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000
FXUS63 KDVN 120803
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
203 AM CST THU DEC 12 2013

.UPDATE...
ISSUED AT 202 AM CST THU DEC 12 2013

MID AND HIGH LEVEL CLOUDS STREAMING ACROSS THE NORTHERN THIRD OF
THE FORECAST AREA...COMBINED WITH INCREASING AN INCREASING
PRESSURE GRADIENT AND LIGHT SOUTH WINDS...WERE RESULTING IN SLOWLY
WARMING TEMPERATURES AS EXPECTED. AS OF 2 AM...ONLY A FEW POCKETS
OF -20 WIND CHILLS WERE OBSERVED NEW OF A CID TO DBQ LINE...WHERE
ACTUAL TEMPERATURES WERE IN THE RANGE OF ZERO TO 4 BELOW.

AT THIS RATE...ADVISORY LEVEL WIND CHILLS NO LONGER LOOK LIKELY
PAST SUNRISE. HAVE THUS UPDATED THE ADVISORY TO MOVE UP THE
EXPIRATION TIME TO 6 AM.

&&

.SYNOPSIS...
ISSUED AT 250 PM CST WED DEC 11 2013

12Z UA ANALYSIS HAD AN 850MB ARCTIC FRONT FROM LAKE HURON INTO
NORTHEAST NEBRASKA WITH AN ARCTIC AIR MASS OVER THE UPPER MIDWEST
AND NORTHERN PLAINS. SATELLITE TRENDS THROUGH MID AFTERNOON SHOW
CLEAR SKIES ACROSS THE AREA FROM THE ARCTIC HIGH WITH HIGH LEVEL
CLOUDS MOVING SOUTHEAST FROM THE NORTHERN PLAINS.

18Z SFC ANALYSIS HAS THE ARCTIC HIGH OVER SOUTHEAST NEBRASKA WITH A
COLD FRONT FROM SOUTHEAST MICHIGAN INTO NORTHERN TEXAS. DEW POINTS
WERE BELOW ZERO OVER THE NORTHERN PLAINS AND UPPER MIDWEST WITH
TEENS AND 20S ABOVE ZERO FROM THE OHIO VALLEY INTO THE SOUTHERN
PLAINS.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 250 PM CST WED DEC 11 2013

QUIET AND BITTER COLD CONDITIONS WILL BE SEEN TONIGHT AS THE ARCTIC
HIGH MOVES THROUGH THE AREA. THE ADDITIONAL DRY SNOW OVER THE AREA
WILL RESULT IN A VERY STRONG NEGATIVE FEEDBACK ALLOWING TEMPERATURES
TO PLUMMET RAPIDLY WITH THE SETTING SUN.

THE CURRENT HEADLINES HAVE BEEN ADJUSTED SLIGHTLY TO BETTER
REFLECT THE BEGINNING OF THE DANGEROUS WIND CHILLS. WIND CHILLS
MAY EXCEED 30 BELOW ZERO IN SOME LOCATIONS THIS EVENING BUT SHOULD
BE SPOTTY AND NOT WIDESPREAD. THUS THE CURRENT HEADLINES WILL
REMAIN AS AN ADVISORY.

BASED ON WHAT OCCURRED LAST MONDAY EVENING...LOWS SHOULD OCCUR FROM
8 PM TO 2 AM FROM WEST TO EAST ACROSS THE AREA WITH MANY AREAS
SEEING 10 TO 15 BELOW ZERO. THE FAVORED COLD AREAS NORTH OF
I-80...THE WAPSI...MAQUOKETA...AND SAUK VALLEYS MAY SEE LOWS CLOSE
TO 20 BELOW IN SOME SPOTS.

RECORD LOWS MAY BE THREATENED IN SOME AREAS DEPENDING UPON WHEN THE
OVERNIGHT LOW OCCURS. REFER TO THE CLIMATE SECTION FOR SPECIFIC
NUMBERS FOR DECEMBER 11TH AND 12TH.

RETURN FLOW DEVELOPING ACROSS THE AREA LATE THIS EVENING AND
OVERNIGHT WILL ALLOW TEMPERATURES TO SLOWLY CLIMB THROUGH SUNRISE
THURSDAY.  CLOUDS WILL BE ON THE INCREASE FROM A DISTURBANCE PASSING
NORTH OF THE AREA.

COLD BUT DRY CONDITIONS WILL BE SEEN ACROSS THE AREA ON THURSDAY
WITH SOME PASSING HIGH LEVEL CLOUDS. THE FAR NORTH AND NORTHEAST
AREAS WILL STRUGGLE TO REACH THE UPPER TEENS WHILE THE REMAINDER OF
THE AREA GETS INTO THE LOW TO MID 20S.    ..08..

