FXUS63 KDVN 272007
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
205 PM CST FRI NOV 27 2009

.SYNOPSIS...
ANALYSIS SHOWS UPPER MIDWEST IN MODERATE NORTHWEST FLOW WITH SURFACE
AND UPPER AIR RIDGING WITH FAIR SKIES AND LIGHT WINDS.  SURFACE HIGH
RIDGE OVER AREA MOVING EAST TO ALLOW WITH MODEST PRESSURE FALLS
FOR LIGHT SE TO S WINDS TONIGHT.  UPSTREAM JET WELL TO OUR NORTHWEST
INDICATING NO FORCING NEAR TERM DESPITE WEAK FRONT TO ARRIVE LATE
SATURDAY WITH GULF CUT OFF FROM MOISTURE...KEEPING CONDITIONS DRY.

&&

.SHORT TERM...TONIGHT AND SATURDAY...
TONIGHT...WILL USE A COMBINATION OF PERSISTENCE LAST NIGHT AND LIGHT
CONVERGENT SE/S WINDS OF 2 TO 5 MPH TO ALLOW FOR PATCHY FOG TO
DEVELOP LATER TONIGHT UNDER A FAIR SKY.  LOCAL TOOLS AND STUDIES
SUPPORT MINS TO BE QUITE VARIED DUE TO STRENGTH OF DECOUPLING AHEAD
OF WEAK WARM FRONT.  SOME MINS TONIGHT...ESPECIALLY NE 1/2 AREA MAY
NEED LOWERING A FEW MORE DEGREES.  WENT MINS NEARLY STEADY AFTER 06
TO 08Z AS WAA SLOWLY INCREASES AHEAD OF APPROACHING WEAK COOL FRONT.

SATURDAY...ANOTHER QUIET AND SEASONABLY MILD WITH SOME PRE-FRONTAL
HEATING SUPPORTING FROM LOTS OF SUNSHINE AND DOWN SLOPE SW WINDS OF 5
TO 10+ MPH FOR HIGHS TO REACH 60F SOUTH AND LOWER 50S NORTH DUE TO
FRONT ARRIVING THERE EARLIER.  IF FRONT IS SLOWER...HIGHS MAY NEED TO
BE BUMPED UP 2 TO 5 DEGREES.  NO MOISTURE AND MID/UPPER LEVEL FORCING
NOTED FOR ANY PRECIPITATION WITH THIS WEAK FRONT.   ..NICHOLS..

.LONG TERM...SATURDAY NIGHT THROUGH NEXT FRIDAY...
A COLD FRONT WILL MOVE THROUGH SATURDAY NIGHT AND SUNDAY MORNING IN
ADVANCE OF AN UPPER TROF MOVING FROM THE NRN PLAINS INTO THE
MID/UPPER MS VALLEY.  MODEL PROGS SHOW SOME WEAK FORCING ASSOCIATED
WITH THE MID LEVEL TROF BUT MOISTURE IN THE LOW LEVELS IS LACKING
AND IT APPEARS THE FRONT WILL PASS THROUGH THE AREA DRY. LOW POPS
WERE MAINTAINED IN THE FAR SE FOR SUNDAY WHEN IT LOOKS LIKE THE
FRONT STARTS TO ENTRAIN BETTER MOISTURE AND MODEL PROGS PLACE
THE BACK EDGE OF THE LIGHT PCPN OVER OR CLOSE TO THE SERN MOST
COUNTIES. BY SUNDAY NIGHT THE DRY NWLY LOW LEVEL FLOW IS ESTABLISHED
AND HAVE REMOVED POPS FROM THE SE CWA.

THE GFS/ECMWF ARE IN REASONABLE AGREEMENT EARLY IN THE WEEK MOVING
THE NRN STREAM TROF EAST...LEAVING A CUTOFF LOW OVER NRN MEX.  DRY
WEATHER IS EXPECTED MONDAY AND TUESDAY AS WEAK SURFACE RIDGING MOVES
THROUGH THE REGION. THE DRY WEATHER SHOULD CONTINUE INTO WEDNESDAY
AS LOW LEVEL FLOW TURNS SOUTHERLY AHEAD OF ANOTHER SYSTEM MOVING
THROUGH THE NRN PLAINS.    TEMPERATURES WILL BE JUST ABOVE NORMAL
EARLY TO MID WEEK STARTING OFF IN THE 20S AND LOW 30S FOR LOWS AND
UPPER 30S TO MID 40S FOR HIGHS MONDAY...THEN MODERATING INTO THE 30S
FOR LOWS AND HIGHS IN THE 40S TO AROUND 50 TUESDAY AND WEDNESDAY.

THE GFS/ECMWF ARE IN BETTER AGREEMENT WITH THE SWRN U.S. LOW GETTING
PICKED UP AHEAD OF A NRN STREAM S/W AND MOVING ENE ACROSS THE SRN
U.S.  BOTH MODELS ARE IN GOOD AGREEMENT THAT THIS SYSTEM WILL STAY
WELL SOUTH AND EAST OF THE MID MS VALLEY.  THE MODELS ARE CONTINUING
TO SHOW DIFFERING SOLUTIONS WITH RESPECT TO THE NORTHERN STREAM WAVE
AND IF/WHEN IT PHASES WITH THE SRN STREAM.  THE GFS REMAINS THE MOST
PROGRESSIVE OF THE TWO MODELS AND MOVES THE SYSTEM INTO THE ERN U.S.
BEFORE PHASING WITH THE SRN STREAM FRIDAY.  THE ECMWF CONTINUES TO
PHASE THE TWO STREAMS OVER THE PLAINS...DEVELOPING A LARGE CLOSED
LOW OVER THE UPPER MS VALLEY AND WESTERN GREAT LAKES THURSDAY AND
FRIDAY.

THE ECMWF HAS BEEN FAIRLY CONSISTENT WITH THIS SOLUTION AND WILL
CONTINUE TO USE IT AS A BASIS FOR LATE NEXT WEEK.  THIS SHOULD
RESULT IN MUCH COLDER AIR POURING INTO THE REGION AS WELL AS SOME
SNOW SHOWERS.  HAVE KEPT SOME LOW CHANCE POPS IN THE FORECAST FOR
WEDNESDAY NIGHT AND THURSDAY TO COVER THIS POTENTIAL.  TEMPS ARE
GENERALLY IN THE 20S FOR LOWS AND 30S FOR HIGHS.  THIS COULD BE ON
THE WARM SIDE IF THE ECMWF VERIFIES. ...DLF...

&&

.AVIATION...
FAIR SKIES AND VFR CONDITIONS ALL TERMINALS THROUGH 06Z.  BETWEEN
08Z AND 15Z...PATCHY FOG TO DEVELOP WITH VSBYS 1-3 MILES THAT COULD
PRODUCE INTERVALS OF MVFR CONDITIONS.  AFTER 15Z...FOG TO DISSIPATE
WITH VSBYS AOA 7 MILES...CONTINUED FAIR SKIES WITH ONLY SOME CIRRUS
THROUGH FORECAST PERIOD.  ..NICHOLS..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

NICHOLS/DLF