FXUS63 KILX 051114
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
514 AM CST SAT DEC 5 2009

.DISCUSSION...
ISSUED 110 AM CST SAT DEC 5 2009

MAIN CONCERNS THIS FORECAST PERIOD ARE THE PRECIPITATION TYPE AND
SNOWFALL AMOUNTS WITH STORM SYSTEM ON TUES NIGHT INTO WED. IN THE
PAST FEW MODEL RUNS...BOTH THE GFS AND THE ECMWF HAVE MADE CHANGES
TO THE TRACK OF THIS LOW. EVEN MINOR CHANGES TO THE TRACK OF A
LOW...CAN HAVE SIGNIFICANT IMPACTS ON PRECIPITATION TYPE. FAVORED
MORE OF A BLEND OF THE TWO.

AT 07Z...SFC RIDGE EXTENDED FROM SOUTHERN IL...NORTHEAST INTO
CENTRAL IN. CLOUD COVER EARLIER THIS EVENING...ASSOCIATED WITH AN
UPPER LEVEL TROF OVER IL...MOVED EAST OF THE FORECAST AREA BY 07Z.

SHORT TERM...SATURDAY THROUGH MONDAY NIGHT
SFC RIDGE MOVES EAST OF IL OVERNIGHT...ALLOWING SOUTHERLY FLOW TO
SET UP. TEMPERATURES GRADUALLY WARM THROUGH SUNDAY. UPPER LEVEL
FLOW BECOMES MORE ZONAL. A TROF OVER THE WESTERN DAKOTAS WL SLOWLY MOVE
EAST...REACHING IL SUNDAY NIGHT. AN UPPER LEVEL DISTURBANCE WL
TRACK EAST...KICKING OFF A SFC LOW...THAT WL TRACK NE ALONG THIS
TROF. NAM AND GFS IN GOOD AGREEMENT ON THE TRACK OF THIS LOW SUN
NIGHT AND MON MORNING...ACROSS NE IL...HOWEVER...THE GFS IS A BIT
QUICKER IN TRACKING THE LOW INTO THE GREAT LAKES REGION. COLD AIR
WL WRAP AROUND THIS LOW...AND MODEL SOUNDINGS INDICATE LIGHT
SNOW. WARMER TEMPERATURES TO THE SOUTH MAY RESULT IN A MIXTURE OF
LIGHT RAIN AND LIGHT SNOW...BEFORE CHANGING TO LIGHT SNOW LATE. MOST
FAVORABLE AREAS FOR SNOW ARE NW OF THE FORECAST AREA...SO SNOWFALL
ACCUMULATIONS SHOULD BE AN INCH OR LESS. A BRIEF BREAK IN THE
PRECIPITATION EXPECTED MONDAY NIGHT...BEFORE NEXT...MORE POTENT
SYSTEM APPROACHES.

LONG TERM...TUESDAY THROUGH FRIDAY
NO CHANGES TO THE FORECAST PAST WEDNESDAY. A BRIEF BREAK IN THE
PRECIPITATION EXPECTED ON TUESDAY. EUROPEAN AND GFS FAIRLY SIMILAR
WITH RESPECT TO TIMING...HOWEVER ECMWF A BIT FURTHER SOUTH WITH
THE TRACK. THE ECMWF TRACKS THE LOW JUST SOUTH OF I-70...THIS
TRACK COULD RESULT IN A HEAVY SNOW BAND NEAR AND JUST NORTH OF THE
ILLINOIS RIVER. A GFS TRACK A BIT FURTHER TO THE NORTH...WOULD
SHIFT THE HEAVIER SNOW FURTHER NORTH. ACROSS THE SOUTHEAST PART OF
THE FORECAST AREA...CLOSER TO THE LOW TRACK...A MIXTURE OF RAIN
AND SNOW CAN BE EXPECTED. THIS SYSTEM PULLS OUT OF THE AREA
WEDNESDAY NIGHT...ALLOWING PRECIPITATION TO COME TO AN END.

DPK
&&

.AVIATION...
ISSUED 514 AM CST SAT DEC 5 2009

VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. CU RULE
INDICATES SOME SCATTERED CU POSSIBLE DURING THE DAY BUT SHOULD
DISSIPATE QUICKLY AROUND SUNSET. THEN CLEAR SKIES DURING THE NIGHT
BEFORE CIRRUS MOVES IN AHEAD OF NEXT SYSTEM. WINDS WILL BE
SOUTHERLY THROUGH THE PERIOD WITH SLIGHTLY STRONGER WINDS DURING
THE DAY.

AUTEN
&&

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

$$