Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 212034
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 PM EST SAT JAN 21 2017

VALID 00Z SUN JAN 22 2017 - 00Z WED JAN 25 2017

DAYS 1-3...

...WEST INTO PLAINS....

A VERY DEEP LOW PRESSURE SYSTEM OFF THE WEST COAST OF THE UNITED
STATES WITH A VERY ACTIVE UPPER JET WILL PUMMEL CA AND THE WEST
OVER THE NEXT TWO DAYS WITH EXTREMELY HEAVY SNOW BEFORE ADVANCING
DOWNSTREAM TOWARD THE ROCKIES/CENTRAL PLAINS ON TUES. THIS IS THE
LAST IN A SERIES OF POWERFUL WEATHER SYSTEMS THAT HAVE BROUGHT
EXCESSIVE SNOWFALL TO FORMERLY PARCHED CENTRAL AND NORTHERN
CALIFORNIA.

WATER VAPOR IMAGERY THIS AFTN SHOWS A DYNAMIC LOW PRESSURE SYSTEM
DIGGING SOUTH AND EAST OVER THE ERN PAC WITH A LONG FETCH OF PAC
AND SUBTROPICAL MOISTURE SPREADING FROM NEAR HAWAII AND DIRECTED
TOWARD CA. THIS PHASED MOISTURE PLUME WILL INUNDATE NRN/CENTRAL CA
AND REACH SRN CA BY LATE SUN. THE GUIDANCE SUGGESTS 2 TO 3 FEET OF
SNOW FOR PARTS OF THE NRN CA MTNS AND ENTIRE SIERRA.

THE FOCUS ON SUN EVENING THROUGH MON SHIFTS TO THE SOUTHERN SIERRA
AND SOUTHERN CA TO THE INTER-MOUNTAIN WEST... WASATCH/TETONS AND
CO ROCKIES. THE VERY ACTIVE JET WITH EXTREMELY FAVORABLE LEFT EXIT
REGION UPPER DYNAMICS WILL POUND THE CENTRAL/SRN SIERRA WITH
ANOTHER 1 TO 2 FEET... AFFECT THE SOUTHERN CA MTNS OF THE SAN
GABRIEL/SAN BERNADINO AND REALLY IMPACT THE INTERIOR TERRAIN WITH
DIFLUENT SWRLY FLOW ALOFT.

BY MON EVENING INTO TUES... THE ENTIRE STORM SYSTEM EMERGES FROM
THE CENTRAL ROCKIES AND BEGINS TO EJECT OUT INTO THE CENTRAL
PLAINS. A DECENT AMOUNT OF SPREAD EXISTS AT THE MOMENT BUT THE
CONSENSUS A STREAK OF HEAVY OVERRUNNING SNOW IS POSSIBLE. WPC
FOLLOWED A COMPROMISE AT THE MOMENT OF THE GFS/ECMWF FOR AN AXIS
OF ACCUMULATING SNOW FROM WY INTO SD/NRN NE.


INTERIOR NORTHEAST AND NEW ENGLAND...

A VERY ACTIVE SOUTHERN STREAM SYSTEM IS BEGINNING TO EMERGE FROM
THE SOUTHERN ROCKIES THIS AFTN AND WILL INTENSIFY ON SUN... AS IT
ROLLS ACROSS THE SRN TIER OF THE COUNTRY. BY MON... THIS LOW
WRAPPED UP LOW PRESSURE SYSTEM ALOFT WILL BEGIN TO TRANSITION FROM
THE SOUTHERN APPALACHIANS TO THE MID-ATL STATES AND INTERACT WITH
A BLOCK OR IMPRESSIVE RIDGE OF HIGH PRESSURE EXTENDING FROM THE
ATLANTIC INTO EASTERN CANADA. A RATHER IMPRESSIVE SQUEEZE PLAY
WILL OCCUR... WHILE MOISTURE EXPANDS NORTHWARD FROM THE SOUTHEAST
TO NRN MID-ATL. ITS THE WESTERN PERIPHERY OF THIS ENHANCED PRECIP
THAT THE LATEST GFS AND ECMWF SUGGEST COULD YIELD SNOW AND
POSSIBLE ICING ACROSS MUCH OF NY STATE/NERN PA. THE MOST
CONCERNING AREA APPEARS TO BE WESTERN NY OR SOUTH OF LAKE
ONTARIO... WHERE THE MODEL DUO INDICATES POSSIBLE 2-4 INCHES WITH
LOCALLY HIGHER AMOUNTS OF 6. THE MID TO UPPER LOW AND NEG TILT
UPPER TROUGH WILL LIFT NORTH AND EAST ON TUES... WHILE A
DEVELOPING AREA OF SURFACE LOW PRESSURE FORMS ALONG THE NERN
SEABOARD. ONCE AGAIN... MINIMAL SPREAD BETWEEN THE GFS/ECMWF
INDICATES POSSIBLE SNOW/FREEZING RAIN ACROSS NY STATE INTO
INTERIOR AND NRN PARTS OF NEW ENGLAND WITH THE LARGEST SNOW
ACCUMULATIONS OCCURRING NORTH OF THE BORDER INTO SOUTHERN QUEBEC.

MUSHER

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