Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 021759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1259 PM CDT MON MAY 2 2016

.UPDATE...1031 AM CDT

SHORTLY BEFORE SUNRISE SKIES BEGAN TO THIN ACROSS NORTHEAST
ILLINOIS AS DRIER AIR BEGAN TO DRIFT SOUTH FROM THE WEAK ANTI-
CYCLONIC FEATURE POSITIONED OVER CENTRAL WISCONSIN AND STRETCHES
WEST THROUGH THE ROCKIES. THIS RIDGE OF HIGH PRESSURE WILL LIKELY
MAINTAIN LESS CLOUD COVER ACROSS FAR NORTHERN IL...HOWEVER THE
FRONTAL BOUNDARY AND STRATUS LAYER WILL PERSIST ALONG AND SOUTH OF
I-80. TEMPERATURES AS A RESULT MAY WARM A DEGREE OR TWO WARMER
INTO THE MIDDLE TO PERHAPS UPPER 50S WHERE SKIES REMAIN SUNNY.
HOWEVER FOR AREAS ADJACENT TO LAKE MICHIGAN TEMPERATURES MAY
REMAIN IN THE UPPER 40S TO AROUND 50 AS WINDS WILL BE FROM A NORTH
TO AT TIMES NORTHEAST DIRECTION.

BEACHLER

&&

.SHORT TERM...
348 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

SOMEWHAT UNSETTLED WEATHER PATTERN WILL CONTINUE ACROSS THE AREA
THROUGH MID-WEEK...AS A LONG WAVE UPPER TROUGH EVOLVES ACROSS
EASTERN NORTH AMERICA. MOSTLY CLOUDY...COOL AND OCCASIONALLY
SHOWERY CONDITIONS WILL PLAGUE THE REGION TODAY AND AGAIN
WEDNESDAY... INTERRUPTED BRIEFLY TUESDAY AS WARMER WESTERLY FLOW
DEVELOPS IN ADVANCE OF STRONG DIGGING SHORT WAVE AND SURFACE COLD
FRONT RESPONSIBLE FOR CARVING OUT THE AFOREMENTIONED LARGE SCALE
EASTERN TROUGH.

IN THE NEAR TERM...MID-LEVEL WAVE AND ASSOCIATED SURFACE LOW
WHICH PROVIDED OUR RAINY WEEKEND WERE MOVING OFF TO THE EAST OF
THE AREA EARLY THIS MORNING...WITH ONLY A FEW SPRINKLES AND PATCHY
DRIZZLE LINGERING MAINLY ACROSS OUR NORTHWEST INDIANA COUNTIES AS
OF 3 AM. LOW LEVEL WINDS BACKING MORE NORTHERLY THIS MORNING WILL
BRING MODEST DRYING WHICH SHOULD SHUT OFF ANY LINGERING LIGHT
PRECIP...AND THIN OUT SOME OF THE EXTENSIVE CLOUD COVER ESPECIALLY
OVER FAR NORTHERN IL. SIGNIFICANT CLEARING IS NOT EXPECTED
HOWEVER...AS ANOTHER STRONG MID-LEVEL WAVE DROPPING SOUTHEAST INTO
THE DAKOTAS EARLY THIS MORNING APPROACHES THE AREA THIS AFTERNOON.
ASSOCIATED HEIGHT FALLS AND COOLING MID-LEVEL TEMPS SHOULD SUPPORT
STRATOCU DEVELOPMENT AND MAY SUPPORT A FEW SPRINKLES MAINLY
WEST/NORTHWEST OF THE CWA BY AFTERNOON. HIGH-RES GUIDANCE ALSO
CONTINUES TO DEPICT SOME LIGHT QPF ACROSS OUR FAR SOUTHEAST
COUNTIES WHERE LOW LEVEL MOISTURE WILL LINGER INTO TONIGHT IN THE
VICINITY OF WEAK SURFACE TROUGH LEFT BEHIND DEPARTING LOW
PRESSURE. NORTHEAST WINDS OFF OF THE LAKE COMBINED WITH
CONSIDERABLE CLOUD COVER AND RELATIVELY COOL TEMPS ALOFT WILL
LIMIT HIGH TEMPS TO THE 50S IN MOST AREAS TODAY...WITH UPPER 40S
LIKELY ALONG THE IMMEDIATE LAKE MICHIGAN SHORE. FAR NORTHWEST
COUNTIES MAY TAG 60 BRIEFLY WELL INLAND OF MAIN LAKE COOLING PUSH
AND WHERE SOME PEAKS OF SUN MAY BE POSSIBLE AT TIMES.

