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000
FXUS63 KLOT 060831
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
331 AM CDT FRI MAY 6 2016

.SHORT TERM...
327 AM CDT

THROUGH SATURDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND HIGH
TEMPS TODAY...INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
SATURDAY...AND THEN WITH PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS NEXT WEEK.

RELATIVELY QUIET THIS MORNING WITH SURFACE RIDGE AXIS SITUATED
ACROSS THE REGION/CWA. SKIES HAVE REMAINED CLEAR OVERNIGHT BUT
LOOKING UPSTREAM ACROSS WISCONSIN...CAN SEE AN EXPANDING AREA OF
MID LEVEL CLOUDS RAPIDLY PUSHING SOUTH INTO THE CWA. SOUTHWARD
DROPPING SPEED MAX AND STRONG WAA LIKELY OWING FOR THIS EXPANSION
AND DONT SEE WHY THIS WILL DIMINISH AS IT PUSHES THROUGH THE CWA.
SO HAVE INCREASED CLOUD COVER THIS MORNING BUT MAY NEED TO DO SOME
LAST MINUTE ADJUSTMENTS TO FURTHER INCREASE...WITH A PERIOD OF AT
LEAST PARTLY SUNNY SKIES LIKELY THIS MORNING FOR MOST AREAS IN
NORTHERN ILLINOIS AND NORTHWEST INDIANA. CAN SEE A STEADILY MOVING
BACK EDGE TO THIS MID LEVEL MOISTURE WHICH IS CONSISTENT WITH
SHORT TERM GUIDANCE INDICATING THIS WILL EXIT TO THE
SOUTH/SOUTHEAST BY AROUND MIDDAY...WITH SUNNY TO PARTLY CLOUDY
SKIES THEN LIKELY IN THE AFTERNOON. ALSO UP NORTH ARE SOME WEAK
RETURNS ON RADAR AT THIS TIME BUT DONT THINK THIS IS REALLY
REACHING THE GROUND. HAVE MAINTAINED A DRY FORECAST THIS MORNING
BUT AN ISOLATED SPRINKLE COULD BE POSSIBLE. WARMER TEMPS STILL
EXPECTED TODAY DESPITE THIS CLOUD COVER. ALTHOUGH IT MAY INITIALLY
HINDER TEMP TRENDS IN THE MORNING...THE STRONG WAA WILL USHER IN A
MUCH WARMER AIRMASS THAT WILL STILL ALLOW TEMPS TO RISE TO THE 80S
IN NORTHERN ILLINOIS AND MID TO UPPER 70S ACROSS NORTHWEST
INDIANA. WITH SURFACE RIDGE AXIS AND LIGHTER FLOW AROUND...AM A
LITTLE CONCERNED FOR A PERIOD OF ONSHORE FLOW TODAY AND DID LOWER
TEMPS NEAR THE LAKE. HAVE MORE LOW TO MID 70S FOR AREAS NEAR THE
LAKE.

AS ONE UPPER LEVEL LOW/TROUGH EXITS TO THE EAST...ANOTHER UPPER
LEVEL SYSTEM WILL DROP SOUTH INTO THE UPPER MIDWEST AND GREAT
LAKES REGION TONIGHT INTO SATURDAY. THIS WILL ALLOW SURFACE LOW
AND FRONTAL BOUNDARY TO DROP SOUTH THROUGH WISCONSIN TONIGHT AND
AS THIS OCCURS...UPSTREAM MOISTURE/INSTABILITY AXIS WILL SWING
THROUGH. GUIDANCE FAIRLY CONSISTENT WITH THIS AND EXPECT
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS EARLY SATURDAY
MORNING. HAVE INCREASED POPS DURING THIS TIME BUT KEPT AT HIGH
CHANCE OWING TO LOWER CONFIDENCE ON COVERAGE. HOWEVER...ITS
APPEARING THAT MOST LOCATIONS WILL OBSERVE AT LEAST A SMALL WINDOW
OF PRECIP SATURDAY MORNING. THUNDER DOES APPEAR POSSIBLE SATURDAY
MORNING BUT AM NOT ANTICIPATING ANYTHING SEVERE DURING THAT TIME.
AM MONITORING THE SATURDAY AFTERNOON PERIOD FOR POSSIBLE
ADDITIONAL THUNDERSTORM DEVELOPMENT...SOME OF WHICH COULD BE
STRONG. ALTHOUGH THE SIGNAL FOR STRONG THUNDERSTORMS APPEARS TO BE
HIGHER FURTHER TO THE SOUTH OF THE CWA...MOISTURE POOLING AHEAD OF
THIS FRONT AND INCREASING INSTABILITY AHEAD OF APPROACHING SPEED
MAX COULD ALLOW FOR SOME ISOLATED STRONG STORMS SOUTH OF A PONTIAC
IL TO FOWLER INDIANA LINE. THIS POTENTIAL SHOULD QUICKLY END BY
THE EARLY EVENING WITH THE ARRIVAL OF DRIER AIR...BUT WITH SHOWERS
STILL POSSIBLE FOR AREAS OVER THE FAR SOUTHERN CWA.

RODRIGUEZ

&&

.LONG TERM...
327 AM CDT

SUNDAY THROUGH FRIDAY...

THE END OF THE WEEKEND WILL BE DRY BUT AN ACTIVE PATTERN WILL
REMAIN IN PLACE OVER THE CONUS. GUIDANCE SHOWING ANOTHER LARGE
UPPER LEVEL SYSTEM WORKING ITS WAY TOWARD THE REGION SUNDAY NIGHT
INTO MONDAY WITH SHOWERS AND THUNDERSTORMS INCREASING ONCE AGAIN
LATE IN THE NIGHT INTO MONDAY MORNING. LOW CONFIDENCE WITH EXACTLY
HOW MONDAY WILL EVOLVE GIVEN ANTICIPATED ONGOING
SHOWER/THUNDERSTORM ACTIVITY BUT GIVEN INCREASING
MOISTURE/INSTABILITY BEHIND LIFTING FRONTAL BOUNDARY AND
PERSISTENT FORCING ALOFT...WILL NEED TO MONITOR ANOTHER PERIOD FOR
POSSIBLE STRONG THUNDERSTORMS SOMEWHERE ACROSS THE REGION. GIVEN
THE ANTICIPATED CLOSED NATURE OF THIS NEXT SYSTEM AM NOT OVERLY
CONFIDENT WITH MODEL SOLUTIONS AT THIS TIME. NONETHELESS...AN
ACTIVE PERIOD IS APPEARING PROBABLY EARLY NEXT WEEK WITH THIS
SYSTEM LIKELY TO LINGER AROUND THE CWA ON TUESDAY AS WELL. IF THIS
WERE TO OCCUR...THUNDERSTORM DEVELOPMENT WILL AGAIN BE POSSIBLE.

RODRIGUEZ

&&

.AVIATION...
FOR THE 06Z TAFS...

MOSTLY CLEAR SKIES PERSIST ACROSS MUCH OF THE AREA. WITH THE LIGHT
TO AT TIMES CALM WINDS...A FEW AREAS OF PATCHY FOG HAVE DEVELOPED
MAINLY ACROSS NORTHWEST INDIANA AIRFIELDS. ALTHOUGH THE FOG SHOULD
REMAIN AS GROUND FOG...AND LIKELY ONLY IMPACT KGYY AIRFIELD. WINDS
WILL BEGIN TO INCREASE AFTER DAYBREAK FROM THE SOUTHWEST BETWEEN
6-10KT. WINDS ALOFT SHOULD REMAIN JUST STRONG ENOUGH TO PREVENT AN
ONSHORE COMPONENT/LAKE BREEZE FROM IMPACTING ORD/MDW. HOWEVER...IF
WINDS END UP BEING LIGHTER THEN THE LAKE BREEZE MAY BE ABLE TO
MOVE INLAND NEAR MDW/ORD BY MID AFTERNOON.

BEACHLER

&&

.MARINE...
258 AM CDT

HIGH PRESSURE CONTINUES TO BE IN CONTROL OF MUCH OF THE GREAT
LAKES REGION TODAY...STRETCHING SOUTH THROUGH THE GULF OF MEXICO.
HOWEVER THIS RIDGE OF HIGH PRESSURE WILL STEADILY DRIFT SOUTH
WHILE A LOW PRESSURE WILL SLIDE EAST ACROSS WESTERN ONTARIO
TOWARDS QUEBEC BY EARLY SATURDAY. THIS WILL PRODUCE A TRAILING
FRONTAL BOUNDARY THAT WILL SAG SOUTH ACROSS LAKE MICHIGAN EARLY
SATURDAY FOR THE NORTHERN HALF OF THE LAKE...THEN STEADILY PUSH
SOUTH TO THE SOUTHERN HALF OF LAKE MICHIGAN. WINDS WILL REMAIN
RELATIVEL LIGHT THIS MORNING...BUT INCREASE THROUGHOUT THE
AFTERNOON FROM THE SOUTH/SOUTHEAST TO 15 TO 25 KT. THIS WILL
RESULT IN WAVES BUILDING ALONG THE NORTHERN HALF OF LAKE
MICHIGAN...HOWEVER WITH THE MUCH WARMER AIR FLOWING OVER THE LAKE
WAVES WILL LIKELY NOT BUILD MUCH BEYOND 3 TO 5 FT.

THE WEAK GRADIENT MAY TURN WINDS SOUTHEASTERLY WITHIN THE ILLINOIS
NEARSHORE WATERS THIS AFTERNOON...BUT THEN AS THE FRONTAL BOUNDARY
SAGS SOUTH OVERNIGHT/EARLY SATURDAY...WINDS WILL INCREASE FROM THE
SOUTH AND THEN BEHIND THE FRONT QUICKLY TURN NORTHWESTERLY TO
NORTHERLY. WAVES WILL BE INCREASING SATURDAY FOR THE SOUTHERN HALF
OF THE LAKE...AND COULD COME CLOSE TO SMALL CRAFT HAZARDS FOR THE
INDIANA NEARSHORE WATERS. WINDS WILL THEN BEGIN TO DIMINISH LATER
SATURDAY EVENING...THEN TURN EASTERLY.

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 060803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
303 AM CDT FRI MAY 6 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 06Z TAFS...

MOSTLY CLEAR SKIES PERSIST ACROSS MUCH OF THE AREA. WITH THE LIGHT
TO AT TIMES CALM WINDS...A FEW AREAS OF PATCHY FOG HAVE DEVELOPED
MAINLY ACROSS NORTHWEST INDIANA AIRFIELDS. ALTHOUGH THE FOG SHOULD
REMAIN AS GROUND FOG...AND LIKELY ONLY IMPACT KGYY AIRFIELD. WINDS
WILL BEGIN TO INCREASE AFTER DAYBREAK FROM THE SOUTHWEST BETWEEN
6-10KT. WINDS ALOFT SHOULD REMAIN JUST STRONG ENOUGH TO PREVENT AN
ONSHORE COMPONENT/LAKE BREEZE FROM IMPACTING ORD/MDW. HOWEVER...IF
WINDS END UP BEING LIGHTER THEN THE LAKE BREEZE MAY BE ABLE TO
MOVE INLAND NEAR MDW/ORD BY MID AFTERNOON.

BEACHLER

&&

.MARINE...
258 AM CDT

HIGH PRESSURE CONTINUES TO BE IN CONTROL OF MUCH OF THE GREAT
LAKES REGION TODAY...STRETCHING SOUTH THROUGH THE GULF OF MEXICO.
HOWEVER THIS RIDGE OF HIGH PRESSURE WILL STEADILY DRIFT SOUTH
WHILE A LOW PRESSURE WILL SLIDE EAST ACROSS WESTERN ONTARIO
TOWARDS QUEBEC BY EARLY SATURDAY. THIS WILL PRODUCE A TRAILING
FRONTAL BOUNDARY THAT WILL SAG SOUTH ACROSS LAKE MICHIGAN EARLY
SATURDAY FOR THE NORTHERN HALF OF THE LAKE...THEN STEADILY PUSH
SOUTH TO THE SOUTHERN HALF OF LAKE MICHIGAN. WINDS WILL REMAIN
RELATIVEL LIGHT THIS MORNING...BUT INCREASE THROUGHOUT THE
AFTERNOON FROM THE SOUTH/SOUTHEAST TO 15 TO 25 KT. THIS WILL
RESULT IN WAVES BUILDING ALONG THE NORTHERN HALF OF LAKE
MICHIGAN...HOWEVER WITH THE MUCH WARMER AIR FLOWING OVER THE LAKE
WAVES WILL LIKELY NOT BUILD MUCH BEYOND 3 TO 5 FT.

