Preliminary Forecasts
Issued by NWS

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FXUS02 KWNH 270533
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1232 AM EST TUE JAN 27 2015

VALID 12Z FRI JAN 30 2015 - 12Z TUE FEB 03 2015

...OVERALL FLOW PATTERN AND GUIDANCE/UNCERTAINTY ASSESSMENT...

TROUGH ENERGIES ALOFT AMPLIFY OVER THE EAST BEFORE SWINGING OFF
THE ATLANTIC COAST SATURDAY. UPSTREAM...A NRN STREAM RIDGE
BUILDING INTO THE NORTHWEST/BRITISH COLUMBIA ALLOWS SHORTWAVE
IMPULSES TO DIG SOUTHEASTWARD TO THE N-CENTRAL U.S TO CARVE OUT AN
AMPLIFIED TROUGH WELL DOWN THROUGH THE CENTRAL AND ERN US. IN A
SRN STREAM...MID-UPPER LEVEL ENERGY OVER SRN CA DAY3/FRI SHOULD
GRADUALLY SLIP SOUTHEASTWARD OVER THE SW US TO NRN MEXICO THIS
WEEKEND TO EARLY NEXT WEEK. MEANWHILE BY EARLY NEXT WEEK...THE
PATTERN BECOMES INCREASING WET FOR THE PAC NW.

THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF THE REASONABLY COMPATABLE 18 UTC GFS/GEFS MEAN
AND 12 UTC ECMWF AND ECMWF/NAEFS ENSEMBLE MEANS. THIS HAS GOOD WPC
CONTINUITY AND AT LEAST AVERAGE PREDICTABILITY.

...SENSIBLE WEATHER HIGHLIGHTS...

MODERATE SNOW WILL BE POSSIBLE WITH THE SURFACE WAVE TRACKING INTO
NEW ENGLAND FRI ALONG WITH POTENTIAL FOR STRONG WINDS ON THE HEELS
OF A MAJOR NORTHEAST SNOWSTORM IN THE SHORT RANGE PERIOD. BEHIND
THIS FEATURE...ANOTHER BIG STORY WILL BE ARCTIC AIR SURGING SOUTH
AND EASTWARD WITH THE BROAD TROUGH CARVING OUT OVER THE
CENTRAL/EASTERN U.S..THE EPICENTER OF THE COLD AIR SHOULD BE FROM
THE UPPER GREAT LAKES INTO INTERIOR NEW ENGLAND. THE RUSH OF COLD
AIR SHOULD ALSO CHURN AMPLE SNOW SHOWERS DOWNWIND OF THE GREAT
LAKES.

UPSTREAM...PACIFIC IMPULSES WORK INTO AN AMBEINT MEAN RIDGE
POSITION EVENTUALLY WITTLE THROUGH INTO THE NWRN US AND ASSOCIATED
LIFT AND MOISTURE BECOMES FAVORABLE IN MOST GUIDANCE TO PRODUCE
MODERATE PRECIPITATION WITH SYSTEM APPROACH/PASSAGE BY EARLY NEXT
WEEK ON DAYS 6/7 ...ESPECIALLY OVER FAVORED TERRAIN.

AT LOWER LATITUDES...EXPECT WIDESPREAD PRECIPITATION OVER THE SWRN
US AND INTO THE UPSLOPE FETCH OUT FROM THE GULF OF MEXICO INLAND
ACROSS THE S-CENTRAL PLAINS/ROCKIES. A LOT OF UNCERTAINTY STILL
EXISTS AS THE ENERGY ALOFT SINKS SOUTHEASTWARD AND PRECIPITATION
SPREADS ENEWD...BUT GUIDANCE SIGNALS A SWATH OF PRECIPITATION THEN
SPREADS OVER ROUGHLY THE SRN 2/3RDS OF THE E-CENTRAL US INTO EARLY
NEXT WEEK. THIS OCCURS WITH COMPLEX STREAM INTERACTION AND INDUCED
WAVY FRONTAL FOCUS THAT LEADS TO EAST COASTAL LOW AND ENHANCED
PCPN GENESIS UP THE COAST INTO MON.
GIVEN THE FRESH SURGE OF ARCTIC AIR SPREADING INTO THE CENTRAL/ERN
U.S. OVERTOP THESE FEATURES...AN ASSOCIATED WINTER WEATHER THREAT
EXISTS ALL ALONG THE NRN EDGE OF THE THIS OVERALL PRECIPITATION
SHIELD.

SCHICHTEL


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