FXUS63 KDVN 150918
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
318 AM CST TUE DEC 15 2009
.SYNOPSIS...
AN ELONGATED RIDGE OF HIGH PRESSURE WAS CENTERED FRM WRN ND SE
THROUGH ERN NE EARLY THIS MORNING. AT 00Z AT BROAD MID LEVEL TROF
WAS CENTERED OVER THE NATIONS MIDSECTION WHILE UPSTREAM A RIDGE
WAS IN PLACE ALONG THE WEST COAST. STRATUS WAS STILL HANGING ON
OVER NW IL AND ADJACENT AREAS OF THE EASTERN IA...BUT SHOULD BE
CLEARING THE CWFA BY 12Z.
&&
.SHORT TERM...TODAY AND TONIGHT...
THE SURFACE HIGH WILL MOVE EAST TODAY AND SHOULD BE CENTERED NEAR
THE MS RIVER BY 12Z WEDNESDAY. CONT CAA EAST OF THE HIGH TODAY WILL
KEEP TEMPERATURES IN CHECK OVER THE AREA DESPITE FULL SUN. CURRENT
FCST HIGHS IN THE SINGLE DIGITS TO AROUND 10 ABOVE OVER THE DEEPER
SNOW-PACK IN THE NRN CWA LOOK REASONABLE AND AGREED WELL WITH
LIMITED MIXING HEIGHT. ALLOWED FOR MORE INFLUENCE FROM THE SUN AND
DEEPER MIXING IN THE SOUTH AND EAST WHERE THE SNOW COVER SHOULD BE
GONE AFTER MONDAYS MELTING. WILL CONTINUE THE WIND CHILL ADVISORY
THIS MORNING. TEMPS/WINDS SHOULD PRODUCE WIND CHILLS CLOSE TO -20
FOR A FEW HOURS AROUND AND AFTER SUNRISE.
TONIGHT MAINLY CLEAR SKIES AND LIGHT WINDS WILL ALLOW TEMPS TO DROP
BELOW MOS GUIDANCE IN MOST AREAS. CURRENT DEWPOINTS IN THE CENTER
OF THE RIDGE OVER ERN NE ARE NEAR -10F SO USED THIS AS A BASIS FOR
MIN TEMPS AND ADJUSTED DOWN SOME IN THE RIVER VALLEYS OVER THE NRN
HALF OF THE CWFA. ..DLF..
.LONG TERM...WEDNESDAY THROUGH MONDAY...
TEMPERATURES ARE THE MAIN FOCUS WITH BRIEF PERIOD OF NEAR ZONAL MID
LEVEL FLOW ALLOWING MODERATION EARLY...THEN RETURN TO COLD BY THE
WEEKEND WITH DEVELOPING UPPER TROUGH.
SURFACE RIDGE AXIS SHIFTS EAST OF THE AREA WED ALLOWING WEAK SHALLOW
LOW LEVEL SOUTHERLY RETURN FLOW. STRONG WARM ADVECTION IN THE PERIOD
OF MORE ZONAL FLOW AT H8 DEVELOPS...BUT THIS WILL NOT BE REALIZED AT
THE SURFACE. BITTER COLD START TO THE DAY...ALONG WITH SNOW COVER
AND LIMITED INSOLATION DUE TO LOW SUN ANGLE AND POTENTIAL CI...WILL
LIMIT MIXING DEPTH TO WELL BELOW 925 MB. HAVE HELD HIGHS NEAR TO
BELOW COLDER GUIDANCE...KEEPING RANGE FROM MID TEENS NORTH TO LOWER
20S CENTRAL...WHILE THE NEARLY SNOW FREE AREAS IN THE FAR SOUTH MAY
APPROACH 30.
00Z MODELS INDICATE A WEAK SURFACE WAVE PASSING TO THE SOUTH LATE
WED NIGHT INTO THU INDUCING A MORE EASTERLY LOW LEVEL FLOW. WITH
LITTLE CHANCE FOR MUCH AIRMASS MODERATION...WILL CONTINUE TO KEEP
TEMPERATURES NEAR OR BELOW COLDEST GUIDANCE WITH SINGLE DIGITS TO
TEENS FOR MINS AND HIGHS THU AND FRI IN THE 20S CENTRAL AND
NORTH...TO MID 30S FAR SOUTH.
ON FRI...UPPER RIDGE DEVELOPS OUT WEST...WHILE LONGWAVE TROUGH
EXTENDING W-SW FROM EASTERN CANADIAN UPPER VORTEX DIVES S-SW INTO
THE UPPER MS VALLEY/GREAT LAKES. THIS PULLS DOWN A REINFORCING SHOT
OF COLD ARCTIC AIR FOR THE WEEKEND INTO EARLY NEXT WEEK AND WILL
KEEP TEMPERATURES WELL BELOW NORMAL SAT THROUGH MON. MODELS HAVE
BEEN ADVERTISING A MID LEVEL SHORTWAVE AND WEAK SURFACE REFLECTION
PASSING SOUTH OF THE AREA FRI INTO FRI NIGHT UNDER DEVELOPING
LONGWAVE TROUGH. LATEST GFS...NAM...GEM AND ECMWF DEPICT ONLY A WEAK
INVERTED TROUGH EXTENDING NORTH FROM A SURFACE LOW TRACKING ACROSS
SOUTHERN MO OR NRN AR CLOSER TO THE TRACK OF THE UPPER VORT. THE
ECMWF IS ALONE IN DEPICTING PRECIPITATION AS FAR NORTH AS THE LOCAL
CWFA. WITH DECENT MODEL AGREEMENT AND LITTLE MOISTURE TO WORK
WITH...HAVE LIMITED POPS TO SLIGHT CHANCE FOR MEASURABLE LIGHT SNOW
FRI AND SAT. GREATEST POTENTIAL FOR MEASURABLE STILL LOOKS TO BE IN
THE FAR SOUTH...WITH FLURRIES ELSEWHERE.
..SHEETS..
&&
.AVIATION...
MVFR CIGS ALONG AND EAST OF THE MS EARLY THIS MORNING WILL BE EAST
OF ALL TAF SITES BY 12Z. OTHERWISE EXPECTED VFR CONDITIONS THROUGH
THE PERIOD. NW WINDS 10-15KTS THIS MORNING WILL BECOME LIGHT AND
VARIABLE THIS EVENING. ..DLF..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WIND CHILL ADVISORY UNTIL 11 AM CST THIS MORNING FOR BENTON-
BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-IOWA-JACKSON-
JOHNSON-JONES-LINN.
IL...NONE.
MO...NONE.
&&
$$
DLF/DLS