THE WEAK GRADIENT MAY TURN WINDS SOUTHEASTERLY WITHIN THE ILLINOIS
NEARSHORE WATERS THIS AFTERNOON...BUT THEN AS THE FRONTAL BOUNDARY
SAGS SOUTH OVERNIGHT/EARLY SATURDAY...WINDS WILL INCREASE FROM THE
SOUTH AND THEN BEHIND THE FRONT QUICKLY TURN NORTHWESTERLY TO
NORTHERLY. WAVES WILL BE INCREASING SATURDAY FOR THE SOUTHERN HALF
OF THE LAKE...AND COULD COME CLOSE TO SMALL CRAFT HAZARDS FOR THE
INDIANA NEARSHORE WATERS. WINDS WILL THEN BEGIN TO DIMINISH LATER
SATURDAY EVENING...THEN TURN EASTERLY.

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 060622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
122 AM CDT FRI MAY 6 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 06Z TAFS...

MOSTLY CLEAR SKIES PERSIST ACROSS MUCH OF THE AREA. WITH THE LIGHT
TO AT TIMES CALM WINDS...A FEW AREAS OF PATCHY FOG HAVE DEVELOPED
MAINLY ACROSS NORTHWEST INDIANA AIRFIELDS. ALTHOUGH THE FOG SHOULD
REMAIN AS GROUND FOG...AND LIKELY ONLY IMPACT KGYY AIRFIELD. WINDS
WILL BEGIN TO INCREASE AFTER DAYBREAK FROM THE SOUTHWEST BETWEEN
6-10KT. WINDS ALOFT SHOULD REMAIN JUST STRONG ENOUGH TO PREVENT AN
ONSHORE COMPONENT/LAKE BREEZE FROM IMPACTING ORD/MDW. HOWEVER...IF
WINDS END UP BEING LIGHTER THEN THE LAKE BREEZE MAY BE ABLE TO
MOVE INLAND NEAR MDW/ORD BY MID AFTERNOON.

BEACHLER

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

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 060622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
122 AM CDT FRI MAY 6 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 06Z TAFS...

MOSTLY CLEAR SKIES PERSIST ACROSS MUCH OF THE AREA. WITH THE LIGHT
TO AT TIMES CALM WINDS...A FEW AREAS OF PATCHY FOG HAVE DEVELOPED
MAINLY ACROSS NORTHWEST INDIANA AIRFIELDS. ALTHOUGH THE FOG SHOULD
REMAIN AS GROUND FOG...AND LIKELY ONLY IMPACT KGYY AIRFIELD. WINDS
WILL BEGIN TO INCREASE AFTER DAYBREAK FROM THE SOUTHWEST BETWEEN
6-10KT. WINDS ALOFT SHOULD REMAIN JUST STRONG ENOUGH TO PREVENT AN
ONSHORE COMPONENT/LAKE BREEZE FROM IMPACTING ORD/MDW. HOWEVER...IF
WINDS END UP BEING LIGHTER THEN THE LAKE BREEZE MAY BE ABLE TO
MOVE INLAND NEAR MDW/ORD BY MID AFTERNOON.

BEACHLER

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

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 052327
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
627 PM CDT THU MAY 5 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

VFR CONDITIONS EXPECTED THROUGH THE PERIOD. LIGHT WINDS TONIGHT
SHOULD PICK UP TO 6-10KT FROM THE SOUTHWEST FRIDAY MORNING.
CURRENTLY EXPECTING ENOUGH OF AN OFFSHORE WIND TO PREVENT A LAKE
BREEZE FROM IMPACTING THE TERMINALS FRIDAY AFTERNOON...THOUGH
CONFIDENCE IS ADMITTEDLY ONLY MODERATE.

IZZI

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
     7 PM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO

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





000
FXUS63 KLOT 052327
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
627 PM CDT THU MAY 5 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

VFR CONDITIONS EXPECTED THROUGH THE PERIOD. LIGHT WINDS TONIGHT
SHOULD PICK UP TO 6-10KT FROM THE SOUTHWEST FRIDAY MORNING.
CURRENTLY EXPECTING ENOUGH OF AN OFFSHORE WIND TO PREVENT A LAKE
BREEZE FROM IMPACTING THE TERMINALS FRIDAY AFTERNOON...THOUGH
CONFIDENCE IS ADMITTEDLY ONLY MODERATE.

IZZI

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
     7 PM THURSDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO

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





000
FXUS63 KLOT 051956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
256 PM CDT THU MAY 5 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 18Z TAFS...

THE LAKE BREEZE HAS BEEN HARD TO DISSEMINATE THIS AFTERNOON...BUT
IT IS BEGINNING TO SHOW ITSELF IN TORD/TMDW DATA IN THE
REFLECTIVITY FIELD AND LOOKS LIKE IT IS PROPOGATING INLAND NOW AT
LEAST NORTH OF DOWNTOWN CHICAGO SUCH THAT THE FLOPPING OF WINDS
BACK AND FORTH BETWEEN NW AND NE LOOKS TO BE ABOUT OVER FOR ORD.
IT IS NOT CLEAR IN THE RADAR FIELD FOR MDW AND IN OBSERVATIONS
WITH THE CRIB DOWNTOWN STILL HOLDING A NW WIND.

BEYOND THE LAKE BREEZE CONCERN LIMITED CONCERNS OVERNIGHT WITH
WINDS BECOMING LIGHT. A WEAK DISTURBANCE WILL PASS OVERHEAD INTO
FRIDAY MORNING BRINGING SOME HIGH CLOUDS. WITH REGARDS TO LAKE
BREEZE TOMORROW...LATEST GUIDANCE KEEPS LOW LEVEL WINDS A BIT
STRONGER TO SUGGEST A LAKE BREEZE WOULD BE CONFINED TO THE
LAKEFRONT...BUT ONE MAY STILL DEVELOP THERE GIVEN THE STRONG
TEMPERATURE DIFFERENTIAL EXPECTED BETWEEN LAND/LAKE. AT THIS
POINT GUIDANCE DOES NOT SUGGEST IT GETTING TO ORD/MDW.

KMD

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
     7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 051956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
256 PM CDT THU MAY 5 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 18Z TAFS...

THE LAKE BREEZE HAS BEEN HARD TO DISSEMINATE THIS AFTERNOON...BUT
IT IS BEGINNING TO SHOW ITSELF IN TORD/TMDW DATA IN THE
REFLECTIVITY FIELD AND LOOKS LIKE IT IS PROPOGATING INLAND NOW AT
LEAST NORTH OF DOWNTOWN CHICAGO SUCH THAT THE FLOPPING OF WINDS
BACK AND FORTH BETWEEN NW AND NE LOOKS TO BE ABOUT OVER FOR ORD.
IT IS NOT CLEAR IN THE RADAR FIELD FOR MDW AND IN OBSERVATIONS
WITH THE CRIB DOWNTOWN STILL HOLDING A NW WIND.

BEYOND THE LAKE BREEZE CONCERN LIMITED CONCERNS OVERNIGHT WITH
WINDS BECOMING LIGHT. A WEAK DISTURBANCE WILL PASS OVERHEAD INTO
FRIDAY MORNING BRINGING SOME HIGH CLOUDS. WITH REGARDS TO LAKE
BREEZE TOMORROW...LATEST GUIDANCE KEEPS LOW LEVEL WINDS A BIT
STRONGER TO SUGGEST A LAKE BREEZE WOULD BE CONFINED TO THE
LAKEFRONT...BUT ONE MAY STILL DEVELOP THERE GIVEN THE STRONG
TEMPERATURE DIFFERENTIAL EXPECTED BETWEEN LAND/LAKE. AT THIS
POINT GUIDANCE DOES NOT SUGGEST IT GETTING TO ORD/MDW.

KMD

&&

.MARINE...
253 PM CDT

NE WINDS CONTINUE TO MAINTAIN ELEVATED WAVES ACROSS THE NEARSHORE
WATERS THIS AFTERNOON...THOUGH EVEN THE WILMETTE BUOY IS NOW DOWN
TO 4-4.5 FEET. HIGH PRESSURE WILL SHIFT OVER THE LAKE
TONIGHT...THEN DRIFT SOUTH ON FRIDAY. EXPECT WINDS TO COLLAPSE
TONIGHT...THEN SHIFT TO SOUTHWESTERLY. LOW PRESSURE WILL MOVE
ACROSS SOUTHERN CANADA IN THE COMING DAYS...BEFORE HIGH PRESSURE
IN MANITOBA EXPANDS OVER THE UPPER MIDWEST. AHEAD OF THIS HIGH A
COLD FRONT WILL SHIFT WINDS BACK TO NORTHERLY POSSIBLY BRINGING A
PERIOD OF WINDS IN EXCESS OF 25 KT. THE HIGH EXPANDS OVER THE LAKE
SUNDAY AND SHIFTS EAST EARLY NEXT WEEK.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
     7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 051914
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
214 PM CDT THU MAY 5 2016

.SHORT TERM...

TONIGHT THROUGH SATURDAY...

214 PM...A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA
TONIGHT WITH WARM AIR SPREADING BACK ACROSS THE AREA. A VERY WEAK
MID LEVEL DISTURBANCE WILL RESULT IN SOME MID CLOUDS LATER TONIGHT
INTO FRIDAY MORNING WITH A SMALL CHANCE FOR SOME SPRINKLES OR A
LIGHT SHOWER AND PERHAPS MAINLY NORTH OF THE CWA. WITH MUCH WARMER
AIR SPREADING ACROSS THE AREA FRIDAY...HIGHS AROUND 80 MAYBE LOWER
80S STILL ON TRACK ACROSS THE IL COUNTIES...70S IN NORTHWEST
INDIANA. LOW LEVEL WINDS ARE EXPECTED TO BE A BIT STRONGER AND
THIS MAY PREVENT A LAKE BREEZE FROM DEVELOPING...EVEN ALONG THE IL
SHORE SO NOW HAVE OFFSHORE FLOW AND WARMER TEMPS ALL THE WAY TO
THE SHORELINE FRIDAY AFTERNOON.

A COLD FRONT WILL MOVE SOUTH ACROSS THE WESTERN GREAT LAKES
REGION LATE FRIDAY NIGHT AND THEN ACROSS THE CWA SATURDAY MORNING
THROUGH SATURDAY AFTERNOON. PRECIP COVERAGE APPEARS TO DIMINISH
SOME DURING THE MORNING BUT BY EARLY AFTERNOON...ACTIVITY MAY
REDEVELOP ALONG THE FRONT AND BY THIS TIME LIKELY BE OVER
SOUTHERN PORTIONS OF THE CWA. MAINTAINED THUNDER MENTION BUT BEST
THUNDER CHANCES MAY ALSO END UP BEING SATURDAY AFTERNOON.

TEMPERATURES ON SATURDAY REMAIN DIFFICULT. LOWS FRIDAY NIGHT MAY
ONLY DROP INTO THE UPPER 50S AND WITH LESS PRECIP EXPECTED
SATURDAY MORNING...TEMPS MAY WARM FASTER AHEAD OF THE FRONT. BUT
THEN TEMPS COULD FALL FAIRLY QUICKLY BEHIND THE FRONT...AT LEAST
NEAR THE LAKE. SOME RECOVERY IN TEMPS IS POSSIBLE NORTH OF THE
FRONT SATURDAY AFTERNOON INLAND BUT BY EVENING...COOLER AIR
FLOWING IN OFF THE LAKE WILL SPREAD ACROSS THE AREA. CMS

&&

.LONG TERM...

SATURDAY NIGHT THROUGH THURSDAY...

214 PM...THE COLD FRONT WILL PUSH INTO SOUTH/CENTRAL IL SATURDAY
NIGHT AND BEGIN TO LIFT BACK NORTH AS A WARM FRONT SUNDAY INTO
SUNDAY NIGHT. IT APPEARS EVEN THE SOUTHERN CWA WILL BE DRY BUT
WITH THIS FRONT NEARBY...MAINTAINED LOW CHANCE POPS SUNDAY. A
RIDGE OF HIGH PRESSURE WILL SLOWLY BE MOVING SOUTHEAST ACROSS THE
LAKES REGION SUNDAY INTO MONDAY AND THIS MAY SLOW THE OVERALL
NORTHWARD PUSH OF THE WARM FRONT ALLOWING SUNDAY NIGHT TO BE DRY
OVER NORTHERN PARTS OF THE AREA. EVENTUALLY LOW PRESSURE OVER THE
PLAINS LIFTS NORTHEAST TO THE SOUTHERN LAKES AND OHIO VALLEY
TUESDAY OR WEDNESDAY. THERE CONTINUES TO BE TIMING DIFFERENCES AS
WELL AS THE LOW WEAKENING AND ANOTHER POSSIBLE HIGH BUILDING SOUTH
FROM ONTARIO MIDWEEK. SEVERAL DAYS OF UNSETTLED WEATHER STILL
POSSIBLE IN ADDITION TO COOL EASTERLY FLOW OFF THE LAKE. CMS

&&

.AVIATION...
FOR THE 18Z TAFS...

