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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0849Z Nov 20, 2014)
 
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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
349 AM EST THU NOV 20 2014

VALID 12Z THU NOV 20 2014 - 12Z SUN NOV 23 2014


DAYS 1 THROUGH 3...


...GREAT LAKES...

HEAVY LAKE EFFECT SNOWS WILL LINGER FOR ONE MORE DAY ACROSS PARTS
OF THE GREAT LAKES ON THURS AND THIS INCLUDES THE AREA HIT HARDEST
BY THIS REGIME OF SWRN NY STATE. ANOTHER STRONG POLAR/ARCTIC
RE-ENFORCING SHORT WAVE TROUGH WILL SWEEP THROUGH THE GREAT LAKES
REGION BEFORE ADVANCING DOWNSTREAM INTO SERN CANADA. THIS WILL
RESULT IN ANOTHER VERY COLD AND ANOMALOUS AIR MASS TO INTERACT
WITH THE WARM LAKES TO IGNITE ANOTHER ROUND OF NON-SHEAR UNIFORM
FLOW ACROSS PARTS OF THE LAKES. THIS WILL RESULT IN SEVERAL
MESOSCALE/LONG FETCH HEAVY LAKE EFFECT SNOW BANDS OFF LAKES ERIE
AND ONTARIO WITH THE MOST OPPORTUNE AREAS FOR SIGNIFICANT
ACCUMULATIONS BEING PARTS OF SWRN NY STATE... NEAR OR JUST SOUTH
OF BUF... AND INTO UPSTATE NY/TUG-HILL PLATEAU. ITS THE AREA OF
SWRN NY STATE THAT IS MOST CONCERNING AS SOME HI RES MODELS AND
NAM/ECMWF DEPICT AN ALMOST SEMI-IDENTICAL SETUP THAT COULD RESULT
IN QUITE IMPRESSIVE SNOW TOTALS. OVERALL WPC STAYED VERY CLOSE TO
THE HI RES NAM/NAM CO-NEST AND ECMWF FOR HEAVY SNOW PROBS ON
THURS. FOR MORE ON SPECIFIC SNOWFALL AMOUNTS... PLEASE REFER TO
YOU LOCAL WEATHER SERVICE FORECAST OFFICE.

...PACIFIC NORTHWEST/NORTHERN ROCKIES/GREAT BASIN...

LATE FRI AND INTO THE WEEKEND... RATHER MOIST ZONAL FLOW OVER THE
PAC WILL REACH THE PAC NW AND SPREAD INTO THE NRN
ROCKIES/INTER-MOUNTAIN WEST. A CLOSED UPPER VORTEX FORMING NEAR
THE ALEUTIAN CHAIN WILL STEER AN ACTIVE UPPER JET AND SPECIFIC JET
STREAK INTO THE PAC NW LATE FRI/EARLY SAT. THIS WILL RESULT IN A
CRASH OF UPPER HEIGHTS AND A WEALTH OF PAC MOISTURE TRANSPORTING
INTO MUCH OF THE WEST. EXPECT IDEAL ONSHORE COMPONENT WITH
OROGRAPHICS AND STEADY LOWERING OF SNOW LEVELS FROM THE WA/OR
CASCADES INTO THE INTERIOR NRN BITTERROOTS AND
BLUE/SAWTOOTH/SALMON RIVER MTNS ON FRI AND ON SAT FROM THIS SAME
AREA DOWNSTREAM INTO THE TETONS/WASATCH AND WRN CO ROCKIES. WPC
GENERALLY FOLLOWED A BLEND OF THE GLOBAL MODELS OR GFS/ECMWF ON
THE HANDLING OF THIS PATTERN CHANGE... SYSTEM ARRIVING INTO THE
WEST... AND THE HEAVY SNOW PROBS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT. 

MUSHER