FXUS63 KILX 150245
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
845 PM CST MON DEC 14 2009

.DISCUSSION...
ISSUED 840 PM CST MON DEC 14 2009

COLD FRONT HAS SWEPT EAST OF OUR AREA THIS EVENING WITH A FAIRLY
TIGHT PRESSURE GRADIENT PRODUCING GUSTY WINDS. AS THE STORM SYSTEM
PULLS AWAY FROM THE AREA OVERNIGHT EXPECT THE WINDS TO SLOWLY 
DIMINISH LATER TNT. BACKEDGE OF CLOUD DECK HAS PUSHED TO JUST WEST
OF THE MISSISSIPPI RIVER. PROFILER WINDS STILL OUT OF THE NNW WHICH
HAS HELPED TO PUSH THE BACKEDGE MORE SOUTH THAN EAST OVER THE PAST
SVL HOURS. HOWEVER...AS THE LOW LEVEL FLOW BECOMES MORE ANTICYCLONIC
OVERIGHT...LOW LEVEL WINDS WILL BACK MORE INTO THE NORTHWEST AND
THE CLEARING LINE WILL WORK ITS WAY INTO AT LEAST THE WRN HALF OF
THE FORECAST AREA. HAVE MADE SOME ADJUSTMENTS TO THE OVERNIGHT SKY
CONDITION AS WELL AS TWEAKED THE OVERNIGHT LOWS ACRS THE NW TO TAKE
INTO ACCOUNT THE QUICKER CLEARING TREND ACRS THE WEST AND NORTHWEST
LATER TNT. UPDATED ZONES SHOULD BE OUT BY 900 PM.  

SMITH
&&

.AVIATION...
ISSUED 528 PM CST MON DEC 14 2009

MAIN FORECAST CONCERN WL BE THE TIMING OF THE CLEARING INTO THE
FORECAST AREA LATE TNT OR TUESDAY MORNING. LARGE AREA OF MVFR WITH
SOME ISOLD IFR CIGS COVERING A GOOD PORTION OF THE MIDWEST.
HOWEVER...IN THE PAST SEVERAL HOURS HAVE NOTICED SOME SIGNIFICANT
BREAKS DEVELOPING ACRS IOWA WITH MOSTLY VFR CIGS WEST OF THE 
MISSISSIPPI RIVER. PROFILER WINDS STILL INDICATING NNW WINDS 
ACRS ERN IOWA SUGGESTING CLOUDS WILL BE SHIFTING MORE SOUTH THAN
EAST OVR THE NEXT FEW HOURS. WL KEEP THE MVFR CIGS GOING THRU MOST
OF THE EVENING BUT INDICATE SOME BKN CIGS DEVELOPING...ESP ACRS 
THE WEST AFTR 03Z. MODELS INDICATING THE LOW LEVELS WL START TO
DRY OUT BY TUESDAY MRNG WITH VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE FORECAST PERIOD. SFC OBSERVATIONS ACRS CNTRL IOWA
INDICATING SOME FLURRIES OCCURRING BUT THOSE ARE ISOLATED AT THIS
TIME SO WL KEEP OUT OF THE TAFS LATER THIS EVENING. GUSTY NW WINDS
WL GRDLY DIMINISH SOME AFTR 04Z...BUT PICK UP AGAIN DURING THE
MORNING HOURS ON TUESDAY WITH AFTN GUSTS AOA 20 KTS. 

SMITH
&&

.PREV DISCUSSION...
ISSUED 255 PM CST MON DEC 14 2009

12Z FORECAST MODELS ARE IN GOOD AGREEMENT THROUGH THU NIGHT WITH
CANADIAN HIGH PRESSURE SETTLING IN DURING MID WEEK WITH ANOTHER
SURGE OF COLDER AIR INTO IL. MODELS DIVERGE A BIT THEREAFTER WITH
HANDLING A NORTHERN SHORT WAVE TROF DIGGING INTO THE EASTERN
STATES FRI/SAT BRINGING CHANCE OF LIGHT SNOW AND FLURRIES. STILL
THINK GFS IS TOO AGGRESSIVE WITH QPF FROM THIS SYSTEM AND LEANED
TOWARD THE LIGHTER GFS AND ECMWF MODELS. GUIDANCE (MAV/MET) TEMPS
FAIRLY SIMILAR THROUGH WED NIGHT AND USED A BLEND.