THE LAKE BREEZE HAS BEEN HARD TO DISSEMINATE THIS AFTERNOON...BUT
IT IS BEGINNING TO SHOW ITSELF IN TORD/TMDW DATA IN THE
REFLECTIVITY FIELD AND LOOKS LIKE IT IS PROPOGATING INLAND NOW AT
LEAST NORTH OF DOWNTOWN CHICAGO SUCH THAT THE FLOPPING OF WINDS
BACK AND FORTH BETWEEN NW AND NE LOOKS TO BE ABOUT OVER FOR ORD.
IT IS NOT CLEAR IN THE RADAR FIELD FOR MDW AND IN OBSERVATIONS
WITH THE CRIB DOWNTOWN STILL HOLDING A NW WIND.

BEYOND THE LAKE BREEZE CONCERN LIMITED CONCERNS OVERNIGHT WITH
WINDS BECOMING LIGHT. A WEAK DISTURBANCE WILL PASS OVERHEAD INTO
FRIDAY MORNING BRINGING SOME HIGH CLOUDS. WITH REGARDS TO LAKE
BREEZE TOMORROW...LATEST GUIDANCE KEEPS LOW LEVEL WINDS A BIT
STRONGER TO SUGGEST A LAKE BREEZE WOULD BE CONFINED TO THE
LAKEFRONT...BUT ONE MAY STILL DEVELOP THERE GIVEN THE STRONG
TEMPERATURE DIFFERENTIAL EXPECTED BETWEEN LAND/LAKE. AT THIS
POINT GUIDANCE DOES NOT SUGGEST IT GETTING TO ORD/MDW.

KMD

&&

.MARINE...
356 AM CDT

LAKE MICHIGAN REMAINS UNDER A MODERATE NORTHERLY GRADIENT EARLY
THIS MORNING BEHIND DEPARTING LOW PRESSURE CENTERED ALONG THE MID
ATLANTIC COAST AND HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST.
THE HIGH WILL CONTINUE TO BUILD SOUTHEAST ACROSS LAKE MICHIGAN
TODAY ALLOWING WINDS TO DIMINISH. THE GALE WARNING WILL BE ALLOWED
TO EXPIRE EARLY THIS MORNING...HOWEVER A SMALL CRAFT ADVISORY
WILL REMAIN IN EFFECT FOR HAZARDOUS WINDS AND WAVES THROUGH MID
MORNING FOR THE ILLINOIS NEARSHORE WATERS...AND THROUGH LATE THIS
AFTERNOON FOR THE INDIANA NEARSHORE WATERS. THE RIDGE AXIS WILL
SETTLE SOUTHEAST OF LAKE MICHIGAN LATE THIS EVENING AND TONIGHT
ALLOWING SOUTHWEST TO SOUTH WINDS TO OVERSPREAD THE LAKE...
INCREASING INTO THE 15 TO 25 KT RANGE BY MIDDAY FRIDAY. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS ONTARIO INTO
QUEBEC ON FRIDAY WITH A TRAILING COLD FRONT PUSHING SOUTH ACROSS
LAKE MICHIGAN FRIDAY NIGHT INTO EARLY SATURDAY WITH NORTHERLY
WINDS TO AROUND 30 KT EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM THURSDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 051836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
136 PM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE LAKE BREEZE HAS BEEN HARD TO DISSEMINATE THIS AFTERNOON...BUT
IT IS BEGINNING TO SHOW ITSELF IN TORD/TMDW DATA IN THE
REFLECTIVITY FIELD AND LOOKS LIKE IT IS PROPOGATING INLAND NOW AT
LEAST NORTH OF DOWNTOWN CHICAGO SUCH THAT THE FLOPPING OF WINDS
BACK AND FORTH BETWEEN NW AND NE LOOKS TO BE ABOUT OVER FOR ORD.
IT IS NOT CLEAR IN THE RADAR FIELD FOR MDW AND IN OBSERVATIONS
WITH THE CRIB DOWNTOWN STILL HOLDING A NW WIND.

BEYOND THE LAKE BREEZE CONCERN LIMITED CONCERNS OVERNIGHT WITH
WINDS BECOMING LIGHT. A WEAK DISTURBANCE WILL PASS OVERHEAD INTO
FRIDAY MORNING BRINGING SOME HIGH CLOUDS. WITH REGARDS TO LAKE
BREEZE TOMORROW...LATEST GUIDANCE KEEPS LOW LEVEL WINDS A BIT
STRONGER TO SUGGEST A LAKE BREEZE WOULD BE CONFINED TO THE
LAKEFRONT...BUT ONE MAY STILL DEVELOP THERE GIVEN THE STRONG
TEMPERATURE DIFFERENTIAL EXPECTED BETWEEN LAND/LAKE. AT THIS
POINT GUIDANCE DOES NOT SUGGEST IT GETTING TO ORD/MDW.

KMD

&&

.MARINE...
356 AM CDT

LAKE MICHIGAN REMAINS UNDER A MODERATE NORTHERLY GRADIENT EARLY
THIS MORNING BEHIND DEPARTING LOW PRESSURE CENTERED ALONG THE MID
ATLANTIC COAST AND HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST.
THE HIGH WILL CONTINUE TO BUILD SOUTHEAST ACROSS LAKE MICHIGAN
TODAY ALLOWING WINDS TO DIMINISH. THE GALE WARNING WILL BE ALLOWED
TO EXPIRE EARLY THIS MORNING...HOWEVER A SMALL CRAFT ADVISORY
WILL REMAIN IN EFFECT FOR HAZARDOUS WINDS AND WAVES THROUGH MID
MORNING FOR THE ILLINOIS NEARSHORE WATERS...AND THROUGH LATE THIS
AFTERNOON FOR THE INDIANA NEARSHORE WATERS. THE RIDGE AXIS WILL
SETTLE SOUTHEAST OF LAKE MICHIGAN LATE THIS EVENING AND TONIGHT
ALLOWING SOUTHWEST TO SOUTH WINDS TO OVERSPREAD THE LAKE...
INCREASING INTO THE 15 TO 25 KT RANGE BY MIDDAY FRIDAY. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS ONTARIO INTO
QUEBEC ON FRIDAY WITH A TRAILING COLD FRONT PUSHING SOUTH ACROSS
LAKE MICHIGAN FRIDAY NIGHT INTO EARLY SATURDAY WITH NORTHERLY
WINDS TO AROUND 30 KT EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM THURSDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 051121
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
621 AM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

A RIDGE OF HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO IOWA
EARLY THIS MORNING AND WILL BUILD TOWARDS THE LOCAL AREA THROUGH
THE DAY ALLOWING WINDS TO CONTINUE TO DIMINISH. MVFR/IFR LEVEL
STRATUS PERSISTS ACROSS MUCH OF INDIANA AND BUILT INTO PORTIONS
OF NORTHEASTERN ILLINOIS OVERNIGHT. THESE LOWER CLOUDS HAVE SINCE
ERODED OVER ORD AND DPA...THOUGH CONTINUE TO IMPACT MDW AND GYY.
ANTICIPATE BOTH TERMINALS TO IMPROVE OVER THE NEXT COUPLE HOURS
BACK TO VFR WHERE THEY SHOULD REMAIN THROUGH THE REMAINDER OF THE
FORECAST PERIOD. NORTH WINDS ARE EXPECTED THROUGH THE MORNING AND
EARLY AFTERNOON...THEN AN AFTERNOON LAKE BREEZE WILL TURN WINDS
NORTHEASTERLY FOR AT ORD/MDW. WINDS WILL DIMINISH AND BECOME
LIGHT AND VARIABLE AROUND OR SHORTLY AFTER SUNSET...THEN SHOULD
BECOME SOUTHWESTERLY AT SOME POINT OVERNIGHT...INCREASING TO
AROUND 10 KT AGAIN FRIDAY MORNING.

BMD

&&

.MARINE...
356 AM CDT

LAKE MICHIGAN REMAINS UNDER A MODERATE NORTHERLY GRADIENT EARLY
THIS MORNING BEHIND DEPARTING LOW PRESSURE CENTERED ALONG THE MID
ATLANTIC COAST AND HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST.
THE HIGH WILL CONTINUE TO BUILD SOUTHEAST ACROSS LAKE MICHIGAN
TODAY ALLOWING WINDS TO DIMINISH. THE GALE WARNING WILL BE ALLOWED
TO EXPIRE EARLY THIS MORNING...HOWEVER A SMALL CRAFT ADVISORY
WILL REMAIN IN EFFECT FOR HAZARDOUS WINDS AND WAVES THROUGH MID
MORNING FOR THE ILLINOIS NEARSHORE WATERS...AND THROUGH LATE THIS
AFTERNOON FOR THE INDIANA NEARSHORE WATERS. THE RIDGE AXIS WILL
SETTLE SOUTHEAST OF LAKE MICHIGAN LATE THIS EVENING AND TONIGHT
ALLOWING SOUTHWEST TO SOUTH WINDS TO OVERSPREAD THE LAKE...
INCREASING INTO THE 15 TO 25 KT RANGE BY MIDDAY FRIDAY. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS ONTARIO INTO
QUEBEC ON FRIDAY WITH A TRAILING COLD FRONT PUSHING SOUTH ACROSS
LAKE MICHIGAN FRIDAY NIGHT INTO EARLY SATURDAY WITH NORTHERLY
WINDS TO AROUND 30 KT EXPECTED BEHIND THE FRONT.

BMD

&&

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

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 051121
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
621 AM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

A RIDGE OF HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO IOWA
EARLY THIS MORNING AND WILL BUILD TOWARDS THE LOCAL AREA THROUGH
THE DAY ALLOWING WINDS TO CONTINUE TO DIMINISH. MVFR/IFR LEVEL
STRATUS PERSISTS ACROSS MUCH OF INDIANA AND BUILT INTO PORTIONS
OF NORTHEASTERN ILLINOIS OVERNIGHT. THESE LOWER CLOUDS HAVE SINCE
ERODED OVER ORD AND DPA...THOUGH CONTINUE TO IMPACT MDW AND GYY.
ANTICIPATE BOTH TERMINALS TO IMPROVE OVER THE NEXT COUPLE HOURS
BACK TO VFR WHERE THEY SHOULD REMAIN THROUGH THE REMAINDER OF THE
FORECAST PERIOD. NORTH WINDS ARE EXPECTED THROUGH THE MORNING AND
EARLY AFTERNOON...THEN AN AFTERNOON LAKE BREEZE WILL TURN WINDS
NORTHEASTERLY FOR AT ORD/MDW. WINDS WILL DIMINISH AND BECOME
LIGHT AND VARIABLE AROUND OR SHORTLY AFTER SUNSET...THEN SHOULD
BECOME SOUTHWESTERLY AT SOME POINT OVERNIGHT...INCREASING TO
AROUND 10 KT AGAIN FRIDAY MORNING.

BMD

&&

.MARINE...
356 AM CDT

LAKE MICHIGAN REMAINS UNDER A MODERATE NORTHERLY GRADIENT EARLY
THIS MORNING BEHIND DEPARTING LOW PRESSURE CENTERED ALONG THE MID
ATLANTIC COAST AND HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST.
THE HIGH WILL CONTINUE TO BUILD SOUTHEAST ACROSS LAKE MICHIGAN
TODAY ALLOWING WINDS TO DIMINISH. THE GALE WARNING WILL BE ALLOWED
TO EXPIRE EARLY THIS MORNING...HOWEVER A SMALL CRAFT ADVISORY
WILL REMAIN IN EFFECT FOR HAZARDOUS WINDS AND WAVES THROUGH MID
MORNING FOR THE ILLINOIS NEARSHORE WATERS...AND THROUGH LATE THIS
AFTERNOON FOR THE INDIANA NEARSHORE WATERS. THE RIDGE AXIS WILL
SETTLE SOUTHEAST OF LAKE MICHIGAN LATE THIS EVENING AND TONIGHT
ALLOWING SOUTHWEST TO SOUTH WINDS TO OVERSPREAD THE LAKE...
INCREASING INTO THE 15 TO 25 KT RANGE BY MIDDAY FRIDAY. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS ONTARIO INTO
QUEBEC ON FRIDAY WITH A TRAILING COLD FRONT PUSHING SOUTH ACROSS
LAKE MICHIGAN FRIDAY NIGHT INTO EARLY SATURDAY WITH NORTHERLY
WINDS TO AROUND 30 KT EXPECTED BEHIND THE FRONT.

