FXUS63 KILX 060842
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
242 AM CST SUN DEC 6 2009

.DISCUSSION...
ISSUED 1127 PM CST SAT DEC 5 2009

MAIN FORECAST CHALLENGE CONTINUES TO BE THE EXACT TRACK OF THE
TUESDAY NIGHT AND WEDNESDAY SYSTEM...AND ASSOCIATED PRECIPITATION TYPE.

COLD FRONT EXTENDING FROM A LOW IN EASTERN MN...TO NE IA AT 07Z.
SOUTH WINDS OF 5 TO 10 MPH NOTED ACROSS THE AREA...RESULTING IN
OVERNIGHT TEMPERATURES A FEW DEGREES WARMER THAN YESTERDAY. CI
STREAMING INTO THE FORECAST AREA AHEAD OF THIS LOW.

SHORT TERM...SUNDAY THROUGH MONDAY NIGHT
NEARLY ZONAL UPPER LEVEL FLOW...WITH A DISTURBANCE ACROSS NV...WHICH
WL TRACK EAST AND HELP MOVE THE FRONT A BIT EAST...AND PUSH THE
LOW NE ALONG THE FRONT. LIGHT SNOW WL DEVELOP ACROSS THE FORECAST
AREA SUNDAY EVENING AS THE SYSTEM PASSES. FORECAST SOUNDINGS
INDICATE DRYING IN THE MID LEVELS...ESPECIALLY SOUTH OF I-74. AFTER
12Z...MOISTURE IS JUST BELOW THE 10C LEVEL. THIS WOULD INDICATE A VERY
LOW LIKELIHOOD OF ICE CRYSTALS IN THE CLOUDS...RESULTING IN THE
PRECIPITATION TO BE DRIZZLE OR FREEZING DRIZZLE. SLIGHTLY DEEPER
MOISTURE PRESENT ACROSS THE NORTH...SO FLURRIES POSSIBLE. NO MAJOR
CHANGES MADE TO PRECIPITATION TYPE OR SNOW ACCUMULATIONS FOR THIS SYSTEM.

HIGH PRESSURE BRIEFLY BUILDS IN MONDAY AND MONDAY NIGHT...BRINGING
AN END TO THE PRECIPITATION. MOSTLY CLOUDY SKIES WILL PERSIST
AHEAD OF THE NEXT SYSTEM.

LONG TERM...TUESDAY THROUGH SATURDAY 
NO CHANGES MADE TO THE FORECAST BEYOND THURSDAY. FORECAST MODELS
ARE ALL SHIFT THE TRACK OF THE TUESDAY NIGHT/WEDNESDAY LOW A BIT
FURTHER NORTH. THE ECMWF NOW TRACKS THE LOW JUST A BIT FURTHER
NORTH THAN THE GFS...HOWEVER TRACK POSITIONS WERE CLOSE...ALTHOUGH
THE GFS WAS FASTER. PREFERRED A BLEND OF THE GFS AND ECMWF. A MORE
NORTHERLY LOW TRACK WOULD SHIFT THE HEAVIER PRECIPITATION
NORTHWEST OF THE FORECAST AREA...AND PLACE A BETTER CHANCE OF
MIXED PRECIPITATION ACROSS THE CENTRAL PART OF THE FA. ACROSS THE
SE...TEMPERATURES ARE WARM ENOUGH FOR RAIN...UNTIL MUCH COLDER AIR
IS PULLED INTO THE AREA ON WEDNESDAY. INCREASED THE COVERAGE OF
THE RAIN AND SNOW MIX...AND CUT BACK ON SNOWFALL TOTALS A BIT TO
THE EAST OF INTERSTATE 55.

VERY TIGHT PRESSURE GRADIENT ON THE BACKSIDE OF THE DEPARTING LOW
WILL RESULT IN GUSTY NW WINDS ON WEDNESDAY. THESE WINDS WILL
RESULT IN SOME  MUCH COLDER AIR TO POUR INTO THE STATE WEDNESDAY.
VERY COLD TEMPERATURES WEDNESDAY AND THURSDAY MORNING CAN BE
EXPECTED. MORNING LOW TEMPERATURES WL BE ESPECIALLY COLD OVER
AREAS WITH A SNOWPACK...TO THE NW OF THE IL RVR.

DPK
&&

.AVIATION...
ISSUED 1115 PM CST SAT DEC 5 2009

LITTLE CHANGE FROM PREVIOUS DISCUSSION. VFR CONDITIONS ARE
EXPECTED THRU THIS FCST PERIOD. THICKENING CIRRUS SHIELD WL
CONTINUE TO SPREAD NE ACRS CNTRL IL INTO SUNDAY. SOUTHERLY
WINDS WILL PREVAIL INTO SUNDAY MORNING AT SPEEDS OF ARND 10
KTS...WITH WINDS BACKING MORE INTO THE SE BY EVENING. FORECAST
SOUNDINGS SUGGEST SOME MID LEVEL MOISTURE WL INCREASE ACRS THE
AREA BY LATE AFTN AND EVENING SO WL INCLUDE A CIG AOA 10000 FEET
AFTR 19Z...WITH A GRADUAL LOWERING OF CIGS SUNDAY EVENING AS A
WEAK WEATHER DISTURBANCE APPRCHS FROM THE CENTRAL PLAINS. WE MAY
SEE SOME MVFR/IFR CIGS DEVELOP AFTR THIS FCST PERIOD AS THE WEAK
STORM SYSTEM MOVES THRU MONDAY MORNING WITH THE PSBLTY OF SOME
LIGHT SNOW LATE TMRW NIGHT OR MONDAY MRNG.  

SMITH
&&

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

$$