NORTHERN PLAINS SHORT WAVE PUSHES SOUTHEAST ACROSS THE AREA
OVERNIGHT AND THEN DRIFTS OFF TO OUR SOUTHEAST ON TUESDAY...WITH A
BRIEF PERIOD OF SUBSIDENCE AND A WEAK SURFACE HIGH PRESSURE RIDGE
OVER THE AREA DURING THE DAY. LOW LEVEL WINDS WILL BACK TO THE
WEST AS THIS RIDGE MOVES OFF TO THE SOUTHEAST IN THE
AFTERNOON...AND IN RESPONSE TO LOW PRESSURE DEVELOPING OVER THE
NORTHERN LAKES IN ASSOCIATION WITH ANOTHER DEEP UPPER LOW DIGGING
SOUTHEAST ACROSS THE REGION. THE GOOD NEWS IS THAT WE BRIEFLY WARM
UP TUESDAY AHEAD OF THIS NEXT SYSTEM... WITH HIGHS IN THE MID-
UPPER 60S EXPECTED. WEST WINDS AHEAD OF THE APPROACHING COLD FRONT
SHOULD LIMIT ANY LAKE COOLING PRIMARILY TO THE SOUTH SHORE OF THE
LAKE IN LAKE/PORTER COUNTIES. RAIN CHANCES RAMP UP QUICKLY AGAIN
TUESDAY EVENING AS THE STRONG MID-LEVEL WAVE AND SURFACE COLD
FRONT APPROACH. GIVEN CONSISTENT SIGNAL IN MODEL RUNS HAVE GONE
WITH LIKELY POPS TUESDAY NIGHT ESPECIALLY ACROSS THE EASTERN HALF
OR SO OF THE CWA...AND INCLUDED SLGT CHANCE MENTION OF THUNDER
GIVEN COOL TEMPS ALOFT WITHIN THE UPPER TROUGH. THE COLD FRONT
CLEARS THE AREA BY WEDNESDAY MORNING...THOUGH PRECIP WILL LIKELY
LINGER DURING THE DAY AS INSTABILITY SHOWERS DEVELOP BY AFTERNOON.
RENEWED PUSH OF COOLER AIR ON BLUSTERY NORTH WINDS WILL LIMIT
TEMPS ONCE AGAIN. HIGHS WEDNESDAY MAY NOT GET OUT OF THE 40S ALONG
THE INDIANA IMMEDIATE LAKE SHORE...THOUGH INLAND PARTS OF NORTHERN
IL MAY REACH 60. PRECIP THREAT DWINDLES WEDNESDAY NIGHT WITH
DIURNAL STABILIZATION. DECREASING WINDS AND CLEARING SKIES LOOK TO
PRODUCE A CHILLY NIGHT FOR EARLY MAY...WITH LOWS DIPPING INTO THE
UPPER 30S IN SOME SPOTS.

RATZER

&&

.LONG TERM...
356 AM CDT

THURSDAY THROUGH SUNDAY...

UPPER PATTERN IS HIGHLY AMPLIFIED BY MID-WEEK...WITH DEEP TROUGHS
OVER BOTH COASTS AND AN UPPER RIDGE ACROSS THE CENTRAL CONUS. AS
THE RIDGE DRIFTS EASTWARD...RISING HEIGHTS/SUBSIDENCE RESULT IN
SURFACE HIGH PRESSURE BUILDING INTO THE REGION THURSDAY AND
BRINGING DRY AND WARMER WEATHER TO THE AREA FOR THE END OF THE
WEEK. THURSDAY WILL STILL BE A BIT ON THE COOL SIDE WITH TEMPS IN
THE UPPER 50S-LOW 60S IN THE VICINITY OF THE SURFACE RIDGE AND
WITH LIGHT NORTHERLY WINDS AND LAKE BREEZES. 70S RETURN FRIDAY AND
SATURDAY HOWEVER AS WINDS TURN SOUTHWEST AS AN AREA OF LOW
PRESSURE TRACKS NORTH OF LAKE SUPERIOR AND TRAILS A COLD FRONT
ACROSS THE UPPER MIDWEST. THIS FRONT WILL SAG ACROSS THE AREA LATE
SATURDAY...WITH AN ATTENDANT CHANCE OF THUNDERSTORMS...THEN BECOME
STATIONARY SOUTH OF THE CWA SUNDAY AS WEAK HIGH PRESSURE SPREADS
ACROSS THE NORTHERN LAKES. THIS WILL LIKELY SET UP A NORTH-SOUTH
GRADIENT OF TEMPS WITH 70S ACROSS CENTRAL IL/IN SUNDAY...AND
COOLER 50S-60S ACROSS FAR NORTHEAST IL NEAR LAKE MICHIGAN.
PRESENCE OF THE SURFACE FRONT AND ELEVATED BAROCLINIC ZONE TO ITS
NORTH WILL MAINTAIN THE POTENTIAL FOR SCATTERED SHOWERS AND
THUNDERSTORMS THROUGH SUNDAY.

RATZER

&&

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

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
300 AM CDT

LOW PRESSURE IS DEPARTING THE REGION EARLY THIS MORNING WITH SOME
LINGERING 15 TO 20 KT WINDS STILL IN PLACE ACROSS SOUTHERN LAKE
MICHIGAN...BUT PROGGED TO CONTINUE TO DIMINISH THROUGH THE
MORNING. HIGH PRESSURE WILL BUILD ACROSS LAKE MICHIGAN THIS
EVENING AND TONIGHT...THEN SOUTHWESTERLY FLOW WILL DEVELOP ON
TUESDAY AS LOW PRESSURE MOVES ACROSS ONTARIO. THE LOW WILL MOVE
SOUTHEAST TO THE EASTERN GREAT LAKES REGION BY WEDNESDAY...BUT A
TRAILING COLD FRONT IS PROGGED TO MOVE SOUTH ACROSS LAKE MICHIGAN
TUESDAY NIGHT. NORTH WINDS GUSTING TO 30 KT ARE EXPECTED TO
DEVELOP BEHIND THE FRONT LATE TUESDAY NIGHT AND CONTINUE THROUGH
THE DAY WEDNESDAY. WINDS SHOULD BEGIN TO DIMINISH THURSDAY AS
ANOTHER RIDGE APPROACHES THE REGION.

BMD

&&

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

$$

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