000
FXUS63 KDVN 132001
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CDT MON OCT 13 2008
.SYNOPSIS...
AT 19Z STRONG COLD FRONT EXTENDED FROM WESTERN WI SOUTHWEST THROUGH
CENTRAL IOWA AND NORTHWEST MO INTO EASTERN KS. AHEAD OF THE FRONT
TEMPS WERE IN THE MID AND UPPER 70S OVER MID MISSISSIPPI VALLEY WITH
40S AND 50S COMMON ON THE COLD SIDE IN WRN IA. MOST OF THE PCPN WAS
OCCURRING POST FRONTAL WITH MAINLY LIGHT TO MODERATE SHRA FROM NW MO
THRU NORTH CENTRAL IA. A FEW SPRINKLES HAD DEVELOPED IN THE WARM
SECTOR ALONG AND EAST OF THE MISSISSIPPI RIVER.
&&
.SHORT TERM...TONIGHT AND TUESDAY...
MODELS ARE IN GOOD AGREEMENT MOVING COLD FRONT THROUGH THE CWFA
OVERNIGHT THEN STALLING IT TO OUR SOUTH TUESDAY AS ANOTHER WAVE
BEGINS TO LIFT NE ALONG THE BOUNDARY. WILL MOVE BAND OF SHRA
THROUGH CWFA FROM NW TO SE TONIGHT WITH PCPN ENDING OVER THE NW LATE
THIS EVENING AND OVERNIGHT. HAVE HELD ONTO SOME POPS IN THE SOUTH
TUESDAY WITH SOME UNCERTAINTY AS TO HOW FAR SOUTH THE FRONT WILL BE
ABLE TO GET BEFORE STALLING AND WITH THE POSSIBILITY OF PCPN
ASSOCIATED WITH SURFACE WAVE MAKING INTO THE SRN CWA BY LATE
AFTERNOON. WENT WITH CATEGORICAL POPS NW THIS EVENING WHEN FORCING
WILL BE THE STRONGEST THAN BACKED OFF TO LIKELY/S OR HIGH CHANCE
POPS AS FORCING DECREASES SOME LATE TONIGHT. LOOKS LIKE BACK EDGE OF
CLOUDS OVER NORTHWEST IA AND NE IS MAKING GOOD PROGRESS EAST AND
EXPECT SOME CLEARING TO MAKE IT INTO THE NW CWA OVERNIGHT. WENT
WITH MID 40S NW TONIGHT FOR MINS BUT THIS WILL DEPEND ON HOW SOON
THE CLEARING SPREADS IN LATE TONIGHT. IF SKIES CLEAR EARLIER THAN
EXPECTED THEN UPPER 30S ARE NOT OUT OF THE QUESTION. BUMPED UP
HIGHS INTO THE LOW 60S MOST AREAS FOR TUESDAY WITH PCPN EXPECTED TO
BE OUT OF MOST OF THE CWFA AND POTENTIAL FOR SOME SUN AT LEAST EARLY
IN THE DAY. ...DLF...
.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...
MAIN FOCUS IS ON MID WEEK RAIN CHANCES...THEN NW FLOW PREVAILS INTO
WEEKEND WITH WEAKER CLIPPER SYSTEMS BRINGING RAIN CHANCES FRI AND
AGAIN SUN NIGHT INTO MONDAY. UPPER SHORTWAVE LIFTING NORTHEAST OUT
OF DESERT SW TO INTERACT WITH STALLED FRONT TO THE SOUTH AND H8
BAROCLINIC AXIS OVER THE CWA ON WED TO PRODUCE WIDESPREAD MODERATE
RAINFALL AMOUNTS. LATEST MODEL RUNS HAVE COME INTO BETTER AGREEMENT
WITH EARLIER SLOWER ECMWF AND GFS TRACK AND TIMING OF THE SURFACE
LOW AND MID LEVEL FORCING. WILL STAY CLOSE TO THE NOW BETTER
SUPPORTED ECMWF/GFS BLEND WITH SURFACE LOW TRACKING ALONG FAVORABLE
AXIS ACROSS MO THROUGH CENTRAL IL INTO NRN IN ON WED.
