Expires:No;;287902
FXUS63 KDVN 270910
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 AM CST FRI NOV 27 2009
.SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING ELONGATED RIDGE AXIS EXTENDING
ALONG AND WEST OF THE MS RVR VALLEY...WITH THIS FEATURE BISECTING
ONGOING GRT LKS CYCLONE AND DEVELOPING WARM FRONT ACRS THE CENTRAL
AND NORTHERN PLAINS. ALOFT...W/V IMAGERY WAS INDICATING A LARGE
PLUME OF MID AND UPPER LEVEL MOISTURE STREAMING IN FROM OFF THE
COAST OF CA AND THEN RIDGE RIDING ACRS CENTRAL CANADA BACK DOWN ACRS
THE UPPER MS RVR VALLEY.
&&
.SHORT TERM...TODAY AND TONIGHT...
WILL HAVE TO WALK OUT SOME LLVL STRATUS ACRS NORTHWEST IL IN
LINGERING CYCLONIC FLOW THIS MORNING...OTHERWISE LOW TO MID LEVEL
RIDGING WILL CONTINUE TO MIGRATE EASTWARD ACRS THE AREA TODAY.
INHERENT LIGHT FLOW AND WEAK MIXING REGIME UNDER THE RIDGE WILL
LIMIT DIURNAL REBOUND FROM COOL START TO THE DAY AND ONGOING TEMPS
GENERALLY LOOK IN LINE. SOME SOUTH TO SOUTHEAST RETURN FLOW WILL
ASSIST TEMPS IN THE FAR SOUTHWEST CLIMB AROUND 50 LATER THIS
AFTERNOON...OTHERWISE PLENTY OF MID TO UPPER 40S. SHORT RANGE
MODELS LOOK TOO BULLISH IN TRYING TO DEVELOP A WING OF MID LEVEL AC
TODAY ACRS THE REGION...BUT BOUTS OF CI SHOULD SPILL DOWN AROUND
THE NORTHERN PLAINS UPPER RIDGE AXIS ACRS THE AREA TO OCCASIONAL
FILTER THE INSOLATION. WILL STILL PAINT THE DAY AS MOSTLY SUNNY AS
OPPOSED TO PARTLY CLOUDY BANKING ON SOME DECAY IN THE INCOMING CI
SHIELD.
TONIGHT...EXPECT A QUICK DROP-OFF IN TEMPS THIS EVENING AS SFC WINDS
DECOUPLE SOME DIURNALLY BEFORE A BETTER SOUTHEASTERLY LLVL GRADIENT
EDGES ACRS THE AREA FROM THE WEST. EXPECT WIDESPREAD LOWER 30S WITH
SOME UPPER 20S IN THE LLVL COOL AIR DRAINAGE LOCATIONS/RVR VALLEYS
AND AGAIN ONGOING TEMPS HANDLING THE CURRENT THINKING AND WILL
CHANGE ONGOING TEMP GRIDS VERY LITTLE. SOME VALLEY FOG POSSIBLE
TOWARD SUNRISE SAT MORNING.     ..12..
.LONG TERM...SATURDAY THROUGH NEXT THURSDAY...
