FXUS63 KILX 061752
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1252 PM CDT MON OCT 6 2008

.DISCUSSION...
ISSUED 1039 AM CDT MON OCT 6 2008

NO CHANGES NEEDED TO THE FORECAST LATE THIS MORNING. VISIBLE
SATELLITE INDICATED AN AREA OF WARM ADVECTION CLOUDS WITH SOME
CIRRUS WHICH WAS FILTERING THE SUNSHINE IN MANY AREAS OF CENTRAL
AND EASTERN ILLINOIS. HOWEVER...THIS CLOUDINESS IS EXPECTED TO
MOVE TO THE NORTHEAST THROUGH THE REGION BY EARLY AFTERNOON
RESULTING IN PLENTY OF SUNSHINE. A VEERING LOW LEVEL WIND FLOW
MORE FROM THE SOUTH WILL ALSO ALLOW TEMPS TO CLIMB INTO THE UPPER
70S AND LOWER 80S BY LATE AFTERNOON.

THE WATER VAPOR LOOP SHOWED THE UPPER TROF IN THE SOUTHERN PLAINS
PROGRESSING EAST-NORTHEAST TOWARD THE MID MS VALLEY. THIS WILL
RESULT IN INCREASING CLOUD COVER THIS EVENING...WITH RAIN
APPROACHING WEST CENTRAL IL TUESDAY MORNING.

&&

.AVIATION...
ISSUED 1251 PM CDT MON OCT 6 2008

THE LATEST WATER VAPOR SATELLITE LOOP INDICATED THAT UPPER LEVEL
RIDGING WHICH HAS RESULTED IN QUIET VFR CONDITIONS THE PAST FEW
DAYS WILL DEPART THE AREA. AN UPPER LEVEL TROF FROM THE SOUTHERN
PLAINS IS EXPECTED TO ROTATE NORTHEASTWARD TOWARD THE MIDWEST
REACHING WESTERN ILLINOIS LATE TUESDAY MORNING ACCORDING TO THE
DISTANCE SPEED TOOL. LOW AND MID LEVEL WARM ADVECTION AHEAD OF
THIS TROF WILL RESULT IN WIDESPREAD ALTOCUMULUS CLOUDS AROUND
7000 FT AFTER 06Z TONIGHT.

THE NAM AND GFS MODELS ARE IN FAIRLY GOOD AGREEMENT ON BRINGING
MVFR CONDITIONS AND SHOWERS INTO WEST CENTRAL IL...INCLUDING PIA
AND SPI. AS A RESULT...ADDED MVFR CIGS AND VSBYS WITH SHOWERS
TO THOSE TWO TAF SITES...BUT WILL LEAVE OUT OF THE REST AS THERE
IS UNCERTAINTY AS TO THE TIMING OF THE RAINFALL IN EASTERN IL.

MILLER

&&

.PREV DISCUSSION...
ISSUED 147 AM CDT MON OCT 6 2008

ONE MORE WARM AND DRY DAY IN STORE ACROSS CENTRAL ILLINOIS...BEFORE
A STORM SYSTEM SPREADS RAIN INTO THE AREA TUESDAY AND WEDNESDAY.

LATEST SURFACE ANALYSIS SHOWS LOW PRESSURE OVER THE DAKOTAS...WITH
WARM FRONT EXTENDING SOUTHEASTWARD ACROSS IOWA INTO CENTRAL
ILLINOIS. NOT MUCH IN THE WAY OF WEATHER ASSOCIATED WITH THE
BOUNDARY ACROSS THE KILX CWA...AS MOST OF THE CLOUD COVER AND
PRECIP HAS SHIFTED FURTHER NORTH INTO THE GREAT LAKES WITH THE
850MB FRONT. ALOFT...RIDGING PREVAILS OVER THE MIDWEST...WHILE
LARGE AMPLITUDE TROUGH SHIFTS EASTWARD THROUGH THE ROCKIES.

SHORT TERM...TODAY THROUGH WEDNESDAY

WEAK SURFACE WARM FRONT WILL LIFT NORTHWARD THIS MORNING...WITH
S/SE FLOW EXPECTED TO PROVIDE ANOTHER VERY WARM DAY ACROSS THE
AREA. WITH LOTS OF SUNSHINE AROUND...AFTERNOON HIGH TEMPS WILL BE
SIMILAR TO YESTERDAY...PERHAPS A DEGREE OR TWO WARMER DUE TO A
WARMER START TO THE DAY EARLY THIS MORNING. MOST LOCATIONS WILL
TOP THE 80 DEGREE MARK.