BMD

&&

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

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 050857
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
357 AM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO THE CENTRAL PLAINS
AND WILL INCH TOWARDS NORTHERN ILLINOIS OVERNIGHT AND THROUGH THE
DAY THURSDAY. A MODEST NORTHERLY GRADIENT PERSISTS ACROSS NORTHERN
ILLINOIS LATE THIS EVENING AHEAD OF THE RIDGE AXIS...WHICH WILL
ALLOW A NORTHERLY BREEZE WITH GUSTS TO AROUND 20 KT AT TIMES TO
CONTINUE THROUGH MUCH OF THE OVERNIGHT HOURS. IN ADDITION...AN UPPER
LOW OVER INDIANA LATE THIS EVENING WILL CONTINUE TO RESULT IN SOME
SHOWERS ACROSS NORTHERN INDIANA AND LAKE MICHIGAN. GYY SHOULD BE THE
ONLY TERMINAL THAT SEES PRECIP...THOUGH MDW IN PARTICULAR MAY BE
CLOSE AND CANNOT RULE OUT A FEW SPRINKLES AND/OR SOME MVFR CIGS
SNEAKING THAT FAR WEST...WITH FEW018 ALREADY SHOWING UP IN THE
MDW OB.

VFR CONDITIONS AND MODEST NORTH WINDS WILL CONTINUE THROUGH THE DAY
THURSDAY...THOUGH SHOULD SEE GUSTS TAPERING THROUGH THE DAY AS THE
RIDGE GETS CLOSER AND THE GRADIENT TO RELAXES. ANTICIPATE A LAKE
BREEZE WILL FORM DURING THE AFTERNOON TURNING WINDS TO THE
NORTHEAST. AROUND SUNSET THURSDAY EVENING...WINDS ARE EXPECTED TO
BECOME LIGHT AND VARIABLE AS THE HIGH MOVES OVERHEAD...THEN
EVENTUALLY BECOME WESTERLY BY EARLY FRIDAY AS THE RIDGE SINKS TO
OUR SOUTH.

BMD

&&

.MARINE...
356 AM CDT

LAKE MICHIGAN REMAINS UNDER A MODERATE NORTHERLY GRADIENT EARLY
THIS MORNING BEHIND DEPARTING LOW PRESSURE CENTERED ALONG THE MID
ATLANTIC COAST AND HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST.
THE HIGH WILL CONTINUE TO BUILD SOUTHEAST ACROSS LAKE MICHIGAN
TODAY ALLOWING WINDS TO DIMINISH. THE GALE WARNING WILL BE ALLOWED
TO EXPIRE EARLY THIS MORNING...HOWEVER A SMALL CRAFT ADVISORY
WILL REMAIN IN EFFECT FOR HAZARDOUS WINDS AND WAVES THROUGH MID
MORNING FOR THE ILLINOIS NEARSHORE WATERS...AND THROUGH LATE THIS
AFTERNOON FOR THE INDIANA NEARSHORE WATERS. THE RIDGE AXIS WILL
SETTLE SOUTHEAST OF LAKE MICHIGAN LATE THIS EVENING AND TONIGHT
ALLOWING SOUTHWEST TO SOUTH WINDS TO OVERSPREAD THE LAKE...
INCREASING INTO THE 15 TO 25 KT RANGE BY MIDDAY FRIDAY. ANOTHER
AREA OF LOW PRESSURE IS EXPECTED TO MOVE ACROSS ONTARIO INTO
QUEBEC ON FRIDAY WITH A TRAILING COLD FRONT PUSHING SOUTH ACROSS
LAKE MICHIGAN FRIDAY NIGHT INTO EARLY SATURDAY WITH NORTHERLY
WINDS TO AROUND 30 KT EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 050824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
324 AM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO THE CENTRAL PLAINS
AND WILL INCH TOWARDS NORTHERN ILLINOIS OVERNIGHT AND THROUGH THE
DAY THURSDAY. A MODEST NORTHERLY GRADIENT PERSISTS ACROSS NORTHERN
ILLINOIS LATE THIS EVENING AHEAD OF THE RIDGE AXIS...WHICH WILL
ALLOW A NORTHERLY BREEZE WITH GUSTS TO AROUND 20 KT AT TIMES TO
CONTINUE THROUGH MUCH OF THE OVERNIGHT HOURS. IN ADDITION...AN UPPER
LOW OVER INDIANA LATE THIS EVENING WILL CONTINUE TO RESULT IN SOME
SHOWERS ACROSS NORTHERN INDIANA AND LAKE MICHIGAN. GYY SHOULD BE THE
ONLY TERMINAL THAT SEES PRECIP...THOUGH MDW IN PARTICULAR MAY BE
CLOSE AND CANNOT RULE OUT A FEW SPRINKLES AND/OR SOME MVFR CIGS
SNEAKING THAT FAR WEST...WITH FEW018 ALREADY SHOWING UP IN THE
MDW OB.

VFR CONDITIONS AND MODEST NORTH WINDS WILL CONTINUE THROUGH THE DAY
THURSDAY...THOUGH SHOULD SEE GUSTS TAPERING THROUGH THE DAY AS THE
RIDGE GETS CLOSER AND THE GRADIENT TO RELAXES. ANTICIPATE A LAKE
BREEZE WILL FORM DURING THE AFTERNOON TURNING WINDS TO THE
NORTHEAST. AROUND SUNSET THURSDAY EVENING...WINDS ARE EXPECTED TO
BECOME LIGHT AND VARIABLE AS THE HIGH MOVES OVERHEAD...THEN
EVENTUALLY BECOME WESTERLY BY EARLY FRIDAY AS THE RIDGE SINKS TO
OUR SOUTH.

BMD

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 050824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
324 AM CDT THU MAY 5 2016

.SHORT TERM...
323 AM CDT

TODAY THROUGH FRIDAY...

DEEP UPPER TROUGH/CLOSED LOW OVER THE OHIO VALLEY WILL LOSE ITS
GRIP ON THE REGION TODAY...MOVING TO THE EAST COAST/MID-ATLANTIC
BY THIS EVENING. SURFACE HIGH PRESSURE RIDGE OVER THE UPPER
MISSISSIPPI VALLEY AND NORTHERN LAKES THIS MORNING WILL SPREAD
ACROSS THE FORECAST AREA FROM THE NORTHWEST LATER TODAY...BENEATH
SUBSIDENCE ASSOCIATED WITH RISING HEIGHTS IN THE WAKE OF THE
DEPARTING TROUGH. THIS SUBSIDENCE AND ADVECTION OF DRIER AIR FROM
THE NORTH WILL WORK TO ERODE LINGERING CLOUD COVER OVER THE
EASTERN PARTS OF THE FORECAST AREA TODAY. TEMPERATURES WILL
MODERATE A BIT TODAY THOUGH STRONGER WARM ADVECTION HOLDS OFF
UNTIL TONIGHT. AFTERNOON HIGHS FROM THE MID 60S WEST TO THE UPPER
50S/AROUND 60 FAR EAST ARE EXPECTED...THOUGH NORTH-NORTHEAST LAKE
BREEZE WINDS WILL KEEP AREAS NEAR LAKE MICHIGAN IN THE 50S.

LOW-LEVEL WARM ADVECTION BEGINS IN EARNEST FROM THE NORTHWEST
TONIGHT AS UPPER RIDGE BUILDS ACROSS THE UPPER MISSISSIPPI VALLEY
AND NORTHERN GREAT LAKES. VARIOUS MODELS INDICATE POTENTIAL FOR
SOME LIGHT PRECIP UPSTREAM ACROSS WI...THOUGH 00Z SOUNDINGS FROM
THE SOURCE REGION OF THE NORTHERN PLAINS AND FAR UPPER MIDWEST
APPEAR PRETTY DRY...AND MODEL FORECASTS OF THE 300-305 K
ISENTROPIC SURFACES DEPICT UNIMPRESSIVE CONDENSATION PRESSURE
DEFICITS WHICH ADDS CONFIDENCE TO KEEPING A DRY FORECAST.

BY FRIDAY MORNING...SURFACE RIDGE AXIS IS OFF TO THE
SOUTH/SOUTHEAST OF THE CWA. WESTERLY LOW LEVEL FLOW...DRY PROFILES
AND 925 MB TEMPS OF +20 TO AROUND +23 C BY AFTERNOON SUPPORT MUCH
WARMER SURFACE TEMPS RANGING FROM THE UPPER 70S ACROSS THE FAR
EASTERN CWA...AND 83-84 F FOR MAXES ACROSS OUR WEST/NORTHWEST
COUNTIES. THE SURFACE PRESSURE GRADIENT SHOULD BE WEAK ENOUGH TO
ALLOW A LAKE BREEZE TO DEVELOP BY FRIDAY AFTERNOON...THOUGH WITH
ENOUGH WEST WIND COMPONENT TO PREVENT IT FROM PUSHING TOO FAR
INLAND OVER NORTHEAST IL. LAKE BREEZE MAY BE A BIT STRONGER INTO
NORTHWEST INDIANA WHERE GRADIENT WILL BE A BIT WEAKER.

RATZER

&&

.LONG TERM...
323 AM CDT

FRIDAY NIGHT THROUGH WEDNESDAY...

GUIDANCE REMAINS STEADFAST IN AMPLIFYING A SHORT WAVE TROUGH
WHICH MOVES ACROSS SOUTHERN CANADA FRIDAY...THEN DIGS SOUTHEAST
AND BREAKS DOWN THE UPPER RIDGE ACROSS THE WESTERN GREAT LAKES
REGION OVER THE WEEKEND. AT THE SURFACE...THIS MANIFESTS AS A
SOUTHEASTWARD MOVING SURFACE LOW AND COLD FRONT WHICH MOVES INTO
THE CWA EARLY SATURDAY MORNING. DESPITE STEEP MID-LEVEL LAPSE
RATES...FORECAST SOUNDINGS INDICATE A LACK OF DEEP SATURATION
COINCIDENT WITH THE FRONT PUSHING ACROSS NORTHERN PARTS OF THE CWA
EARLY SATURDAY. THIS...ALONG WITH DIURNAL MINIMUM FOR NEAR-SURFACE
BASED INSTABILITY SUGGESTS LIMITED POPS INITIALLY ACROSS THE
NORTHERN HALF OF THE CWA. CONVECTION POTENTIAL LOOKS A LITTLE
BETTER ACROSS THE SOUTHERN COUNTIES OF THE FORECAST AREA LATE
MORNING/EARLY AFTERNOON WHERE DIURNALLY WARMING BOUNDARY LAYER
SHOULD SUPPORT GREATER NEAR-SURFACE BASED CAPES. ELEVATED CAPE IS
INDICATED FARTHER NORTH ON THE COOL SIDE OF THE BOUNDARY INTO THE
AFTERNOON ATOP COOL BOUNDARY LAYER WHICH MAY SUPPORT RAIN/EMBEDDED
THUNDER POTENTIAL AS LARGE SCALE FORCING INCREASES. TEMPERATURES
WILL BE TRICKY ON SATURDAY WITH FRONT MOVING THROUGH DURING THE
MORNING/MIDDAY. MILD START TO THE DAY WILL LIKELY ALLOW MOST
LOCATIONS TO WARM INTO THE 60S BEFORE STRONGER NORTHERLY COOL PUSH
DEVELOPS BEHIND THE FRONT...AND SOUTHERN COUNTIES LIKELY TAPPING
THE LOW-MID 70S. FALLING TEMPS ARE EXPECTED NEAR LAKE MICHIGAN
HOWEVER...WHERE READINGS WILL LIKELY DIP INTO THE 50S.

THE FRONT THEN PUSHES WELL SOUTH OF THE CWA INTO THE OHIO VALLEY
SATURDAY NIGHT...WITH WEAK SURFACE HIGH PRESSURE SPREADING ACROSS
THE REGION. THIS SHOULD TAKE PRECIP CHANCES SOUTH OF THE FORECAST
AREA SATURDAY NIGHT AND SUNDAY WHILE DRY...MODESTLY COOL WEATHER
LINGERS LOCALLY.

DAYS 5-7 SEE A CONTINUATION OF SPLIT FLOW ALOFT...WITH A CLOSED
UPPER LOW OVER THE WESTERN CONUS EVENTUALLY WEAKENING AND LIFTING
NORTHEAST ACROSS THE MIDWEST THROUGH WEDNESDAY. DIFFERENCES IN
GUIDANCE ABOUND THOUGH THERE IS GENERAL CONSENSUS THAT THE FRONT
TO OUR SOUTH LIFTS BACK INTO THE AREA AS A WARM FRONT SUNDAY NIGHT
INTO MONDAY... BECOMING NEARLY STATIONARY AS THE ASSOCIATED
SURFACE LOW MOVES INTO OUR AREA LATE TUESDAY/WEDNESDAY. THIS SETS
UP THE POTENTIAL FOR A POTENTIALLY WET EARLY-MID WEEK PERIOD WITH
TEMPS NEAR NORMAL IN THE 60S/LOW 70S...AND ALSO SOME DAILY LAKE
COOLING.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO THE CENTRAL PLAINS
AND WILL INCH TOWARDS NORTHERN ILLINOIS OVERNIGHT AND THROUGH THE
DAY THURSDAY. A MODEST NORTHERLY GRADIENT PERSISTS ACROSS NORTHERN
ILLINOIS LATE THIS EVENING AHEAD OF THE RIDGE AXIS...WHICH WILL
ALLOW A NORTHERLY BREEZE WITH GUSTS TO AROUND 20 KT AT TIMES TO
CONTINUE THROUGH MUCH OF THE OVERNIGHT HOURS. IN ADDITION...AN UPPER
LOW OVER INDIANA LATE THIS EVENING WILL CONTINUE TO RESULT IN SOME
SHOWERS ACROSS NORTHERN INDIANA AND LAKE MICHIGAN. GYY SHOULD BE THE
ONLY TERMINAL THAT SEES PRECIP...THOUGH MDW IN PARTICULAR MAY BE
CLOSE AND CANNOT RULE OUT A FEW SPRINKLES AND/OR SOME MVFR CIGS
SNEAKING THAT FAR WEST...WITH FEW018 ALREADY SHOWING UP IN THE
MDW OB.

