Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 211952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
252 PM CDT THU MAY 21 2015

.SHORT TERM...
247 PM CDT

THROUGH SATURDAY...

HIGH PRESSURE IS OVER THE PLAINS AND SPREADING ACROSS CENTRAL AND
SOUTHERN IL.  EARLY MORNING CLOUDS HAVE CLEARED NICELY AND
TEMPERATURES ROSE QUICKLY IN RESPONSE TO THE AMPLE SUNSHINE.  A WEAK
LOW PRESSURE TROUGH AND COLD FRONT ARE OVER THE NORTHERN END OF LAKE
MICHIGAN AND THE FRONT WILL SLIDE DOWN THE LAKE OVERNIGHT. WHILE A
FEW LIGHT RAIN SHOWERS ARE EXPECTED WITH FRONT OVER THE
LAKE...THINKING IT WILL BE TOO DRY FOR PRECIP TO FALL OVER THE LAND
BASED CWA.  WINDS BECOME NORTH BEHIND THE FRONT LATE TONIGHT INTO
FRIDAY MORNING.

WINDS DROP OFF QUICKLY AS HIGH PRESSURE BUILDS OVERHEAD. FLOW WILL
BE OFF THE LAKE AND EXPECTING WINDS AROUND 10 MPH ALONG THE LAKE
FRIDAY.  AREAS WELL AWAY FROM THE LAKE WILL GET INTO THE MID 60S TO
AROUND 70...WHILE AREAS ALONG THE LAKE WILL ONLY BE IN THE 50S TO
LOW 60S.  OUTSIDE OF CHILLIER TEMPS ALONG THE LAKE...EXPECTING A
BEAUTIFULLY SUNNY DAY. OVERNIGHT LOWS WILL VARY FROM THE LOW 40S TO
AROUND 50.

THE HIGH SHIFTS EAST SATURDAY BUT EXPECTING ANOTHER DRY DAY WITH
INCREASING CLOUD COVER.  THE NEXT LOW FORMS OVER THE CENTRAL PLAINS
TOMORROW BUT THE UPPER LEVEL RIDGE REMAINS OVER THE MIDWEST.
THINKING THE DRY AIR WILL KEEP THE REGION PRECIP FREE THROUGH
SATURDAY AFTERNOON. SOUTH WINDS ARE EXPECTED AND A WEAK LAKE BREEZE
IS POSSIBLE. THINKING THE LAKE BREEZE WILL HUG THE SHORE AND
PROBABLY ONLY PUSH OVER LAND OVER LAKE COUNTY IL.  AS SUCH KEPT
DAYTIME HIGH TEMPS IN THE 60S ALONG THE LAKE BUT EXPECTING ALL OTHER
REGIONS TO CLIMB INTO THE MID 70S. IF CLOUD COVER IS SLOWER THAN
FORECAST...COULD SEE A FEW SITES REACH 80...BUT DECIDED TO GO THE
SAFER ROUTE AND BET ON INCREASING CLOUD COVER. HAVE MEDIUM-HIGH
CONFIDENCE IN HIGH TEMPS FOR SATURDAY.

JEE

&&

.LONG TERM...
255 AM CDT

FRIDAY THROUGH WEDNESDAY...

FRIDAY LOOKS TO BE SUNNY AND MILD AWAY FROM THE LAKE...THOUGH
NORTHEAST WINDS OFF THE LAKE IN THE WAKE OF THE BACK DOOR FRONT WILL
HOLD TEMPS ALONG THE SHORE IN THE 50S.

HIGH PRESSURE OVER THE WESTERN LAKES REGION FRIDAY WILL MOVE RATHER
SWIFTLY TO THE SOUTHEAST AND OFF THE MID ATLANTIC COAST BY SATURDAY
EVENING. BROAD SWATH OF SOUTHERLY WINDS ON THE BACK SIDE OF THAT
HIGH WILL BEGIN THE PROCESS OF DRAWING MODIFIED GULF MOISTURE
NORTHWARD TOWARD THE REGION. UPPER RIDGE WILL BE POSITIONING ITSELF
OVERHEAD SATURDAY...SO IT LOOKS DRY AND WARMER THOUGH SLIGHT LAKE
BREEZE COULD KEEP MAINLY ILLINOIS SHORE A BIT COOLER SATURDAY
AFTERNOON.

