FXUS63 KILX 300119
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
719 PM CST SUN NOV 29 2009

.DISCUSSION...
ISSUED 719 PM CST SUN NOV 29 2009

01Z SURFACE ANALYSIS SHOWS COLD FRONT PUSHING OUT OF THE FAR SE
KILX CWA...WITH WINDS AT KLWV COMING AROUND TO THE NORTHWEST.
DESPITE FROPA...PLENTY OF CLOUDS BLANKET CENTRAL ILLINOIS...AS
WELL AS UPSTREAM ACROSS IOWA AND MINNESOTA. SATELLITE IMAGERY HAS
BEEN SHOWING A FEW BREAKS IN THE LOW OVERCAST ACROSS EASTERN
IOWA...HOWEVER THESE WILL BECOME OBSCURED BY A MID-LEVEL CLOUD
DECK STREAMING NORTHEASTWARD ACROSS THE REGION. END RESULT WILL BE
CLOUDY SKIES THROUGHOUT THE NIGHT...WITH CLEARING TREND POSTPONED
UNTIL MONDAY MORNING. BASED ON SATELLITE TRENDS AND 18Z NAM-WRF
FORECAST SOUNDINGS...HAVE UPDATED FORECAST TO GO WITH OVERCAST
CONDITIONS TONIGHT...FOLLOWED BY CLEARING SKIES ON MONDAY. DUE TO
THE CLOUD COVER...HAVE ALSO RAISED LOW TEMPS BY A COUPLE OF
DEGREES...WITH READINGS RANGING FROM AROUND 30 NORTHWEST OF THE
ILLINOIS RIVER...TO THE UPPER 30S SOUTH OF I-70.

BARNES
&&

.AVIATION...
ISSUED 552 PM CST SUN NOV 29 2009

COLD FRONT CURRENTLY EXTENDING FROM CENTRAL INDIANA INTO SOUTHERN
ILLINOIS WILL PUSH FURTHER SOUTHEAST OVERNIGHT...HOWEVER CLOUDS
WILL HANG ON THROUGHOUT THE NIGHT ACROSS CENTRAL ILLINOIS. LATEST
SATELLITE IMAGERY SHOWS A FEW BREAKS IN THE OVERCAST ACROSS
EASTERN IOWA/WESTERN WISCONSIN...HOWEVER THESE WILL BECOME
OBSCURED BY MID/HIGH CLOUDS STREAMING UP FROM THE SOUTHWEST. ASIDE
FROM THOSE FEW BREAKS...PLENTY OF LOW CLOUDS BLANKET
IOWA/MINNESOTA. 18Z NAM-WRF 1000-850MB LAYER RH FIELD DEPICTS THE
CLOUD COVER QUITE WELL...AND DOES NOT SHOW IT BREAKING UP AND
COMPLETELY EXITING THE AREA UNTIL MONDAY MORNING. WILL THEREFORE
MAINTAIN CURRENT CEILINGS OF 2000FT THROUGH THE EVENING...WITH A
GRADUAL RISE TO AROUND 3500FT AFTER MIDNIGHT. WILL BEGIN
SCATTERING THE CLOUDS OUT AT KSPI AND KPIA BY 17Z...THEN FURTHER
EAST AT KCMI BY 19Z. WINDS WILL INITIALLY BE FROM THE NORTHWEST AT
AROUND 10KT TONIGHT...THEN WILL BACK TO THE WEST MONDAY
MORNING...THEN TO THE SOUTHWEST BY MONDAY AFTERNOON.

