FXUS63 KLOT 281144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
544 AM CST SAT NOV 28 2009

.DISCUSSION...
238 AM CST

HIGH PRESSURE RIDGING OFF TO OUR EAST OPENS UP THE GATES TO WARM AIR 
ADVECTION INTO THE MIDWEST. UPR WEST TO SW FLOW IS PERMITTING 850 
TEMPS TO PUSH UP TO 10C TO 12C TODAY...WARMING SFC TEMPS TO THE MID 
50S. AMPLE SUNSHINE AND LIGHT WINDS WILL ASSIST. ANOTHER TERRIFIC 
SHOPPING DAY IS THUS IN STORE...CONFLICTING WITH THE NORMAL LATE
NOVEMBER HIGHS NEAR 40.

THIS WARM SPELL IS OUT AHEAD OF AN APPROACHING COLD FRONT THAT 
STRETCHES FROM NW MINNESOTA TO NORTHWEST KANSAS EARLY THIS MORNING. 
THIS FRONT IS PROGGED TO MOVE SOUTHEAST INTO NRN IL EARLY SUNDAY. 
INCREASING WAA CLOUDINESS WILL PRECEDE THIS FRONTAL APPROACH LATE 
TONIGHT. HOWEVER RAIN CHANCES HAVE BETTER PROSPECTS NORTH AND SOUTH 
OF THE FORECAST AREA. TIMING OF A DEEPENING UPPER TROF PHASING 
WITH THIS SFC FEATURE WILL DETERMINE WHEN AND WHERE RAINS BECOME 
MORE ACTIVE ALONG THIS SFC BOUNDARY. PRESENT TRENDS INDICATE THAT 
THE COLD FRONT WILL BE THROUGH THE FORECAST AREA BEFORE BLOWING UP 
ACROSS THE OHIO VALLEY INTO HEAVIER AND MORE WIDESPREAD SHOWERS. 
PROBABILITIES HOWEVER WOULD RELY ON THE FACT THAT THE LONGER IT
TAKES FOR THE FRONT TO MOVE THROUGH AN AREA ON SUNDAY...THE HIER IS 
THE LIKELIHOOD OF SUCCUMBING TO A HIER CHANCE OF RAIN. FOR NOW ONLY 
A SLIGHT CHANCE EXISTS ACROSS THE AREA WITH HIER POPS IN THE 
SOUTHEAST PORTION OF THE FORECAST AREA. IF ANY RAIN SHOULD 
DEVELOP...IT SHOULD BE SHORTLIVED AND ONLY A FEW HUNDREDTHS AT BEST. 
THUS THIS SHOULD NOT BE A DETERRENT FROM CONTINUING THE POST 
THANKSGIVING SHOPPING MARATHON INTO SUNDAY.

SFC HIGH PRESSURE BUILDING ACROSS THE PLAINS AND INTO THE MIDWEST 
LATE SUNDAY AND MONDAY WILL NOT OFFER MUCH CLEARING UNTIL THE MAIN 
UPPER TROF SWINGS THRU THE LAKES REGION LATE ON MONDAY. SHORTLY 
AFTER THAT ANOTHER SFC LOW WILL WORK EAST OUT OF MANITOBA TUESDAY
AND ACROSS SRN ONTARIO TUES NIGHT.

MODELS VARY AFTER THIS POINT ON TIMING OF ANOTHER UPR TROF DROPPING 
SE THRU THE MIDWEST. PRESENTLY LEANING TO A SOLUTION WITH A WARMUP 
WEDNESDAY AND A COOLING UPR TROF PASSAGE LATE THURSDAY. OTHERS 
SUGGEST A CHILLING COLD FRONTAL PASSAGE WEDNESDAY...COMPOUNDING CAA 
EVEN FURTHER WITH THE UPR TROF PASSAGE THURSDAY.

TO CURTAIL THE FLIP FLOPPING POSSIBILITIES...WILL LEAVE THE EXTENDED
PORTION OF THE FORECAST AS IS FROM MIDWEEK ON.

RLB

&&

.AVIATION...
545 AM CST

1200 UTC TAFS...GENERALLY QUIET WEATHER THROUGH MUCH OF THE PERIOD.

TWO MINOR CONCERNS FOR THE 12Z TAF PERIOD...WIND SHIFT FROM SELY
TO SWLY AND POSSIBLE BR DEVELOPMENT OVERNIGHT. THE SFC RIDGE HAS
PUSHED WELL TO THE EAST AND BROAD SFC TROUGHING CONTINUES TO
DEVELOP OVER THE PLAINS AND SLOWLY MOVE EWD. WHILE THE TROUGH
REMAINS TO THE WEST OF THE TERMINALS...WINDS WILL REMAIN SELY. THE
GRADIENT IS RATHER WEAK ACROSS THE REGION...SO WINDS WILL REMAIN
UNDER 10KT. AS THE TROUGH...AND ASSOCIATED WEAK COLD FRONT...SLOWLY
PUSHES THROUGH THE AREA EARLY THIS EVENING...WINDS WILL GO THROUGH
A PERIOD OF WEAK SSWLY AND LGT/VRBL. WINDS WILL FINALLY SHIFT MORE
WLY AND NWLY TOMORROW. OVERNIGHT TONIGHT...WHEN WINDS BECOME
LGT/VRBL...TEMPS MAY DROP ENOUGH FOR DEWPOINT DEPRESSIONS TO DROP
TO 1-2 DEGREES. THIS SHOULD BE ADEQUATE FOR VISIBILITY TO DROP TO
4-5SM. SKIES WILL REMAIN MOSTLY CLEAR WITH ONLY PERIODS OF SCT CI
THROUGH MUCH OF THE PERIOD...WHICH WILL HELP WITH RADIATIVE
COOLING TONIGHT AS WELL.

KREIN

&&

.MARINE...
127 PM CST

A RIDGE OF HIGH PRESSURE EXTENDS FROM THE EASTERN GULF COAST
NORTHWARD ACROSS THE EASTERN GREAT LAKES REGION AND ONTARIO. THE
RIDGE WILL GRADUALLY SHIFT EAST TO THE ATLANTIC SEABOARD BY
SATURDAY EVENING. MEANWHILE...A BROAD TROUGH OF LOW PRESSURE OVER
THE PLAINS WILL CONSOLIDATE INTO A WEAK LOW OVER SOUTHERN
WISCONSIN SATURDAY NIGHT. THIS LOW WILL MOVE ACROSS CENTRAL LAKE
MICHIGAN SUNDAY MORNING. AS THE LOW CONTINUES EASTWARD...A LARGE
AREA OF HIGH PRESSURE OVER THE ROCKIES WILL EXPAND ACROSS THE
SOUTHERN PLAINS TO THE LOWER OHIO VALLEY. BY TUESDAY THIS HIGH
WILL EXTEND FROM THE CAROLINAS TO TEXAS.

&&

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

$$