MODERATE TO STRONG MID LEVEL LIFT WILL BE PROVIDED BY THE H5 VORT
LIFTING THROUGH CENTRAL IA TO SOUTHERN WI ON WED...WITH ADDITIONAL
UPPER LEVEL SUPPORT FROM STRONG DIVERGENCE ASSOCIATED WITH ENTRANCE
REGION TO H3 JET MOVING ACROSS UPPER GREAT LAKES. ONSET OF RAIN WILL
LIKELY OCCUR LATE TUE NIGHT IN THE SW AS ISENTROPIC LIFT COMMENCES
WITH THE LOW LEVEL CIRCULATION THAT WILL FEEDS AN UNSEASONABLY MOIST
LOW TO MID LEVEL AIRMASS BACK NORTHWARD INTO THE CWA. WILL KEEP HIGH
CHANCE POPS GOING TUE NIGHT OVER ESPECIALLY THE SW...THEN RAISED TO
LIKELY CATEGORY OVER ALL BUT FAR NORTH ON WED DURING PERIOD OF BEST
LIFT. HAVE ALSO RAISED QPF VALUES WED CLOSE TO HPC AMOUNTS WITH
WIDESPREAD 1/2 INCH PLUS ON WED. WILL LIKELY SEE A BROAD SWATH OF
HALF TO 1 INCH AMOUNTS ALONG I-80 CORRIDOR AS INDICATED BY 12Z
ECMWF...AND LIKELY NEED TO RAISE THESE AMOUNTS IN THE FORECAST AS
THIS PERIOD NEARS. ADDED POTENTIAL FOR THUNDERSTORMS IN FAR SOUTH
WED...WHERE GFS FORECAST SOUNDINGS SUGGEST POTENTIAL FOR SOME
ELEVATED INSTABILITY BEFORE ENTIRE COLUMN SATURATES. CLOUDS AND
PRECIP WILL LIMIT THE DIURNAL TEMPERATURE SWINGS AND KEPT ON WARM
SIDE OF GUIDANCE FOR TUE NIGHT AND BELOW GUIDANCE ON WED...WITH MUCH
OF THE AREA STRUGGLING TO GET OUT OF THE 50S. WITH SLOWER
TIMING...EXTENDED RAIN CHANCES INTO EARLY WED EVENING OVER MAINLY
THE EAST.
HIGH PRESSURE FOLLOWS LATE WED NIGHT THROUGH THU FOR RETURN TO MORE
TYPICAL OCT TEMPS. CLIPPER SYSTEM IN NW FLOW BRINGS RAIN CHANCES
LATE THU NIGHT INTO FRI. WILL KEEP CHANCES LOW FOR NOW AND LEAVE
ROOM FOR LATER FORECASTS TO ADJUST UPWARDS AS CONFIDENCE INCREASES.
ANOTHER WEAK FRONT INDICATED FOR EITHER LATE SUN OR MON AND HAVE
SLIGHT TO LOW CHANCE POPS WITH TEMPERATURES NEAR CLIMO.
..SHEETS..
&&
.AVIATION...
STRONG COLD FRONT WILL MOVE THROUGH THE REGION LATE THIS AFTERNOON
AND THIS EVENING. BAND SHRA ALONG WITH MVFR AND SOME IFR CIGS/VSBYS
BEHIND THE FRONT WILL MOVE THROUGH ALL TAF SITES OVER NIGHT.
CONDITIONS EXPECTED TO RETURN TO VFR AT KCID/KDBQ BETWEEN 08Z AND
10Z AND AT KMLI/BRL BETWEEN 10Z AND 15Z. ...DLF...
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
DLF/SHEETS
