON THE LAKE THROUGH NEXT WEEK.
SOUTHERLY WINDS WILL FRESHEN UP JUST A BIT TUESDAY NIGHT AHEAD OF
A COLD FRONT THAT WILL MOVE ACROSS THE LAKE WEDNESDAY...FOLLOWED
BY WEAK HIGH PRESSURE AND THEN ANOTHER WEAK FRONTAL PASSAGE TOWARD
END OF THE WEEK.

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 260525
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1225 AM CDT SUN JUL 26 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 260525
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1225 AM CDT SUN JUL 26 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST WINDS COULD APPROACH 10KT AT TIMES SUNDAY AFTERNOON

IZZI

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

NO SIGNIFICANT WEATHER EXPECTED THROUGH THE TAF CYCLE. SCT-BKN
MID-HIGH LEVEL CLOUDINESS EXPECTED THROUGH MUCH OF THE PERIOD AS
SCATTERED SHRA/TSRA TRACK WEST OF THE TERMINALS. FOR CHICAGO
TERMINALS...LIGHT WINDS WILL PICK UP FROM THE EAST/NORTHEAST
SUNDAY AFTERNOON AIDED BY LAKE BREEZE. ANTICIPATE WINDS TO
PRIMARILY HOLD SHY OF 10KT...HOWEVER CANNOT RULE OUT BRIEFLY
TAGGING 10 OR 11KT AT TIMES SUNDAY AFTERNOON.

IZZI

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 260304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT ON SUNDAY.

RODRIGUEZ

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

BOUNDARY/LAKE BREEZE HAS SINCE PUSHED WELL INLAND THIS EVENING
WITH SPEEDS AROUND 10 KT CONTINUING AT THIS TIME. EXPECT THIS
BOUNDARY TO CONTINUE PUSHING THROUGH AREAS IN NORTHERN ILLINOIS
AND NORTHWEST INDIANA...BUT EXPECT SPEEDS TO DROP OFF
SIGNIFICANTLY OVER THE NEXT ONE TO TWO HOURS ON BOTH SIDES OF THE
BOUNDARY. ANY THUNDERSTORM ACTIVITY THIS EVENING INTO OVERNIGHT
WILL REMAIN WELL AWAY FROM THE TERMINALS...WITH VFR CONDITIONS
EXPECTED. INCREASING MID/HIGH LEVEL CLOUD COVER WILL BE OBSERVED
ON SUNDAY AS WIND SPEEDS INCREASE ONCE AGAIN OUT OF THE EAST.
ALTHOUGH THE BEST SHOWER/THUNDERSTORM DEVELOPMENT ON SUNDAY SHOULD
STAY TO THE WEST OF THE TERMINALS...SOME LOWER CONFIDENCE TO ITS
EASTWARD PUSH REMAINS. DID INCLUDE VCTS FOR ROCKFORD...AND WILL
NEED TO MONITOR THUNDERSTORM POTENTIAL SUNDAY INTO SUNDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 260304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT ON SUNDAY.

RODRIGUEZ

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

BOUNDARY/LAKE BREEZE HAS SINCE PUSHED WELL INLAND THIS EVENING
WITH SPEEDS AROUND 10 KT CONTINUING AT THIS TIME. EXPECT THIS
BOUNDARY TO CONTINUE PUSHING THROUGH AREAS IN NORTHERN ILLINOIS
AND NORTHWEST INDIANA...BUT EXPECT SPEEDS TO DROP OFF
SIGNIFICANTLY OVER THE NEXT ONE TO TWO HOURS ON BOTH SIDES OF THE
BOUNDARY. ANY THUNDERSTORM ACTIVITY THIS EVENING INTO OVERNIGHT
WILL REMAIN WELL AWAY FROM THE TERMINALS...WITH VFR CONDITIONS
EXPECTED. INCREASING MID/HIGH LEVEL CLOUD COVER WILL BE OBSERVED
ON SUNDAY AS WIND SPEEDS INCREASE ONCE AGAIN OUT OF THE EAST.
ALTHOUGH THE BEST SHOWER/THUNDERSTORM DEVELOPMENT ON SUNDAY SHOULD
STAY TO THE WEST OF THE TERMINALS...SOME LOWER CONFIDENCE TO ITS
EASTWARD PUSH REMAINS. DID INCLUDE VCTS FOR ROCKFORD...AND WILL
NEED TO MONITOR THUNDERSTORM POTENTIAL SUNDAY INTO SUNDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 260304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT ON SUNDAY.

RODRIGUEZ

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

BOUNDARY/LAKE BREEZE HAS SINCE PUSHED WELL INLAND THIS EVENING
WITH SPEEDS AROUND 10 KT CONTINUING AT THIS TIME. EXPECT THIS
BOUNDARY TO CONTINUE PUSHING THROUGH AREAS IN NORTHERN ILLINOIS
AND NORTHWEST INDIANA...BUT EXPECT SPEEDS TO DROP OFF
SIGNIFICANTLY OVER THE NEXT ONE TO TWO HOURS ON BOTH SIDES OF THE
BOUNDARY. ANY THUNDERSTORM ACTIVITY THIS EVENING INTO OVERNIGHT
WILL REMAIN WELL AWAY FROM THE TERMINALS...WITH VFR CONDITIONS
EXPECTED. INCREASING MID/HIGH LEVEL CLOUD COVER WILL BE OBSERVED
ON SUNDAY AS WIND SPEEDS INCREASE ONCE AGAIN OUT OF THE EAST.
ALTHOUGH THE BEST SHOWER/THUNDERSTORM DEVELOPMENT ON SUNDAY SHOULD
STAY TO THE WEST OF THE TERMINALS...SOME LOWER CONFIDENCE TO ITS
EASTWARD PUSH REMAINS. DID INCLUDE VCTS FOR ROCKFORD...AND WILL
NEED TO MONITOR THUNDERSTORM POTENTIAL SUNDAY INTO SUNDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252344
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
644 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT OVER THE NEXT HOUR...AND ONCE
  AGAIN ON SUNDAY.

