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000
FXUS63 KDVN 122326
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
526 PM CST THU DEC 12 2013

.SYNOPSIS...
ISSUED AT 328 PM CST THU DEC 12 2013

12Z UA ANALYSIS HAS A WEAK DISTURBANCE PASSING THROUGH THE GREAT
LAKES WITH A CUT OFF LOW NEAR BAJA CALIFORNIA. THE EDGE OF THE
ARCTIC AIR MASS WAS INTO THE TENNESSEE VALLEY. SATELLITE TRENDS
THROUGH MID AFTERNOON HAVE A LAYER OF MID/HIGH CLOUDS MOVING THROUGH
THE AREA ASSOCIATED WITH THE DISTURBANCE WITH ADDITIONAL HIGH CLOUDS
ACROSS THE NORTHERN PLAINS.

18Z SFC ANALYSIS HAS THE ARCTIC HIGH FROM THE OHIO VALLEY INTO THE
LOWER MISSISSIPPI VALLEY WITH A DEVELOPING WARM FRONT IN THE
NORTHERN PLAINS. DEW POINTS WERE IN THE SINGLE DIGITS AND TEENS
ACROSS MUCH OF THE MIDWEST WITH 20S ACROSS SOUTHERN PLAINS.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 328 PM CST THU DEC 12 2013

QUIET AND DRY CONDITIONS WILL BE SEEN TONIGHT ACROSS THE AREA WITH
PASSING HIGH LEVEL CLOUDS. THE CLOUD COVER AND SOUTHERLY FLOW WILL
HELP KEEP TEMPERATURES WARMER THAN LAST NIGHT. A WEAK BOUNDARY WILL
DROP SOUTH LATE TONIGHT AND SHOULD BE APPROACHING THE I-80 CORRIDOR
AROUND SUNRISE. ATTENTION THEN TURNS TO THE APPROACHING SYSTEM FOR
FRIDAY.

FRIDAY MORNING WILL SEE AN INCREASE IN CLOUDS ACROSS THE AREA. THE
WEAK BOUNDARY WILL MOVE SOUTH DURING THE DAY ALLOWING DRY EASTERLY
FLOW TO DEVELOP ACROSS THE NORTHERN HALF OF THE AREA. THIS DRY AIR
WILL HAVE TO SATURATE BEFORE PRECIPITATION BEGINS.

THE BETTER FORCING REMAINS SOUTH OF THE AREA FRIDAY MORNING SO MOST
OF THE AREA WILL SEE A DRY MORNING. THE POSSIBILITY DOES EXIST THAT
PRECIP MAY BEGIN IN THE FAR SOUTHWEST PARTS OF THE AREA JUST PRIOR
TO MID DAY.

FRIDAY AFTERNOON THE ATMOSPHERE RAPIDLY SATURATES ACROSS THE SOUTH
THIRD TO HALF OF THE AREA ALLOWING PRECIPITATION TO DEVELOP. THE
FORECAST SOUNDINGS SUGGEST THE POTENTIAL FOR SOME SLEET TO OCCUR
PRIOR TO THE ATMOSPHERE SATURATES AND TURNS TO ALL SNOW.

BY THE EVENING COMMUTE ON FRIDAY...ACCUMULATING SNOW OF AN INCH OR
TWO SHOULD BE SEEN MAINLY SOUTH OF A KOTM TO KGBG LINE WITH POSSIBLY
A DUSTING TO HALF INCH NEARLY TO I-80.

BASED ON EXPECTED SNOW AMOUNTS AND SNOW CONTINUING INTO FRIDAY
NIGHT/SATURDAY...A WINTER STORM WATCH HAS BEEN ISSUED FOR AREAS
GENERALLY ALONG/SOUTH OF MEMPHIS MISSOURI...TO BURLINGTON...TO
GALESBURG LINE. THIS WATCH WILL LIKELY TRANSITION OVER TO A WINTER
WEATHER ADVISORY IN THE NEXT 15 HOURS AND MAY BE EXPANDED NORTHWARD.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 328 PM CST THU DEC 12 2013