MID AFTERNOON SURFACE MAP SHOWS 1007 MB LOW PRESSURE IN SW LOWER
MI WITH A POLAR COLD FRONT EXTENDING SW ACROSS CENTRAL IL AND SE
MO EAST OF I-55 AND JUST PAST DECATUR. 1032 MB CANADIAN HIGH
PRESSURE WAS OVER WESTERN CANADA AND RIDGING SE ACROSS THE GREAT
PLAINS. BRISK WNW WINDS 15 TO 20 MPH WITH GUSTS 20 TO 25 MPH
BEHIND THE COLD FRONT ALONG AND WEST OF I-55 COOLING TEMPS. TEMPS
RANGE FROM 36F AT GALESBURG TO 40-45F ALONG I-55 TO THE UPPER 40S
AND LOWER 50S AHEAD OF THE COLD FRONT IN EASTERN IL WHERE MORE
SUNSHINE EARLIER TODAY. EVEN MID TO UPPER 50S ALONG THE WABASH RIVER.
MOSTLY CLOUDY TO OVERCAST LOW CLOUDS NOW OVER IL. ALOFT A 592 DM
500 MB HIGH WAS SE OF FL WITH LARGE UPPER LEVEL TROF/LOW OVER
CANADA AND ROCKIES WITH IL IN A SW UPPER LEVEL FLOW. DEEPER
MOISTURE HAS STAYED WELL SOUTH OF IL OVER THE GULF COAST STATES.

SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT.

SHORT RANGE MODELS TAKE WEAK LOW PRESSURE INTO THE EASTERN GREAT
LAKES BY 06Z/MIDNIGHT WHILE DRIVING THE COLD FRONT SE OF
LAWRENCEVILLE BY 00Z/6 PM. MOST AREAS SHOULD REMAIN DRY INTO
TONIGHT WITH JUST SOME PATCHY DRIZZLE POSSIBLE IN SE IL INTO EARLY
EVENING AND FEW FLURRIES OVER CENTRAL IL. LOW CLOUDS WILL DECREASE
FROM NW TO SE OVERNIGHT INTO TUE MORNING WITH MOSTLY SUNNY SKIES
BY TUE AFTERNOON AS LARGE CANADIAN HIGH PRESSURE BUILDS INTO THE
CENTRAL PLAINS. SHORT WAVES ROTATING EAST ACROSS THE GREAT LAKES
REGION AROUND POLAR LOW IN EASTERN CANADA THROUGH TUE NIGHT WILL
KEEP ITS LOW CLOUDS AND LIGHT SNOW SHOWERS NE OF CENTRAL IL. BRISK
NW WINDS WILL USHER IN MUCH COLDER AIR INTO IL TONIGHT AND TUE.
LOWS TONIGHT RANGE FROM THE TEENS FROM I-55 NW TO MID TO UPPER
20S IN SE IL. HIGHS TUE RANGE FROM THE UPPER TEENS AND LOWER 20S
NORTH OF LINCOLN TO THE LOW TO MID 30S IN SE IL. 

EVEN COLDER TUE NIGHT AS MODELS A BIT QUICKER MOVING CANADIAN HIGH
PRESSURE OVER IL BY DAWN WED WITH CLEAR SKIES AND LIGHTER WINDS.
LOWS TUE NIGHT RANGE FROM THE SINGLE DIGITS NW OF I-55 TO THE MID
TO UPPER TEENS IN EASTERN IL WHERE NW WINDS LIGHTER UP LATER IN
THE NIGHT. HIGH PRESSURE DRIFTS JUST EAST OF IL BY SUNSET WED
ENSURING AMPLE SUNSHINE AND LIGHT WINDS BUT CONTINUED COLD TEMPS.
HIGHS WED IN THE UPPER 20S AND LOWER 30S EXCEPT MID 30S IN SE IL. 

SEMI ZONAL UPPER LEVEL FLOW TEMPORARILY SETS UP WED/THU WITH HIGH
PRESSURE DRIFTING INTO THE MID ATLANTIC STATES BY SUNSET THU AND
TEMPS MODIFYING CLOSER TO NORMAL OVER IL UNDER PARTLY TO MOSTLY
SUNNY SKIES. HIGHS THU RANGE FROM THE MID 30S NORTH TO THE LOWER
40S SE IL. 

LONG TERM...FRIDAY THROUGH MONDAY.

EXTENDED MODELS CONTINUE TO SHOW A NORTHERN STREAM SHORT WAVE
DIGGING A TROF INTO THE EASTERN USA FRI/SAT. STILL LOOKS LIKE A
SMALL CHANCE OF LIGHT SNOW NW OF I-55 FRI MAINLY FRI AFTERNOON AND
20-30% CHANCE OF LIGHT SNOW FRI NIGHT/SAT. GFS STILL APPEARS TO
HEAVY WITH QPF FRI/SAT AND LEANED ON LIGHTER ECMWF AND GEM MODELS.
MODELS HAVE TRENDED COLDER SO RAIN/SNOW MIX APPEARS TO HAVE
SHIFTED SOUTH OF CENTRAL/SE IL. MODELS ALSO HAVE TRENDED COLDER
THIS WEEKEND WITH UPPER LEVEL TROF DIGGING DEEPER INTO THE EASTERN
STATES SO TRENDED TEMPS DOWNWARD A BIT. SOME MODELS ARE LINGERING
LIGHT SNOW AND FLURRY CHANCES EARLY NEXT WEEK LIKE GFS DUE TO
NEARBY STRONG UPPER LEVEL TROF. BUT KEEPING IT DRY SUN/MON WITH
COLD TEMPS AS CANADIAN HIGH PRESSURE SETTLES INTO THE MS VALLEY
NEXT MON. 

HUETTL

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$