RODRIGUEZ

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

BOUNDARY/LAKE BREEZE HAS SINCE PUSHED WELL INLAND THIS EVENING
WITH SPEEDS AROUND 10 KT CONTINUING AT THIS TIME. EXPECT THIS
BOUNDARY TO CONTINUE PUSHING THROUGH AREAS IN NORTHERN ILLINOIS
AND NORTHWEST INDIANA...BUT EXPECT SPEEDS TO DROP OFF
SIGNIFICANTLY OVER THE NEXT ONE TO TWO HOURS ON BOTH SIDES OF THE
BOUNDARY. ANY THUNDERSTORM ACTIVITY THIS EVENING INTO OVERNIGHT
WILL REMAIN WELL AWAY FROM THE TERMINALS...WITH VFR CONDITIONS
EXPECTED. INCREASING MID/HIGH LEVEL CLOUD COVER WILL BE OBSERVED
ON SUNDAY AS WIND SPEEDS INCREASE ONCE AGAIN OUT OF THE EAST.
ALTHOUGH THE BEST SHOWER/THUNDERSTORM DEVELOPMENT ON SUNDAY SHOULD
STAY TO THE WEST OF THE TERMINALS...SOME LOWER CONFIDENCE TO ITS
EASTWARD PUSH REMAINS. DID INCLUDE VCTS FOR ROCKFORD...AND WILL
NEED TO MONITOR THUNDERSTORM POTENTIAL SUNDAY INTO SUNDAY EVENING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252344
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
644 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT OVER THE NEXT HOUR...AND ONCE
  AGAIN ON SUNDAY.

RODRIGUEZ

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

BOUNDARY/LAKE BREEZE HAS SINCE PUSHED WELL INLAND THIS EVENING
WITH SPEEDS AROUND 10 KT CONTINUING AT THIS TIME. EXPECT THIS
BOUNDARY TO CONTINUE PUSHING THROUGH AREAS IN NORTHERN ILLINOIS
AND NORTHWEST INDIANA...BUT EXPECT SPEEDS TO DROP OFF
SIGNIFICANTLY OVER THE NEXT ONE TO TWO HOURS ON BOTH SIDES OF THE
BOUNDARY. ANY THUNDERSTORM ACTIVITY THIS EVENING INTO OVERNIGHT
WILL REMAIN WELL AWAY FROM THE TERMINALS...WITH VFR CONDITIONS
EXPECTED. INCREASING MID/HIGH LEVEL CLOUD COVER WILL BE OBSERVED
ON SUNDAY AS WIND SPEEDS INCREASE ONCE AGAIN OUT OF THE EAST.
ALTHOUGH THE BEST SHOWER/THUNDERSTORM DEVELOPMENT ON SUNDAY SHOULD
STAY TO THE WEST OF THE TERMINALS...SOME LOWER CONFIDENCE TO ITS
EASTWARD PUSH REMAINS. DID INCLUDE VCTS FOR ROCKFORD...AND WILL
NEED TO MONITOR THUNDERSTORM POTENTIAL SUNDAY INTO SUNDAY EVENING.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH VFR CONDITIONS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

MONDAY...VFR.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF TSRA LATE.

RODRIGUEZ

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT THROUGH EARLY EVENING.

RODRIGUEZ

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION IN THE NEAR TERM.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

RODRIGUEZ

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT THROUGH EARLY EVENING.

RODRIGUEZ

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION IN THE NEAR TERM.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

RODRIGUEZ

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT THROUGH EARLY EVENING.

RODRIGUEZ

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION IN THE NEAR TERM.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

RODRIGUEZ

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252220
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
520 PM CDT SAT JUL 25 2015

.MESOSCALE DISCUSSION...
506 PM CDT

MONITORING ISOLATED THUNDERSTORM DEVELOPMENT EARLY THIS
EVENING...MAINLY ACROSS EASTERN WILL AND LAKE/PORTER COUNTIES IN
INDIANA. CURRENT STORMS ARE DEVELOPING ALONG SYNOPTICALLY
ENHANCED LAKE BREEZE...STEADILY PUSHING INTO AREAS IN NORTHERN
ILLINOIS AND NORTHWEST INDIANA. ENVIRONMENT OUT AHEAD OF THIS
BOUNDARY IS NOTED BY MODERATELY/STRONGLY UNSTABLE
ENVIRONMENT...WITH MLCAPE OF 2000-4000J/KG AND MID TO UPPER 70S
DEWPOINT AIR. WITH FORCING ALOFT RATHER WEAK...LOW LEVEL
CONVERGENCE LIMITED...AND WITH WEAK MID LEVEL LAPSE RATES...DONT
ANTICIPATE COVERAGE TO INCREASE TOO MUCH BEYOND WHAT IS CURRENTLY
GOING ON. EXPECT MAINLY ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT ALONG AND SOUTH OF A LINE FROM MENDOTA TO BEECHER
ILLINOIS...TO WHEATFIELD INDIANA OVER THE TWO TO THREE HOURS.
INTENSITY WILL LIKELY REMAIN SIMILAR TO WHAT IS CURRING
NOW...HOWEVER...CANNOT RULE OUT AN ISOLATED STRONGER STORM
WHEREVER BETTER LOW LEVEL CONVERGENCE CAN BE REALIZED. STRONG WIND
GUSTS AND TORRENTIAL HEAVY RAINFALL WOULD BE THE LIKELY HAZARDS
WITH ANY STRONGER STORMS EARLY THIS EVENING.

RODRIGUEZ

&&

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* EAST/NORTHEAST WINDS AROUND 10KT THROUGH EARLY EVENING.

RODRIGUEZ

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION IN THE NEAR TERM.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

RODRIGUEZ

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 252011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...
306 PM CDT

MONDAY NIGHT THROUGH SATURDAY...

WARM AND MUGGY CONDITIONS LOOK TO BE THE RULE TO START THE
WEEK...WITH SOME OCCASIONAL LOWER CHANCES FOR THUNDERSTORMS...WITH
HIGHER CHANCES MIDWEEK. COOLER AND DRIER CONDITIONS EXPECTED TO
END THE WEEK.

SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES SUNDAY NIGHT
GENERALLY REMAINS IN PLACE ON MONDAY...WHICH WILL KEEP A STATIONARY
FRONT LOCKED IN PLACE OVER OR JUST TO THE SOUTH AND WEST OF OUR
SOUTHWESTERN COUNTIES. THIS COMBINED WITH THE UPPER RIDGE BUILDING
SUNDAY NIGHT SHOULD KEEP THINGS FAIRLY QUIET OVER MUCH OF THE AREA
FOR SUNDAY NIGHT AND FOR THE MOST PART MONDAY TOO. THE EXCEPTION
WOULD BE CLOSER TO THE FRONT...WHICH AT THIS POINT WOULD LIKELY BE
INTO CENTRAL AND WESTERN ILLINOIS. HAVE HUNG ONTO SOME LOW POPS FOR
THESE AREAS AS WEAK MID LEVEL DISTURBANCES AHEAD OF THE WESTERN U.S.
TROUGH INTERACT WITH A WARM AND MOIST AIR MASS...WITH MUCH OF THE
METRO AREA AND ESPECIALLY NORTHERN AND EASTERN AREAS DRY. HEAT
INDICES MONDAY CREEP INTO MID TO UPPER 90S COURTESY OF UPPER 60S TO
MID 70S DEWPOINTS...HIGHEST SOUTH.

MODELS ARE IN GOOD AGREEMENT ABOUT A BUILDING MID/UPPER LEVEL RIDGE
OVER THE AREA ON TUESDAY. THIS WOULD LARGELY TRANSLATE TO CONTINUED
WARMER AND MUGGIER CONDITIONS ON TUESDAY. ALL THIS HINGES ON
CONVECTION TO THE WEST WHICH MAY SEND SOME DEBRIS CLOUDINESS THROUGH
THE AREA. THIS PATTERN WOULD SUGGEST A DRY DAY TUESDAY TOO...BUT
MUCH OF THE GUIDANCE HAS SOME PRECIPITATION BREAKING OUT AS MID
LEVEL DISTURBANCES ATTEMPT TO RIDE THE BUILDING RIDGE AND MODEST SW
RETURN FLOW DEVELOPS. SOME THIS APPEARS TO BE REMNANTS FROM
CONVECTION OFF TO OUR NORTHWEST WHERE THE BETTER FORCING WILL
RESIDE...COUPLED WITH LESS IN THE WAY OF AFTERNOON CONVECTION NEAR
THE LINGERING SURFACE FRONT AND ANY POSSIBLE OUTFLOW BOUNDARIES.
HAVE HELD ONTO SOME LOWER POP CHANCES DURING THIS TIME GIVEN THESE
UNCERTAINTIES. IT WILL REMAIN MUGGY WITH HIGHS WELL INTO THE 80S
AND POSSIBLY 90S...HINGING ON CLOUD COVER...PUSHES HEAT INDICES TO
NEAR/ABOVE 100 IN SPOTS.

THE DEEP UPPER TROUGH WILL MOVE THROUGH THE UPPER MIDWEST
WEDNESDAY...WHICH WILL FLATTEN THE RIDGE TUESDAY NIGHT INTO
WEDNESDAY. ADDITIONALLY...A MODEST COLD FRONT WILL MOVE THROUGH
NORTHEAST ILLINOIS DURING THE DAY WEDNESDAY AND NORTHWEST INDIANA
WEDNESDAY EVENING. PRECIP CHANCES INCREASE OVERNIGHT INTO
WEDNESDAY...WITH THE BEST CHANCE FOR ORGANIZED CONVECTION IN OUR
SOUTHEASTERN AREAS AHEAD OF THE COLD FRONT ON THE SOUTHERN FRINGE OF
THE STRONGER WESTERLIES ALOFT. HIGH PWAT AGAIN AHEAD OF THE FRONT
WILL MEAN LOCALLY HEAVY DOWNPOURS ARE ONCE AGAIN POSSIBLE.

DRY AND LESS MUGGY CONDITIONS RETURN FOR THE LATTER HALF OF THE WEEK
AS HIGH PRESSURE BUILDS BACK OVER THE REGION.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
306 PM CDT

WEAK HIGH PRESSURE OVER THE UPPER MIDWEST WILL BUILD INTO THE
WESTERN LAKES REGION TONIGHT...THEN SLOWLY MOVE EAST TO THE MID
ATLANTIC STATES BY TUESDAY. THIS WILL RESULT IN NO MAJOR CONCERNS
OVER THE LAKE AS TYPICAL SUMMERTIME LAKE/LAND BREEZE WIND PATTERNS
SET UP. ANOTHER LOW PRESSURE SYSTEM ORGANIZES OVER THE NORTHERN
PLAINS EARLY NEXT WEEK. THE LOW WILL TRACK NORTHEAST INTO ONTARIO BY
MIDWEEK WITH A TRAILING COLD FRONT MOVING ACROSS THE LAKE LATE
WEDNESDAY INTO EARLY THURSDAY.

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 251948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE/BEACH

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE/BEACH

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251829
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
129 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251829
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
129 PM CDT SAT JUL 25 2015

.SHORT TERM...
128 PM CDT

THROUGH SUNDAY...

REMNANTS CLOUDS FROM A MORNING COMPLEX OVER IOWA HAVE BEGUN TO ERODE
AND SHIFT SOUTH...ALONG WITH A FRONTAL BOUNDARY DRIFTING SOUTH
ACROSS THE HEART OF THE CWFA THIS AFTERNOON. SOME WEAK CONVERGENCE
IN THE LOW LEVELS IS NOTED FROM SURFACE OBSERVATIONS...HOWEVER
VISIBLE IMAGERY DOES NOT APPEAR TO INDICATE ANY SUBSTANTIAL VERTICAL
GROWTH TO THE CUMULUS FIELD. AS THE BOUNDARY CONTINUES TO SAG
SOUTH/SOUTHEAST ACROSS THE REGION...WINDS WILL SHIFT TO NORTHWEST
THEN NORTH AS A SFC RIDGE CENTERED OVER WISC BEGINS TO SHIFT
SOUTHEAST. THIS ANTI-CYCLONIC FEATURE SHOULD AID IN MAINTAINING A
DRY ATMOSPHERE FOR MUCH OF THE CWFA THIS EVENING. THE EXCEPTION WILL
BE THE FAR SOUTHERN CWFA WHERE THE BOUNDARY WILL BE SLOW TO
MOVE...SETTING UP ADDITIONAL LLVL CONVERGENCE AND MARGINAL
INSTABILITY. MESOANALYSIS WOULD INDICATE THE LACK OF WIND IN THE MID-
LVLS...SO NOT EXPECTING ANY SIZABLE GROWTH TO ANY CONVECTION THAT
WOULD DEVELOP THIS AFTN. HOWEVER...THE ONE ELEMENT THAT IS WORTH
POINTING OUT IS THE NEAR 2 INCH PWAT AND DEW POINTS IN THE LOW/MID
70S ALONG AND SOUTH OF I-80 THIS AFTN. BEHIND THE BOUNDARY DEW
POINTS ONLY DROP INTO THE UPR 60S.

