FXUS63 KILX 040243
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
843 PM CST THU DEC 3 2009

.DISCUSSION...
ISSUED 843 PM CST THU DEC 3 2009

CLOUD SHIELD ASSOCIATED WITH UPPER LOW OVER SOUTHERN WISCONSIN IS
NOW WORKING ITS WAY INTO CENTRAL ILLINOIS...WITH ALL AREAS ALONG
AND WEST OF THE ILLINOIS RIVER CURRENTLY OVERCAST. CLOUDS WILL
CONTINUE TO SPREAD FURTHER EAST OVERNIGHT...RESULTING IN MOSTLY
CLOUDY CONDITIONS ACROSS THE BOARD. RADAR MOSAIC/SURFACE OBS SHOW
SNOW FLURRIES AS FAR SOUTH AS SOUTHERN IOWA. THESE WILL PUSH E/NE
INTO THE FAR NORTHERN KILX CWA FROM PEORIA NORTHWARD OVERNIGHT.
BASED ON RADAR TRENDS...HAVE REMOVED CHANCE FOR FLURRIES FURTHER
SOUTH IN THE SPRINGFIELD AREA. 02Z TEMPS HAVE ALREADY SLIPPED INTO
THE UPPER 20S IN MOST LOCATIONS...SO HAVE ADJUSTED OVERNIGHT LOWS
DOWN BY A COUPLE OF DEGREES. SHOULD MAINLY SEE LOWER TO MIDDLE
20S...WITH A FEW TEENS POSSIBLE ACROSS THE ILLINOIS RIVER VALLEY.

BARNES
&&

.AVIATION...
ISSUED 540 PM CST THU DEC 3 2009

VIGOROUS UPPER LOW SPINNING OVER NORTHERN IOWA WILL CONTINUE TO
PROVIDE PLENTY OF CLOUD COVER TO CENTRAL ILLINOIS THROUGH THE
ENTIRE 00Z TAF PERIOD. RADAR MOSAIC/SURFACE OBS SHOW BULK OF
PRECIP REMAINING ALONG AND NORTH OF THE LOW TRACK ACROSS NORTHERN
IOWA INTO FAR NORTHERN ILLINOIS/SOUTHERN WISCONSIN. FURTHER
SOUTH...A FEW SNOW FLURRIES MAY DRIFT ACROSS THE NORTHERN
TERMINALS OVERNIGHT. CURRENT SKY CONDITIONS ACROSS THE KILX TAF
SITES REVEAL SCT-BKN CLOUD COVER AT 5000FT...HOWEVER A LOWER DECK
OF CLOUDS AT AROUND 3500FT IS PUSHING ACROSS THE MISSISSIPPI
RIVER. BASED ON TIMING TOOLS...THESE LOWER CEILINGS WILL REACH
KPIA BY 02Z...THEN FURTHER EAST TO KCMI BY 06Z. FORECAST SOUNDINGS
ARE SUGGESTING A FURTHER LOWERING OF CEILINGS LATE TONIGHT INTO
FRIDAY MORNING...AS VORT LOBE SWINGS AROUND PARENT UPPER LOW INTO
CENTRAL ILLINOIS. HAVE THEREFORE INTRODUCED A PERIOD OF 2500FT CEILINGS
FROM 09Z THROUGH 18Z. AFTER THAT...SOUNDINGS INDICATE CONTINUED
CLOUDY CONDITIONS FOR FRIDAY AFTERNOON...WITH CEILINGS RISING BACK
TO AROUND 3500FT. WINDS WILL REMAIN WESTERLY AT 10 TO 15KT THROUGH
00Z SAT.

BARNES
&&

.PREV DISCUSSION...
ISSUED 300 PM CST THU DEC 3 2009

BELOW NORMAL TEMPS WILL CONTINUE THROUGH THE NEXT WEEK...AS THE
UPPER TROUGH AND COLD POOL IN PLACE GIVE WAY TO A MUCH DEEPER
TROUGH FOR TUESDAY/WEDNESDAY. 

