Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 170531
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1131 PM CST TUE DEC 16 2014

.UPDATE...
ISSUED AT 1131 PM CST TUE DEC 16 2014

CLOUDS...AND CLOSELY RELATED TEMPERATURE FORECAST REMAINS A
CHALLENGE LATE THIS EVENING. A LOOP OF SATELLITE FOG CHANNEL SHOWS
THE BACK EDGE OF THE EXTENSIVE STRATUS DECK ROUGHLY EAST OF THE
I-35 CORRIDOR WITH A GRADUAL CLEARING TREND SUGGESTED INCHING
SOUTHEAST OUT OF NW IA AND SW MN...IN A SUBSIDENCE REGION SOUTH OF
THE SHEARING UPPER LOW ADVANCING SE ACROSS NW WI. SHORT TERM
MODELS HAVE A POOR HANDLE ON LOW LEVEL MOISTURE AND CLOUD
TRENDS...OVERALL BEING TOO FAST OR OPTIMISTIC WITH THE CLEARING
TREND SO FAR. HOWEVER...AS THE LOW LEVEL FLOW TRENDS FROM WEAKLY
ANTICYCLONIC TO NEARLY NEUTRAL AS THE PLAINS RIDGE PUSHES
EAST...TAKING INTO ACCOUNT THE DEVELOPING MID LEVEL
CONFLUENCE/SUBSIDENCE...THERE IS GOOD SUPPORT FOR LEAST PARTIAL
CLEARING OVER THE NEXT 6 TO POSSIBLY 12 HOURS.

WILL THUS KEEP AN OVERALL MOSTLY CLOUDY FORECAST GOING FOR THE
REST OF THE NIGHT WITH AT LEAST PARTLY SUNNY CONDITIONS FOR
WEDNESDAY. BETTER SUPPORT FOR CLEARING OF THE LOW CLOUDS WILL
ARRIVE WED MORNING...JUST IN TIME FOR HIGH CLOUDS TO MOVE IN AHEAD
OF THE SYSTEM MOVING INTO THE SW U.S.  BASED ON HOURLY TRENDS SO
FAR TONIGHT HAVE ADJUSTED TONIGHT/S LOWS TO THE MID TEENS NW WITH
UPPER TEENS TO LOWER 20S ELSEWHERE.

&&

.SYNOPSIS...
ISSUED AT 246 PM CST TUE DEC 16 2014

12Z UA ANALYSIS HAS AN EXTRATROPICAL CYCLONE OVER THE GREAT LAKES
WITH AN UPPER LEVEL RIDGE OVER THE ROCKIES. SATELLITE TRENDS
THROUGH MID AFTERNOON SHOW A HOLE IN THE CLOUDS ACROSS WESTERN
IOWA THAT HAS BEEN SLOWLY FILLING AS IT MOVES SOUTHEAST.

18Z SFC ANALYSIS HAS THE OCCLUDED LOWS OVER LOWER MICHIGAN WITH A
SECONDARY FRONT RUNNING FROM THE STRAITS OF MACKINAC INTO SOUTHWEST
ARKANSAS. SEVERAL SUBTLE TROFS WERE BEHIND THE COLD FRONT FROM
ILLINOIS INTO MINNESOTA. DEW POINTS WERE IN THE TEENS AND 20S ACROSS
THE PLAINS WITH 30S AND 30S FROM THE GREAT LAKES INTO THE LOWER
MISSISSIPPI VALLEY.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 246 PM CST TUE DEC 16 2014

A ROUND OF FLURRIES AND ISOLATED LIGHT SNOW SHOWERS ARE ASSOCIATED
WITH THE TROF MOVING THROUGH SOUTHEAST MINNESOTA INTO NORTHERN IOWA.
THESE FLURRIES SHOULD PERSIST THROUGH LATE AFTERNOON AS FORCING FROM
THE UPPER LEVEL DISTURBANCE MOVES FROM MINNESOTA INTO SOUTHERN
WISCONSIN.

ANY LINGERING FLURRIES WILL QUICKLY END THIS EVENING LEAVING QUIET
CONDITIONS THROUGH SUNRISE WEDNESDAY.

THE NEXT QUESTION IS WHEN IF ANY CLEARING TAKES PLACE. BASED ON
SATELLITE TRENDS...SOME CLEARING SHOULD BEGIN LATE THIS AFTERNOON
ACROSS THE SOUTHWEST THIRD OF THE AREA. EXTRAPOLATION OF SAID
CLEARING WOULD SUPPORT THE SOUTH HALF SEEING SOME CLEARING OVERNIGHT
IN THE WAKE OF THE PASSING DISTURBANCE.

QUIET AND DRY CONDITIONS WILL BE SEEN ACROSS THE AREA ON WEDNESDAY
AS HIGH PRESSURE SLOWLY MOVES THROUGH THE MIDWEST. SOME ADDITIONAL
CLEARING SHOULD TAKE PLACE ACROSS THE AREA DURING THE DAY.
TEMPERATURES SHOULD AVERAGE SLIGHTLY BELOW NORMAL.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 246 PM CST TUE DEC 16 2014

MAIN FORECAST PROBLEM FOR THE MEDIUM RANGE IS THE SYSTEM THAT WILL
AFFECT SOUTHERN ZONES WEDNESDAY NIGHT INTO THURSDAY.  THIS SYSTEM
LOOKS TO BRING A QUICK SHOT OF SNOW TO THE SOUTHERN MOST EXTENT OF
OUR CWA.  AFTER THIS SYSTEM MOVES THROUGH OUR AREA...THE MAIN
FORECAST PROBLEM TURNS TO THE END OF THE EXTENDED AND THE CHANCE FOR
A SYSTEM COMING THROUGH EARLY NEXT WEEK.