AS THE CLOUDS HAVE ERODED NORTH OF I-80...TEMPS HAVE EASILY WARMED
INTO THE MIDDLE AND UPPER 80S. A FEW POINTS COULD STILL TOUCH 90 DEG
THIS AFTN BEFORE THE BOUNDARY ARRIVES. THIS COUPLED WITH HIGH DEW
POINTS WILL PUSH HEAT INDEX VALUES TO THE LOW/MID 90S.

THE LAKE BREEZE HAS BEGUN TO PUSH INLAND EARLY THIS AFTN...AND
SHOULD CONTINUE TO PUSH SOUTHWEST ACROSS CHICAGO AND THE WESTERN
SUBURBS. HELPING TO LOWER DEW POINTS/TEMPS...THEN WITH SFC RIDGE
INFLUENCING THE OVERNIGHT...LIGHT WINDS WILL DEVELOP. WHILE THE
GRADIENT REMAINS MINIMAL OVERNIGHT...TEMPS SHUD FALL INTO THE
MID/UPR 60S AND ARND 70 CLOSER TO DOWNTOWN CHICAGO. HAVE HELD OUT ON
INCLUDING PATCHY FOG OVERNIGHT...BUT SOME AREAS OF FOG COULD DEVELOP
AND PRODUCE SOME MINOR REDUCTIONS TO VISIBILITIES WELL AFTER
MIDNIGHT.

SUNDAY... GUIDANCE CONTINUES TO SUGGEST A COMPLEX OF THUNDERSTORMS
WILL BE SLIDING EAST ACROSS THE CENTRAL PLAINS EARLY SUN. THE MOST
LIKELY PATH WILL BE ALONG THE QUASI-STATIONARY BOUNDARY...WHICH
SHOULD BE ORIENTED FROM SOUTHERN IOWA EAST THROUGH CENTRAL IL/IN.
THERE IS SOME STEERING TO THE NORTH THAT MAY OCCUR FROM A DEVELOPING
SFC WAVE SUN AFTN...THAT COULD BRING THE BOUNDARY NORTH BY SUN
AFTN/EVE. THE MOST PROBABLY TIMING APPEARS TO BE LATE AFTN...WITH
STEADILY INCREASING CHANCES FOR SHOWERS/THUNDERSTORMS FROM THE FAR
SOUTH/SOUTHWEST TO NORTH. THE WILDCARD WILL BE THE WEAK SFC RIDGE
WHICH APPEARS TO BE RATHER STUBBORN ON DEPARTING THE GREAT LAKES
REGION SUN. SFC WINDS WILL LIKELY REMAIN EASTERLY UNTIL LATE
AFTN...WHICH COULD HELP SHARPEN THE BOUNDARY AND BAROCLINIC ZONE
ACROSS EASTERN IOWA/FAR WESTERN IL. TEMPS SUN WILL BE A CHALLENGE
DEPENDING ON CLOUD COVER AND PRECIP...SO HAVE ONLY MADE MINOR
ADJUSTMENTS WITH HIGHS GENERALLY IN THE LOW/MID 80S.

BEACHLER

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251754 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1254 PM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE


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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251754 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1254 PM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

HIGH PRESSURE REMAINS OVER THE REGION AS A WEAK COLD FRONT IS
SLOWLY SHIFTING SOUTH THROUGH NORTHERN IL. WITH THE LIGHT GRADIENT
OVERHEAD...EXPECTING WINDS TO TURN NORTHWEST BEHIND THE COLD
FRONT AT RFD AND THEN FLIP TO NORTHEAST TO EAST BEHIND A LAKE
BREEZE AT THE EASTERN TERMINALS. THE LAKE BREEZE HAS FINALLY
FORMED WITH THE BUOY OFF THE CHICAGO SHORE SHOWING EAST WINDS AT
11 KT. GUIDANCE VARIES WITH THE TIME OF ARRIVAL OF THE LAKE BREEZE
AT ORD FROM 19 TO 21Z SO KEPT 20Z GOING. ALSO KEPT 10G15KT AT ORD
AND MDW AS THIS LAKE BREEZE SHOULD HAVE A GOOD PUSH OF WIND BEHIND
IT. WINDS DIMINISH THIS EVENING WITH LIGHT AND VARIABLE TO CALM
WINDS OVERNIGHT.

NOT EXPECTING ANY SHOWERS OR STORMS AT THE TERMINALS AS ANY ISOL
TO SCATTERED DEVELOPMENT WILL OCCUR WELL SOUTH OF THE TERMINALS.

VFR CONDITIONS CONTINUE TOMORROW WITH EAST TO NORTHEAST WINDS TO 9
KT AT THE EASTERN TERMINALS...AND SOUTHEAST WINDS AT RFD.

JEE


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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251620
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1120 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251620
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1120 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251620
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1120 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251402
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
902 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251402
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
902 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251402
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
902 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN AROUND 20Z THIS AFTN.

JEE

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN A LAKE BREEZE FLIPPING WINDS TO NE AT OR
  ABOVE 10 KT THIS AFTN...MEDIUM CONFIDENCE IN TIMING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN 20-22Z THIS AFTERNOON

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WIND SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >=10KT

IZZI

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN 20-22Z THIS AFTERNOON

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WIND SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >=10KT

IZZI

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN 20-22Z THIS AFTERNOON

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WIND SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >=10KT

IZZI

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 251132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE 10-15KT EXPECTED BETWEEN 20-22Z THIS AFTERNOON

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
OR STORM THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY.
LAKE BREEZE FRONT WILL DEVELOP THIS AFTERNOON AND PUSH THROUGH
THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON. EXPECT WINDS
TO PICK UP TO AROUND 10KT BEHIND THE LAKE BREEZE AND THEN
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN SOME LIGHT
EASTERLY DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WIND SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >=10KT

IZZI

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

SUNDAY NIGHT THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF
SHRA OR TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY AND FRIDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250901
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
401 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT SAT JUL 25 2015

.SHORT TERM...