SATURDAY THE MAIN INTEREST IS THE COLD FRONT THAT DROPS SOUTHEAST
ACROSS THE AREA DURING THE AFTERNOON AND EVENING.  AHEAD OF THE
FRONT...WE WILL WARM UP QUITE NICELY...WITH WARM AIR ALOFT AND
DAYTIME MIXING TO BRING IT DOWN.  HOWEVER...WE WILL NOT MIX VERY
DEEPLY...AND DO NOT EXPECT GREATER THAN 925-950MB DEPTH.  THIS
SHOULD BRING THE SOUTH UP INTO THE UPPER 50S...AND TO AROUND 50
ACROSS THE NORTH.  THIS IS BECAUSE THERE IS A VERY LARGE GRADIENT
FROM NORTH TO SOUTH IN THE 925MB TEMPERATURES.  AS IT DROPS THROUGH
THE AREA ON SATURDAY...THERE IS NOT ENOUGH MOISTURE AVAILABLE TO
GENERATE ANY PRECIPITATION WITH THE FRONT SATURDAY OR SATURDAY
NIGHT.  HOWEVER...THE FRONT DOES USHER IN COLDER AIR...AND
TEMPERATURES SATURDAY NIGHT SHOULD DROP DOWN INTO THE 30S.  AN UPPER
LEVEL SHORTWAVE MOVING OUT OF THE ROCKIES WILL INTERACT WITH OUR
COLD FRONT SUNDAY AND SUNDAY NIGHT...AND AS IT WILL HAVE DRAWN
ADDITIONAL MOISTURE UP FROM THE GULF...AND THERE WILL BE SOME
DYNAMICS...EXPECT PRECIPITATION TO DEVELOP ALONG AND NORTH OF THE
BOUNDARY SUNDAY AND SUNDAY NIGHT...AND PERHAPS AFFECT THE
SOUTHEASTERN PORTIONS OF THE FORECAST AREA BEFORE THE ENTIRE SYSTEM
MOVES TOO FAR SOUTHEAST.  FOR NOW HAVE CONTINUED THE SLIGHT CHANCE
POPS WE HAD GOING...THOUGH I DID SHIFT THEM SLIGHTLY SOUTH AND
REDUCE THEM AS IT APPEARS WE WILL ONLY BE ON THE NORTHERN FRINGES OF
THE PRECIPITATION BAND.  HAVE BROUGHT IN MUCH COLDER TEMPERATURES
SUNDAY AND SUNDAY NIGHT...AND IF THE PRECIPITATION IS STILL ONGOING
OVER THE AREA BY EARLY MONDAY MORNING...THERE IS THE POSSIBILITY IT
MAY BRIEFLY MIX WITH SNOW.  THIS IS SOMEWHAT UNLIKELY...BUT HAVE
INCLUDED IT IN THE FORECAST FOR NOW.  WE CLEAR OUT BEHIND THAT
SYSTEM FOR MONDAY AND MONDAY NIGHT...FOR RATHER CHILLY TEMPERATURES
MONDAY WITH MAX TEMPS ONLY IN THE LOW TO MID 40S...AND MIN TEMPS
MONDAY NIGHT IN THE 20S.  TUESDAY ON OUT THERE IS SOME SIGNIFICANT
UNCERTAINTY AS ANOTHER SHORTWAVE MOVES THROUGH THE NORTHERN STREAM
AND DRAGS A COLD FRONT THROUGH THE AREA ON TUESDAY.  THE SOUTHERN
STREAM IS MORE ACTIVE AND CARRIES MORE MOISTURE...AND ON TUESDAY A
CUT OFF UPPER LOW WILL BE CROSSING TEXAS WITH PRECIPITATION ACROSS
MUCH OF THE WESTERN GULF COAST.  HOW MUCH THESE TWO WAVES IN THE
CURRENTLY SEPARATE SOUTHERN AND NORTHERN STREAMS WILL INTERACT COULD
MAKE SOME SIGNIFICANT DIFFERENCES IN THE FORECAST FOR TUESDAY ON
OUT...AND HAVE LEFT ALONE FOR NOW UNTIL MODELS CAN COME INTO BETTER
AGREEMENT ON THESE PERIODS.       ..LE..
&&
.AVIATION...
GENERALLY A VFR TAF PERIOD WITH JUST VARYING BOUTS OF CI AND SOME AC
ACRS THE TERMINALS TODAY. A LIGHT SFC WIND REGIME WILL BE REPLACED BY
SOUTH TO SOUTHEAST FLOW FROM 130 TO 160 DEGREES LATER THIS AFTERNOON
AND TONIGHT. THE ONLY FLY IN THE OINTMENT TO VFR CONDITIONS WILL
BE SOME POSSIBLE MVFR FOG OF 3-5SM THIS MORNING AND THEN AGAIN LATE
TONIGHT WITH ALL TERMINALS AT RISK.    ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
12/LE