FRIDAY NIGHT...CONTINUING WITH THOUGHTS OF SLOWER PHASING OR TRYING
TO PHASE PROCESS OF SOUTHERN AND NORTHERN STREAM WAVES AND SPLIT
FLOW LIKE PATTERN TRYING TO MELD ALONG AND WEST OF THE MS RVR
VALLEY...12Z RUN MODEL DISCREPANCIES CONTINUE TO CREEP INTO FRI
NIGHT. WITH THE LOCAL AREA SEEMINGLY UNDER THE SPLIT INITIALLY BUT
THEN PHASING TRYING TO OCCUR RIGHT OVERHEAD...THE GENERAL IDEA IS FOR
THE INVERTED LLVL TROF/CONVERGENT FOCAL POINT TO BE FURTHER SOUTH
INITIALLY FRI EVENING THEN TRY AND PIVOT BACK NORTHWARD INTO THE
OVERNIGHT. SREF/MODEL BLEND GENERALLY SUGGESTS THIS SFC TROF/BOUNDARY
TO UNDULATE GENERALLY IN THE VCNTY OF MEMPHIS MO...NORTHEASTWARD TO
NORTH OF BRL...AND THEN TOWARD THE PRINCETON IL AREA FOR MUCH OF THE
NIGHT BEFORE SHIFTING OFF TO THE EAST ACRS EASTERN IL BY SAT MORNING.
THIS AXIS COULD BE A REGION OF ENHANCED SNOWFALL AMOUNTS...BUT AGAIN
DISCREPANCIES OF SOME POSITIONING AND AMOUNT OF MOISTURE FEED
AVAILABLE INTO THIS FEATURE IF NOT TOO INTERRUPTED FROM THE
SOUTH/SOUTHEAST BY MORE SIGNIFICANT PRECIP FIELDS ACRS THE TN/OH RVR
VALLEYS. INCREASING LOW TO MID LEVEL NORTH TO NORTHEAST FEED WILL
CONTINUE TO SHUTTLE DRIER AIR TOWARD TH AREA AS WELL AND MAY MAKE FOR
A SHARP CUT-OFF/NORTHERN EDGE TO THE ACCUMULATING SNOW FIELDS OR DEF
ZONE-TYPE PRECIP REGION. INTERESTING THAT THE 1Z RUN GFS AND NAM ARE
LESS PHASED...IN-BETWEEN UPPER JET STRUCTURES...AND MORE INFLUENCED
BY LLVL COLD CONVEYOR DOWN THE NORTHERN PLAINS AND HAVE MADE
SIGNIFICANT SOUTHWARD ADJUSTMENTS IN BOTH PRECIP FIELDS AND BOUNDARY
PLACEMENT FROM THEIR PREVIOUS RUNS. THE 12Z GFS SNOW ALGORITHM JUST
HAS 1-2 INCHES NOW THROUGH 12Z SAT ALONG AND SOUTH OF THE HWY 34
CORRIDOR IN SE IA/WEST CENTRAL IL...WHILE THE NAM HAS 1-3 INCHES
PIVOTING FROM KEOKUK IN FAR SE IA...TO THE I80 CORRIDOR EAST OF THE
QUAD CITIES. THE NEW 12Z ECMWF SNOW ALGORITHM IS MORE CONSISTENT
WITH IT/S PREVIOUS FEW RUNS...AND THE MODEL IS A BIT MORE PHASED AND
FURTHER NORTH WITH IT/S SYNOPTIC SCALE FEATURES. IT PRODUCES
WIDESPREAD 2-4 INCHES BY 12Z SAT FROM I80 ON SOUTHWARD...WITH THE 4
INCH AXIS ALONG THE SFC TROF FROM JUST NORTH OF BRL TO SOUTHEAST OF
PRINCETON IL. BEING A LITTLE LEARY OF THE SUDDEN JOG SOUTH OF THE
AMERICAN MODELS...FOR NOW WILL LEAN TOWARD THE FORCING AND SATURATION
OF THE ECMWF BUT WITH A SLIGHT SOUTHWARD ADJUSTMENT IN THINKING AS A
COMPROMISE FOR NOW. THIS RESULTS IN 12 HR SNOWFALL AMOUNTS/USING
CLIMO 13:1 LSRS/ FROM 00Z-12Z SAT OF 2-4 INCHES ALONG AND SOUTH OF A
LINE FROM FAIRFIELD IA...TO ALEDO IN WEST CENTRAL IL...AND TO EAST OF
PRINCETON IL. BEST CHC OF THE 4+ INCH AMOUNTS RIGHT NOW APPEAR TO BE
IN THE FAR SOUTHEASTERN CWA CARTHAGE IL TO SOUTHEAST OF MONMOUTH...
BUT ANOTHER ENHANCED SNOW BAND COULD ALONG ALONG AND JUST TO THE
NORTH OF THE INVERTED TROF AXIS WHERE EVER THAT EVENTUALLY LAYS OUT.
WILL ADVERTISE LESS THAN AN INCH NORTH OF I80 AND PROBABLY A DUSTING
TO A HALF INCH NORTH OF HWY 30. EVENT TOTALS FOR NOW TAKING INTO
ACCOUNT FRI AFTERNOON AMOUNTS...2 TO 5+ INCHES ALONG AND SOUTHEAST OF
A LINE FROM SOUTH OF SIGOURNEY IA...TO JUST SOUTH OF MLI..AMD TO
NORTHEAST OF PRINCETON IL. SOME LOCALIZED 6 INCH AMOUNTS POSSIBLE
SOUTH OF CARTHAGE IL TO MACOMB IL. AS FOR LOW TEMPS FRI NIGHT IN THE
TEENS NORTHWEST OF THE TROF...TO THE LOWER 20S SOUTHEAST OF THE
BOUNDARY.