THROUGH SUNDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES ALONG WITH
LAKE BREEZES.

A WEAK FRONTAL BOUNDARY/WIND SHIFT EXTENDS FROM EASTERN LAKE
SUPERIOR INTO NORTHEAST IOWA EARLY THIS MORNING. THIS FRONT WILL
MOVE SOUTHEAST INTO THE NORTHERN CWA THIS MORNING. ISOLATED
SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE AFTER SUNRISE
AS THIS FRONT MOVES ACROSS THE AREA. WEAK FORCING SHOULD LIMIT
COVERAGE TO ISOLATED AND MAINTAINED SLIGHT CHANCE POPS FOR NOW
BUT ITS LIKELY THEIR DURATION CAN BE TRIMMED IN THE GRIDS AS
TRENDS EMERGE THIS MORNING. AS THE FRONT MOVES INTO THE SOUTHERN
CWA THIS AFTERNOON...ALONG WITH A LAKE BREEZE MOVING INLAND...
DAYTIME HEATING AND SOME MOISTURE POOLING ALONG THE FRONT...THAT
COVERAGE MAY INCREASE ACROSS NORTHWEST INDIANA AND ACROSS EAST
CENTRAL IL. STILL LOW CONFIDENCE BUT BUMPED POPS UP A TAD. IT
WOULD BE DURING THIS TIME PERIOD...MID AFTERNOON THRU EARLY
EVENING THAT ANY STRONG OR POSSIBLY SEVERE STORMS WILL BE POSSIBLE
WITH GUSTY WINDS THEY MAIN THREAT...ALONG WITH LOCALLY HEAVY RAIN
WITH AN OVERALL DECREASE IN COVERAGE THIS EVENING INTO TONIGHT.

HIGH TEMPS IN THE MID/UPPER 80S TODAY COMBINED WITH DEWPOINTS IN
THE LOWER/MID 70S WILL PUSH HEAT INDICES INTO THE MID 90S...
PERHAPS UPPER 90S SOUTHERN AREAS. DEWPOINTS WILL LIKELY DROP BACK
INTO THE UPPER 60S ACROSS THE NORTH THIS AFTERNOON AND THEN TEMPS
WILL DROP A FEW DEGREES BEHIND THE LAKE BREEZE INLAND...AND LIKELY
INTO THE 70S RIGHT AT THE LAKE FRONT.

HIGH PRESSURE SETTLES ACROSS THE GREAT LAKES REGION LATER TONIGHT
AND ONLY SLOWLY DRIFTS EAST ON SUNDAY. THIS WILL LIKELY KEEP THE
THREAT OF PRECIP GENERALLY WEST AND SOUTHWEST OF THE CWA SUNDAY.
MAINTAINED SLIGHT CHANCE POPS ACROSS THE WESTERN HALF OR SO OF THE
AREA DUE TO UNCERTAINTY AND POSSIBLY AFTERNOON CONVECTION BUT ITS
POSSIBLE SUNDAY COULD END UP DRY FOR MOST OF THE AREA. ANOTHER
LAKE BREEZE SUNDAY WILL MAINTAIN COOLER TEMPS AT THE LAKE. CMS

&&

.LONG TERM...

SUNDAY NIGHT THROUGH FRIDAY...

311 AM...MAIN FORECAST CONCERNS ARE CONVECTIVE CHANCES AND HIGH
TEMPS.

WITH HIGH PRESSURE STILL OVER THE SOUTHERN/EASTERN LAKES SUNDAY
NIGHT AND MONDAY...ANY ORGANIZED CONVECTION APPEARS UNLIKELY
PERHAPS UNTIL WEDNESDAY. BUT THERE IS TOO MUCH UNCERTAINTY TO
REMOVE POPS COMPLETELY. BUT HAVE LOWERED POPS INTO SLIGHT CHANCE
FOR SEVERAL PERIODS WITH THE BEST CHANCE OF ORGANIZED PRECIP NOT
UNTIL LATE TUESDAY NIGHT OR WEDNESDAY AS A COLD FRONT APPROACHES.
DECENT RUN TO RUN CONSISTENCY WITH THIS FRONT MOVING SOUTH OF THE
AREA BY THURSDAY MORNING WITH DRY WEATHER AND SEASONAL TEMPS
THURSDAY AND FRIDAY.

LESS PRECIP WILL LEAD TO MORE SUN AND THE POTENTIAL FOR WARMER
TEMPS ESPECIALLY TUESDAY AND WEDNESDAY WHEN HIGHS IN THE UPPER
80S/LOWER 90S WILL BE POSSIBLE. WITH DEWPOINTS BACK INTO THE
LOWER/MID 70S BOTH DAYS...HEAT INDICES COULD REACH THE UPPER 90S
NORTH TO 100-105 SOUTHERN AREAS. SO THIS PERIOD WILL NEED TO BE
MONITORED. CMS

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250718
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
218 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250718
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
218 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250718
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
218 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250718
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
218 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
218 AM CDT

NO SIGNIFICANT WINDS OR WAVES ANTICIPATED ON THE LAKE THROUGH THE
FORECAST PERIOD. TYPICAL SUMMERTIME LAKE/LAND BREEZE CIRCULATIONS
WILL LIKELY DEVELOP DIURNALLY THROUGH THE PERIOD.