VFR CONDITIONS AND MODEST NORTH WINDS WILL CONTINUE THROUGH THE DAY
THURSDAY...THOUGH SHOULD SEE GUSTS TAPERING THROUGH THE DAY AS THE
RIDGE GETS CLOSER AND THE GRADIENT TO RELAXES. ANTICIPATE A LAKE
BREEZE WILL FORM DURING THE AFTERNOON TURNING WINDS TO THE
NORTHEAST. AROUND SUNSET THURSDAY EVENING...WINDS ARE EXPECTED TO
BECOME LIGHT AND VARIABLE AS THE HIGH MOVES OVERHEAD...THEN
EVENTUALLY BECOME WESTERLY BY EARLY FRIDAY AS THE RIDGE SINKS TO
OUR SOUTH.

BMD

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 050521
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1221 AM CDT THU MAY 5 2016

.UPDATE...
843 PM CDT

ONLY MINOR CHANGES MADE TO THE FORECAST THROUGH THURSDAY MORNING.
A SHARPLY DEFINED COMMA-HEAD SIGNATURE ASSOCIATED WITH AN UPPER
LOW IS OVER NORTHERN INDIANA/SOUTHERN MICHIGAN THIS EVENING.
FORCING FOR ASCENT WITH THIS HAS RETROGRADED WESTWARD INTO THE
FORECAST AREA BUT WILL BEGIN TO SHIFT MORE SOUTHWARD THE REST OF
TONIGHT. SOME LIGHT RAIN SHOWERS MAY REACH AS FAR EAST AS NEAR
I-57...BUT FOR THE MOST PART SHOULD ONLY BE IN NORTHWEST INDIANA.
THE PRESSURE GRADIENT TIGHTENING AROUND THE SYSTEM WILL LEAD TO AN
INCREASE IN BLUSTERY CONDITIONS THE REST OF TONIGHT IN FAR
NORTHEAST ILLINOIS AND FAR NORTHWEST INDIANA. HAVE BUMPED UP
CLOUD FORECAST FOR EASTERN AREAS EARLY THURSDAY BUT STILL
EXPECTING CLEARING BY LATE MORNING. THE TEMPERATURE FORECAST LOOKS
ON TRACK.

MTF

&&

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

237 PM...FORECAST CONCERNS INCLUDE VERY WARM TEMPS FRIDAY...
CHANCE OF THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY AHEAD OF
A COLD FRONT AND THEN AN UNSETTLED PATTERN NEXT WEEK.

A RIDGE OF HIGH PRESSURE WILL BE MOVING ACROSS THE AREA THURSDAY
NIGHT. AS WARM AIR ADVECTION BEGINS TO SPREAD ACROSS THE REGION...
THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE/CLOUDS AND THERE
IS A SMALL POTENTIAL FOR A FEW LIGHT SHOWERS OR SPRINKLES FRIDAY
MORNING BUT MAINTAINED A DRY FORECAST FROM THIS DISTANCE. THE REST
OF FRIDAY IS SHAPING UP TO BE VERY WARM WITH HIGHS INTO THE LOWER
80S MOST AREAS IN ILLINOIS AND MID/UPPER 70S IN NORTHWEST INDIANA.
LOW LEVEL WINDS AROUND/JUST UNDER 10KTS FRIDAY AFTERNOON WOULD
SUGGEST A LAKE BREEZE PROBABLY WILL FORM ALONG THE IL SHORE BUT
PERHAPS NOT MOVE TOO FAR INLAND BUT CONFIDENCE IS LOW GIVEN HOW
COLD THE LAKE REMAINS AND HOW WARM INLAND TEMPS WILL BE. POSSIBLE
THAT THE LAKE BREEZE COULD MOVE FURTHER INLAND THEN CURRENTLY
EXPECTED...ESPECIALLY BY LATE AFTERNOON/EARLY EVENING.

A COLD FRONT WILL MOVE SOUTH ACROSS LAKE MICHIGAN FRIDAY NIGHT
ARRIVING INTO NORTHERN IL JUST AFTER DAYBREAK SATURDAY MORNING
AND THEN CONTINUING SOUTH ACROSS THE AREA DURING THE MORNING.
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE FROM EARLY
SATURDAY MORNING THROUGH MID SATURDAY AFTERNOON...ENDING NORTH TO
SOUTH. TEMPS WILL BE TRICKY SATURDAY...LIKELY REMAINING STEADY
NEAR THE LAKE...PERHAPS ONLY IN THE 50S. THEN RISING SOUTH OF THE
FRONT IN THE MORNING THEN RISING NORTH OF THE FRONT...AWAY FROM
THE LAKE IN THE AFTERNOON AS SKIES CLEAR. BUT FOR MUCH OF THE AREA
NORTH OF THE KANKAKEE/ILLINOIS RIVERS...SATURDAY WILL BE MUCH
COOLER. THE FRONT SHOULD MOVE FAR ENOUGH SOUTH OF THE AREA TO END
PRECIP CHANCES EVERYWHERE SATURDAY EVENING...BUT CLOSE ENOUGH TO
MAINTAIN LOW CHANCE POPS ACROSS THE FAR SOUTH.

WEAK HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION
SUNDAY AND SUNDAY NIGHT...AS THE COLD FRONT BEGINS TO MOVE BACK
NORTH AS A WARM FRONT MONDAY AHEAD OF LOW PRESSURE WHICH WILL MOVE
ACROSS THE AREA TUESDAY OR WEDNESDAY. THERE REMAINS SOME LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SO CONFIDENCE
REGARDING TIMING IS LOW BUT CHANCE POPS WARRANTED FROM SUNDAY
NIGHT THROUGH WEDNESDAY...THOUGH THERE WILL LIKELY BE PROLONGED
DRY PERIODS. WITH THE CURRENT EXPECTED LOW TRACK SOUTH OF THE
LAKE...THAT WILL LIKELY MEAN EASTERLY FLOW AND COOLER ONSHORE
FLOW...FOR PERHAPS SEVERAL DAYS. CMS

&&

.AVIATION...
FOR THE 06Z TAFS...

HIGH PRESSURE STRETCHES FROM LAKE SUPERIOR INTO THE CENTRAL PLAINS
AND WILL INCH TOWARDS NORTHERN ILLINOIS OVERNIGHT AND THROUGH THE
DAY THURSDAY. A MODEST NORTHERLY GRADIENT PERSISTS ACROSS NORTHERN
ILLINOIS LATE THIS EVENING AHEAD OF THE RIDGE AXIS...WHICH WILL
ALLOW A NORTHERLY BREEZE WITH GUSTS TO AROUND 20 KT AT TIMES TO
CONTINUE THROUGH MUCH OF THE OVERNIGHT HOURS. IN ADDITION...AN UPPER
LOW OVER INDIANA LATE THIS EVENING WILL CONTINUE TO RESULT IN SOME
SHOWERS ACROSS NORTHERN INDIANA AND LAKE MICHIGAN. GYY SHOULD BE THE
ONLY TERMINAL THAT SEES PRECIP...THOUGH MDW IN PARTICULAR MAY BE
CLOSE AND CANNOT RULE OUT A FEW SPRINKLES AND/OR SOME MVFR CIGS
SNEAKING THAT FAR WEST...WITH FEW018 ALREADY SHOWING UP IN THE
MDW OB.

VFR CONDITIONS AND MODEST NORTH WINDS WILL CONTINUE THROUGH THE DAY
THURSDAY...THOUGH SHOULD SEE GUSTS TAPERING THROUGH THE DAY AS THE
RIDGE GETS CLOSER AND THE GRADIENT TO RELAXES. ANTICIPATE A LAKE
BREEZE WILL FORM DURING THE AFTERNOON TURNING WINDS TO THE
NORTHEAST. AROUND SUNSET THURSDAY EVENING...WINDS ARE EXPECTED TO
BECOME LIGHT AND VARIABLE AS THE HIGH MOVES OVERHEAD...THEN
EVENTUALLY BECOME WESTERLY BY EARLY FRIDAY AS THE RIDGE SINKS TO
OUR SOUTH.

BMD

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 7
     PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 050145 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
845 PM CDT WED MAY 4 2016

.UPDATE...
843 PM CDT

ONLY MINOR CHANGES MADE TO THE FORECAST THROUGH THURSDAY MORNING.
A SHARPLY DEFINED COMMA-HEAD SIGNATURE ASSOCIATED WITH AN UPPER
LOW IS OVER NORTHERN INDIANA/SOUTHERN MICHIGAN THIS EVENING.
FORCING FOR ASCENT WITH THIS HAS RETROGRADED WESTWARD INTO THE
FORECAST AREA BUT WILL BEGIN TO SHIFT MORE SOUTHWARD THE REST OF
TONIGHT. SOME LIGHT RAIN SHOWERS MAY REACH AS FAR EAST AS NEAR
I-57...BUT FOR THE MOST PART SHOULD ONLY BE IN NORTHWEST INDIANA.
THE PRESSURE GRADIENT TIGHTENING AROUND THE SYSTEM WILL LEAD TO AN
INCREASE IN BLUSTERY CONDITIONS THE REST OF TONIGHT IN FAR
NORTHEAST ILLINOIS AND FAR NORTHWEST INDIANA. HAVE BUMPED UP
CLOUD FORECAST FOR EASTERN AREAS EARLY THURSDAY BUT STILL
EXPECTING CLEARING BY LATE MORNING. THE TEMPERATURE FORECAST LOOKS
ON TRACK.

MTF

&&

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

237 PM...FORECAST CONCERNS INCLUDE VERY WARM TEMPS FRIDAY...
CHANCE OF THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY AHEAD OF
A COLD FRONT AND THEN AN UNSETTLED PATTERN NEXT WEEK.

A RIDGE OF HIGH PRESSURE WILL BE MOVING ACROSS THE AREA THURSDAY
NIGHT. AS WARM AIR ADVECTION BEGINS TO SPREAD ACROSS THE REGION...
THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE/CLOUDS AND THERE
IS A SMALL POTENTIAL FOR A FEW LIGHT SHOWERS OR SPRINKLES FRIDAY
MORNING BUT MAINTAINED A DRY FORECAST FROM THIS DISTANCE. THE REST
OF FRIDAY IS SHAPING UP TO BE VERY WARM WITH HIGHS INTO THE LOWER
80S MOST AREAS IN ILLINOIS AND MID/UPPER 70S IN NORTHWEST INDIANA.
LOW LEVEL WINDS AROUND/JUST UNDER 10KTS FRIDAY AFTERNOON WOULD
SUGGEST A LAKE BREEZE PROBABLY WILL FORM ALONG THE IL SHORE BUT
PERHAPS NOT MOVE TOO FAR INLAND BUT CONFIDENCE IS LOW GIVEN HOW
COLD THE LAKE REMAINS AND HOW WARM INLAND TEMPS WILL BE. POSSIBLE
THAT THE LAKE BREEZE COULD MOVE FURTHER INLAND THEN CURRENTLY
EXPECTED...ESPECIALLY BY LATE AFTERNOON/EARLY EVENING.

A COLD FRONT WILL MOVE SOUTH ACROSS LAKE MICHIGAN FRIDAY NIGHT
ARRIVING INTO NORTHERN IL JUST AFTER DAYBREAK SATURDAY MORNING
AND THEN CONTINUING SOUTH ACROSS THE AREA DURING THE MORNING.
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE FROM EARLY
SATURDAY MORNING THROUGH MID SATURDAY AFTERNOON...ENDING NORTH TO
SOUTH. TEMPS WILL BE TRICKY SATURDAY...LIKELY REMAINING STEADY
NEAR THE LAKE...PERHAPS ONLY IN THE 50S. THEN RISING SOUTH OF THE
FRONT IN THE MORNING THEN RISING NORTH OF THE FRONT...AWAY FROM
THE LAKE IN THE AFTERNOON AS SKIES CLEAR. BUT FOR MUCH OF THE AREA
NORTH OF THE KANKAKEE/ILLINOIS RIVERS...SATURDAY WILL BE MUCH
COOLER. THE FRONT SHOULD MOVE FAR ENOUGH SOUTH OF THE AREA TO END
PRECIP CHANCES EVERYWHERE SATURDAY EVENING...BUT CLOSE ENOUGH TO
MAINTAIN LOW CHANCE POPS ACROSS THE FAR SOUTH.

