FXUS63 KILX 012331
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
531 PM CST TUE DEC 1 2009

.DISCUSSION...
ISSUED 240 PM CST TUE DEC 1 2009

LATEST SURFACE MAP SHOWING A SURFACE LOW OVER NORTH CENTRAL
MINNESOTA...WITH AN ASSOCIATED COLD FRONT PUSHING SOUTHEAST ACROSS
IOWA. SOUTHERLY FLOW FROM HIGH PRESSURE ACROSS THE MID-ATLANTIC
REGION HAS HELPED PUSH TEMPERATURES INTO THE MID TO UPPER 50S OVER
THE CWA. THIS WILL BE THE LAST TIME IN THE FORESEEABLE FUTURE THAT
SUCH MILD WEATHER WILL BE IN THIS AREA...AS A LOW PRESSURE CENTER
DEVELOPS OVER ONTARIO AND PUSHES WAVES OF COLD AIR INTO THE
MIDWEST LATER THIS WEEK.

MAIN FORECAST ISSUE FOR THIS PACKAGE INVOLVES TIMING OF
PRECIPITATION ON WEDNESDAY...AND ASSOCIATED CHANGEOVER TO SNOW. 

SHORT TERM...TONIGHT THROUGH FRIDAY...

LOW PRESSURE CURRENTLY IN THE NORTHWEST GULF OF MEXICO WILL LIFT
NORTHEAST OVER THE NEXT COUPLE OF DAYS. MODELS ARE IN FAIR AGREEMENT
ON THE EXACT TRACK OF THIS LOW...WITH THE GFS A BIT FURTHER EAST
BY 00Z THURSDAY THAN THE REMAINING MODELS. WILL GO WITH MORE OF A
CONSENSUS FAVORING THE NAM MODEL. 

RAIN SHOULD BEGIN MOVING INTO THE SOUTHEAST CWA BY LATE WEDNESDAY
MORNING...SPREADING NORTH AND WEST TO COVER MOST AREAS EAST OF THE
ILLINOIS RIVER BY LATE AFTERNOON. MAIN ISSUE AT THIS POINT
INVOLVES THE TRANSITION FROM RAIN TO SNOW. BUFKIT SOUNDINGS
INDICATING THE WESTERN CWA SHOULD BEGIN TO SWITCH BY SUNSET...WITH
THE I-55 CORRIDOR CHANGING OVER EARLY IN THE EVENING AND AREAS
EAST OF I-57 HOLDING OFF UNTIL MIDNIGHT OR LATER. HOWEVER...THE
PRECIPITATION SHOULD BE ON THE WANE WHEN THE TRANSITION
OCCURS. BECAUSE OF THIS...AND THE FAIRLY WARM GROUND...AM NOT
LOOKING FOR ANY SIGNIFICANT ACCUMULATIONS...PROBABLY ON THE ORDER
OF A HALF INCH OR LESS. 

BRISK WEST TO NORTHWEST WINDS WILL OCCUR WEDNESDAY NIGHT THROUGH
THURSDAY...WITH A TIGHT PRESSURE GRADIENT OVER THE AREA. A PIECE OF
ENERGY FROM THE ONTARIO UPPER LOW WILL DROP INTO THE UPPER
MIDWEST...AND SWING EASTWARD ACROSS THE REGION THROUGH FRIDAY. ANY
DECENT SNOW CHANCES SHOULD REMAIN TO OUR NORTH...BUT CANNOT RULE
OUT SCATTERED FLURRIES AS THIS FEATURE PASSES. COLDEST WEATHER
DURING THE PERIOD IS EXPECTED ON FRIDAY...WITH AREAS NORTHWEST OF
THE ILLINOIS RIVER LIKELY TO STAY BELOW FREEZING FOR HIGHS.

LONG TERM...SATURDAY THROUGH TUESDAY...

LONGER RANGE MODELS ADVERTISE THE ONTARIO LOW TO FINALLY WEAKEN
AND MOVE EAST AS THE WEEKEND PROGRESSES. QUIET WEATHER IS EXPECTED
MUCH OF THE EXTENDED FORECAST PERIOD...WITH THE MAIN STORM TRACK
REMAINING TO THE SOUTH. TOWARD THE END OF THE PERIOD...THE MODELS
ARE SUGGESTING THE UPPER FLOW BEGINS TO COME OUT OF THE DESERT
SOUTHWEST...AS AN UPPER LOW PUSHES SOUTH THROUGH THE WESTERN
STATES. LATEST ECMWF MODEL QUITE BULLISH IN CRANKING UP A STORM
SYSTEM OVER THE CENTRAL PLAINS...PUSHING NORTHEAST INTO IOWA BY
TUESDAY EVENING...AS IT PUSHES THE UPPER ENERGY EASTWARD AT A
FASTER CLIP. WILL ONLY INCLUDE SILENT 20 POPS AT THIS POINT...DUE
TO NOTICEABLE DIFFERENCES WITH THE GFS AT THIS RANGE.

GEELHART

&&

.AVIATION...
ISSUED 523 PM CST TUE DEC 1 2009

LOW PRESSURE SYSTEM JUST OFF THE TX GULF COAST...WL TRACK NE OVER
THE NEXT 24 HOURS. CI AHEAD OF THIS LOW WILL THICKEN OVERNIGHT AND
WED MORNING...AND MID LEVEL CLOUDS THEN BUILD IN DURING THE
MORNING. IN ADDITION...A COLD FRONT OVER IA TO MOVE INTO CENTRAL
IL...REACHING PIA JUST BEFORE 12Z. AS A RESULT...S WINDS
OVERNIGHT...WILL BACK TO THE N AS THIS FRONT SLOWLY PASSES THE
CENTRAL IL TERMINALS. SOME LIGHT SN WL BE SEEN AT PIA...SPI AND
BMI AFTER 22Z...AS PRECIPITATION INITIATES IN THE COLDER AIR
BEHIND THE FRONT. IN THE EASTERN TERMINALS...RA WL BE THE
PRECIPITATION TYPE. CEILINGS START TO LOWER AFTER 20Z...AS THE LOW
APPROACHES FROM THE SOUTH.

DPK
&&

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

$$