Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 302214
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
514 PM CDT MON MAR 30 2015

.SHORT TERM...
339 PM CDT

TONIGHT THROUGH WEDNESDAY NIGHT...

MAIN FOCUS IN THE NEAR TERM IS ON THE CLIPPERY-LIKE SYSTEM
CURRENTLY DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. SURFACE LOW
PRESSURE ANALYZED OVER SOUTHWEST MINNESOTA IS PROGGED TO CONTINUE
TO MOVE SOUTHEAST OVER NORTHEAST ILLINOIS LATE TONIGHT...THEN MOVE
QUICKLY OFF INTO OHIO BY TUESDAY MORNING. AHEAD OF THE
LOW...BREEZY WESTERLY WINDS HAVE WARMED TEMPS INTO THE 60S AND
EVEN AROUND 70 (STERLING IL) THIS AFTERNOON. AS THE LOW MOVES
SOUTHEAST TOWARD THE AREA HOWEVER...WINDS WILL LIKELY BACK TO THE
EAST/SOUTHEAST THIS EVENING AND WILL LIKELY CAUSE SOME TEMPERATURE
FLUCTUATONS AS FLOW SHIFT FROM OFFSHORE TO ONSHORE ALONG THE
ILLINOIS LAKE MICHIGAN SHORE. THUS OUR CURRENT MILD WEATHER WILL
LIKELY TURN CHILLIER AT LEAST ALONG THE LAKE LATER THIS EVENING.
IN ADDITION...AREA OF LIGHT TO MODERATE RAIN ACROSS WI WILL ALSO
SHIFT SOUTHEAST EARLY THIS EVENING... CLIPPING NORTHEAST IL AND
NORTHWEST INDIANA INTO TONIGHT. WHILE MUCH OF THE RAIN WILL BE
LIGHT...STEEP MID-LEVEL LAPSE RATES NOTED IN RAP SOUNDINGS AND A
PERIOD OF DECENT F-GEN FORCING AROUND 850 MB MAY PRODUCE SOME
HEAVIER BANDED SHOWERS THIS EVENING. SHOWERS WILL GRADUALLY PULL
OFF TO THE EAST AFTER MIDNIGHT AS THE BEST FORCING AND WARM/MOIST
ADVECTION SHIFTS AWAY FROM THE CWA WITH THE WAVE.

COOLER NORTH-NORTHEAST WINDS ARE IN STORE FOR THE AREA
TUESDAY...AS WEAK HIGH PRESSURE RIDGING SPREADS ACROSS THE REGION.
WHILE HIGHS IN THE 55-60 RANGE ARE EXPECTED WELL WEST/SOUTHWEST OF
THE LAKE... READINGS CLOSER TO THE SHORE WILL LIKELY NOT MAKE IT
OUT OF THE MID 40S. THE GOOD NEWS HOWEVER IS THAT THIS COOL DOWN
WILL BE BRIEF... AS UPPER RIDGE DEVELOPS ACROSS THE CENTRAL CONUS
TUESDAY NIGHT INTO WEDNESDAY...AS A DEEP TROUGH WORKS OUT OF THE
NORTHERN ROCKIES AND OUT ACROSS THE CANADIAN PRAIRIES. SURFACE
PRESSURE FALLS ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST WILL
ALLOW WINDS TO SHIFT SOUTH WEDNESDAY...INCREASING THROUGH
WEDNESDAY NIGHT AS THE SURFACE LOW TRACKS NORTH OF THE BORDER.
WARMER TEMPS...IN THE UPPER 60S TO LOWER 70S...WILL MAKE FOR A
BREEZY MORE SPRING-LIKE DAY. A COLD FRONT TRAILING FROM THE
CANADIAN LOW WILL APPROACH THE AREA LATE WEDNESDAY NIGHT...WITH
MILD AND MORE HUMID CONDITIONS AHEAD OF THE BOUNDARY.
PRECIPITATION CHANCES WILL BE BEST IMMEDIATELY ALONG/AHEAD OF THE
FRONT AND MAINLY WEST OF OUR CWA THROUGH THE EVENING...BEFORE
INCREASING POTENTIAL FOR SHOWERS/THUNDERSTORMS SPREADS ACROSS
NORTHERN IL LATE WEDNESDAY NIGHT.

RATZER

&&

.LONG TERM...
339 PM CDT

THURSDAY THROUGH MONDAY...

SURFACE COLD FRONT CONTINUES TO PUSH SOUTHEAST ACROSS THE
FORECAST AREA ON THURSDAY...WITH BEST CHANCE OF SHOWERS AND
THUNDERSTORMS FOR MOST OF THE CWA. POTENTIAL FOR SOME STRONG
THUNDERSTORMS MAY EVOLVE SOUTH OF THE FRONT (MAINLY OUR SOUTH
COUNTIES) DEPENDING UPON CLOUD COVER AND DESTABILIZATION BY
AFTERNOON...AS UPPER JET STREAK MOVES OVERHEAD AND SUPPORTS STRONG
DEEP LAYER SHEAR IN EXCESS OF 40 KTS. WITH THE FRONT MOVING
SLOWLY...TEMPS SHOULD REMAIN FAIRLY MILD...IN THE 60S EXCEPT FOR
AREAS NEAR THE LAKE WHERE WINDS MAY SHIFT ONSHORE BEHIND THE FRONT
LATER IN THE DAY.

