000
FXUS63 KDVN 062330
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
530 PM CST FRI DEC 6 2013

.SYNOPSIS...
ISSUED AT 307 PM CST FRI DEC 6 2013

THE LATEST SFC ANALYSIS WAS INDICATING LARGE COLD CORE 1040+ MB
RIDGE DOMINATING MUCH OF THE MID CONUS/MIDWEST. 12Z UPPER AIR
ANALYSIS SHOWING SUBSTANTIAL POOL OF -20C OR COLDER AIR AT H85 MB
DUMPING DOWN MUCH OF THE NORTHERN PLAINS AND UPPER MS RVR VALLEY/
NORTHWESTERN GRT LKS. BUT THE SOUTHWARD SURGE IS STALLING AS IT
ENCOUNTERS STOUT SOUTHWESTERLIES/MID-UPPER JET STRUCTURE ALONG AND
SOUTH OF THE REGION...THUS BRUNT OF LLVL COLD POOL SHOULD GET SHUNTED
NORTH AND NORTHEAST OF THE DVN CWA THOUGH SAT. STILL H85 MB VALUES OF
-13C TO AS COLD AS -18C IN THE NORTH TO MAKE IT ACRS THE AREA THROUGH
TONIGHT. LARGE L/W UPPER TROF COMPLEX CONTINUED TO GET SHEARED OUT IN
ENE-TO-WSW FASHION ACRS THE NORTHWEST 2/3S OF THE CONUS AND MUCH OF
CANADA...WITH SUNDAY/S SNOW MAKER WAVE NOTED ON WATER VAPOR IMAGERY
ROLLING SOUTHWARD JUST OFF THE PACIFIC NORTHWEST COAST.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 307 PM CST FRI DEC 6 2013

TONIGHT...BULK OF 12Z RUN SHORT RANGE MODELS AND SREF OUTPUT IN GOOD
AGREEMENT OF SUGGESTING STRONG SFC RIDGE TO CONTINUE TO ESTABLISH-
IMPLANT ITSELF ACRS THE NW HIGH PLAINS AND DOWN INTO THE TN VALLEY
REGION TONIGHT. SOME LLVL PRESSURE GRADIENT MAINTAINING ACRS THE
AREA ENOUGH DURING THIS PROCESS TO KEEP SFC WINDS GOING OF 5-10 MPH
OVERNIGHT. LARGE MID AND UPPER LEVEL CLOUD SHIELD OFF THE SOUTHERN
PLAINS STORM SYSTEM SHOULD CONTINUE TO MOVE EASTWARD OUT OF THE
DVN CWA EARLY THIS EVENING...WITH JUST SOME SECONDARY MID AND HIGH
LEVEL CLOUD PATCHES STREAMING UP ACRS THE REGION FROM TIME TO TIME
OUT OF THE SOUTHWESTERN PLAINS INTO TONIGHT. BUT PERIODS OF MAINLY
CLEAR SKIES TOO...ALONG WITH ENOUGH SFC WIND DECREASE TO MAKE FOR A
VERY COLD NIGHT ESPECIALLY TAKING INTO ACCOUNT THE LACK OF SNOW COVER
LOCALLY. SUBZERO LOWS ACRS THE NORTHWESTERN THIRD OF THE FCST AREA...
TO THE LOW TO MID SINGLE DIGITS ABOVE ZERO IN THE SOUTHEAST. TEMPS
THIS COLD WHEN COMBINED WITH 5-10 MPH WINDS WILL STILL PRODUCE WIND
CHILLS OF -15 TO -18 DEGREES BELOW ZERO LATE TONIGHT AND BE MORE
WIDESPREAD ALONG AND WEST OF ALINE FROM IOWA CITY...TO EAST OF
ANAMOSA IA...AND TO NEAR GALENA IN JO DAVIESS CO IN NW IL. VALUES OF
-5 TO -15 F CAN BE EXPECTED EAST OF THOSE AREAS LATE TONIGHT INTO
MID SAT MORNING.

SATURDAY...AS RIDGE CENTER MIGRATES ALONG AND NORTH OF THE AREA OUT
OF THE NORTHERN PLAINS...FAIR WX BUT COLD DAY IN STORE FOR SAT. AS
STATED ABOVE...BITING WIND CHILLS NOT ALL THAT FAR OFF ADVISORY
LEVELS THROUGH MID MORNING FOR A GOOD CHUNK OF THE FCST AREA. AFTER A
VERY COLD START TO THE DAY...HIGH TEMP RECOVERY EXPECTED ONLY BACK
INTO THE MID TEENS TO NEAR 20 IN LIGHTER WIND REGIME DESPITE MOSTLY
SUNNY SKIES. SAYING MOSTLY SUNNY SKIES AS OPPOSED TO SUNNY AS STILL
EXPECT ROUNDS OF INSOLATION-FILTERING CIRRUS ALONG ACTIVE
SOUTHWESTERLY UPPER JET AXIS STREAKING ACRS THE CENTRAL PLAINS TO GRT
LKS. THU SOME AREAS MAY HAVE TROUBLE WARMING OUT OF THE LOWER TEENS.
HIGH CLOUDS TO THICKEN FROM THE WEST LATE IN THE DAY AS WELL AHEAD OF
THE INCOMING SNOW MAKING SYSTEM.    ..12..

