FXUS63 KILX 261136
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
536 AM CST SAT DEC 26 2009
.DISCUSSION...
ISSUED 245 AM CST SAT DEC 26 2009
LIGHT SNOW ACCUMULATIONS LIKELY TODAY AND SUNDAY...AS DEEP UPPER
LOW REMAINS IN THE VICINITY.
SHORT TERM...TODAY THROUGH MONDAY
MAIN WEATHER MAKER THIS WEEKEND WILL BE A DEEP UPPER LOW CURRENTLY
ANALYZED OVER NORTH-CENTRAL ILLINOIS. NUMEROUS SHORT-WAVES WILL
ROTATE AROUND THE PARENT LOW...BRINGING OFF AND ON SNOW-SHOWERS TO
THE AREA. 07Z WATER VAPOR IMAGERY SHOWS IMPRESSIVE WAVE OVER
WESTERN IOWA/EASTERN NEBRASKA...WHILE A WEAKER FEATURE IS CROSSING
THE MISSISSIPPI RIVER INTO WEST-CENTRAL ILLINOIS. INITIAL DISTURBANCE
IS ALREADY TRIGGERING LIGHT SNOW ALONG AND WEST OF I-55...WITH
MANY OB SITES REPORTING VISBYS IN THE 2 TO 4SM RANGE. THIS AREA OF
LIGHT SNOW WILL LIFT E/NE EARLY THIS MORNING...MAINLY IMPACTING
LOCATIONS ALONG AND NORTH OF I-72. STRONGER WAVE TO THE WEST WILL
GRADUALLY WORK ITS WAY INTO CENTRAL ILLINOIS TOWARD MIDDAY...WITH
BOTH THE NAM-WRF AND GFS TAKING THE CENTER OF THE VORT MAX FROM
NEAR KUIN AT 18Z TO KIKK BY 00Z. THE CORRESPONDING VALUES OF OMEGA
ARE HIGHEST ALONG AND NORTH OF THE VORT PATH DURING THE AFTERNOON.
FORECAST SOUNDINGS INDICATE AMPLE MID AND LOW-LEVEL MOISTURE IN
CONJUNCTION WITH THE FORCING ASSOCIATED WITH THE WAVE..WHICH WILL
LEAD TO OCCASIONAL SNOW SHOWERS ACROSS THE N/NW KILX CWA. HAVE
INCREASED POPS TO CATEGORICAL ALONG AND NORTHWEST OF A RUSHVILLE
TO BLOOMINGTON LINE...WHERE AROUND 1 INCH OF SNOW WILL ACCUMULATE
BY LATE AFTERNOON. LOCALIZED 2 INCH AMOUNTS WILL BE POSSIBLE AS
WELL...ESPECIALLY IMMEDIATELY UNDER THE APPROACHING VORT MAX.
FURTHER SOUTH AND EAST...POPS WILL STEADILY DECLINE...WITH ONLY
30S SOUTH OF I-70.
AFTER MAIN SHORT-WAVE PUSHES INTO NORTHERN INDIANA...WEAK SUBSIDENCE
IN ITS WAKE WILL BRING A TEMPORARY LULL TO THE SNOW-SHOWERS THIS
EVENING. YET ANOTHER WAVE ROTATING AROUND THE SLOW-MOVING UPPER LOW
WILL APPROACH FROM THE NORTHWEST AFTER MIDNIGHT...BRINGING A
RENEWED CHANCE FOR PRECIP BACK INTO CENTRAL ILLINOIS. WILL
THEREFORE CARRY SCATTERED SNOW SHOWERS TONIGHT...WITH THE BEST
CHANCE FOR SNOW AFTER MIDNIGHT. SNOW SHOWERS WILL CONTINUE INTO
SUNDAY...WITH LESS THAN ONE INCH ADDITIONAL ACCUMULATION EXPECTED.
