Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 030757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 AM CDT WED JUN 3 2015

.SHORT TERM...
142 PM CDT

THROUGH WEDNESDAY NIGHT...

A RELATIVELY QUIET AND DRY PERIOD OF WEATHER IS SETTING UP FOR NRN
IL/NWRN IN THROUGH AT LEAST WEDNESDAY NIGHT.  FOR THE REMAINDER OF
THIS AFTERNOON...A RIDGE OF HIGH PRESSURE EXTENDING FROM THE ERN
GREAT LAKES THROUGH THE MIDDLE MISSISSIPPI VALLEY WILL HELP KEEP
SKIES MOSTLY SUNNY WITH LIGHT WINDS.  THE RIDGE IS ALSO ASSOCIATED
WITH A RATHER DRY AIRMASS...WITH DEWPOINTS ONLY IN THE LOWER TO
MIDDLE 40S ACROSS MUCH OF THE REGION.  UNDER AMPLE SUNSHINE AND WITH
DRY AIR IN PLACE...EXPECT THAT TEMPERATURES SHOULD TOP OUT IN THE
MIDDLE 70S THIS AFTERNOON.  THE EXCEPTION WILL BE THE
LAKEFRONT...WHERE A WEAK PRESSURE GRADIENT...LIGHT WINDS AND STRONG
DIFFERENTIAL HEATING BETWEEN THE COOL LAKE WATERS AND THE WARMER
LAND WILL SET UP A LAKE BREEZE.  SO...LAKEFRONT
LOCATIONS...INCLUDING DOWNTOWN CHICAGO SHOULD SEE HIGH TEMPS TODAY
ONLY IN THE UPPER 50S TO AROUND 60F.  FOR TONIGHT...MOSTLY CLEAR
SKIES...LIGHT WINDS AND DRY AIR SHOULD ALLOW FOR TEMPERATURES TO
DROP OFF INTO THE LOWER 50S.  SOME ISOLATED...SHELTERED LOCATIONS
COULD EVEN SEE TEMPS DROP INTO THE MIDDLE TO UPPER 40S.  THE URBAN
HEAT ISLAND OF THE CHICAGO METRO AREA SHOULD REMAIN A BIT
WARMER...WITH LOWS IN THE MIDDLE TO UPPER 50S.

WEDNESDAY SHOULD BE A NEAR REPEAT PERFORMANCE...THOUGH WITH THE HIGH
SHIFTING TO THE EAST...WHILE THE WESTERN PLAINS LOW REMAINS OVER WRN
KS...LOW LEVEL FLOW WILL BECOME MORE SSELY AS THE RIDGE AXIS SHIFTS
TO THE OHIO VALLEY.  THE REGION WILL REMAIN CUT OFF FROM GULF
MOISTURE...SO MOSTLY SUNNY SKIES ARE LIKELY AGAIN...WITH TEMPS A BIT
HIGHER...TOPPING OUT IN THE UPPER 70S TO AROUND 80F.  A WEAK
GRADIENT WILL ALLOW FOR LAKE BREEZE DEVELOPMENT AGAIN
TOMORROW...HOWEVER...THE LAKE BREEZE IS EXPECTED TO SET UP A LITTLE
LATER IN THE AFTERNOON THAN TODAY...SO LAKE FRONT LOCATIONS SHOULD
GET A LITTLE WARMER...WITH HIGHS IN THE MIDDLE 60S.  FOR WEDNESDAY
NIGHT...STILL EXPECTING QUIET WEATHER...BUT WITH INCREASING CLOUD
COVER AS THE CANADIAN LOW BEGINS TO DRAG A COLD  FRONT ACROSS THE
UPPER MISSISSIPPI VALLEY TO NEAR THE NORTHERN END OF LAKE MICHIGAN.
THE RIDGE IS EXPECTED TO REMAIN NEARLY STATIONARY ALONG THE OHIO
VALLEY...SO ANY PCPN ASSOCIATED WITH THE SYSTEM WILL BE SHUNTED TO
THE NORTH OF THE CWA...MAINLY IN WISCONSIN AND ERN IOWA BY LATE
WEDNESDAY NIGHT.  INCREASING CLOUD COVER AND RISING SFC DEWPOINTS
SHOULD LIMIT OVERNIGHT COOLING...WITH LOWS BY EARLY THURSDAY MORNING
EXPECTED TO BE IN THE UPPER 50S TO LOWER 60S.

KREIN

&&

.LONG TERM...
335 PM CDT

THURSDAY THROUGH TUESDAY...