WEAK HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION
SUNDAY AND SUNDAY NIGHT...AS THE COLD FRONT BEGINS TO MOVE BACK
NORTH AS A WARM FRONT MONDAY AHEAD OF LOW PRESSURE WHICH WILL MOVE
ACROSS THE AREA TUESDAY OR WEDNESDAY. THERE REMAINS SOME LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SO CONFIDENCE
REGARDING TIMING IS LOW BUT CHANCE POPS WARRANTED FROM SUNDAY
NIGHT THROUGH WEDNESDAY...THOUGH THERE WILL LIKELY BE PROLONGED
DRY PERIODS. WITH THE CURRENT EXPECTED LOW TRACK SOUTH OF THE
LAKE...THAT WILL LIKELY MEAN EASTERLY FLOW AND COOLER ONSHORE
FLOW...FOR PERHAPS SEVERAL DAYS. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

THE PRIMARY AVIATION ITEMS OF INTEREST ARE NORTH/NORTHEAST WINDS
AND SPORADIC GUSTS THROUGH THURSDAY MORNING...WITH A SMALL CHANCE
FOR SOME SHOWERS AT ORD AND MDW TONIGHT.

THE CYCLONIC FLOW THAT WAS IN PLACE MUCH OF THE DAY WEDNESDAY
WILL CONTINUE TONIGHT AS A WEATHER SYSTEM NEAR DETROIT MOVES
LITTLE...IN FACT PARTLY RETROGRADES TONIGHT. THAT SHOULD ALLOW
FOR SOME SHOWERS TO APPROACH GYY AND CANNOT TOTALLY RULE OUT LIGHT
SHOWERS REACHING ORD OR MDW. MVFR CIGS ARE LIKELY TO PUSH BACK
WEST TO GYY AND POSSIBLY MDW BY 03Z-06Z.

THE NORTHEAST WINDS ARE ALSO LIKELY TO SLIGHTLY INCREASE LATER
THIS EVENING AND CONTAIN SOME SPORADIC GUSTS...POSSIBLY UP TO 20
TO 23 KT AT ORD OR MDW. CONFIDENCE IN THIS IS LOW RIGHT NOW SO
HAVE NOT MENTIONED IN THE TAF...PLUS THE MAIN STORY IS THE
CONTINUING NORTHEAST WIND DIRECTION. SPEEDS WILL GRADUALLY
SLACKEN LATE THURSDAY MORNING INTO THE AFTERNOON. A LAKE BREEZE
SHOULD DEVELOP DURING THE AFTERNOON AND LIKELY KEEP SPEEDS 8-10 KT
AT ORD AND MDW. THESE WILL QUICKLY DROP OFF AFTER SUNDOWN THURSDAY
EVENING.

MTF

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 050145 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
845 PM CDT WED MAY 4 2016

.UPDATE...
843 PM CDT

ONLY MINOR CHANGES MADE TO THE FORECAST THROUGH THURSDAY MORNING.
A SHARPLY DEFINED COMMA-HEAD SIGNATURE ASSOCIATED WITH AN UPPER
LOW IS OVER NORTHERN INDIANA/SOUTHERN MICHIGAN THIS EVENING.
FORCING FOR ASCENT WITH THIS HAS RETROGRADED WESTWARD INTO THE
FORECAST AREA BUT WILL BEGIN TO SHIFT MORE SOUTHWARD THE REST OF
TONIGHT. SOME LIGHT RAIN SHOWERS MAY REACH AS FAR EAST AS NEAR
I-57...BUT FOR THE MOST PART SHOULD ONLY BE IN NORTHWEST INDIANA.
THE PRESSURE GRADIENT TIGHTENING AROUND THE SYSTEM WILL LEAD TO AN
INCREASE IN BLUSTERY CONDITIONS THE REST OF TONIGHT IN FAR
NORTHEAST ILLINOIS AND FAR NORTHWEST INDIANA. HAVE BUMPED UP
CLOUD FORECAST FOR EASTERN AREAS EARLY THURSDAY BUT STILL
EXPECTING CLEARING BY LATE MORNING. THE TEMPERATURE FORECAST LOOKS
ON TRACK.

MTF

&&

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

237 PM...FORECAST CONCERNS INCLUDE VERY WARM TEMPS FRIDAY...
CHANCE OF THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY AHEAD OF
A COLD FRONT AND THEN AN UNSETTLED PATTERN NEXT WEEK.

A RIDGE OF HIGH PRESSURE WILL BE MOVING ACROSS THE AREA THURSDAY
NIGHT. AS WARM AIR ADVECTION BEGINS TO SPREAD ACROSS THE REGION...
THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE/CLOUDS AND THERE
IS A SMALL POTENTIAL FOR A FEW LIGHT SHOWERS OR SPRINKLES FRIDAY
MORNING BUT MAINTAINED A DRY FORECAST FROM THIS DISTANCE. THE REST
OF FRIDAY IS SHAPING UP TO BE VERY WARM WITH HIGHS INTO THE LOWER
80S MOST AREAS IN ILLINOIS AND MID/UPPER 70S IN NORTHWEST INDIANA.
LOW LEVEL WINDS AROUND/JUST UNDER 10KTS FRIDAY AFTERNOON WOULD
SUGGEST A LAKE BREEZE PROBABLY WILL FORM ALONG THE IL SHORE BUT
PERHAPS NOT MOVE TOO FAR INLAND BUT CONFIDENCE IS LOW GIVEN HOW
COLD THE LAKE REMAINS AND HOW WARM INLAND TEMPS WILL BE. POSSIBLE
THAT THE LAKE BREEZE COULD MOVE FURTHER INLAND THEN CURRENTLY
EXPECTED...ESPECIALLY BY LATE AFTERNOON/EARLY EVENING.

A COLD FRONT WILL MOVE SOUTH ACROSS LAKE MICHIGAN FRIDAY NIGHT
ARRIVING INTO NORTHERN IL JUST AFTER DAYBREAK SATURDAY MORNING
AND THEN CONTINUING SOUTH ACROSS THE AREA DURING THE MORNING.
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE FROM EARLY
SATURDAY MORNING THROUGH MID SATURDAY AFTERNOON...ENDING NORTH TO
SOUTH. TEMPS WILL BE TRICKY SATURDAY...LIKELY REMAINING STEADY
NEAR THE LAKE...PERHAPS ONLY IN THE 50S. THEN RISING SOUTH OF THE
FRONT IN THE MORNING THEN RISING NORTH OF THE FRONT...AWAY FROM
THE LAKE IN THE AFTERNOON AS SKIES CLEAR. BUT FOR MUCH OF THE AREA
NORTH OF THE KANKAKEE/ILLINOIS RIVERS...SATURDAY WILL BE MUCH
COOLER. THE FRONT SHOULD MOVE FAR ENOUGH SOUTH OF THE AREA TO END
PRECIP CHANCES EVERYWHERE SATURDAY EVENING...BUT CLOSE ENOUGH TO
MAINTAIN LOW CHANCE POPS ACROSS THE FAR SOUTH.

WEAK HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION
SUNDAY AND SUNDAY NIGHT...AS THE COLD FRONT BEGINS TO MOVE BACK
NORTH AS A WARM FRONT MONDAY AHEAD OF LOW PRESSURE WHICH WILL MOVE
ACROSS THE AREA TUESDAY OR WEDNESDAY. THERE REMAINS SOME LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SO CONFIDENCE
REGARDING TIMING IS LOW BUT CHANCE POPS WARRANTED FROM SUNDAY
NIGHT THROUGH WEDNESDAY...THOUGH THERE WILL LIKELY BE PROLONGED
DRY PERIODS. WITH THE CURRENT EXPECTED LOW TRACK SOUTH OF THE
LAKE...THAT WILL LIKELY MEAN EASTERLY FLOW AND COOLER ONSHORE
FLOW...FOR PERHAPS SEVERAL DAYS. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

THE PRIMARY AVIATION ITEMS OF INTEREST ARE NORTH/NORTHEAST WINDS
AND SPORADIC GUSTS THROUGH THURSDAY MORNING...WITH A SMALL CHANCE
FOR SOME SHOWERS AT ORD AND MDW TONIGHT.

THE CYCLONIC FLOW THAT WAS IN PLACE MUCH OF THE DAY WEDNESDAY
WILL CONTINUE TONIGHT AS A WEATHER SYSTEM NEAR DETROIT MOVES
LITTLE...IN FACT PARTLY RETROGRADES TONIGHT. THAT SHOULD ALLOW
FOR SOME SHOWERS TO APPROACH GYY AND CANNOT TOTALLY RULE OUT LIGHT
SHOWERS REACHING ORD OR MDW. MVFR CIGS ARE LIKELY TO PUSH BACK
WEST TO GYY AND POSSIBLY MDW BY 03Z-06Z.

THE NORTHEAST WINDS ARE ALSO LIKELY TO SLIGHTLY INCREASE LATER
THIS EVENING AND CONTAIN SOME SPORADIC GUSTS...POSSIBLY UP TO 20
TO 23 KT AT ORD OR MDW. CONFIDENCE IN THIS IS LOW RIGHT NOW SO
HAVE NOT MENTIONED IN THE TAF...PLUS THE MAIN STORY IS THE
CONTINUING NORTHEAST WIND DIRECTION. SPEEDS WILL GRADUALLY
SLACKEN LATE THURSDAY MORNING INTO THE AFTERNOON. A LAKE BREEZE
SHOULD DEVELOP DURING THE AFTERNOON AND LIKELY KEEP SPEEDS 8-10 KT
AT ORD AND MDW. THESE WILL QUICKLY DROP OFF AFTER SUNDOWN THURSDAY
EVENING.

MTF

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 042342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
642 PM CDT WED MAY 4 2016

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

237 PM...FORECAST CONCERNS INCLUDE VERY WARM TEMPS FRIDAY...
CHANCE OF THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY AHEAD OF
A COLD FRONT AND THEN AN UNSETTLED PATTERN NEXT WEEK.

A RIDGE OF HIGH PRESSURE WILL BE MOVING ACROSS THE AREA THURSDAY
NIGHT. AS WARM AIR ADVECTION BEGINS TO SPREAD ACROSS THE REGION...
THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE/CLOUDS AND THERE
IS A SMALL POTENTIAL FOR A FEW LIGHT SHOWERS OR SPRINKLES FRIDAY
MORNING BUT MAINTAINED A DRY FORECAST FROM THIS DISTANCE. THE REST
OF FRIDAY IS SHAPING UP TO BE VERY WARM WITH HIGHS INTO THE LOWER
80S MOST AREAS IN ILLINOIS AND MID/UPPER 70S IN NORTHWEST INDIANA.
LOW LEVEL WINDS AROUND/JUST UNDER 10KTS FRIDAY AFTERNOON WOULD
SUGGEST A LAKE BREEZE PROBABLY WILL FORM ALONG THE IL SHORE BUT
PERHAPS NOT MOVE TOO FAR INLAND BUT CONFIDENCE IS LOW GIVEN HOW
COLD THE LAKE REMAINS AND HOW WARM INLAND TEMPS WILL BE. POSSIBLE
THAT THE LAKE BREEZE COULD MOVE FURTHER INLAND THEN CURRENTLY
EXPECTED...ESPECIALLY BY LATE AFTERNOON/EARLY EVENING.

A COLD FRONT WILL MOVE SOUTH ACROSS LAKE MICHIGAN FRIDAY NIGHT
ARRIVING INTO NORTHERN IL JUST AFTER DAYBREAK SATURDAY MORNING
AND THEN CONTINUING SOUTH ACROSS THE AREA DURING THE MORNING.
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE FROM EARLY
SATURDAY MORNING THROUGH MID SATURDAY AFTERNOON...ENDING NORTH TO
SOUTH. TEMPS WILL BE TRICKY SATURDAY...LIKELY REMAINING STEADY
NEAR THE LAKE...PERHAPS ONLY IN THE 50S. THEN RISING SOUTH OF THE
FRONT IN THE MORNING THEN RISING NORTH OF THE FRONT...AWAY FROM
THE LAKE IN THE AFTERNOON AS SKIES CLEAR. BUT FOR MUCH OF THE AREA
NORTH OF THE KANKAKEE/ILLINOIS RIVERS...SATURDAY WILL BE MUCH
COOLER. THE FRONT SHOULD MOVE FAR ENOUGH SOUTH OF THE AREA TO END
PRECIP CHANCES EVERYWHERE SATURDAY EVENING...BUT CLOSE ENOUGH TO
MAINTAIN LOW CHANCE POPS ACROSS THE FAR SOUTH.

