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000
FXUS63 KLOT 160909
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
409 AM CDT SUN JUN 16 2013

.DISCUSSION...
253 AM CDT

TODAY AND TONIGHT...
BROAD AREA OF LOW PRESSURE EXTENDS ACROSS THE CANADIAN PRAIRIES INTO
THE NORTHERN GREAT LAKES REGION WITH A WEAK COLD FRONT SAGGING SOUTH
INTO NORTHERN ILLINOIS. THIS FEATURE WILL CLEAR THE SOUTHERN
COUNTIES MID TO LATE THIS AFTERNOON WITH A THREAT FOR SOME
THUNDERSTORMS GENERALLY ALONG OF THE FRONTAL TROUGH. MODELS INDICATE
MODERATE INSTABILITY DEVELOPING AHEAD OF THE FRONT TODAY BUT LITTLE
UPPER LEVEL SUPPORT OR IMPETUS BESIDES THE SLOWLY SAGGING
FRONT...WHICH ITSELF HAS WEAK CONVERGENCE AND LITTLE DENSITY
CONTRAST ACROSS THE BOUNDARY. THUS ANY RESULTING THUNDERSTORMS
SHOULD BE LOW IN COVERAGE AND REMAIN CONFINED CLOSE TO THE FRONT.
WEAK SURFACE HIGH QUICKLY TAKES HOLD BEHIND THE FRONT WITH A STRONG
PUNCH OF DRY AIR/SUBSIDENCE ALOFT HELPING TO ELIMINATE THE PRECIP
CHANCES NORTHWEST TO SOUTHEAST THROUGH THE DAY. THE WEAKENING
GRADIENT MAY ALLOW A LAKE BREEZE TO DEVELOP BUT THE MODEST WESTERLY
WINDS SHOULD KEEP IT FROM PUSHING TOO FAR INLAND INTO ILLINOIS. A
BETTER PUSH INTO NORTHWEST INDIANA IS EXPECTED.

MONDAY THROUGH THURSDAY...
GENERALLY QUIET WEATHER IS EXPECTED THROUGH MUCH OF THE UPCOMING
WEEK. HIGH PRESSURE SHOULD BE IN PLACE OVERHEAD MONDAY WITH
RELATIVELY LIGHT FLOW SUPPORTING LAKE BREEZE DEVELOPMENT IN THE
AFTERNOON. TEMPERATURES SHOULD RISE INTO THE LOW TO MID 80S BEFORE
FALLING NEAR THE LAKE FRONT. A SHEARED VORT LOBE WILL ROTATE
SOUTHEAST ACROSS ONTARIO AND QUEBEC MONDAY ALLOWING THE
AFOREMENTIONED BROAD AREA OF LOW PRESSURE TO CONSOLIDATE OVER
SOUTHERN QUEBEC. IT ALSO DISLODGES SOME COOLER AIR FROM OVER HUDSON
BAY SOUTH INTO THE GREAT LAKES REGION. THIS SECONDARY COLD FRONT
WILL SLOWLY WORK DOWN LAKE MICHIGAN MONDAY REACHING NORTHERN
ILLINOIS TUESDAY WITH H85 TEMPS FALLING TO JUST UNDER 10C ACROSS THE
NORTHERN CWA. THIS WILL SUPPORT TEMPERATURES IN THE MID 70S FOR MUCH
OF THE CWA...BUT FLOW OFF THE LAKE THROUGH THE DAY WILL KEEP
TEMPERATURES IN THE 60S NEAR THE LAKE FRONT.  A BROAD AREA OF HIGH
PRESSURE WILL SETTLE OVER THE GREAT LAKES WEDNESDAY AND THURSDAY.
TEMPERATURES SHOULD MODERATE A FEW DEGREES EACH DAY FROM MIDWEEK ON.