ROCKIES UPPER TROUGH WILL SLOWLY TRACK EASTWARD TONIGHT...SPREADING
CLOUDS AND RAIN INTO THE MISSISSIPPI RIVER VALLEY. MODELS IN GOOD
AGREEMENT WITH THE INITIAL TIMING OF THIS SYSTEM AND GENERALLY
KEEP ANY RAINFALL WEST OF THE CWA THROUGH 12Z TUESDAY. SINCE
PRECIP WILL BE ATTEMPTING TO TRACK EASTWARD INTO THE SURFACE/UPPER
RIDGING IN PLACE ACROSS THE AREA...THINK A SLOWER SOLUTION IS THE
WAY TO GO. WILL THEREFORE KEEP CONDITIONS DRY FOR TONIGHT.

AS TROUGH GETS CLOSER AND ATMOSPHERE SLOWLY MOISTENS...RAIN
CHANCES WILL BEGIN TO SPREAD ACROSS THE AREA FROM WEST TO EAST
ON TUESDAY. STILL SOME MINOR DISCREPANCIES AMONG THE MODELS AS TO
HOW FAST RAIN WILL MOVE IN...BUT CONSENSUS SUGGESTS PRECIP ACROSS
THE ENTIRE KILX CWA BY LATE TUESDAY AFTERNOON. WILL FEATURE ONLY
SLIGHT CHANCE POPS ALONG AND EAST OF I-57 DURING THE MORNING...WITH
CHANCE TO LIKELY POPS FURTHER WEST...THEN WILL GO WITH LIKELY POPS
ACROSS THE BOARD BY AFTERNOON. INSTABILITY PARAMETERS APPEAR TO BE
ON THE MEAGER SIDE...SO EXPECT MAINLY RAIN SHOWERS WITH MAYBE A
FEW EMBEDDED THUNDERSTORMS. WILL CARRY THUNDER DURING THE DAY
TUESDAY WHEN INSTABILITY WILL BE GREATEST...BUT WILL DROP THUNDER
MENTION AFTER THAT.

RAIN SHOWERS WILL CONTINUE TUESDAY NIGHT...BUT WILL THEN BEGIN TO
DECREASE ON WEDNESDAY. GFS CONTINUES TO CLOSE OFF AN UPPER LOW
OVER ILLINOIS ON WEDNESDAY...HOWEVER IT IS NOT NEARLY AS STRONG
WITH THIS FEATURE AS IN PREVIOUS RUNS...AND APPEARS TO BE TRENDING
TOWARD THE MORE OPEN STRUCTURE OF BOTH THE NAM-WRF/ECMWF. DESPITE
MODEL DIFFERENCES WITH THE HEIGHT FIELD...TIMING OF DEPARTURE IS
STILL ON TRACK FOR WEDNESDAY NIGHT...WITH ALL PRECIP EAST OF
ILLINOIS BY THURSDAY.

LONG TERM...THURSDAY THROUGH SUNDAY

DRY AND SEASONABLE CONDITIONS CAN BE EXPECTED ON THURSDAY AND
FRIDAY...BEFORE THE NEXT SYSTEM BEGINS TO IMPACT THE REGION OVER
THE WEEKEND. MEDIUM RANGE MODELS ARE IN POOR AGREEMENT WITH THE
EVOLVING UPPER PATTERN IN THE EXTENDED...AS THE NEXT UPPER TROUGH
DIGS ACROSS THE ROCKIES AND PLAINS STATES. ECMWF CONTINUES TO BE
THE SLOWEST WITH THIS PROCESS...ESSENTIALLY KEEPING UPPER FEATURE
AND ASSOCIATED FRONT WELL TO THE WEST UNTIL LATE SUNDAY.
MEANWHILE...GFS/CANADIAN ARE BOTH MUCH FASTER AND BRING A FRONT
ACROSS ILLINOIS LATE FRIDAY NIGHT INTO SATURDAY. BASED ON RATHER
POOR RUN-T0-RUN CONSISTENCY AND LACK OF MODEL CONSENSUS...HAVE
OPTED TO LEAVE THE FORECAST DRY THROUGH SUNDAY AT THIS TIME.

BARNES


&&

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

$$




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