SATURDAY AND SUNDAY...SOME LINGERING LIGHT SNOW SHOWERS OR FLURRIES
POSSIBLE FOR PART OF SAT UNDER MAIN L/W TROF AXIS WITH JUST MINIMAL
ADDITIONAL SNOW ACCUMULATIONS POSSIBLE. HIGHS IN THE LOWER 20S IN
THE NORTHWEST...TO THE UPPER 20S/NEAR 30 IN THE SOUTHEAST. MODELS
WANT TO KEEP SAT AND SAT NIGHT CLOUDY WITH WRAP AROUND STRATUS...
BUT WONDER IF SOME BREAKS WILL DEVELOP BY SAT NIGHT. IF THEY DO...
ALONG WITH THE DECREASING WINDS OVER FRESH SNOW PACK SOME TEMPS MAY
DIP IN THE LOW SINGLE DIGITS OR EVEN CLOSE TO ZERO. OTHERWISE 5-12
ABOVE WITH CLOUDS. DRY SUNDAY WITH HIGHS IN THE TEENS TO LOWER 20S.
SUNDAY NIGHT CLIPPER IN NORTHWEST STEERING FLOW ACRS THE UPPER
MIDWEST MAY PRODUCE LIGHT SNOW OR FLURRIES IN THE NORTHERN CWA...THE
NEW 12Z ECMWF ACTUALLY PRODUCES UP TO AN INCH BY MON MORNING ALONG
AND NORTH OF I-80. WILL GO WITH SLIGHT CHC POPS SUN NIGHT ALONG AND
NORTH OF HWY 30 FOR NOW. LOWS 10-16 DEGREES.

MONDAY THROUGH NEXT THURSDAY...LLVL WARM TEMP DRAW SOUTH OF DIGGING
NORTHWESTERN GRT LKS CLIPPER SYSTEM COULD BOOST TEMPS OVER FREEZING
ON MONDAY. MODEL FCST SOUNDINGS SUGGEST THAT TEMPS COULD WARM INTO
THE 40S IF IT WERE NOT FOR THE SNOW COVER WHICH WILL LIKELY KEEP
TEMPS DOWN IN THE 30S. LONGER RANGE SIGNALS SUGGEST ROUNDS OF DIGGING
CLIPPER ENERGY TO EVENTUALLY CARVE OUT ANOTHER L/W TROF ACRS THE GRT
LKS AND OH RVR VALLEY FOR ANOTHER POSSIBLE COLD DUMP INTO THE UPPER
MIDWEST BY LATE TUE OR INTO WED...BUT CURRENT SIGNS SUGGEST IT NOT
TO BE AS BRUTALLY COLD AS WHAT WE JUST WENT THROUGH.   ..12..

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 522 PM CST THU DEC 12 2013

A CLEAR AND VFR NIGHT IS EXPECTED OVERNIGHT...LASTING THROUGH MID
MORNING FRIDAY. THIS IS DUE TO HIGH PRESSURE SLOWLY MOVING EAST
AWAY FROM THE AREA...WITH LOW PRESSURE DEVELOPING IN THE PLAINS.
LIGHT SOUTHEAST WINDS TO EAST WINDS WILL CONTINUE AT 5 TO 8 KTS. A
WINTER STORM WILL SWEEP EAST TO NORTHEAST FRIDAY...BRINGING A SWATH
OF LIGHT TO MODERATE SNOW INTO SOUTHEAST IOWA AND CENTRAL
ILLINOIS. THIS SNOW IS EXPECTED TO REACH BRL BY MID
AFTERNOON...AND COULD REACH TO NEAR THE MLI AREA BY 21Z. SNOW IS
EXPECTED TO BRING IFR VISIBILITIES...POSSIBLY LIFR AT TIMES AT
BRL. OTHERWISE...MVFR CIGS AROUND 1500 TO 2500 FT WILL DEVELOP BY
MID TO LATE MORNING FRIDAY IN ALL SITES AS THE STORM SYSTEM NEARS
THE REGION.
ERVIN

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY
     MORNING FOR DES MOINES-LEE.

IL...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY
     MORNING FOR HANCOCK-HENDERSON-MCDONOUGH-WARREN.

MO...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY
     MORNING FOR CLARK-SCOTLAND.

&&

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...12
AVIATION...ERVIN