SHORT TERM...TONIGHT THROUGH SUNDAY.

SATELLITE IMAGES THIS AFTERNOON SHOW THE SWIRL OF A SHORTWAVE
ACROSS IOWA MOVING EAST TOWARD THE NORTHERN HALF OF ILLINOIS.
LIGHT SNOW SHOWERS/FLURRIES ARE OCCURRING AS THE WAVE PROGRESSES
EASTWARD. SHORT TERM MODELS INDICATE THE BEST CHANCES OF VERY LIGHT
MEASURABLE SNOW WILL REMAIN NORTH OF OUR CWA. WE WILL KEEP
FLURRIES TONIGHT FOR AREAS NORTH OF SPRINGFIELD TO PARIS.

COLD SURFACE HIGH PRESSURE IS EXPECTED TO PREVAIL ACROSS CENTRAL
IL THROUGH THE WEEKEND...AS THE UPPER TROUGH AXIS REMAINS JUST
WEST OF IL. SUNDAY SHOULD BE THE WARMEST DAY OF THE NEXT
WEEK...AS SOUTHEAST WINDS INCREASE AHEAD OF THE NEXT SHORTWAVE FOR
SUNDAY NIGHT. STILL...BELOW NORMAL TEMPS ARE EXPECTED...DESPITE
SOME DECEMBER SUNSHINE THIS WEEKEND.

LONG TERM...SUNDAY NIGHT THROUGH THURSDAY.

SUNDAY NIGHT THE NEXT SHORTWAVE WILL ARRIVE FROM THE CENTRAL
PLAINS. A BRIEF SHOT OF ISENTROPIC LIFT WILL ACCOMPANY A FAST
MOVING POTENTIAL VORTICITY /PV/ ANOMALY. THERE WILL BE THE
POTENTIAL FOR A DUSTING OF SNOW...AS SURFACE LOW PRESSURE LIFTS
FROM NORTHERN MISSOURI AT MIDNIGHT SUNDAY NIGHT...ACROSS NW IL...TO
EASTERN WIS BY NOON ON MONDAY.

A MORE SIGNIFICANT SYSTEM IS EXPECTED FOR LATE TUESDAY THROUGH
WED MORNING OF NEXT WEEK. A HIGH AMPLITUDE UPPER TROUGH WILL
DEVELOP IN THE SW STATES ON MONDAY AND REACH IL ON WEDNESDAY.
BY TUESDAY MORNING...SURFACE CYCLOGENESIS WILL INTENSIFY OVER THE
SOUTHERN MISSISSIPPI RIVER VALLEY...AND LIFT NORTH-NORTHEAST
TUESDAY NIGHT...REACHING NEAR OHIO BY WED AFTERNOON.

THIS STORM TRACK HAS BEEN HIGHLY VARIABLE IN THE RECENT MODEL
RUNS...SO POPS WERE HELD OUT OF THE LIKELY CATEGORY TUESDAY
AFTN/NIGHT. THE GFS TAKES A LOW WELL SE OF IL...WHILE THE ECMWF
TAKES THE LOW ACROSS THE NW CORNER OF OUR CWA. HIGHLY DIFFERENT
OUTCOMES WOULD OCCUR IN EACH CASE. FOR NOW...WE TRENDED WITH THE
ECMWF...AND KEPT A BROAD MID CHANCE POP EVERYWHERE TUESDAY AFTN
AND TUESDAY NIGHT....WITH LINGERING POPS WED MORN. IF THE GFS
SOLUTION PANS OUT...A BAND OF LIGHT SNOW COULD DEVELOP ACROSS THE
CWA FROM RUSHVILLE/JACKSONVILLE TO BMI DURING THAT TIME.

WILL KEEP A CLOSE EYE ON THE EXPECTED TRACK OF THAT LOW...AND THE
POTENTIAL FOR MEASURABLE SNOWS NEXT WEEK.

CHILLY HIGH PRESSURE IS EXPECTED TO RETURN FOR THURSDAY BEHIND
THAT MID WEEK LOW.

&&

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

$$