THE AREA WILL STAY ON EASTERN PERIPHERY OF MID/UPPER RIDGING OVER
CENTRAL CONUS THURSDAY THROUGH SATURDAY...WITH A FEW CONVECTIVELY
DRIVEN DISTURBANCES PIVOTING AROUND RIDGE AXIS. MODELS INDICATE
DECAYING CONVECTION TRYING TO MAKE IT INTO OUR AREA ON
THURSDAY...MOST BULLISH ON THE LATEST 12Z ECMWF...BUT HAVE FAVORED
GUIDANCE THAT WEAKENS REMNANT CONVECTION AND KEPT POPS LOW IN
NORTHWEST 1/2 OF CWA. UNLESS THERE IS MORE IMPACT FROM
CLOUDS/CONVECTION THAN EXPECTED...HIGHS SHOULD REACH THE LOWER TO
MID 80S...WITH UPPER 70S ALONG IL SHORE AS A LAKE BREEZE FORMS
DURING THE AFTERNOON. A LAKE ENHANCED FRONT WILL BE DRIVEN
SOUTHWARD LATE THURSDAY NIGHT INTO FRIDAY...SO A MUCH COOLER DAY
WILL RESULT NEAR LAKE MICHIGAN...BUT SOUTH OF THE FRONT MID 70S TO
LOW 80S APPEAR PROBABLE. UNCERTAINTY ON POPS...AS NAM AND
ESPECIALLY GFS ARE STRONGER AND FARTHER NORTH WITH A MIDLEVEL
DISTURBANCE. GENERALLY MAINTAINED HIGH CHANCE POPS FROM PREVIOUS
FORECAST FOR SHOWERS/SCT`D TSRA.

SATURDAY LOOKS QUIETER AND FAIRLY COOL ESPECIALLY NEAR THE LAKE
WITH ONSHORE FLOW THEN RETURN FLOW QUICKLY RETURNS ON SUNDAY AS A
SURFACE LOW TRACKS SOMEWHERE NEARBY..WITH RESULTING SHOWER AND
TSRA CHANCES. DESPITE A UPPER LOW/TROUGH SETTING UP OVER THE
NORTHERN LAKES ON MONDAY AND TUESDAY...AIR MASS WILL REMAIN
SEASONABLY WARM BEHIND SUNDAY FROPA WITH GENERALLY LOW POPS...BUT
ANOTHER LAKE ENHANCED FROPA COULD OCCUR ON TUESDAY.

RC

&&

.AVIATION...

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

* LAKE BREEZE WITH EASTERLY WINDS NEAR 10 KTS THIS AFTERNOON.
  CMS

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

A RIDGE OF HIGH PRESSURE ACROSS THE EASTERN LAKES AND OHIO
VALLEY WILL SLOWLY SHIFT EAST TODAY AND TONIGHT. WINDS WILL
BECOME MORE SOUTHEASTERLY THIS MORNING BUT WITH THE WEAK GRADIENT
A LAKE BREEZE IS EXPECTED WHICH WILL LIKELY SHIFT THE WINDS MORE
EASTERLY AT ORD/MDW...NORTHEASTERLY AT GYY...THIS AFTERNOON.
DIFFICULT TO DETERMINE SPECIFIC WIND SPEEDS...BUT THERE COULD BE
A PERIOD OF 10KTS BEHIND THE LAKE BREEZE FOR A FEW HOURS. CMS

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

* HIGH FOR A LAKE BREEZE...MEDIUM FOR TIMING AND ASSOCIATED WIND
  SPEEDS. CMS

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

* THURSDAY...SMALL CHANCE OF A THUNDERSTORM...OTHERWISE VFR.
  SOUTHEAST WINDS.
* FRIDAY...CHANCE OF SHRA/TSRA. MVFR LIKELY. NORTHEAST WINDS.
* SATURDAY...SLIGHT CHANCE OF SHRA. MVFR POSSIBLE. NORTHEAST
  WINDS.
* SUNDAY...CHANCE OF SHRA/TSRA. SOUTHWEST WINDS BECOMING NORTHWEST
  LATE.
* MONDAY...MAINLY DRY/VFR. GUSTY WEST WINDS.

KJB

&&

.MARINE...

257 AM...A RIDGE OF HIGH PRESSURE FROM QUEBEC TO THE OHIO VALLEY
WILL SLOWLY SHIFT EAST TODAY. STRONGER HIGH PRESSURE WILL BUILD
ACROSS ONTARIO THURSDAY NIGHT AND FRIDAY...PUSHING A COLD FRONT
SOUTH ACROSS LAKE MICHIGAN LATE THURSDAY NIGHT INTO FRIDAY
MORNING. THERE REMAINS UNCERTAINTY REGARDING HOW STRONG THE
GRADIENT WILL BECOME BEHIND THIS FRONT. CURRENTLY MAINTAINING
10-20 KTS FROM THE NORTH/NORTHEAST BUT ITS POSSIBLE THAT SPEEDS
COULD BE STRONGER. AS THE HIGH MOVES EAST OVER THE WEEKEND...
WINDS WILL TURN SOUTHEASTERLY SATURDAY NIGHT AND THEN SHIFT
WESTERLY SUNDAY NIGHT AS LOW PRESSURE MOVES ACROSS THE NORTHERN
LAKES...DRAGGING A COLD FRONT ACROSS THE LAKE. CMS

&&

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

$$

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