BARNES
&&

.PREV DISCUSSION...
ISSUED 115 PM CST SUN NOV 29 2009

LATEST SURFACE ANALYSIS INDICATING A COLD FRONT STRETCHING FROM
NE IL SW THRU THE INTERSTATE 55 CORRIDOR. SCATTERED SHOWERS
DEVELOPED ALONG THE BOUNDARY EARLIER THIS MRNG AND CONTINUE TO
MARCH EAST WITH THE FRONT. EVEN HAD SOME LIGHTNING STRIKES ACRS
NE IL EARLIER THIS MRNG WITH A LARGER AREA OF SHOWERS WHICH 
MOVED TO OUR NORTH. FAIRLY STEEP MID LEVEL LAPSE RATES ON MRNG
SOUNDINGS ALONG THE FRONTAL BOUNDARY...SO WOULDN'T BE SURPRISED
IF WE SEE SOME ISOLD THUNDER WITH THE DEVELOPING RAIN BAND. NW OF
THE FRONT...TEMPERATURES HAVING A TOUGH TIME GETTING OUT OF THE
40S...WHILE TO THE EAST OF THE FRONT...EARLY AFTN READINGS WERE
IN THE MID 50S.

MAIN FORECAST CHALLENGE CONTINUE TO REVOLVE AROUND THE STORM
SYSTEM EXPECTED TO TAKE SHAPE ACRS THE SRN MISSISSIPPI VALLEY
LATE TUE INTO WEDNESDAY...AND THEN SWING NE SOUTH OF THE OHIO
RIVER WED INTO EARLY THURSDAY. MODELS (NAM...ECMWF AND CANADIAN
GLOBAL) TRENDING A BIT SLOWER WITH THE SYSTEM AND KEEPING THE
BULK OF THE SIGNIFICANT RAIN/SNOW JUST TO OUR SOUTH. AFTER THAT
SYSTEM PUSHES OFF TO THE EAST OF THE AREA ON THURSDAY...THE 
COLDEST AIR MASS OF THE SEASON SO FAR IS POISED TO DROP SE INTO
THE MIDWEST.

SHORT TERM...TONIGHT THROUGH WEDNESDAY

COLD FRONT WILL SHIFT EAST OF THE FORECAST AREA BY EARLY THIS
EVENING TAKING MOST OF THE LIGHT RAIN WITH IT. WL CARRY CHANCE
POPS ALONG THE I-70 CORRIDOR TNT WITH ALL OF THE PRECIP TO OUR
SOUTH AND EAST BY LATE TNT. FORECAST SOUNDINGS SUGGEST LOW LEVEL 
MOISTURE TO DECREASE FROM NW TO SE OVERNIGHT...AS A RESULT WE
SHOULD SEE THE CLOUDS PUSH OUT OF ALL AREAS EXCEPT THE SE BY
MORNING. HAVE TRENDED A BIT COLDER THAN GUID NW WHERE SKIES ARE
EXPECTED TO CLEAR FIRST...AND STAYED CLOSER TO GUID TO THE EAST
AND SOUTH.

ON MONDAY...HIGH PRESSURE SHOULD MOVE SOUTH OF THE AREA WITH 
MODELS INDICATING SOME WEAK SHORTWAVE ENERGY TRACKING TO OUR 
NORTH DURING THE AFTN. SEEING SOME WEAK ISENT ASCENT AND LOWER
PRES DEFICITS ACRS THE NORTH AHEAD OF THIS FEATURE BUT THE MAIN
SUPPORT/LIFT FOR ANY PRECIP WILL REMAIN TO OUR NORTH. WL TEND TO
STAY A BIT CLOSER TO THE NAM-12 2 METER TEMPS FOR AFTN HIGHS ON
MONDAY.

MONDAY NIGHT THROUGH TUESDAY NIGHT...QUIET WEATHER EXPECTED WITH
A WARMING TREND IN STORE FOR THE AREA ON TUESDAY. PLENTY OF SUNSHINE
COUPLED WITH A LOW LEVEL SOUTHWEST FLOW SHOULD HELP TO PUSH AFTN 
TEMPS AT OR ABOVE GUID VALUES...RESULTING IN HIGHS RANGING FROM
THE MID TO UPPER 50S FROM NW TO SE. MODELS SHOWING NRN STREAM ENERGY
TRACKING EWD ACRS THE UPPER MIDWEST LATE TUE DRAGGING ANOTHER COLD
FRONT ACRS IOWA TUE AFTN. IMPRESSIVE 850 MB WARM AXIS JUST AHEAD
OF THE FRONT WITH +10 DEGREES C POKING INTO WRN IL LATE TUE. IF
MODELS CONTINUE THIS TREND...WE MAY HAVE TO BUMP HIGHS UP A
CATEGORY FOR TUESDAY AFTN.