.LONG TERM...(THURSDAY NIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 250 PM CST WED DEC 11 2013

THURSDAY NIGHT...LATEST 12Z RUN MODELS IN GENERAL AGREEMENT THAT
INCOMING LLVL BOUNDARY WILL SAG ACRS THE CWA AND SLOW/STALL ALONG
I80 IN A WEST-SOUTHWEST-TO-EAST NORTHEAST FASHION INTO FRI MORNING.
THIS TO LEE OF SPLIT FLOW ACRS THE WEST CENTRAL PLAINS...TROFFINESS
IN SOUTHERN STREAM ACRS THE GRT BSN...AND NORTHWESTERLIES FROM WEST
CENTRAL CANADA TO THE MID ATLANTIC. A DRY NIGHT...AND AREAS IN
RETURN FLOW SOUTH OF THE INCOMING BOUNDARY WILL HAVE TEMPS HELD UP IN
THE TEENS OVERNIGHT. DROPPING BELOW 10F INTO THE SINGLE DIGITS
NORTH OF THE BOUNDARY/NORTH OF I80.

FRIDAY AND SATURDAY...MAIN FOCUS THIS PERIOD WILL BE THE POTENTIAL
SNOW EVENT IN THE SOUTHERN CWA. THE GRT BSN/SOUTHERN STREAM WAVE
WILL PUSH EASTWARD TOWARD THE LOWER MS RVR VALLEY SAT MORNING...WITH
NORTHERN UPPER TROF ENERGY TRYING TO PHASE WITH IT OVER THE MID AND
UPPER MS RVR VALLEY. SFC REFLECTION LOW PRESSURE WILL LOOK TO
DEVELOP AND MOVE TOWARD THE LOWER MS RVR VALLEY...WITH INVERTED TROF
COMPLEX ARCING UP AND MELDING WITH SFC BOUNDARY SOMEWHERE ACRS THE
SOUTHERN OR SOUTHEASTERN THIRD OF THE DVN CWA BY FRI EVENING. THIS
FEATURE TO ACT AS A LLVL CONVERGENT FOCAL POINT FOR MOISTURE
CONVERGENCE AND UPPER WAVE LIFT FOR A LIKELY SNOW EVENT IN AT LEAST
THE SOUTHEASTERN THIRD OF THE DVN CWA. WILL THROW OUT THE LESS
ORGANIZED NAM WITH DRIER MOISTURE PARAMETERS AND THE LLVL TROF
ITSELF...AND TAKE A BLEND OF THE 12Z RUN ECMWF/GFS SOLUTIONS WHICH
ARE IN GENERAL AGREEMENT. SNOW SHOULD SPREAD UP ACRS THE SOUTHERN
CWA BY MID AFTERNOON AFTER SOME COLUMN SATURATION IS OVERCOME. FCST
SOUNDINGS IN THE SOUTHERN CWA HAVE TRENDED AWAY FROM A PERIOD OF
SLEET AND ALTHOUGH THERE MAY BE SOME BRIEF PERIODS OF IT STILL...
WILL JUST ADVERTISE SNOW AS THE PRIMARY PRECIP FRI AFTERNOON INTO THE
EVENING. HALF INCH TO UP TO OVER AN INCH POSSIBLE BY 00Z SAT ALONG
AND SOUTH OF A LINE FROM KEOSAUQUA IA...TO MONMOUTH IL. FLURRIES
POSSIBLY TO I80 BY SUNSET. DEEPER FORCING/ASCENT OCCURS THEN FROM
00Z-06Z SAT WITH ALMOST A DEF ZONE TYPE SNOW SHIELD FORMING
ALONG/OVER INVERTED TROF AXIS. TAKING INTO ACCOUNT LSR/S OF 12:1
TO 15:1...OMEGAS AND SATURATION...ANOTHER 1-4 INCHES OF SNOW
POSSIBLE THROUGH 12Z SAT GENERALLY ALONG AND SOUTH OF A LINE FROM
PRINCETON IL...TO MOLINE...AND TO FAIRFIELD IN SOUTHEASTERN IA.
WITH THE POTENTIAL OF 2 TO 4.5 INCHES...CURRENT INDICATIONS SUGGEST
A WINTER WX ADVISORY WILL EVENTUALLY BE NEEDED IN THE SOUTHEASTERN
THIRD OF THE DVN CWA. AREAS MOST LIKELY ALONG AND SOUTH OF A
PRINCETON IL...TO KEITHSBURG IL ON THE MS RVR...AND TO FAIRFIELD IA.
0.5 TO 1.5 ALONG I80...LESS THAN AN INCH TO THE NORTH OF THAT. FEEL
THE SYSTEM WILL BE PULLING OUT/FORCING SHIFTING EASTWARD FOR NOT
THAT MUCH MORE IN THE WAY OF ADDITIONAL ACCUM/S IN THE EASTERN CWA
SAT MORNING THROUGH 18Z. LINGERING LIGHT SNOW SHOWERS AND FLURRIES
DURING THE DAY. FRI HIGHS AHEAD OF THE SYSTEM MILDER IN THE MID TO
UPPER 20S...SAT HIGHS SIMILAR DESPITE MORE SNOW WITH IN-WRAPPING
LLVL CONVEYOR MODERATING THE TEMPS FROM THE SOUTHEAST. BUT INCOMING
SFC RIDGE LOBE SAT NIGHT MY MAKE FOR LOWS COLDER THAN GUIDANCE
ESPECIALLY OVER FRESH SNOWPACK AREAS...MANY SINGLE DIGITS ABOVE
ZERO AGAIN WITH A ZERO OR SUBZERO READING POSSIBLE IF SKIES CLEAR OUT
AND SFC WINDS DECOUPLE.