FRIDAY AND SATURDAY...
TOWARDS THE END OF THE WEEK...EXPECT THE UPPER PATTERN TO BEGIN TO
AMPLIFY WITH STRONG RIDGING BUILDING ACROSS THE MIDDLE PART OF THE
COUNTRY. GFS AND ECMWF BOTH ADVERTISE 20C AT H85 BY SATURDAY WHICH
IF PANS OUT COULD INDICATE 90S RETURNING TO THE AREA. THERE WILL BE
SOME CHANCE FOR THUNDERSTORMS THIS PERIOD AS THE WARM FRONT LIFTS
NORTH ACROSS THE AREA AND GULF MOISTURE OPENS UP TO THE MIDWEST.

BMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* NONE

IZZI

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

DECAYING THUNDERSTORM COMPLEX OVER CENTRAL ILLINOIS AND RESULTING
MESO-HIGH COMBINED WITH SUFACE TROUGH MOVING IN FROM THE NW
RESULTING IN A RAMPING UP OF SOUTHWEST WINDS...GUSTING AS HIGH AS
40KT IN THE PAST HOUR AT ORD. THESE WINDS SHOULD QUICKLY SUBSIDE
EARLY THIS MORNING AS MESO-HIGH WEAKENS AND TROUGH MOVES EAST WITH
WINDS LIKELY TO VEER TO MORE WESTERLY AS THEY SUBSIDE. SOME ISOLD
SHRA AND TSRA COULD CONTINUE TO PERCOLATE UP OVERNIGHT IN THE AREA
BUT COVERAGE LIKELY TO REMAIN LIMITED ENOUGH TO JUST RUN WITH VCSH
IN TAFS WITH MOST LOCATIONS EXPECTED TO REMAIN DRY. SUNDAY LOOKS
TO BE GENERALLY DRY WITH LIKELY A STRONG ENOUGH OF A WEST WIND TO
KEEP ANY LAKE BREEZE EAST OF THE TERMINALS WITH VFR CONDITIONS
EXPECTED.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN ALL ELEMENTS

IZZI

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

MON...VFR. CHC TSRA.

TUE THROUGH THU...VFR. NO SIG WX.

FRI...VFR. SLGT CHC TSRA.

TRS

&&

.MARINE...
404 PM CDT

LARGE HIGH PRESSURE OVER THE EASTERN UNITED STATES WILL SLOWLY
CONTINUE EAST WHILE A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY
OVER THE UPPER MISSISSIPPI VALLEY SHIFT EAST ACROSS THE LAKE
TONIGHT. WITH THIS IN PLACE...EXPECT GENERALLY SOUTHERLY FLOW TO
SPAN THE LAKE BEFORE WINDS TURN MORE TO THE SOUTHWEST OVERNIGHT.
WEAK HIGH PRESSURE WILL THEN BUILD EAST ACROSS THE SOUTHERN GREAT
LAKES ON SUNDAY...WITH A TROUGH OF LOW PRESSURE EXTENDING FROM
SOUTHERN QUEBEC WEST TO SOUTHERN ONTARIO. THIS TROUGH OF LOW
PRESSURE WILL SLOWLY SHIFT SOUTH DOWN THE LAKE SUNDAY NIGHT INTO
MONDAY. WESTERLY WINDS WILL TURN TO THE NORTHWEST AND NORTH AS
THIS TROUGH AND ASSOCIATED BOUNDARY WORK DOWN THE LAKE. WINDS AND
WAVES WILL INCREASE BEHIND THIS TROUGH/BOUNDARY...BUT STILL
REMAINING AT 10 TO 20 KT. HIGH PRESSURE WILL THEN MOVE SOUTHEAST
FROM THE CANADIAN PRAIRIES INTO THE GREAT LAKES BEHIND THIS FRONT
BY MIDWEEK.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...DENSE FOG ADVISORY...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ868-LMZ870-LMZ872-LMZ874
     UNTIL 9 AM SUNDAY.

&&

$$

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