.LONG TERM...(SATURDAY NIGHT THROUGH NEXT FRIDAY)
ISSUED AT 307 PM CST FRI DEC 6 2013

THERE CONTINUES TO BE RELATIVELY GOOD AGREEMENT AMONG THE
OPERATIONAL MODELS ON THE SNOW EVENT FOR THE REGION SUNDAY AND
SUNDAY NIGHT.  MODELS SHOW A S/W MOVING THROUGH NORTHERN MO AND
SOUTHERN IA LATE SUNDAY SUPPORTING SNOW OVER THE ENTIRE AREA WITH
THE HIGHER AMOUNTS OVER THE NORTHWEST THIRD OR NORTHWEST OF THE VORT
TRACK.  TIMING THE BEGINNING OF THE SNOW CONTINUES TO BE A CHALLENGE
WITH DRY LOW LEVELS AN WEAK MID LEVEL FORCING SUNDAY MORNING
SUGGESTING SNOW AMOUNTS MAY BE VERY LIGHT ESPECIALLY NEAR AND EAST
OF THE MISSISSIPPI RIVER.  MODEL TIME HEIGHT SECTIONS SHOW A FAIRLY
RAPID MOISTENING OF THE LOW LEVELS BY LATE MORNING OR EARLY
AFTERNOON AND BETTER FORCING FOR THE AFTERNOON AND EARLY EVENING
HOURS. MOST OF THE ACCUMULATIONS SHOULD OCCUR BY MID EVENING WITH
THE SNOW TAPERING OFF AFTER MIDNIGHT. GIVEN THE SPEED OF THE SYSTEM
AND LIMITED AVAILABLE MOISTURE THE QPF/SNOWFALL AMOUNTS WERE LOWERED
SOME FROM PREVIOUS FORECASTS WITH AMOUNTS RANGING FROM AROUND .15
NORTHWEST TO .05 SOUTHEAST.  SNOW TO LIQUID RATIOS SHOULD BE IN THE
15 TO 20 TO 1 RANGE SUPPORTING SNOWFALL AMOUNTS AROUND AN INCH SOUTH
TO JUST OVER 3 INCHES NORTHWEST.  THE WIND DURING AND JUST AFTER THE
EVENT SHOULD BE AROUND 10 KTS OR LESS SO BLOWING AND DRIFTING
THROUGH SUNDAY NIGHT SHOULD NOT BE A SIGNIFICANT ISSUE.

AFTER SUNDAYS SYSTEM EXITS THE AREA...TEMPERATURES WILL BE THE MAIN
CONCERN THROUGH THE REST OF THE FORECAST PERIOD.  BROAD UPPER
TROFFING REMAINING OVER THE CENTRAL U.S. THROUGH MOST OF NEXT WEEK
AND FRESH SNOW COVER WILL CONTINUE TO SUPPORT COLDER THAN NORMAL
TEMPERATURES OVER THE AREA.   A COUPLE OF WEAK SYSTEMS PROGGED
TO MOVE THROUGH REGION BY BOTH THE GFS AND ECM WILL ALSO HAVE A
SIGNIFICANT IMPACT ON TEMPERATURES DEPENDING ON HOW MUCH CLOUD COVER
IS ASSOCIATED WITH EACH FEATURE AND WHEN THEIR TRAILING HIGH
PRESSURE SYSTEMS MOVE OVER THE AREA.  FOR NOW HAVE STAYED CLOSE TO
THE BLENDED GUIDANCE TEMPERATURES WITH MINS IN THE SINGLE DIGITS AND
HIGHS IN THE TEENS AND 20S MONDAY THROUGH THURSDAY. IF THE TIMING OF
ONE OF THE SURFACE HIGHS WORKS OUT THAT IT/S OVER THE AREA OVERNIGHT
AND SKIES REMAIN CLEAR...THEN BELOW ZERO TEMPERATURES ARE POSSIBLE.

FOR FRIDAY THE MODELS ARE SUGGESTING THAT A DEEPENING SOUTHERN
STREAM TROF MOVING ACROSS THE SOUTHWESTERN U.S. WILL BACK THE FLOW
ENOUGH OVER THE MIDWEST TO DRAW SOME WARMER AIR NORTH...PUSHING
TEMPERATURES INTO THE 30S.  THE MODELS ARE ALSO SUGGESTING SOME
LIGHT PRECIPITATION PUSHING NORTH AHEAD OF THE TROF BUT FOCUS THE
PRECIP MAINLY EAST OF THE FORECAST AREA...SO KEPT FRIDAY DRY FOR
NOW.    DLF

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 526 PM CST FRI DEC 6 2013

NOT MUCH CHANGE IN THE AVIATION WEATHER FOR THE NEXT 24 HOURS
WITH CONTINUED NORTHWEST SURFACE WINDS AROUND 10 KTS AND VFR
CONDITIONS. OCCASIONAL VFR CIGS CAN BE EXPECTED OVERNIGHT.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...DLF
AVIATION...DMD