THE COLD FRONT CONTINUES TO SAG SOUTH THURSDAY NIGHT INTO
FRIDAY...THOUGH GUIDANCE DOES SUPPORT A CONTINUED CHANCE OF PRECIP
INTO FRIDAY AS ANOTHER WAVE IS DEPICTED MOVING ALONG THE ELEVATED
BAROCLINIC ZONE NORTH OF THE SURFACE FRONT. COOLER AND DRIER
WEATHER DOES LOOK TO DEVELOP LATER FRIDAY AND FRIDAY NIGHT AS WEAK
HIGH PRESSURE MOVES IN. THE HIGH PRESSURE RIDGE THEN MOVES SOUTH
INTO OHIO VALLEY SATURDAY...WITH WINDS SHIFTING WEST AND ALLOWING
ANOTHER WARM UP. LONG RANGE SOLUTIONS INDICATE A SHORT WAVE MOVING
ACROSS THE NORTHERN LAKES AND TRAILING A COLD FRONT INTO AREA BY
SATURDAY EVENING HOWEVER...WITH ANOTHER WEAK HIGH MOVING ACROSS
THE AREA SATURDAY NIGHT AS COLD FRONT CONTINUES TO SAG SOUTH.

MODELS DIFFER A BIT IN DETAILS BY DAYS 6-7...BUT GENERALLY
INDICATE FRONT LIFTING BACK NORTH AS A WARM FRONT SUNDAY AS
SURFACE LOW PRESSURE DEVELOPS ACROSS THE PLAINS. PRECIP CHANCES
INCREASE DURING THE PERIOD IN THIS SCENARIO...WITH MILDER
TEMPERATURES POSSIBLY MUCH WARMER IF MORE AGGRESSIVE GFS PANS OUT
WITH WARM FRONT NORTH OF THE AREA.

RATZER

&&

.AVIATION...

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

* NORTHEAST WINDS DEVELOP AND INCREASE TO AROUND 10KT THIS EVENING

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

IZZI

//DISCUSSION...UPDATED 22Z...

SENT EARLY AMD TO ORD/MDW TAF DUE TO EXPECTED INCREASING NORTHEAST
WINDS EARLY THIS EVENING AS LAKE ENHANCED NE WIND DEVELOPS AND
LIKELY PUSHES SPEEDS UP TO AT LEAST AROUND 10KT FOR A COUPLE HOURS
EARLY THIS EVENING. LOOKING LIKE WINDS COULD REMAIN NORTHEAST
THROUGH REST OF THE EVENING AND INTO THE OVERNIGHT THOUGH
CONFIDENCE IS LOW IN WHEN NE WINDS PICK UP TO 10KT EXACTLY AND ON
WIND DIRECTION IN GENERAL OVERNIGHT.

IZZI

UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

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

* MEDIUM CONFIDENCE IN WINDS THIS EVENING...LOW CONFIDENCE IN
  WINDS OVERNIGHT...MEDIUM-HIGH CONFIDENCE IN WINDS TUESDAY

* LOW MEDIUM CONFIDENCE IN MVFR CIGS POTENTIAL TUES MORNING

IZZI

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

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
134 PM CDT

STRONGER WESTERLY WINDS OVER THE LAKE HAVE SINCE DIMINISHED THIS
AFTERNOON WITH A WEAK RIDGE OF HIGH PRESSURE OVERHEAD. ALONG WITH
THE DIMINISHING TREND THIS AFTERNOON...WINDS HAVE BECOME HIGHLY
VARIABLE ACROSS THE ENTIRE THE LAKE. EXPECT EITHER AN ONSHORE
COMPONENT OR A PERIOD OF VARIABLE WINDS OVER THE NEARSHORE THIS
AFTERNOON INTO THE EVENING...WITH A SOUTH TO EAST WIND OVER THE
OPEN WATERS. THIS WILL OCCUR UNTIL LATE IN THE EVENING...WHEN A
LOW PRESSURE SYSTEM QUICKLY MOVES SOUTHEAST TO THE SOUTHERN END OF
THE LAKE. INCREASING SPEEDS OVER THE ENTIRE LAKE BUT STILL
VARIABLE OVER THE SOUTH HALF...WILL THEN TRANSITION TO A NORTHERLY
WIND OVER ALL OF THE LAKE BY EARLY TUESDAY MORNING. SPEEDS MAY
STILL BE IN THE 15 TO 25 KT RANGE INITIALLY WITH THIS
TRANSITION...BUT WILL LIKELY OBSERVE A QUICK DIMINISHING TREND
THROUGH MIDDAY.

RODRIGUEZ

&&

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

$$

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