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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2112Z Feb 28, 2015)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
412 PM EST SAT FEB 28 2015

VALID 00Z SUN MAR 01 2015 - 00Z WED MAR 04 2015


...MID MS VALLEY AND OH VALLEY INTO NORTHEAST/MID-ATL...

A WEAK MID-LEVEL DISTURBANCE... FROM THE SWRN SRN STREAM UPPER
LOW... WILL STREAM THROUGH THE OH VALLEY INTO THE NORTHEAST/NRN
MID-ATL ON SUN BEFORE REACHING COASTAL NEW ENGLAND ON MON AND TEAM
WITH A DIGGING NRN STREAM TROUGH FOR RAPID CYCLOGENESIS. DESPITE
THE RELATIVE WEAK NATURE OF THE IMPULSE... ENOUGH MOISTURE FLUX IS
AVAILABLE TO OVERRUN A COLD GRADUALLY RETREATING ARCTIC HIGH FOR
WIDESPREAD WINTER WEATHER.

THE MAIN THREAT SAT EVENING THROUGH SUN EVENING WILL BE AN AXIS OF
HEAVY SNOWFALL JUST NORTH AND WEST OF THE OH RIVER AND THE THREAT
FOR ICING WITH POSSIBLY A HIGH-END EVENT EAST OF THE APPALACHIANS
IN THE MID-ATL. THE GUIDANCE SHOWS LITTLE SPREAD WITH THE WEAK
500MB VORT AND TREMENDOUS ISENTROPIC LIFT WITH POSSIBLE MESOSCALE
BANDING WITH A .50 INCH QPF OR GREATER FROM EAST CENTRAL IL
THROUGH CENTRAL IN AND OH INTO WRN PA AND CENTRAL APPALACHIANS.
THIS CORRIDOR FROM IND TO CMH TO JUST NORTH OF PIT WILL BE THE
POTENTIAL FOR 6-8 INCHES WITH LOCALLY HIGHER AMOUNTS. VERY COMPLEX
FCST EAST OF THE MTNS... AS A STEADY TREND IN THE GUIDANCE IN
INCREASING QPF AMOUNTS BUT NOTHING ON THE SCALE OF THE 12Z NAM.
HOWEVER... DESPITE THE RETREATING HIGH AND NOT VERY STRONG WARM
NOSE WITH THE FLAT SYSTEM... ARCTIC/SHALLOW AIR MASS IS EXPECTED
TO HOLD STRONG AND COULD REPRESENT THE THREAT OF ICING FROM THE
WRN CAROLINAS INTO THE NRN MID-ATL STATES. ITS THE CORRIDOR WEST
OF I95 THATS MOST WORRISOME ESPECIALLY FROM WRN NC THROUGH SWRN VA
INTO THE DC/BAL AREAS AND POSSIBLY EXTENDING INTO SERN PA. WPC
GENERALLY FOLLOWED THE GFS HERE ON QPF AND A BLEND OF 12Z THERMAL
PROFILES FOR A .10 TO .25 ACCUMULATIONS FROM CLT TO PHL. 

A COASTAL LOW WILL FORM OFFSHORE OF MAINE EARLY MON AND WITH THE
UPSTREAM DIGGING NRN STREAM ARRIVING ALLOWING THIS LOW TO LIFT
RAPIDLY NORTH AND EAST ALONG WITH GOING THROUGH A RAPID CYCLE OF
CYCLOGENESIS. EXPECT 4-6 INCH AMOUNTS ACROSS THE FAVORED NEW
ENGLAND TERRAIN AND POSSIBLE AXIS OF SIMILAR AMOUNTS ACROSS SRN
NEW ENGLAND... MAINLY FROM SUN EVENING THROUGH MON MORNING.

...FOUR CORNERS REGION INTO UPPER MIDWEST/GREAT LAKES/OH VALLEY...

A CLOSED UPPER LOW ALONG THE ACTIVE SRN BRANCH WILL DRIVE A LONG
HEAVY SNOWFALL EVENT ACROSS A LARGE PART OF THE FOUR CORNERS
REGION ON SUN/MON BEFORE THE ENTIRE SHORT WAVE EJECTS OUT INTO THE
UPPER MIDWEST ON TUES... AHEAD OF ANOTHER DIGGING SHOT OF ARCTIC
AIR... FOR WIDESPREAD WINTER WEATHER ACROSS THE UPPER MS
VALLEY/GREAT LAKES AND OH VALLEY.

THE HEAVIEST SNOWFALL ACCUMULATIONS WILL TAKE PLACE ON SUN AND MON
ACROSS THE FOUR CORNERS REGION. WRLY TO INCREASING SWRLY UPPER
DIFLUENT 700-500MB FLOW WILL CONSUME THE FOUR STATES FOR IDEAL
OROGRAPHICS. THE MAIN IMPACT ON SUN WITH THE WRLY FLOW ACROSS WEST
CENTRAL AND SWRN CO OR THE CO ROCKIES AND SAN JUANS. THEN MON...
INCREASING SWRLY MOIST COMPONENT WILL RESULT IN VERY HEAVY SNOWS
FROM NWRN AZ/SRN UT WASATCH BUT ALSO CONTINUED HEAVY MTN SNOWS FOR
WRN CO. WPC WENT WITH PROBS OF A FOOT OR MORE BOTH DAYS.

THE SYSTEM BREAKS DOWN AND SHOOTS INTO THE CENTRAL PLAINS COME
TUES MORNING... AHEAD OF A DIGGING NRN STREAM TROUGH AND ARCTIC
COLD FRONT. THIS SHOULD RESULT IN A SURFACE WAVE SLIDING FROM NWRN
KS TO LOWER MI ON TUES WHILE TAPPING IN TO INCREASING AVAILABLE
GULF OF MEXICO MOISTURE FOR A FLOURISHING PRECIP SHIELD... WHILE
AN ARCTIC COLD FRONT CREEPS IN FROM THE NORTH AND WEST. THE
RESULTANT BASED ON A BLEND OF THERMAL PROFILES SUGGESTS HEAVY
SNOWFALL POTENTIAL FROM NRN IA/SRN MN INTO WI/MI WITH A POSSIBLE
TRANSITION ZONE THROUGH THE OH VALLEY INTO THE CENTRAL
APPALACHIANS. THERE IS STILL ENOUGH SPREAD AT THE MOMENT WITH THE
GUIDANCE ON THE EXACT AXIS OF SNOW/ICE AND POSSIBLE AMOUNTS.
MEANWHILE ON THE TAIL END OF THE ARCTIC COLD FRONT PLUNGING DOWN
THE FRONT RANGE OF THE ROCKIES... EXPECT POSSIBLE UPSLOPE SNOWFALL
FROM MT/WY INTO CO.

MUSHER