FXUS63 KILX 232100
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
300 PM CST WED DEC 23 2009

.DISCUSSION...
ISSUED 235 PM CST WED DEC 23 2009

12Z MODELS ARE IN FAIR AGREEMENT INTO THIS CHRISTMAS WEEKEND. THEY 
CONTINUE TO SHOW A LARGE DEEPENING LOW PRESSURE SYSTEM MOVING
NORTHWARD FROM TEXAS INTO IOWA BY DAWN FRI AND BRINGING ROUNDS OF
HEAVY RAIN OF A COUPLE INCHES AND POSSIBLE THUNDERSTORMS INTO
CENTRAL/SE IL INTO THU NIGHT. FORECAST CONCERN IS RAINFALL AMOUNTS
AND FLOOD POTENTIAL. ALSO ADDRESSING STRONG WINDS ESPECIALLY THU
WHICH COULD GET CLOSE TO WIND ADVISORY CRITERIA. MUCH COLDER AIR
USHERS INTO IL BY FRI MORNING CHANGING RAIN TO LIGHT SNOW SHOWERS
WHICH LINGERS THROUGH AT LEAST SAT WITH BEST CHANCES OF LIGHT
ACCUMULATIONS UP TO 1 INCH OVER THE IL RIVER VALLEY.

MID AFTERNOON SURFACE MAP SHOWS 997 MB LOW PRESSURE DEEPENING OVER
SW TEXAS WITH A FRONTAL BOUNDARY EXTENDING TO A WEAKER 1004 MB LOW
PRESSURE IN SE KS AND FRONT THEN EXTENDING INTO WESTERN IA. A WARM
FRONT WAS OVER CENTRAL MO...SOUTHERN IL SOUTH OF I-64 INTO CENTRAL KY.
FIRST ROUND OF OF RAINS WAS ALONG AND NORTH OF I-72 AND LIFTING
NNE AND BROUGHT HALF TO 1 INCH OF RAIN ALONG AND WEST OF I-57 WITH
LOCALLY HIGHER AMOUNTS OF 1 TO 1.5 INCHES FROM SPRINGFIELD SW.
FREEZING RAIN HAS LIFTED NORTH OF CENTRAL IL BY MIDDAY FROM I-80
NORTH. TEMPERATURES RANGED FROM THE MID 30S FROM PEORIA AND
BLOOMINGTON NORTH TO THE MID TO UPPER 40S SOUTH OF I-70. BREEZY
ESE WINDS 10 TO 20 MPH WITH GUSTS OF 20 TO 25 MPH.

SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT.

LOW PRESSURE IN SW TEXAS TO EJECT NNE TO THE AR/MO BORDER BY
SUNSET THU THEN TO SE IA BY SUNRISE FRI. THIS DYNAMIC STORM SYSTEM
HAS DEEP GULF MOISTURE TO WORK WITH AND WILL BRING ANOTHER ROUND
OF MODERATE TO HEAVY RAIN TO CENTRAL IL LATER TONIGHT THROUGH THU
EVENING WITH ANOTHER 1 TO 2 INCHES LIKELY AND A FEW THUNDERSTORMS
POSSIBLE ESPECIALLY SW OF LINCOLN. THIS WILL BRING A STORM TOTAL
OF 2 TO 3 INCH WITH LOCALLY 3 TO 4 INCHES FROM SPRINGFIELD SW.
TEMPERATURES WILL BE NEARLY STEADY OR SLOWLY RISE TONIGHT AND
REACH HIGHS IN THE 40S THU WITH LOWER 40S FROM I-74 NORTH AND
UPPER 40S TO NEAR 50F SW AREAS. INCREASED SE WINDS THU TO 20 TO 25
MPH WITH GUSTS IN THE 30S INTO THU EVENING AND MAY APPROACH WIND
ADVISORY CRITERIA.

HEAVY RAIN THREAT WILL SHIFT NNE OF CENTRAL IL OVERNIGHT THU NIGHT
AS MUCH COLDER AIR STARTS TO USHER IN LATER THU NIGHT FROM SW TO
NE. HAVE RAIN MIXING WITH AND CHANGING TO LIGHT SNOW SW AREAS
LATER THU NIGHT AND ACROSS AREA FRI MORNING. A DRY SLOT WILL
AFFECT EASTERN IL FRI WITH LESS OF A CHANCE OF LIGHT SNOW THERE
WILL MORE LIKELY CHANCES OF LIGHT SNOW NW OF THE IL RIVER. STRONG
CUTOFF LOW OVER IA SAT WILL CONTINUE CHANCE OF LIGHT SNOW SHOWERS
ESPECIALLY OVER THE IL RIVER VALLEY WHERE UP TO 1 INCH OF SNOW POSSIBLE.

STRONG CUTOFF LOW MOVES EAST ACROSS NORTHERN IL/IN SUNDAY KEEPING
A CHANCE OF LIGHT SHOW SHOWERS AND FLURRIES AROUND ALONG WITH
LOW CLOUDS AND COLDER TEMPERATURES. 

LONG TERM...MONDAY THROUGH WEDNESDAY.

A QUIETER WX PATTERN WILL OCCUR NEXT WORK WEEK AS STRONG UPPER
LEVEL LOW PULLS FURTHER AWAY FROM IL MON WITH UPPER LEVEL RIDGE
BUILDING INTO IL TUE. MORE SUNSHINE TO APPEAR MON AND ESPECIALLY
TUE AS TEMPERATURES MODIFY CLOSER TO NORMAL TUE WITH HIGHS IN THE
LOW TO MID 30S. ECMWF MODEL SHOWS LIGHT SNOW WED WITH UPPER LEVEL
TROF APPROACHING IL WITH ITS HEAVIER QPF SOUTH OF IL AND A BIT
HEAVIER NORTH OF CENTRAL IL AS WELL. GFS AND DGEX ARE SLOWER WITH THIS
FEATURE KEEPING IL DRIER WED AND FOLLOWED THAT ROUTE FOR NOW.

HUETTL

&&

.AVIATION...
ISSUED 1145 AM CST WED DEC 23 2009

LIFR CONDITIONS WILL PREVAIL AT THE TERMINALS FOR MUCH OF THE 18Z
TAF PERIOD. A SHIELD OF LIGHT TO MODERATE RAIN IS CURRENTLY
LIFTING NORTHWARD THROUGH CENTRAL ILLINOIS...HOWEVER BASED ON
RADAR TRENDS...IT APPEARS THERE WILL BE A LULL IN THE PRECIP LATER
THIS AFTERNOON INTO THE EVENING. HAVE ENDED THE PREDOMINANT RAIN
IN FAVOR OF VCSH AT KSPI...KDEC...AND KCMI AFTER 21Z. FURTHER WEST
AND NORTH...HAVE CONTINUED THE STEADY RAIN UNTIL 02Z...THEN
REPLACED IT WITH -SHRA. A SECOND WAVE OF STEADY RAIN WILL DEVELOP
TO THE SOUTH AND MOVE INTO THE AREA LATE TONIGHT INTO THURSDAY
MORNING. HAVE THEREFORE BROUGHT PREDOMINANT RAIN BACK TO THE TAF
SITES AFTER 09Z. BRISK E/SE WINDS GUSTING TO 25KT THIS
AFTERNOON/EVENING...WILL GRADUALLY INCREASE BY LATE TONIGHT AND
THURSDAY...WITH GUSTS UP TO 30KT.

BARNES
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH THURSDAY EVENING FOR ILZ027>031-036>038-
040>057-061>063-066>068-071>073.

&&

$$