Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 251813
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1213 PM CST WED FEB 25 2015

.UPDATE...
ISSUED AT 1159 AM CST WED FEB 25 2015

CONTINUE TO ASSESS THE EVOLUTION OF THE CLIPPER SYSTEM TO TRY AND
RESOLVE ANY CHANGES TO HEADLINES LATER THIS AFTERNOON. INITIAL
THOUGHTS THAT HEAVIER FORCING/H8-H7 MB BASED FRONTOGENETICAL BAND
WITH THE HEAVY SNOW RATES CURRENTLY ACRS NE IA INTO WEST CENTRAL
IA MAY EXPAND SOME AND DROP SOUTHEASTWARD ACRS THE WESTWARD THIRD
FROM MID AFTERNOON TO EARLY EVENING...AND EXPAND ACRS THE SOUTHERN
THIRD OF THE DVN CWA THIS EVENING THROUGH MIDNIGHT WITH GREATEST
RATE OF ACCUMULATIONS OCCURRING UNDER IT. THE 12Z 4KM WRF MAY BE ON
TO SOMETHING AND SHOWS SIMILAR HANDLING.  SOME CONCERN IF THE
BAND PROGRESSES LIKE THE WRF SHOWS THAT SNOW AMOUNTS IN THE
NORTHWESTERN HALF OF THE WARNING AREA MAY BE TOO HIGH BY A FEW
INCHES...THE CURRENTLY ADVERTISED 6-9 INCHES MAY BE MORE LIKE 4-7
INCHES IN THOSE AREAS. NORTHEASTERN ADVISORY AREAS MORE LIKE 2-4
INCHES AS OPPOSED TO 3-6 INCHES. ONGOING AMOUNTS SOUTH OF I80
STILL LOOK ON TARGET FOR THE MOST PART WITH BULK OF ACCUMS DOWN
THERE OCCURRING AFTER 5 PM THIS EVENING. THERE MAY BE A NEED TO
EXPAND ADVISORY INTO BUREAU COUNTY IF THE WESTERN PART OF THAT
COUNTY WILL BE IN LINE FOR WIDESPREAD 3-4 INCHES. CHALLENGES
APLENTY FOR THE AFTERNOON.   ..12..

&&

.SYNOPSIS...
ISSUED AT 330 AM CST WED FEB 25 2015

AT 330 AM...MID LEVEL CLOUDS WERE STREAMING INTO THE AREA AHEAD OF
A ROBUST CLIPPER SYSTEM. SNOW WAS CONTINUING TO DEVELOP ACROSS
PARTS OF SOUTH DAKOTA AND SOUTHWEST MINNESOTA. EARLY MORNING
TEMPERATURES WERE IN THE TEENS TO LOWER 20S AT MOST LOCATIONS.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CST WED FEB 25 2015

THE MAIN FORECAST ISSUE IS THE IMPENDING POTENT CLIPPER SYSTEM AND
ASSOCIATED SNOWFALL AMOUNTS AND COVERAGE.

LOOKING AT THE VARIOUS SYNOPTIC AND HIGH RES MODELS...LATEST
TRENDS HAVE BEEN TOWARD HIGHER SNOWFALL AMOUNTS AND A SLIGHTLY
FARTHER NORTH AXIS OF THE HEAVIEST SNOW. THE INITIAL ISSUE IS
TIMING OF THE ONSET OF SNOW...DEPENDENT ON HOW THE DEFORMATION
ZONE/DRY SLOT SET UP. THE WRF IS A BIT FASTER IN BRINGING SNOW
INTO THE WEST THIS MORNING...WHILE THE RAP HAS A MORE PRONOUNCED
DRY SLOT EARLY IN THE EVENT. FOR PURPOSES OF THE FORECAST GRIDS
AND HEADLINES...HAVE GONE WITH THE EARLIER TIMING...WHICH CAN BE
ADJUSTED THROUGH THE DAY.

GIVEN THE STRENGTH AND DEPTH OF THE FORCING THROUGH THE DENDRITIC
LAYER...THE HIGHER SNOWFALL AMOUNTS LOOK REASONABLE BASED ON
AVERAGE SNOW RATIOS THROUGH THE BULK OF THE EVENT IN THE 14-19:1
RANGE. ALSO FAVORED CONSENSUS QPF...WHICH IS SLIGHTLY HIGHER TO
THE NORTH THAN WPC VALUES. THE END RESULT IS ROUGHLY 6-9 INCHES
FROM INDEPENDENCE...TO WAPELLO...FORT MADISON AND POINTS EAST.
HAVE UPGRADED THESE AREAS TO A WINTER STORM WARNING. FROM
DUBUQUE...THROUGH THE QUAD CITIES...WEST CENTRAL ILLINOIS...AND
FAR NORTHEAST MISSOURI...EXPECTING GENERAL 3-6 INCH AMOUNTS WITH A
WINTER WEATHER ADVISORY IN EFFECT. LOCALLY ENHANCED HIGHER SNOWFALL
AMOUNTS ARE NOT OUT OF THE QUESTION IN THE ADVISORY AREA.
ADJUSTMENTS TO SNOWFALL AMOUNTS/HEADLINES ARE INEVITABLE AS WE
HEAD THROUGH THE DAY AND INTO THIS EVENING.