NOT SHOCKINGLY...GFS HAS SLOWED THE EASTWARD PROGRESSION OF THE BIG
WESTERN TROUGH AND NOW WOULD SUGGEST A MUCH DRIER SUNDAY OVER THE
AREA WHILE ECMWF AND GEM STILL LOOK WETTER. REALLY THE ENTIRE PERIOD
SUNDAY THROUGH WEDNESDAY LOOKS TO BE PRETTY SIMILAR FORECAST-WISE
WITH DISTURBED SOUTHWEST FLOW ALOFT OVER THE AREA AND LOW LEVEL
BAROCLINIC ZONE NEAR ENOUGH BY TO PUT US IN THE POTENTIAL ZONE OF
SHOWERS AND THUNDERSTORMS. WHILE MODERATE-HIGH POPS ARE GOING TO BE
CARRIED THROUGH THE PERIOD...IT IS ALSO QUITE LIKELY THERE WILL BE
MANY DRY HOURS THOUGH ALSO THE THREAT OF AT LEAST OCCASIONALLY
LOCALLY HEAVY RAINFALL. TEMPERATURES SHOULD GENERALLY BE RATHER WARM
AND MUGGY...ONLY POTENTIAL FLY IN THE TEMP OINTMENT WOULD BE ANY
SOUTHWARD DISPLACEMENT OF THE FRONT BY ANY MORE ORGANIZED MCS
ACTIVITY WHICH OFTEN ISN`T TERRIBLY WELL PREDICTED A COUPLE/FEW DAYS
OUT LET ALONE A WEEK OUT.

IZZI

&&

.AVIATION...

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

* NE WINDS GREATER THAN 10 KT ON FRIDAY MORNING.

MM

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

SOME DAYTIME HEATING DRIVEN CUMULUS FORMING AHEAD OF AN UPPER
LEVEL SHORTWAVE IN WISCONSIN. THIS WAVE COMES THROUGH THIS EVENING
WHICH IS NOT A FAVORED TIME FOR ANY SHOWER ACTIVITY...THOUGH WILL
SEE A SCT AND POSSIBLY BROKEN VFR DECK 6-9K FT WITH IT. EXPECT
WEST WINDS WITH GUSTS TO 20 KT THIS AFTERNOON BEFORE EASING THIS
EVENING. FOCUS IS THEN ON THE BACKDOOR COLD FRONT CURRENTLY
REACHING NORTHERN LAKE MICHIGAN. THIS FRONT IS SLATED TO MOVE
INTO THE TERMINALS DURING THE EARLY MORNING HOURS. EXPECT A RAPID
SHIFT TO NORTHEAST WINDS WITH THE FRONT AND SPEEDS/GUSTS ABOVE 10
KT AT LEAST INTO THE START OF THE FRIDAY MORNING RUSH. EXPECT
WINDS TO TURN MORE EASTERLY DURING THE DAY WITH LIGHTER SPEEDS.

KMD

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

* MEDIUM-HIGH ON NE WIND TIMING AND MEDIUM ON SPEEDS.

MM

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

* FRIDAY NIGHT...DRY/VFR. SOUTHEAST WINDS.
* SATURDAY...DRY/VFR. SOUTH WINDS.
* SUNDAY...SHRA LIKELY. CHANCE OF TSRA. MAINLY VFR. SOUTHEAST WINDS.
* MONDAY...SHRA/TSRA LIKELY. MVFR POSSIBLE. GUSTY SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA/TSRA. MVFR POSSIBLE. GUSTY SOUTHWEST
  WINDS.
* WEDNESDAY...CHANCE OF SHRA/TSRA. MAINLY VFR. SOUTHWEST WINDS.

BMD

&&

.MARINE...
247 PM CDT

A COLD FRONT IS OVER THE NORTHERN END OF THE LAKE AND IT WILL SINK
SOUTH ACROSS THE LAKE. EXPECTING IT TO CLEAR THE SOUTHERN END OF THE
LAKE EARLY FRIDAY MORNING...WITH WINDS BECOMING NORTH BEHIND THE
FRONT.  COULD SEE A FEW GUSTS TO 20-25 KT IMMEDIATELY BEHIND THE
FRONT. WINDS DIMINISH TO 5 TO 10 KT FRIDAY MORNING AS A SURFACE HIGH
SPREADS OVER THE REGION.  EXPECTING ONSHORE FLOW ACROSS THE LAKE
FRIDAY AFTERNOON WITH GUSTS ARND 15 KT PSBL. SOUTH WINDS SET UP
BEHIND THE HIGH FRIDAY NIGHT AND SATURDAY. COULD SEE GUSTS TO 25 KT
OVER THE NORTHERN HALF OF THE LAKE SATURDAY. A WEAK LAKE BREEZE IS
ALSO PSBL ALONG THE IL SHORE SATURDAY AND MAYBE SUNDAY.  HAVE HIGHER
CONFIDENCE IN SATURDAY/S LAKE BREEZE THAN SUNDAY/S. SOUTH WINDS ARE
EXPECTED THROUGH AT LEAST MONDAY WITH SPEEDS UP TO 20 KT.

JEE

&&

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

$$

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