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 250531
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1231 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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 250531
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1231 AM CDT SAT JUL 25 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* WIND SHIFT TO NE...LIKELY 10KT+...BETWEEN 20-22Z SATURDAY

IZZI

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

WEAK COLD FRONT WILL MOVE THROUGH THE TERMINALS THIS MORNING
CAUSING LIGHT SOUTH-SOUTHWEST WINDS TO GRADUALLY VEER WEST THEN
PROBABLY A BIT NORTH OF WEST BY EARLY AFTERNOON...BUT ALL
GENERALLY LESS THAN 10KT. CANNOT TOTALLY RULE OUT A BRIEF SHOWER
THIS MORNING...BUT CHANCES ARE SLIM AND NOT TAF WORTHY. LAKE
BREEZE FRONT WILL LIKELY DEVELOP SATURDAY AFTERNOON AND PUSH
THROUGH THE CHICAGO TERMINALS DURING THE MID-LATE AFTERNOON.
MODEL GUIDANCE IS MOSTLY TARGETING THE 22Z-00Z TIME FRAME FOR WIND
SHIFT AT ORD/MDW...HOWEVER GUIDANCE TENDS TO BE A BIT SLOW AND
INHERITED 19Z WIND SHIFT...SO FELT TRENDING A HAIR SLOWER TO 20Z
WAS A GOOD COMPROMISE THOUGH PERHAPS STILL A BIT FAST. WINDS
DIMINISH DURING THE EVENING THOUGH LIKELY MAINTAIN EASTERLY
DIRECTION.

IZZI

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

* HIGH CONFIDENCE IN WIND SHIFT TO NE SAT MID-LATE AFTERNOON
* MEDIUM-HIGH CONFIDENCE ON 20Z-22Z TIME WINDOW FOR WINDOW SHIFT
* MEDIUM CONFIDENCE ON SPEEDS >10KT

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 06Z...

SUNDAY THROUGH TUESDAY...GENERALLY VFR. SLIGHT CHANCE OF SHRA OR
TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

IZZI

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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 250252
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
952 PM CDT FRI JUL 24 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* POSSIBLE MVFR CEILINGS EARLY SATURDAY MORNING.

* SCATTERED SHOWERS...WITH POSSIBLE THUNDER SATURDAY MORNING.

* WIND SHIFT TO THE NORTHEAST EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

VFR AND DRY CONDITIONS WILL CONTINUE THIS EVENING AND
OVERNIGHT...WITH ATTENTION THEN TURNING TOWARDS APPROACHING COLD
FRONT. THIS FRONT WILL HELP BRING THE POSSIBILITY OF LOWER
CEILINGS AND PRECIP TO THE TERMINALS SATURDAY MORNING. DO THINK
SCATTERED SHOWERS WILL BE AROUND THE TERMINALS BY EARLY SATURDAY
MORNING...BUT HAVE LOWER CONFIDENCE IF EXACTLY THEY WILL BE
IMPACTED OR IF THUNDER WILL ALSO BE PRESENT.
HOWEVER...INSTABILITY WILL BE INCREASING TONIGHT AND SO THUNDER
WILL BE A DEFINITE POSSIBILITY. LOOKING UPSTREAM ACROSS
MN/IA/WI...VFR CEILINGS WITH ISOLATED MVFR CEILINGS ARE PRESENT.
THESE CEILINGS WILL MOVE ACROSS THE TERMINALS SATURDAY MORNING BUT
AM NOT CONFIDENT WITH MVFR POTENTIAL AT THIS TIME. IF THEY DO
OCCUR...THEY WILL BE BRIEF. FRONT WILL CONTINUE THROUGH WITH WINDS
SHIFTING TO THE NORTHWEST...AND THEN SHIFTING TO THE NORTHEAST
WITH SPEEDS AT OR ABOVE 10KT BY EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

* MEDIUM CONFIDENCE WITH POSSIBLE MVFR CEILINGS.

* MEDIUM CONFIDENCE WITH SCATTERED SHOWERS...LOW CONFIDENCE WITH
  THUNDER.

* HIGH CONFIDENCE WITH WIND SHIFT...MEDIUM HIGH CONFIDENCE OF
  TIMING.

RODRIGUEZ

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

SUNDAY...CHANCE OF TSRA.

MONDAY...CHANCE OF TSRA.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

RODRIGUEZ

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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 250252
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
952 PM CDT FRI JUL 24 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* POSSIBLE MVFR CEILINGS EARLY SATURDAY MORNING.

* SCATTERED SHOWERS...WITH POSSIBLE THUNDER SATURDAY MORNING.

* WIND SHIFT TO THE NORTHEAST EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

VFR AND DRY CONDITIONS WILL CONTINUE THIS EVENING AND
OVERNIGHT...WITH ATTENTION THEN TURNING TOWARDS APPROACHING COLD
FRONT. THIS FRONT WILL HELP BRING THE POSSIBILITY OF LOWER
CEILINGS AND PRECIP TO THE TERMINALS SATURDAY MORNING. DO THINK
SCATTERED SHOWERS WILL BE AROUND THE TERMINALS BY EARLY SATURDAY
MORNING...BUT HAVE LOWER CONFIDENCE IF EXACTLY THEY WILL BE
IMPACTED OR IF THUNDER WILL ALSO BE PRESENT.
HOWEVER...INSTABILITY WILL BE INCREASING TONIGHT AND SO THUNDER
WILL BE A DEFINITE POSSIBILITY. LOOKING UPSTREAM ACROSS
MN/IA/WI...VFR CEILINGS WITH ISOLATED MVFR CEILINGS ARE PRESENT.
THESE CEILINGS WILL MOVE ACROSS THE TERMINALS SATURDAY MORNING BUT
AM NOT CONFIDENT WITH MVFR POTENTIAL AT THIS TIME. IF THEY DO
OCCUR...THEY WILL BE BRIEF. FRONT WILL CONTINUE THROUGH WITH WINDS
SHIFTING TO THE NORTHWEST...AND THEN SHIFTING TO THE NORTHEAST
WITH SPEEDS AT OR ABOVE 10KT BY EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

* MEDIUM CONFIDENCE WITH POSSIBLE MVFR CEILINGS.

* MEDIUM CONFIDENCE WITH SCATTERED SHOWERS...LOW CONFIDENCE WITH
  THUNDER.

* HIGH CONFIDENCE WITH WIND SHIFT...MEDIUM HIGH CONFIDENCE OF
  TIMING.

RODRIGUEZ

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

SUNDAY...CHANCE OF TSRA.

MONDAY...CHANCE OF TSRA.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

RODRIGUEZ

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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 250252
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
952 PM CDT FRI JUL 24 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* POSSIBLE MVFR CEILINGS EARLY SATURDAY MORNING.

* SCATTERED SHOWERS...WITH POSSIBLE THUNDER SATURDAY MORNING.

