Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 271610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT MON JUL 27 2015

.SHORT TERM...
250 AM CDT

THROUGH TUESDAY...

WEAK SURFACE HIGH PRESSURE OVER THE WESTERN GREAT LAKES TODAY WILL
MOVE EAST TO MID ATLANTIC AND NEW ENGLAND TUESDAY AS UPPER RIDGING
BUILDS EAST INTO THE AREA AHEAD OF A VIGOROUS UPPER LEVEL TROUGH
TRACKING NORTHEAST FROM THE NORTHERN ROCKIES TOWARD HUDSON BAY
THROUGH MID WEEK.

RISING UPPER HEIGHTS AND OBVIOUS FOCUSING MECHANISMS WOULD TEND TO
POINT TOWARD DRY CONDITIONS TODAY AND TONIGHT WITH JUST SOME SCT-BKN
CIRRUS AND MAINLY DIURNAL CUMULUS AWAY FROM THE LAKE BREEZE COOLED
AIR MASS. HIGHS TODAY SHOULD CLIMB INTO THE MID TO UPPER 80S EXPECT
ONLY TOP OUT IN THE UPPER 70S ALONG THE LAKE MICHIGAN SHORE LINE.

LOW LEVEL FLOW SHOULD BECOME INCREASINGLY INFLUENCED BY CYCLONE
TRACKING NORTHEAST ACROSS MANITOBA TUESDAY MEANING A MORE PRONOUNCED
SOUTH TO SOUTHEAST WIND...WHICH LOOKS TO BE WEAK/BACKED ENOUGH TO
ALLOW AN ILLINOIS NORTH SHORE LAKE BREEZE TO KEEP THOSE AREAS A BIT
COOLER WHILE ELSEWHERE HIGHS LOOK LIKELY TO CLIMB INTO THE UPPER 80S
OR LOWER 90S WITH HEAT INDICES IN THE MID 90S TO NEAR 100 WESTERN
AND SOUTHERN CWA WHERE CORN-FED DEWPOINTS ARE LIKELY TO CLIMB WELL
INTO THE 70S.

IZZI

&&

.LONG TERM...
250 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

COLD FRONT IS SLATED TO MOVE ACROSS THE CWA LATER TUESDAY NIGHT INTO
WEDNESDAY...THOUGH FAIRLY EXTENSIVE CONVECTION TO OUR NORTHWEST
TUESDAY AFTERNOON COULD RESULT IN THE SYNOPTIC FRONT BECOMING
MUDDLED AND DIFFICULT TO LOCATE WITH CONVECTIVE OUTFLOW.
REGARDLESS...IT LOOKS LIKE WHAT IS LEFT OF TUES AFTERNOON CONVECTION
TO OUR NORTHWEST WILL BEGIN TO SPILL SE INTO OUR CWA LATER TUES
EVENING AND THROUGH THE OVERNIGHT HOURS. CONVECTION COULD LINGER
INTO OUR SE CWA WED MORNING...BUT BY THAT POINT ITS DEBATABLE HOW
MUCH ACTIVITY WILL BE LEFT. COMPOSITE SYNOPTIC FRONT AND OUTFLOW
COULD BE CLOSE ENOUGH TO OUR FAR SE CWA TO JUSTIFY CHANCE POPS
WEDNESDAY AFTERNOON...BUT MAJORITY OF THE ACTIVITY LOOKS LIKELY TO
BE OUT OF OUR AREA BY WEDNESDAY AFTERNOON.

LOOKS TO BE A PRETTY TYPICAL SUMMER FRONT WITH WEAK BAROCLINICITY
AND ONLY A VERY GRADUAL DECREASE IN DEWPOINTS EXPECTED THROUGH THE
DAY WEDNESDAY AND INTO WEDNESDAY NIGHT. THURSDAY AND FRIDAY LOOK TO
BE SEASONABLY WARM WITH COMFORTABLE HUMIDITY...AMPLE SUNSHINE...AND
ENOUGH WESTERLY WIND TO LIKELY PREVENT AND SIGNIFICANT LAKE BREEZES
FROM COOLING THE BEACHES. HUMIDITY WILL BEGIN TO INCREASE OVER THE
WEEKEND WITH TEMPS INCHING UPWARD A BIT TOO WITH NEXT CHANCE OF
STORMS PROBABLY HOLDING OFF UNTIL SUNDAY AS ANOTHER WEAK COLD FRONT
MOVES THROUGH.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* EAST WINDS TODAY GUSTING INTO THE LOW TEENS.

LENNING

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN GREAT LAKES TODAY
AND SLOWLY SHIFT EAST TONIGHT AND TUESDAY. LIGHT/VARIABLE WINDS TO
START WILL BECOME EASTERLY THIS MORNING AND SHOULD INCREASE TO
AROUND 10KT BY LATE MORNING OR EARLY AFTERNOON. THESE WINDS WILL
DIMINISH TO 5KT OR LESS AFTER SUNSET THIS EVENING.

AREAS OF FOG GENERALLY SOUTH OF INTERSTATE 80 WILL DISSIPATE OVER
THE NEXT HOUR OR TWO. NOT MUCH CHANGE TO THE AIRMASS IS EXPECTED
TONIGHT SO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE BUT CONFIDENCE
REMAINS LOW TO INCLUDE IN THE TAFS.

DRY WEATHER IS EXPECTED AT THE TERMINALS THROUGH THE PERIOD WITH
ANY ISOLATED ACTIVITY REMAINING WELL WEST AND SOUTHWEST OF THE
TERMINALS. CMS

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH FOR ALL ELEMENTS.

LENNING

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

* TUESDAY NIGHT...CHANCE OF TSRA. SOUTHWEST WINDS.
* WEDNESDAY...CHANCE OF MORNING TSRA. STRONG/GUSTY WEST WINDS.
* THURSDAY...DRY/VFR. NORTHWEST WINDS.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY AND SUNDAY...CHANCE OF TSRA. WESTERLY WINDS.

&&

.MARINE...

211 AM...HIGH PRESSURE WILL REMAIN ACROSS THE GREAT LAKES REGION
TODAY...SLOWLY MOVING ACROSS THE EASTERN LAKES TONIGHT AND TO NEW
ENGLAND TUESDAY. THIS WILL ALLOW FOR LIGHT WINDS INTO TONIGHT THAT
WILL EVENTUALLY TURN SOUTHERLY TUESDAY AND BEGIN TO INCREASE AS
THE GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. BY
TUESDAY NIGHT...SOUTHERLY WINDS MAY INCREASE INTO THE 15-25KT
RANGE ACROSS THE NORTHERN PORTION OF THE LAKE. WINDS WILL TURN
WESTERLY ON WEDNESDAY AS THE COLD FRONT MOVES SOUTHEAST OF THE
LAKE. WITH LOW PRESSURE ACROSS HUDSON BAY AND HIGH PRESSURE
BUILDING ACROSS THE CENTRAL PLAINS...THE WESTERLY WINDS MAY REMAIN
IN THE 15-25KT RANGE WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE
THE GRADIENT WEAKENS BUT CONFIDENCE REGARDING SPEEDS DURING THIS
TIME IS LOW. CMS

&&

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

$$

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