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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0856Z Feb 22, 2018)
 
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PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 AM EST THU FEB 22 2018

VALID 12Z THU FEB 22 2018 - 12Z SUN FEB 25 2018


DUE TO CONTINUED DATA ISSUES, THE ONLY GUIDANCE AVAILABLE FOR WPC
WWD ON THERMALS WAS THE 00Z GFS, 00Z NAM, 00Z NAM CONEST AND
18Z/21 GEFS MEAN AT VARYING PERCENTAGES EACH DAY. THE MASS FIELDS
WITH THIS FOURSOME SHOW REASONABLE CONTINUITY AND LIMITED SPREAD
BUT DETAILS SURROUNDING THE WINTER WEATHER FORECAST ARE NOT VERY
CONFIDENT WITH THE LACK OF FULL OPERATIONAL AND ENSEMBLE DATA.

...THURSDAY...

MULTIPLE AREAS OF FROZEN PRECIP WILL BE LIKELY. A STREAK OF HEAVY
SNOW AND ICING WILL BE POSSIBLE FROM PARTS OF PA AND SOUTHERN NY
STATE INTO SPOTS OF SOUTHERN NEW ENGLAND. A SURGE OF DEEP MOISTURE
CONTENT UPSTREAM FROM THE LOWER MS VALLEY TO THE WESTERN OH VALLEY
WILL SURGE TOWARD THE NORTHERN MID-ATL REGION. THIS MOISTURE WILL
OVERRUN INTO A STRENGTHENING COLD SECTOR WITH A 1040+ SURFACE
RIDGE AND NARROW ZONE OF FROZEN PRECIP IS POSSIBLE. THE PRIME SPOT
FOR SNOW ACCUMULATIONS APPEARS LIKELY FROM NORTHERN PA/SOUTHERN NY
STATE INTO NORTHERN CT/WESTERN MA. ICING MAY EXTEND SOUTH INTO THE
CENTRAL APPALACHIANS OVER SOUTH CENTRAL PA INTO EXTREME WESTERN MD.

A FEW ROUNDS OF FROZEN PRECIP WILL BE LIKELY ACROSS THE PLAINS AND
MID TO UPPER MS VALLEY. A CONCENTRATED SHIELD OF SNOW AND FREEZING
RAIN IS ALREADY PRESENT FROM OK/KS NEWRD INTO NE/IA/NWRN MO. THIS
PLUME OF MOISTURE WILL GRADUALLY WEAKEN DURING THE COURSE OF THE
DAY, AS VERTICAL LIFT DECREASES AND THE ASSOCIATED PLUME OF DEEPER
MOISTURE ADVANCES DOWNSTREAM INTO THE NORTHERN MID-ATL STATES.
MEANWHILE UPSTREAM, A SHORT WAVE OVER THE FOUR CORNERS REGION WILL
MOVE THROUGH THE CENTRAL/SOUTHERN ROCKIES AND EJECT OUT INTO THE
CENTRAL PLAINS BEFORE REACHING THE MID TO UPPER MS VALLEY. ONCE
AGAIN, MOST OF THE FOCUS WILL BE NEAR A FRONT TO THE SOUTH BUT
ENOUGH MOISTURE AND LIFT WILL ALLOW ANOTHER CONCENTRATED PRECIP
SHIELD TO FLOURISH NEAR A DEVELOPING SURFACE WAVE. THIS MEANS SNOW
ACCUMULATIONS POSSIBLE FROM NE AND EASTERN SD/SERN ND INTO MN/NWRN
IA AND NORTHERN WI/UP OF MI AND ICE POTENTIAL FROM NORTHERN
TX/CENTRAL OK UP THROUGH EASTERN KS/SERN NE/NORTHERN MO INTO
IA/SERN MN AND SOUTHERN WI.

FINALLY A VERY STRONG SHORT WAVE TROUGH OVER THE PAC NW WILL DIVE
SOUTH TOWARD CA AND THE WESTERN GREAT BASIN. MAINLY WIDESPREAD
LIGHT TO MODERATE OROGRAPHIC SNOW IS LIKELY ACROSS THE WEST WITH
THE LACK OF SIGNIFICANT PAC MOISTURE TRANSPORT.

...FRIDAY...

3 SPOTS FOR CONCERN ON FRI, NORTHEAST, GREAT BASIN/CENTRAL ROCKIES
INTO CENTRAL PLAINS AND THE PAC NW/NORTHERN ROCKIES. THE SURFACE
WAVE THAT BEGINS TO FORM OVER THE UPPER MS VALLEY FROM THURS/EARLY
FRI WILL SHIFT UP INTO EASTERN CANADA AND MOISTURE WILL ONCE AGAIN
OVERRUN INTO THE COLD SECTOR WITH A RETREATING AREA OF HIGH
PRESSURE FOR POTENTIAL ICING FROM PARTS OF PA/NORTHERN NJ
NORTHWARD, WHILE HEAVIER SNOW REMAINS MOSTLY NORTH OF THE BORDER.

POTENT SHORT WAVE WILL SLIDE EAST THROUGH THE GREAT
BASIN/INTER-MOUNTAIN WEST TO THE CENTRAL ROCKIES/FRONT RANGE TO
PRODUCE HEAVY OROGRAPHIC SNOWFALL FROM THE UT WASATCH TO THE CO
ROCKIES WITH SOME SNOW REACHING THE FRONT RANGE OF THE CENTRAL
ROCKIES INTO THE CENTRAL PLAINS. A LIGHT TRANSITION ZONE WILL BE
POSSIBLE FROM KS NEWRD INTO NORTHERN MO/SOUTHERN IA.

FINALLY ANOTHER VIGOROUS UPPER-LEVEL SHORT WAVE TROUGH WILL STREAM
INTO THE PAC NW TO PRODUCE INTENSE SNOW ACROSS THE WA OLYMPICS AND
CASCADES INTO THE NORTHERN ROCKIES.

...SATURDAY...

2 HOT SPOTS FOR THE BEGINNING OF THE WEEKEND, UPPER MIDWEST/MS
VALLEY AND PAC NW/NORTHERN INTER-MOUNTAIN WEST. A POWERFUL SHORT
WAVE EMERGING FROM THE CENTRAL ROCKIES WILL LIFT TOWARD THE UPPER
MS VALLEY AND TAKE A NEG TILT. AN ASSOCIATED SURFACE LOW NEAR THE
TX PANHANDLE WILL INTENSIFY RAPIDLY, WHILE TRACKING NORTH AND EAST
TO REACH WI/MI. THE RESULTANT WILL BE A POTENTIAL MAJOR SNOW
STORM, AS THE SYSTEM INGESTS DEEP MOISTURE TO DEVELOP A HEALTHY
COMMA HEAD/DEFORMATION ZONE. RIGHT NOW BASED ON LIMITED GUIDANCE,
THE MAIN CORRIDOR FOR SIGNIFICANT ACCUMULATIONS WOULD BE FROM
EASTERN NE/SERN SD/NWRN IA THROUGH SERN MN AND NWRN WI, WHICH
WOULD INCLUDE THE MSP METRO AREA.

THE SHORT WAVE ARRIVING INTO THE PAC NW ON FRI WILL DIVE TOWARD
THE CENTRAL/SOUTHERN ROCKIES ON SAT, ONLY TO BE FOLLOWED UP BY
ANOTHER SET OF LOWERING UPPER HEIGHTS INTO THE NW. EXPECT THE
FAVORED TERRAIN FROM THE NW THROUGH THE INTER-MOUNTAIN WEST TO SEE
HEAVY SNOWFALL PROBS.   


MUSHER