* WIND SHIFT TO THE NORTHEAST EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

VFR AND DRY CONDITIONS WILL CONTINUE THIS EVENING AND
OVERNIGHT...WITH ATTENTION THEN TURNING TOWARDS APPROACHING COLD
FRONT. THIS FRONT WILL HELP BRING THE POSSIBILITY OF LOWER
CEILINGS AND PRECIP TO THE TERMINALS SATURDAY MORNING. DO THINK
SCATTERED SHOWERS WILL BE AROUND THE TERMINALS BY EARLY SATURDAY
MORNING...BUT HAVE LOWER CONFIDENCE IF EXACTLY THEY WILL BE
IMPACTED OR IF THUNDER WILL ALSO BE PRESENT.
HOWEVER...INSTABILITY WILL BE INCREASING TONIGHT AND SO THUNDER
WILL BE A DEFINITE POSSIBILITY. LOOKING UPSTREAM ACROSS
MN/IA/WI...VFR CEILINGS WITH ISOLATED MVFR CEILINGS ARE PRESENT.
THESE CEILINGS WILL MOVE ACROSS THE TERMINALS SATURDAY MORNING BUT
AM NOT CONFIDENT WITH MVFR POTENTIAL AT THIS TIME. IF THEY DO
OCCUR...THEY WILL BE BRIEF. FRONT WILL CONTINUE THROUGH WITH WINDS
SHIFTING TO THE NORTHWEST...AND THEN SHIFTING TO THE NORTHEAST
WITH SPEEDS AT OR ABOVE 10KT BY EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

* MEDIUM CONFIDENCE WITH POSSIBLE MVFR CEILINGS.

* MEDIUM CONFIDENCE WITH SCATTERED SHOWERS...LOW CONFIDENCE WITH
  THUNDER.

* HIGH CONFIDENCE WITH WIND SHIFT...MEDIUM HIGH CONFIDENCE OF
  TIMING.

RODRIGUEZ

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

SUNDAY...CHANCE OF TSRA.

MONDAY...CHANCE OF TSRA.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

RODRIGUEZ

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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
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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 250252
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
952 PM CDT FRI JUL 24 2015

.SHORT TERM...
331 PM CDT

THROUGH SATURDAY...

THE UPPER LEVEL RIDGE IS FLATTENING ACROSS THE PLAINS THIS AFTERNOON
WITH NORTHWEST FLOW BECOMING ZONAL OVER THE REGION THIS EVENING INTO
SATURDAY MORNING. ZONAL FLOW WILL ALLOW UPPER LEVEL DISTURBANCES TO
TRAVEL EAST THROUGH THE CWA.

THE SURFACE HIGH IS CENTERED OVER INDIANA AND ITS CENTER WILL SLOWLY
SHIFT EAST THROUGH SATURDAY WHILE WE WILL STILL BE UNDER ITS
INFLUENCE.  A LOW IS OVER NORTHWEST ONTARIO WITH ITS COLD FRONT
EXTENDING THROUGH MINNESOTA AND THEN DOWN THROUGH THE CENTRAL
PLAINS.  THE LOW WILL DEEPEN AND SHIFT OVER HUDSON BAY BY SATURDAY
EVENING WHILE ITS COLD FRONT SWINGS THROUGH DURING THE DAY ON
SATURDAY.

EXPECTING THE DRY CONDITIONS TO CONTINUE THROUGH THIS EVENING AND
HAVE LOW CONFIDENCE IN PRECIP CHANCES OVERNIGHT AND TOMORROW. I/M
NOT OVERLY IMPRESSED WITH FORCING OR MOISTURE ALONG THE FRONT. RIGHT
NOW THE ONLY CONVECTION IS THE MCS MOVING INTO NORTHERN MISSOURI.
FORECAST SOUNDINGS FEATURE 1000-1500 J/KG OF CAPE SATURDAY MORNING
THROUGH THE EARLY AFTN HOURS WITH DECREASING VALUES THROUGH THE
AFTN. SO CAPPED POPS IN THE LOW CHANCE RANGE ACROSS THE MAJORITY OF
THE CWA BECAUSE I/M THINKING WILL SEE ISOLATE THUNDERSTORM COVERAGE
AT BEST LATE TONIGHT THROUGH SATURDAY MORNING. DEBATED GOING
DRY...BUT DID NOT HAVE ENOUGH CONFIDENCE TO BE THAT DETERMINISTIC.
GUIDANCE VARIES ON HOW THE UPPER LEVEL VORT MAXES TRAVEL THROUGH THE
REGION AND THINKING STORMS WILL BE CLOSELY TIED TO THEM SINCE THEY
WILL PROVIDE EXTRA FORCING. THE ECMWF BRINGS A VORT RIGHT THROUGH
NORTHERN IL AND NW INDIANA SATURDAY AFTN...WITH STORMS FIRING ACROSS
THE CWA. OTHER GUIDANCE KEEPS THE VORTS TO OUR WEST AND SOUTHWEST
WITH CONVECTION FIRING OVER IOWA AND CENTRAL IL. DECIDED TO SIDE
WITH THE MAJORITY OF OPINIONS KEEPING A CHANCE OF STORMS SATURDAY
WEST OF A LASALLE TO PIPER CITY IL LINE AND A SLIGHT CHANCE ACROSS
THE REST OF THE REGION. IF THE VORT DOES TRAVEL CLOSER TO THE
CWA...THUNDERSTORM ACTIVITY WILL LIKELY BE MORE THAN FORECAST.

TO COMPLICATE THINGS FURTHER...GUIDANCE SUGGESTS THE COLD FRONT WILL
STALL JUST SOUTH OF THE CWA ACROSS CENTRAL IL LATE SATURDAY AFTN OR
EVENING. ADDITIONAL CONVECTION COULD FIRE ALONG THE BOUNDARY.

WINDS WILL TURN NORTHWEST BEHIND THE FRONT AND DIMINISH THROUGH THE
AFTN. THINKING THE LIGHT GRADIENT WILL RESULT IN A LAKE BREEZE
SATURDAY AFTN SO HAVE TEMPS ONLY IN THE LOWER 80S ALONG THE LAKE.
HIGH TEMPS WILL BE IN THE UPPER 80S AWAY FROM THE LAKE WITH HEAT
INDICES IN THE LOW TO MID 90S.

JEE

&&

.LONG TERM...
334 PM CDT

SUNDAY THROUGH FRIDAY...