WEAK HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION
SUNDAY AND SUNDAY NIGHT...AS THE COLD FRONT BEGINS TO MOVE BACK
NORTH AS A WARM FRONT MONDAY AHEAD OF LOW PRESSURE WHICH WILL MOVE
ACROSS THE AREA TUESDAY OR WEDNESDAY. THERE REMAINS SOME LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SO CONFIDENCE
REGARDING TIMING IS LOW BUT CHANCE POPS WARRANTED FROM SUNDAY
NIGHT THROUGH WEDNESDAY...THOUGH THERE WILL LIKELY BE PROLONGED
DRY PERIODS. WITH THE CURRENT EXPECTED LOW TRACK SOUTH OF THE
LAKE...THAT WILL LIKELY MEAN EASTERLY FLOW AND COOLER ONSHORE
FLOW...FOR PERHAPS SEVERAL DAYS. CMS

&&

.AVIATION...
FOR THE 00Z TAFS...

THE PRIMARY AVIATION ITEMS OF INTEREST ARE NORTH/NORTHEAST WINDS
AND SPORADIC GUSTS THROUGH THURSDAY MORNING...WITH A SMALL CHANCE
FOR SOME SHOWERS AT ORD AND MDW TONIGHT.

THE CYCLONIC FLOW THAT WAS IN PLACE MUCH OF THE DAY WEDNESDAY
WILL CONTINUE TONIGHT AS A WEATHER SYSTEM NEAR DETROIT MOVES
LITTLE...IN FACT PARTLY RETROGRADES TONIGHT. THAT SHOULD ALLOW
FOR SOME SHOWERS TO APPROACH GYY AND CANNOT TOTALLY RULE OUT LIGHT
SHOWERS REACHING ORD OR MDW. MVFR CIGS ARE LIKELY TO PUSH BACK
WEST TO GYY AND POSSIBLY MDW BY 03Z-06Z.

THE NORTHEAST WINDS ARE ALSO LIKELY TO SLIGHTLY INCREASE LATER
THIS EVENING AND CONTAIN SOME SPORADIC GUSTS...POSSIBLY UP TO 20
TO 23 KT AT ORD OR MDW. CONFIDENCE IN THIS IS LOW RIGHT NOW SO
HAVE NOT MENTIONED IN THE TAF...PLUS THE MAIN STORY IS THE
CONTINUING NORTHEAST WIND DIRECTION. SPEEDS WILL GRADUALLY
SLACKEN LATE THURSDAY MORNING INTO THE AFTERNOON. A LAKE BREEZE
SHOULD DEVELOP DURING THE AFTERNOON AND LIKELY KEEP SPEEDS 8-10 KT
AT ORD AND MDW. THESE WILL QUICKLY DROP OFF AFTER SUNDOWN THURSDAY
EVENING.

MTF

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

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

&&

$$

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

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





000
FXUS63 KLOT 041937
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
237 PM CDT WED MAY 4 2016

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...

THURSDAY NIGHT THROUGH WEDNESDAY...

237 PM...FORECAST CONCERNS INCLUDE VERY WARM TEMPS FRIDAY...
CHANCE OF THUNDERSTORMS LATE FRIDAY NIGHT INTO SATURDAY AHEAD OF
A COLD FRONT AND THEN AN UNSETTLED PATTERN NEXT WEEK.

A RIDGE OF HIGH PRESSURE WILL BE MOVING ACROSS THE AREA THURSDAY
NIGHT. AS WARM AIR ADVECTION BEGINS TO SPREAD ACROSS THE REGION...
THERE WILL BE AN INCREASE IN MID LEVEL MOISTURE/CLOUDS AND THERE
IS A SMALL POTENTIAL FOR A FEW LIGHT SHOWERS OR SPRINKLES FRIDAY
MORNING BUT MAINTAINED A DRY FORECAST FROM THIS DISTANCE. THE REST
OF FRIDAY IS SHAPING UP TO BE VERY WARM WITH HIGHS INTO THE LOWER
80S MOST AREAS IN ILLINOIS AND MID/UPPER 70S IN NORTHWEST INDIANA.
LOW LEVEL WINDS AROUND/JUST UNDER 10KTS FRIDAY AFTERNOON WOULD
SUGGEST A LAKE BREEZE PROBABLY WILL FORM ALONG THE IL SHORE BUT
PERHAPS NOT MOVE TOO FAR INLAND BUT CONFIDENCE IS LOW GIVEN HOW
COLD THE LAKE REMAINS AND HOW WARM INLAND TEMPS WILL BE. POSSIBLE
THAT THE LAKE BREEZE COULD MOVE FURTHER INLAND THEN CURRENTLY
EXPECTED...ESPECIALLY BY LATE AFTERNOON/EARLY EVENING.

A COLD FRONT WILL MOVE SOUTH ACROSS LAKE MICHIGAN FRIDAY NIGHT
ARRIVING INTO NORTHERN IL JUST AFTER DAYBREAK SATURDAY MORNING
AND THEN CONTINUING SOUTH ACROSS THE AREA DURING THE MORNING.
SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE FROM EARLY
SATURDAY MORNING THROUGH MID SATURDAY AFTERNOON...ENDING NORTH TO
SOUTH. TEMPS WILL BE TRICKY SATURDAY...LIKELY REMAINING STEADY
NEAR THE LAKE...PERHAPS ONLY IN THE 50S. THEN RISING SOUTH OF THE
FRONT IN THE MORNING THEN RISING NORTH OF THE FRONT...AWAY FROM
THE LAKE IN THE AFTERNOON AS SKIES CLEAR. BUT FOR MUCH OF THE AREA
NORTH OF THE KANKAKEE/ILLINOIS RIVERS...SATURDAY WILL BE MUCH
COOLER. THE FRONT SHOULD MOVE FAR ENOUGH SOUTH OF THE AREA TO END
PRECIP CHANCES EVERYWHERE SATURDAY EVENING...BUT CLOSE ENOUGH TO
MAINTAIN LOW CHANCE POPS ACROSS THE FAR SOUTH.

WEAK HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION
SUNDAY AND SUNDAY NIGHT...AS THE COLD FRONT BEGINS TO MOVE BACK
NORTH AS A WARM FRONT MONDAY AHEAD OF LOW PRESSURE WHICH WILL MOVE
ACROSS THE AREA TUESDAY OR WEDNESDAY. THERE REMAINS SOME LARGE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SO CONFIDENCE
REGARDING TIMING IS LOW BUT CHANCE POPS WARRANTED FROM SUNDAY
NIGHT THROUGH WEDNESDAY...THOUGH THERE WILL LIKELY BE PROLONGED
DRY PERIODS. WITH THE CURRENT EXPECTED LOW TRACK SOUTH OF THE
LAKE...THAT WILL LIKELY MEAN EASTERLY FLOW AND COOLER ONSHORE
FLOW...FOR PERHAPS SEVERAL DAYS. CMS

&&

.AVIATION...
FOR THE 18Z TAFS...

LOW END VFR CLOUDS WILL SCATTER OUT THIS EVENING. WILL LIKELY SEE
ISOLATED TO WIDELY SCATTERED LIGHT RAIN SHOWERS THROUGH THIS
AFTERNOON. KEPT A VCSH GOING AS ONE OF THESE SHOWERS MAY WANDER
OVER THE TERMINALS...BUT EXPECTING A MOSTLY DRY AFTERNOON. WINDS
ARE SLIGHTLY MORE NORTHWEST THAN EXPECTED AND THEY WILL REMAIN
GUSTY ESPECIALLY AT GYY THROUGH THE AFTERNOON. WINDS BECOME DUE
NORTH AND BEGIN EASING THIS EVENING. HIGH PRESSURE SPREADS OVER
THE REGION TOMORROW WITH WINDS BECOMING NORTHEAST AROUND 10 KT. A
LAKE BREEZE IS EXPECTED TOMORROW.

JEE

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

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

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 041914
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
214 PM CDT WED MAY 4 2016

.SHORT TERM...
213 PM CDT

THROUGH THURSDAY...

THE REMAINDER OF THE AFTERNOON WILL CONTINUE TO BE GLOOMY AND
BLUSTERY WITH CLOUDY SKIES AND GUSTY NORTH-NORTHWEST WINDS.  HI-RES
GUIDANCE CONTINUES TO BACK OFF ON SHOWER ACTIVITY THIS AFTERNOON.
SURFACE DEWPOINT DEPRESSIONS ARE ALSO A BIT HIGHER THAN I WOULD LIKE
TO SEE...BUT DECIDED TO KEEP ISOLATED LIGHT RAIN SHOWERS IN THE
FORECAST THIS AFTERNOON AS A FEW SPRINKLES ARE POSSIBLE. NOT
EXPECTING MUCH PRECIP AT ALL...AND THINKING THE VAST MAJORITY OF THE
REGION WILL SEE DRY CONDITIONS THROUGH TONIGHT.  KEPT A CHANCE OF
SHOWERS OVER NORTHWEST INDIANA LATE THIS EVENING AS GUIDANCE
INDICATES THAT THE BAND OF SHOWERS OVER MICHIGAN WILL ROTATE
SOUTHWEST THIS EVENING.

HIGH PRESSURE THEN SPREADS OVER THE REGION THURSDAY. CLOUDS SCATTER
OUT THROUGH THE MORNING AND WINDS LIGHTEN. EXPECTING A LAKE BREEZE
TO FORM IN THE AFTERNOON. HIGH TEMPS WILL BE IN THE 60S AWAY FROM
THE LAKE AND IN THE 50S ALONG THE LAKE SHORE.

JEE

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

LOW END VFR CLOUDS WILL SCATTER OUT THIS EVENING. WILL LIKELY SEE
ISOLATED TO WIDELY SCATTERED LIGHT RAIN SHOWERS THROUGH THIS
AFTERNOON. KEPT A VCSH GOING AS ONE OF THESE SHOWERS MAY WANDER
OVER THE TERMINALS...BUT EXPECTING A MOSTLY DRY AFTERNOON. WINDS
ARE SLIGHTLY MORE NORTHWEST THAN EXPECTED AND THEY WILL REMAIN
GUSTY ESPECIALLY AT GYY THROUGH THE AFTERNOON. WINDS BECOME DUE
NORTH AND BEGIN EASING THIS EVENING. HIGH PRESSURE SPREADS OVER
THE REGION TOMORROW WITH WINDS BECOMING NORTHEAST AROUND 10 KT. A
LAKE BREEZE IS EXPECTED TOMORROW.

JEE

&&

.MARINE...
213 PM CDT

HEADLINES...WILL CONTINUE THE GALE WARNING AND SMALL CRAFT AS
PLANNED.

WINDS AND WAVES SUBSIDE AS HIGH PRESSURE BUILDS OVERHEAD TONIGHT.
WINDS BECOME SOUTH TO SOUTHWEST BY FRIDAY MORNING AND INCREASE
THROUGH THE DAY AHEAD OF THE NEXT LOW PRESSURE SYSTEM THAT PASSES
OVER ONTARIO. THE LOWS COLD FRONT SHIFTS DOWN THE LAKE FRIDAY NIGHT
INTO SATURDAY MORNING WITH WINDS BECOMING NORTH TO 30 KT BEHIND IT.
A SMALL CRAFT ADVISORY MAY BE NEEDED FOR HIGH WAVES SATURDAY.
ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE LAKE SUNDAY BEFORE
QUICKLY SHIFTING EAST OVER THE EAST COAST EARLY MONDAY MORNING.
WHILE GUIDANCE DIFFERS ON THE PATH OF THE LOW MID NEXT WEEK...BOTH
AGREE THAT A LOW MAY IMPACT THE MIDWEST REGION IN THE MIDDLE PART OF
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

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

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 041740
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1240 PM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

LOW END VFR CLOUDS WILL SCATTER OUT THIS EVENING. WILL LIKELY SEE
ISOLATED TO WIDELY SCATTERED LIGHT RAIN SHOWERS THROUGH THIS
AFTERNOON. KEPT A VCSH GOING AS ONE OF THESE SHOWERS MAY WANDER
OVER THE TERMINALS...BUT EXPECTING A MOSTLY DRY AFTERNOON. WINDS
ARE SLIGHTLY MORE NORTHWEST THAN EXPECTED AND THEY WILL REMAIN
GUSTY ESPECIALLY AT GYY THROUGH THE AFTERNOON. WINDS BECOME DUE
NORTH AND BEGIN EASING THIS EVENING. HIGH PRESSURE SPREADS OVER
THE REGION TOMORROW WITH WINDS BECOMING NORTHEAST AROUND 10 KT. A
LAKE BREEZE IS EXPECTED TOMORROW.