PEAK SNOWFALL INTENSITY EXPECTED IN THE AFTERNOON/EVENING...WHICH
WILL MAKE FOR A HAZARDOUS COMMUTE WITH SNOW COVERED ROADS AND
REDUCED VISIBILITY. A NORTHWEST WIND AROUND 15 MPH WITH HIGHER
GUSTS WILL LIKELY PRODUCE SOME SHALLOW DRIFTING SNOW AT TIMES. THE
SNOW WILL TAPER OFF FROM NORTHWEST TO SOUTHEAST LATE TONIGHT INTO
THURSDAY MORNING.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 330 AM CST WED FEB 25 2015

THURSDAY AND FRIDAY...VERY COLD PERIOD AS ARCTIC ~1042 MB HIGH
BUILDS INTO THE MIDWEST. FRESH POWDERY SNOW ON THE GROUND/LIGHT
WINDS (POSSIBLY DECOUPLED AT TIMES)/AND MAINLY CLEAR SKIES WILL SET
THE STAGE FOR VERY COLD OVERNIGHT LOWS. CURRENT FORECAST FAVORS THE
RAW GFS/ECMWF AS SUPERBLEND/NAM SEEM TO BE TOO WARM.

EXPECT WIDESPREAD LOWS BETWEEN -10 TO -15 F WHICH WOULD BE NEAR
RECORD TERRITORY FOR LATE FEBRUARY...SINGLE DIGIT SUB-ZERO LOWS ARE
MORE LIKELY SOUTH OF BURLINGTON. WINDS WILL REMAIN ON THE LIGHT SIDE
BUT EVEN AT 5-7 KTS THEY WILL BE ENOUGH TO CREATE DANGEROUS WIND
CHILLS BETWEEN -20 TO -30 F AT TIMES. VALUES NEAR -30 F SHOULD BE
RELATIVELY ISOLATED AND SHORT-LIVED. HIGHS ARE FORECAST TO BE IN THE
UPPER SINGLE DIGITS TO MID TEENS.

SATURDAY AND SUNDAY...SIGNIFICANT PATTERN CHANGE WILL OCCUR DURING
THIS TIME AS UPPER JET DIGS OUT A LARGE TROUGH OVER THE WESTERN U.S.
WHICH WILL CAUSE A BIG SHIFT IN THE ORIENTATION OF THE 850 MB
BAROCLINIC ZONE TO A SW-NE DIRECTION.

THERE HAS BEEN A CONSISTENT SIGNAL OF SIGNIFICANT LOW/MID LEVEL
MOISTURE ADVECTION FROM THE SW U.S. AND FROM THE GULF OF MEXICO FOR
SAT NIGHT INTO SUN. THEREFORE...A PERIOD OF SNOW IS LIKELY WITH
AMOUNTS UNCERTAIN THIS FAR OUT. WITH THE LACK OF A STRONG SHORTWAVE
TROUGH/VORTICITY MAX...MODELS DEVELOP LINEAR-LOOKING FRONTAL PRECIP
AND DO NOT DEVELOP A COHERENT SFC LOW WHICH WOULD PUT SOMEWHAT OF A
LIMIT ON THIS SYSTEM. DAYTIME TEMPS WILL BE IN THE 20S ON SAT AND
THE UPPER 20S TO LOWER 30S ON SUN.

MONDAY AND TUESDAY...CHANCE OF PRECIP MORE LIKELY LATER IN THE DAY
AND INTO TUE. MODELS STILL STRUGGLING WITH WHEN TO EJECT ORGANIZED
500 MB VORTICITY MAX OUT OF THE FOUR CORNERS AREA. THE GFS HAS A
WELL ORGANIZED SFC LOW TRACKING FROM OKLAHOMA TO NORTHERN INDIANA
WHICH IS FAVORABLE FOR WIDESPREAD PRECIP IN THE DVN CWA. WARMER AIR
ALOFT MAY MAKE IT FAR ENOUGH NORTH TO BRING VARYING PRECIP TYPES TO
PORTIONS OF THE FORECAST AREA. STAY TUNED. EARLY LOOK AT FORECAST
HIGHS ARE IN THE UPPER 20S TO MIDDLE 30S ON TUE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1147 AM CST WED FEB 25 2015

SNOW COMING IN AND SATURATING FOR LOW MVFR TO LIFR CONDITIONS AT
DBQ AND CID ALREADY...MLI BY 1-2 PM AND BRL MAINLY 2-3 PM. EAST
WINDS TO BACK TO THE NORTH TO NORTHEAST THIS EVENING INTO THU
MORNING. 10-20 KT WINDS COMBINING WITH FALLING SNOW COMPOUNDING
VSBYS THIS AFTERNOON THOUGH THE EVENING. CONDITIONS TO IMPROVE FROM
NORTH TO SOUTH AFTER MIDNIGHT TONIGHT THROUGH MID THU MORNING...
FIRST AT DBQ/CID WHICH MAY BE MVFR BY SUNRISE.   ..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR CLINTON-
     DELAWARE-DUBUQUE-JACKSON-JONES-SCOTT.

     WINTER STORM WARNING UNTIL 6 AM CST THURSDAY FOR CEDAR-DES
     MOINES-HENRY IA-JEFFERSON-LEE-LOUISA-MUSCATINE-VAN BUREN.

     WINTER STORM WARNING UNTIL 3 AM CST THURSDAY FOR BENTON-BUCHANAN-
     IOWA-JOHNSON-KEOKUK-LINN-WASHINGTON.

IL...WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR HENRY IL-
     MERCER-ROCK ISLAND.

     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM CST
     THURSDAY FOR HANCOCK-HENDERSON-MCDONOUGH-WARREN.

MO...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM CST
     THURSDAY FOR CLARK-SCOTLAND.

&&

$$

UPDATE...12
SYNOPSIS...RP KINNEY
SHORT TERM...RP KINNEY
LONG TERM...UTTECH
AVIATION...12





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