A SHORTWAVE TROUGH IS FORECAST TO ADVECT INTO THE AREA WEDNESDAY
NIGHT AND INTO THURSDAY.  MODELS DEPICT THAT DRY AIR WILL BE IN
PLACE ACROSS THE AREA.  THIS DRY AIR SHOWS UP EVEN CLEARER WHEN YOU
WATCH THE TREND OF THE QPF AS THE SYSTEM APPROACHES THE AREA.
ACROSS CENTRAL MO...QPF IS ROBUST AND THEN WEAKENS AS IT ENCOUNTERS
THE DRIER AIR.  MODELS ARE IN AGREEMENT THAT THE QPF WILL BE
SLACKENING AS IT APPROACHES...THIS MAKES FOR A DIFFICULT FORECAST.
WILL THE DRY AIR HOLD OFF THE PRECIP AND IF IT DOES WHERE WILL IT
STOP.  CURRENT THINKING IS THAT THE SOUTHERN MOST ZONES WILL SEE -SN
FROM THIS EVENT WILL ACCUMULATIONS WELL UNDER HALF AN INCH AND MORE
LIKELY ONLY A TRACE ACROSS OUR MO COUNTIES.  THIS SYSTEM WILL LIKELY
BE ONE OF THESE EVENTS WHERE THE SPECIFICS WONT BE KNOWN UNTIL THE
PRECIP APPROACHES THE AREA FROM THE SOUTH.

THROUGH THE WEEKEND...ANOTHER SYSTEM MOVES TO THE SOUTH OF AREA
THROUGH THE CENTRAL AND SOUTHERN MISSISSIPPI RIVER VALLEY.  THE
MODELS ARE IN GOOD AGREEMENT THAT THIS SYSTEM WILL REMAIN SOUTH OF
THE CWA AND SHOULD NOT HAVE ANY AFFECT ON PRECIPITATION ACROSS OUR
AREA.  HOWEVER...THIS SYSTEM IS STILL OVER THE PACIFIC...SO IT HAS
NOT BEEN MEASURED WELL BY OUR RAOB NETWORK.  THE NEXT COUPLE OF RUNS
SHOULD GIVE US A DECENT HANDLE ON IF THE SYSTEM WILL SHIFT NORTH OR
SOUTH THIS WEEKEND.

EARLY NEXT WEEK APPEARS TO BE OUR NEXT DECENT CHANCE FOR
PRECIPITATION.  MODELS ARE IN AGREEMENT THAT THERE WILL BE A TROUGH
AND RESULTANT SURFACE LOW ACROSS THE CENTRAL UNITED STATES.  THIS SYSTEM
WILL LEAD TO PRECIPITATION ACROSS THE AREA DURING THE EARLY PART OF
THIS WEEK.  CURRENT THERMAL PROFILES SUGGEST A RASN MIX ACROSS
CENTRAL PORTIONS OF THE CWA AND RAIN ACROSS SOUTHERN PORTIONS OF THE CWA
ALONG WITH SOME SNOW ACROSS THE NORTHERN CWA.  IT IS IMPERATIVE TO
UNDERSTAND THAT THE SPECIFICS OF THIS SYSTEM HAVE A LOW
FORECASTABILITY AT THIS TIME.  THERE MOST LIKELY WILL BE A WEATHER
SYSTEM WITH SENSIBLE WEATHER IMPACTS ACROSS OUR AREA.  ANY MORE
SPECIFIC INFORMATION COULD SUBJECT TO DRAMATIC CHANGES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1131 PM CST TUE DEC 16 2014

LINGERING LOW CLOUDS OVER IL AND THE EASTERN HALF OF IA WILL BE
SLOW TO MOVE OUT LATE TONIGHT AND WEDNESDAY MORNING...RESULTING IN
CONTINUED MVFR CONDITIONS DUE TO CIGS. SCATTERED FLURRIES WILL
REMAIN POSSIBLE ESPECIALLY AT CID AND MLI LATE TONIGHT. THE
UPDATED FORECASTS CONTINUE A GRADUAL CLEARING TREND...LIFTING
CLOUD BASES TO WELL ABOVE MVFR THRESHOLDS...IN A LOW CONFIDENCE
12Z TO 18Z TIMEFRAME. THERE IS HIGHER CONFIDENCE THAT ALL SITES
WILL BE VFR FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING. NW
WINDS WILL DIMINISH THROUGHOUT AND BECOMING LIGHT FROM THE NORTH
WEDNESDAY NIGHT AS HIGH PRESSURE BUILDS INTO THE UPPER MS VALLEY.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...08
SHORT TERM...08
LONG TERM...GIBBS
AVIATION...SHEETS





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