HIGH PRESSURE QUICKLY BUILDS IN SATURDAY NIGHT RESULTING IN
SUBSIDENCE BEHIND ANY POSSIBLE AFTERNOON ACTIVITY. WE REMAIN IN AN
ACTIVE WESTERLY FLOW INTO SUNDAY AND EARLY NEXT WEEK.
THEREFORE...THE HIGH WILL QUICKLY SHIFT EASTWARD. THE BAROCLINIC
ZONE WILL STALL OUT IN OUR SOUTHWESTERN AREAS DURING THE DAY ON
SUNDAY. THE AIR MASS IN THE VICINITY OF THE BOUNDARY SHOULD BE
MODERATELY UNSTABLE WITH READINGS IN THE 80S AND DEWPOINTS IN THE
70S. WITH THE ACTIVE FLOW FAST MOVING DISTURBANCES COUPLED WITH THE
UNSTABLE AIRMASS LOOK TO TRIGGER A BETTER CHANCE FOR THUNDERSTORMS
IN THE AFTERNOON. SLIGHTLY LOWER DEWPOINTS NORTH AND EAST WOULD
SUGGEST THE BEST THREAT WOULD REMAIN CLOSER TO THE BOUNDARY. 30-35
KT OF 500 MB WIND WOULD ALSO INDICATE A CHANCE FOR SOME SEVERE
STORMS WITH HAIL/WIND BEING THE MAIN CONCERNS.

INTO NEXT WEEK...A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC
NORTHWEST WILL AMPLIFY...AND IN TURN THE UPPER RIDGE ACROSS THE
CENTRAL PLAINS WILL AMPLIFY AS WELL. EARLY IN THE WEEK THE RIDGE
DOES NOT LOOK TO BE STRONG ENOUGH TO PRECLUDE ANY WAVES PROPAGATING
AHEAD OF THE WESTERN U.S. TROUGH FROM MIGRATING THROUGH THE RIDGE AT
TIMES THROUGH TUESDAY...THE FIRST AS EARLY AS SUNDAY NIGHT. THESE
SPECIFIC DISTURBANCES ARE NOT VERY WELL HANDLED BY MID RANGE
GUIDANCE AS WELL AS THE PLACEMENT OF THE LOW LEVEL BOUNDARY...THUS
WILL CARRY CHANCE POPS INTO TUESDAY.

MID TO LATE WEEK THE WESTERN U.S. TROUGH WILL MIGRATE EASTWARD
THROUGH THE NORTHERN TIER OF STATES AND WILL PUSH A COLD FRONT
THROUGH THE AREA LATER WEDS INTO THURSDAY WHICH BRING ONE MORE
CHANCE OF STORMS BEFORE A DRIER AIRMASS RETURNS.

KMD

&&

.AVIATION...

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

* POSSIBLE MVFR CEILINGS EARLY SATURDAY MORNING.

* SCATTERED SHOWERS...WITH POSSIBLE THUNDER SATURDAY MORNING.

* WIND SHIFT TO THE NORTHEAST EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

VFR AND DRY CONDITIONS WILL CONTINUE THIS EVENING AND
OVERNIGHT...WITH ATTENTION THEN TURNING TOWARDS APPROACHING COLD
FRONT. THIS FRONT WILL HELP BRING THE POSSIBILITY OF LOWER
CEILINGS AND PRECIP TO THE TERMINALS SATURDAY MORNING. DO THINK
SCATTERED SHOWERS WILL BE AROUND THE TERMINALS BY EARLY SATURDAY
MORNING...BUT HAVE LOWER CONFIDENCE IF EXACTLY THEY WILL BE
IMPACTED OR IF THUNDER WILL ALSO BE PRESENT.
HOWEVER...INSTABILITY WILL BE INCREASING TONIGHT AND SO THUNDER
WILL BE A DEFINITE POSSIBILITY. LOOKING UPSTREAM ACROSS
MN/IA/WI...VFR CEILINGS WITH ISOLATED MVFR CEILINGS ARE PRESENT.
THESE CEILINGS WILL MOVE ACROSS THE TERMINALS SATURDAY MORNING BUT
AM NOT CONFIDENT WITH MVFR POTENTIAL AT THIS TIME. IF THEY DO
OCCUR...THEY WILL BE BRIEF. FRONT WILL CONTINUE THROUGH WITH WINDS
SHIFTING TO THE NORTHWEST...AND THEN SHIFTING TO THE NORTHEAST
WITH SPEEDS AT OR ABOVE 10KT BY EARLY SATURDAY AFTERNOON.

RODRIGUEZ

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

* MEDIUM CONFIDENCE WITH POSSIBLE MVFR CEILINGS.

* MEDIUM CONFIDENCE WITH SCATTERED SHOWERS...LOW CONFIDENCE WITH
  THUNDER.

* HIGH CONFIDENCE WITH WIND SHIFT...MEDIUM HIGH CONFIDENCE OF
  TIMING.

RODRIGUEZ

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

SUNDAY...CHANCE OF TSRA.

MONDAY...CHANCE OF TSRA.

TUESDAY...CHANCE OF TSRA.

WEDNESDAY...CHANCE OF TSRA.

THURSDAY...VFR.

RODRIGUEZ

&&

.MARINE...
344 PM CDT

HIGH PRESSURE CENTERED JUST SOUTH OF THE GREAT LAKES WILL MOVE EAST
THROUGH TONIGHT. LOW PRESSURE ACROSS NORTH CENTRAL ONTARIO LATE THIS
AFTERNOON WILL MOVE SLOWLY TO JAMES BAY BY SATURDAY MORNING. THIS
WILL STEER A COLD FRONT DOWN THE LAKE SATURDAY MORNING. HIGH
PRESSURE WILL BRIEFLY BUILD BACK OVER LAKE MICHIGAN SATURDAY NIGHT
INTO THE DAY SUNDAY. A WARM FRONT IS EXPECTED TO LIFT NORTHWARD OVER
THE LAKE SOMETIME EARLY NEXT WEEK. BY MID WEEK...A SLIGHTLY STRONGER
LOW WILL PASS BY TO THE NORTH OF THE LAKE...WITH A COLD FRONT MOVING
THROUGH WEDNESDAY NIGHT.

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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