ONE FINAL WEAK WAVE PUSHES THROUGH THE AREA SUNDAY EVENING...BEFORE
THE WHOLE SYSTEM FINALLY BEGINS TO PULL FURTHER AWAY LATE SUNDAY
NIGHT. NOT REALLY SEEING MUCH IN THE WAY OF OMEGA WITH THIS
LAST FEATURE...HOWEVER THINK A MENTION OF SCATTERED SNOW FLURRIES
WOULD BE PRUDENT...ESPECIALLY SUNDAY EVENING. UPPER LOW WILL BE
SLOW TO EXIT ON MONDAY...WHILE SURFACE RIDGING REMAINS TO THE WEST
ACROSS THE PLAINS. DESPITE INCREASING SUBSIDENCE/DRYING AT MID-
LEVELS...LOW-LEVELS WILL REMAIN MOIST. WILL THEREFORE MAINTAIN
MOSTLY CLOUDY SKIES THROUGH MONDAY MORNING...BEFORE CLEARING
THINGS OUT MONDAY AFTERNOON. WITH HIGH PRESSURE EXPECTED TO SHIFT
TO ALONG THE MISSISSIPPI RIVER BY 12Z TUE...CLEAR SKIES AND LIGHT
WINDS WILL MAKE MONDAY NIGHT THE COLDEST NIGHT IN THE FORECAST
PERIOD. HAVE UNDERCUT GUIDANCE BY A FEW DEGREES...ESPECIALLY
ACROSS THE N/NW WHERE A DECENT SNOW-COVER WILL BE IN PLACE. LOW
TEMPS BY EARLY TUESDAY MORNING WILL RANGE FROM AROUND 10 DEGREES
FAR NORTHWEST...TO 20 DEGREES FAR SOUTHEAST.
LONG TERM...TUESDAY THROUGH FRIDAY
MOSTLY SUNNY AND DRY WEATHER WILL BE ON TAP TUESDAY...BEFORE THE
NEXT APPROACHING SYSTEM SPREADS CLOUDS INTO THE AREA TUESDAY NIGHT
AND WEDNESDAY. MODELS IN FAIRLY GOOD AGREEMENT...FEATURING A
NORTHERN STREAM SYSTEM SKIRTING ACROSS SOUTHERN CANADA AND A
SOUTHERN STREAM FEATURE TRACKING ALONG THE GULF COAST. WITH THE
TWO SYSTEMS REMAINING UNPHASED...FORCING WILL BE WEAK ACROSS
CENTRAL ILLINOIS...SO PRECIP CHANCES SHOULD REMAIN RATHER MEAGER.
WILL INTRODUCE SLIGHT CHANCE POPS FOR LIGHT SNOW TUESDAY
NIGHT...THEN LINGER THEM THROUGH WEDNESDAY...AS NORTHERN STREAM
WAVE DRIVES A COLD FRONT THROUGH ILLINOIS. AFTER THAT...MUCH
COLDER AIR WILL SETTLE INTO THE REGION FOR THE END OF NEXT WEEK.
&&
.AVIATION...
ISSUED 530 AM CST SAT DEC 26 2009
DEEP STORM SYSTEM THAT PRODUCED THE RAIN...WIND AND LIGHT SNOWS
OVR THE PAST 24 HOURS WILL CONTINUE TO BE A FACTOR IN THE WX
ACRS THE FORECAST AREA THIS PERIOD. WEAK UPPER LEVEL DISTURBANCES
CONTINUE TO ROTATE AROUND THE LARGE STORM SYSTEM TO OUR WEST
BRINGING PERIODS OF LIGHT SNOW/FLURRIES TO CENTRAL IL. EXPECT THIS
PATTERN TO HOLD ACRS OUR AREA INTO THIS EVENING. CURRENT WAVE
PUSHING ACRS WRN IL BRINGING MVFR TO LOCALLY IFR CIGS AND VSBYS
IN SNOW TO AREAS MAINLY WEST OF INTERSTATE 55. THIS WAVE WILL SHIFT
EAST OF THE TAF SITES BY 15Z...WITH A TEMPORARY LULL IN THE PRECIP
BUT ANOTHER SHORTWAVE NOTED ON SATELLITE ACRS SW IA INTO NE MO
PUSHING IN OUR DIRECTION WITH ADDL SNOW SHOWERS. CIGS FURTHER WEST
GO BACK INTO THE VFR RANGE FOR A TIME...BUT NOT REAL CONFIDENT THAT
WL GET UP TO PIA OR BMI THIS MRNG. WE SHOULD SEE A CONTINUATION OF
THE SCATTERED SNOW SHOWERS AND BRIEFLY LOWER VSBYS INTO THIS EVE
BUT TRYING TO TIME AND PINPOINT ANY ONE LOCATION WL BE DIFFICULT
AT BEST AT THIS POINT. WINDS WL CONTINUE FROM A SOUTH TO SOUTHWEST
DIRECTION TODAY WITH SPEEDS OF 15 TO 20 KTS...WITH OCCASIONAL GUSTS
AOA 25 KTS. WNDS SHOULD GRDLY VEER MORE INTO THE SOUTHWEST TNT.
SMITH
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 4 PM CST THIS AFTERNOON FOR ILZ051.
&&
$$