SUNDAY THROUGH NEXT WEDNESDAY...AFTER COLD START TO THE DAY...LATEST
MEDIUM RANGE MODELS SUGGEST ONGOING NORTH-WESTERLIES WILL LOOK
TO USHER A CLIPPER ACRS/TOWARD THE NORTHWESTERN GRT LKS SUNDAY INTO
SUNDAY NIGHT. WAA TO THE SOUTH OF THIS FEATURE TO MAKE FOR TEMP
REBOUND BACK WELL UP INTO THE TEENS SUNDAY AFTERNOON. FLURRIES OR
EVEN LIGHT SNOW FROM ELEVATED WAA WING INDUCED BY THE CLIPPER WAVE...
MAY CLIP THE NORTHERN CWA SUNDAY NIGHT NORTH OF HWY 30. AS FOR EARLY
NEXT WEEK...LONG RANGE INDICATIONS CONTINUE TO SUGGEST MORE OF A
BROAD NORTHWEST FLOW PATTERN EMBEDDED WITH OCCASIONAL CLIPPERS
SCOOTING FROM THE NORTHWESTERN HIGH PLAINS TO THE GRT LKS. ALTHOUGH
NOT A WARM PATTERN...IT MAY TEMPORARILY BLOCK ANY REAL ARCTIC
INTRUSIONS FROM DUMPING DOWN INTO THE REGION THROUGH AT LEAST TUE.
SNOW CHANCES WILL LOOK TO OCCUR MAINLY ALONG AND NORTH OF THE
LOCAL FCST AREA MON INTO WED...BUT CANNOT RULE OUT SNOW IN THE
NORTHERN DVN CWA AREA WITH ANY SOUTHWARD BAROCLINICITY ADJUSTMENT TO
THE CLIPPER PATHWAY.    ..12..

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY EVENING)
ISSUED AT 1123 PM CST WED DEC 11 2013

BITTERLY COLD TEMPERATURES AND LIGHT WINDS UNDER CLEAR VFR SKIES
WILL CONTINUE THROUGH EARLY MORNING IN ALL SITES AS HIGH
PRESSURE MOVES OVER HEAD. SOME CIRRUS AND HIGH BASED ALTOCUMULUS IS
LIKELY AT TIMES...WITH NO LOW CLOUDS. AFTER SUNRISE...SOUTHWEST
WINDS OF 8 TO 10 KTS WITH VFR CONDITIONS CONTINUING.


&&

.CLIMATE...
ISSUED AT 250 PM CST WED DEC 11 2013

RECORD LOWS FOR DECEMBER 11...

MOLINE.........-18 IN 1972
CEDAR RAPIDS...-13 IN 1976
DUBUQUE........-15 IN 1976
BURLINGTON.....-10 IN 1972

RECORD LOWS FOR DECEMBER 12...

MOLINE.........-11 IN 2000
CEDAR RAPIDS...-12 IN 2000
DUBUQUE........-11 IN 2000
BURLINGTON.....-10 IN 1989

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WIND CHILL ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR BENTON-
     BUCHANAN-CEDAR-CLINTON-DELAWARE-DUBUQUE-IOWA-JACKSON-
     JOHNSON-JONES-LINN-MUSCATINE-SCOTT.

IL...WIND CHILL ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR BUREAU-
     CARROLL-HENRY IL-JO DAVIESS-PUTNAM-ROCK ISLAND-STEPHENSON-
     WHITESIDE.

MO...NONE.
&&

$$

UPDATE...SHEETS
SYNOPSIS...08
SHORT TERM...08
LONG TERM...12
AVIATION...ERVIN
CLIMATE...08