JEE

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

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

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 041130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

MVFR CONDITIONS THIS MORNING AND GUSTY NORTHERLY WINDS THROUGH THE
DAY MAKE UP THE MAKE FORECAST CONCERNS FOR TODAY. EARLY THIS
MORNING...A COLD FRONT HAS DROPPED SOUTH OF THE TERMINALS WITH
SOME LINGERING LIGHT SHOWERS WHICH SHOULD CLEAR THE TERMINALS BY
AROUND 12Z. WINDS HAVE QUICKLY RAMPED UP THIS MORNING...IN PART
DUE TO CONVECTIVE OUTFLOW FROM THE SHOWERS. WITH THAT IN MIND DO
STILL ANTICIPATE WINDS TO SETTLE SOME AS THE SHOWERS DEPART WITH
PREVAILING WIND DIRECTION BETWEEN 350-010 THROUGH MUCH OF THE
DAY...AND GUSTS INTO THE LOW TO MID 20 KT RANGE. MVFR CIGS THIS
MORNING ARE EXPECTED TO RISE WITH DAYTIME HEATING...AND EXPECT VFR
CONDITIONS TO RETURN BY AROUND MIDDAY...EXCEPT AT GYY WHERE LOWER
CONDITIONS AND STRONGER WINDS WILL LIKELY PERSIST DOWN FETCH OF
LAKE MICHIGAN. SCATTERED LIGHT SHOWERS AND SPRINKLES ARE POSSIBLE
THIS AFTERNOON...THOUGH COVERAGE SHOULD BE TOO LOW TO INCLUDE IN
THE TAFS AT THIS DISTANCE.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 041130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

MVFR CONDITIONS THIS MORNING AND GUSTY NORTHERLY WINDS THROUGH THE
DAY MAKE UP THE MAKE FORECAST CONCERNS FOR TODAY. EARLY THIS
MORNING...A COLD FRONT HAS DROPPED SOUTH OF THE TERMINALS WITH
SOME LINGERING LIGHT SHOWERS WHICH SHOULD CLEAR THE TERMINALS BY
AROUND 12Z. WINDS HAVE QUICKLY RAMPED UP THIS MORNING...IN PART
DUE TO CONVECTIVE OUTFLOW FROM THE SHOWERS. WITH THAT IN MIND DO
STILL ANTICIPATE WINDS TO SETTLE SOME AS THE SHOWERS DEPART WITH
PREVAILING WIND DIRECTION BETWEEN 350-010 THROUGH MUCH OF THE
DAY...AND GUSTS INTO THE LOW TO MID 20 KT RANGE. MVFR CIGS THIS
MORNING ARE EXPECTED TO RISE WITH DAYTIME HEATING...AND EXPECT VFR
CONDITIONS TO RETURN BY AROUND MIDDAY...EXCEPT AT GYY WHERE LOWER
CONDITIONS AND STRONGER WINDS WILL LIKELY PERSIST DOWN FETCH OF
LAKE MICHIGAN. SCATTERED LIGHT SHOWERS AND SPRINKLES ARE POSSIBLE
THIS AFTERNOON...THOUGH COVERAGE SHOULD BE TOO LOW TO INCLUDE IN
THE TAFS AT THIS DISTANCE.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
411 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
UPDATE FOR 09Z TAFS...
STABLE CONDITIONS BEHIND THE DEPARTING LINE OF SHOWERS HAS SLOWED
THE ARRIVAL OF GUSTIER NORTHERLY WINDS TO THE TERMINALS THIS
MORNING...HOWEVER ANTICIPATE WINDS TO VEER BACK TO THE NORTH AND
INCREASE OVER THE NEXT HOUR OR TWO. MEANWHILE...MVFR/IFR CIGS ARE
NOW NOTED IN OBS OVER SOUTHEAST WI AND INTO FAR NE IL AND ALSO
EXPECT THOSE TO OVERSPREAD THE CHICAGO AREA TERMINALS OVER THE
NEXT COUPLE HOURS...THEN GRADUALLY LIFT DIURNALLY AFTER DAYBREAK.
CONFIDENCE IN HOW FAR WEST THESE WILL SPREAD IS LOW HOWEVER...SO
HAVE BACKED OFF ON LOWEST CIGS AT RFD...AND MAY HAVE TO FOLLOW
SUIT AT DPA.

PREVIOUS DISCUSSION FOR THE 06Z TAFS...
LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS BY
AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
411 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
UPDATE FOR 09Z TAFS...
STABLE CONDITIONS BEHIND THE DEPARTING LINE OF SHOWERS HAS SLOWED
THE ARRIVAL OF GUSTIER NORTHERLY WINDS TO THE TERMINALS THIS
MORNING...HOWEVER ANTICIPATE WINDS TO VEER BACK TO THE NORTH AND
INCREASE OVER THE NEXT HOUR OR TWO. MEANWHILE...MVFR/IFR CIGS ARE
NOW NOTED IN OBS OVER SOUTHEAST WI AND INTO FAR NE IL AND ALSO
EXPECT THOSE TO OVERSPREAD THE CHICAGO AREA TERMINALS OVER THE
NEXT COUPLE HOURS...THEN GRADUALLY LIFT DIURNALLY AFTER DAYBREAK.
CONFIDENCE IN HOW FAR WEST THESE WILL SPREAD IS LOW HOWEVER...SO
HAVE BACKED OFF ON LOWEST CIGS AT RFD...AND MAY HAVE TO FOLLOW
SUIT AT DPA.

PREVIOUS DISCUSSION FOR THE 06Z TAFS...
LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS BY
AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
328 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONICFLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
328 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONICFLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040747
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
247 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040747
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
247 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040513
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1213 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 040139 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
839 PM CDT TUE MAY 3 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 00Z TAFS...

MAIN FORECAST CONCERNS ARE WITH SHOWER AND THUNDER CHANCES LATER
TONIGHT...LOW END MVFR AND IFR CEILINGS...AND STRONG NORTHERLY
WINDS WEDNESDAY MORNING.

WESTERLY WINDS AND VFR CEILINGS OCCURRING EARLY THIS EVENING WILL
CONTINUE FOR MOST OF THE EVENING UNTIL AN AREA OF LOW PRESSURE AND
FRONTAL BOUNDARY QUICKLY PUSH SOUTH ACROSS THE REGION. DO EXPECT
AROUND A THREE HOUR WINDOW OF PREVAILING SHOWERS WITH SOME
EMBEDDED THUNDER TO OCCUR JUST AFTER THE MIDNIGHT TIME FRAME
TONIGHT. THE MAIN AREA OF PRECIP WILL SWING THROUGH BUT THERE DOES
APPEAR TO BE SOME IMMEDIATE SHOWER DEVELOPMENT STILL POSSIBLE
AFTER. VFR CEILINGS WILL QUICKLY LOWER TO LOW END MVFR AND IFR
DURING THAT TIME AND STAY IN PLACE THROUGH EARLY WEDNESDAY
MORNING. WINDS WILL ALSO QUICKLY SHIFT TO THE NORTH WITH
SPEEDS/GUSTS RAMPING UP...AND LOOKING TO STAY GUSTY OUT OF THE
NORTH FOR MOST OF WEDNESDAY. HAVE CONTINUED MENTION OF ADDITIONAL
SHOWER CHANCES THROUGHOUT THE DAY ON WEDNESDAY AND HAVE CONFIDENCE
OF OCCURRENCE...BUT LOWER CONFIDENCE WITH COVERAGE AND DURATION.

RODRIGUEZ

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742...3 AM WEDNESDAY TO 3 PM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...3 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 032351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
651 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 00Z TAFS...

MAIN FORECAST CONCERNS ARE WITH SHOWER AND THUNDER CHANCES LATER
TONIGHT...LOW END MVFR AND IFR CEILINGS...AND STRONG NORTHERLY
WINDS WEDNESDAY MORNING.

WESTERLY WINDS AND VFR CEILINGS OCCURRING EARLY THIS EVENING WILL
CONTINUE FOR MOST OF THE EVENING UNTIL AN AREA OF LOW PRESSURE AND
FRONTAL BOUNDARY QUICKLY PUSH SOUTH ACROSS THE REGION. DO EXPECT
AROUND A THREE HOUR WINDOW OF PREVAILING SHOWERS WITH SOME
EMBEDDED THUNDER TO OCCUR JUST AFTER THE MIDNIGHT TIME FRAME
TONIGHT. THE MAIN AREA OF PRECIP WILL SWING THROUGH BUT THERE DOES
APPEAR TO BE SOME IMMEDIATE SHOWER DEVELOPMENT STILL POSSIBLE
AFTER. VFR CEILINGS WILL QUICKLY LOWER TO LOW END MVFR AND IFR
DURING THAT TIME AND STAY IN PLACE THROUGH EARLY WEDNESDAY
MORNING. WINDS WILL ALSO QUICKLY SHIFT TO THE NORTH WITH
SPEEDS/GUSTS RAMPING UP...AND LOOKING TO STAY GUSTY OUT OF THE
NORTH FOR MOST OF WEDNESDAY. HAVE CONTINUED MENTION OF ADDITIONAL
SHOWER CHANCES THROUGHOUT THE DAY ON WEDNESDAY AND HAVE CONFIDENCE
OF OCCURRENCE...BUT LOWER CONFIDENCE WITH COVERAGE AND DURATION.

RODRIGUEZ

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742...3 AM WEDNESDAY TO 3 PM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...3 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 032034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
334 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 032000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
300 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 031928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
228 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 031741
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1241 PM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 031741
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1241 PM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 031122
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
622 AM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

RIDGE AXIS IN PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA
EARLY THIS MORNING WILL SHIFT SOUTH TODAY ALLOWING WESTERLY
WINDS TO PICK UP THROUGH THE DAY. GUSTS TO NEAR 20 KT ARE POSSIBLE
DURING THE AFTERNOON HOURS AS THE GRADIENT TIGHTENS AHEAD OF AN
APPROACHING COLD FRONT. EXPECT VFR CONDITIONS WITH MAINLY MID/HIGH
LEVEL CLOUD COVER TODAY. LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS...A COLD FRONT WILL SWEEP ACROSS THE REGION.
EXPECT SCATTERED SHOWERS AND A PERHAPS A FEW THUNDERSTORMS TO BE
IN PLACE AHEAD OF THE FRONT LATE THIS EVENING. GIVEN THE OVERNIGHT
TIMING OF THE FRONT AND VERY WEAK INSTABILITY NOTED IN FORECAST
SOUNDINGS THIS EVENING...WILL NOT MENTION THUNDER IN THE TAFS FOR
NOW...THOUGH THEY REMAIN A SMALL POSSIBILITY. ONCE THE FRONT
SWEEPS THROUGH...PRECIP SHOULD TAPER AND LOW MVFR OR EVEN IFR CIGS
ALONG WITH STRONG NORTHERLY WINDS ARE EXPECTED TO OVERSPREAD THE
TERMINALS. GUSTS INTO THE LOW TO MID 20 KT RANGE ARE POSSIBLE LATE
TONIGHT AND THROUGH MUCH OF THE DAY WEDNESDAY. CIGS SHOULD LIFT
DURING THE DAY WEDNESDAY AS WE HEAT UP...AND BY WEDNESDAY
AFTERNOON...ADDITIONAL SCATTERED SHOWERS ARE POSSIBLE.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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

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





000
FXUS63 KLOT 031122
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
622 AM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

RIDGE AXIS IN PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA
EARLY THIS MORNING WILL SHIFT SOUTH TODAY ALLOWING WESTERLY
WINDS TO PICK UP THROUGH THE DAY. GUSTS TO NEAR 20 KT ARE POSSIBLE
DURING THE AFTERNOON HOURS AS THE GRADIENT TIGHTENS AHEAD OF AN
APPROACHING COLD FRONT. EXPECT VFR CONDITIONS WITH MAINLY MID/HIGH
LEVEL CLOUD COVER TODAY. LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS...A COLD FRONT WILL SWEEP ACROSS THE REGION.
EXPECT SCATTERED SHOWERS AND A PERHAPS A FEW THUNDERSTORMS TO BE
IN PLACE AHEAD OF THE FRONT LATE THIS EVENING. GIVEN THE OVERNIGHT
TIMING OF THE FRONT AND VERY WEAK INSTABILITY NOTED IN FORECAST
SOUNDINGS THIS EVENING...WILL NOT MENTION THUNDER IN THE TAFS FOR
NOW...THOUGH THEY REMAIN A SMALL POSSIBILITY. ONCE THE FRONT
SWEEPS THROUGH...PRECIP SHOULD TAPER AND LOW MVFR OR EVEN IFR CIGS
ALONG WITH STRONG NORTHERLY WINDS ARE EXPECTED TO OVERSPREAD THE
TERMINALS. GUSTS INTO THE LOW TO MID 20 KT RANGE ARE POSSIBLE LATE
TONIGHT AND THROUGH MUCH OF THE DAY WEDNESDAY. CIGS SHOULD LIFT
DURING THE DAY WEDNESDAY AS WE HEAT UP...AND BY WEDNESDAY
AFTERNOON...ADDITIONAL SCATTERED SHOWERS ARE POSSIBLE.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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