WEDNESDAY...TAKING THE SLOWER SOLUTION DEPICTED ON THE NAM...ECMWF
AND CANADIAN MODELS...SFC LOW PRESSURE ACRS CNTRL LOUISIANA IS 
FORECAST TO EJECT NE INTO NW ALABAMA BY EVENING...WHILE THE NRN
STREAM WAVE AND ATTENDANT COLD FRONT SHIFT EWD ACRS THE LOWER
LAKES. RAIN SHOULD SLOWLY SPREAD NE INTO SE IL DURING THE DAY AND
CONTINUE INTO THE EVENING BEFORE BECOMING MIXED WITH OR CHANGING
TO SNOW AS MUCH COLDER AIR FILTERS SE INTO THE REGION. STILL QUITE
A BIT OF UNCERTAINTY WITH THE TRACK OF THE UPPER LOW AND
ASSOCIATED SFC LOW...AS WELL AS ANY DEVELOPMENT OFF THE EAST COAST
WED NIGHT...WHICH WOULD CUT DOWN ON QPF AMTS OVR SE IL. LOOKS LIKE
A RATHER SHARP BACKEDGE TO THE PRECIP SHIELD TO THE NORTHWEST WITH
THE REMAINDER OF THE FORECAST AREA JUST SEEING LOW CHANCE POPS
OVERNIGHT.

LONG TERM...THURSDAY THROUGH SUNDAY

COLDEST AIR OF THE SEASON...SO FAR...EXPECTED TO PUSH INTO CNTRL
IL AS DEEP LOW PRESSURE MOVES ACRS THE NE PORTION OF THE COUNTRY.
OUR AREA WILL BE UNDER THE INFLUENCE OF DEEP CYCLONIC FLOW AND
STRONG COLD AIR ADVECTION WHICH WILL BRING GUSTY WINDS...SCATTERED
SNOW SHOWERS AND AFTN TEMPERATURES HOLDING IN THE 30S. THIS SHOULD
HOLD INTO AT LEAST EARLY SATURDAY BEFORE THE PATTERN SLOWLY RELAXES
OVER THE MIDWEST NEXT WEEKEND. THE UPPER TROF SHOULD PUSH EAST OF
US LATE SATURDAY INTO SUNDAY ALLOWING RIDGING TO DEVELOP ACRS THE
MIDWEST ON SUNDAY. THIS SHOULD BRING WARMER TEMPERATURES BACK INTO
THE REGION SUNDAY ALONG WITH AN INCREASE IN CLOUDS. ECMWF AND 
CANADIAN MODELS SHOWING SOME SIGNIFICANT SPREAD WITH RESPECT TO
JUST HOW QUICKLY THE PATTERN DEAMPLIFIES ACRS THE REGION WITH THE
CURRENT ECMWF SHOWING THE MOST VOLATILITY OVER THE PAST 24 HOURS
WITH RESPECT TO THE FLOW PATTERN OVR THE EASTERN PACIFIC...WHICH
IS NOW ADVERISED TO UNDERCUT THE RIDGE ACRS ALASKA WITH THE LOWER
48 FORECAST TO HAVE MORE OF A ZONAL FLOW LATE IN THE PERIOD. 

WL KEEP TEMPS BELOW NORMAL THRU THE PERIOD AND HOLD OFF ON ANY 
PRECIP LATER IN THE PERIOD UNTIL MODELS START TO SHOW A BIT MORE
CONSISTENCY. 

&&

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

$$