Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 242002
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
401 PM EDT FRI OCT 24 2014

VALID 00Z SAT OCT 25 2014 - 00Z TUE OCT 28 2014


DAYS 1 THROUGH 3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

MOISTURE AND LIFT ASSOCIATED WITH A STRONG SHORTWAVE PRESENTLY OFF
OF THE CA COAST WILL PRODUCE QPF AND SNOWFALL ACROSS THE PACIFIC
NORTHWEST INTO THE NORTHERN ROCKIES. FOR THE MOST PART...THE QPF
PORTION OF THE FORECAST WAS BASED ON A BLEND OF THE 12Z NAM..06Z
GFS..00Z ECMWF AND THE LATEST WPC QPF. THE THERMAL PORTION OF THE
FORECAST WAS BASED ON A BLEND OF THE 12Z NAM..09Z SREF..06Z GFS
AND THE 00Z ECMWF.  AS NOTED IN THE PMDHMD..THE 12Z GFS HAS SLOWED
CONSIDERABLY FROM ITS PREVIOUS RUN AND WAS A RELATIVE OUTLIER
AMONG THE 12Z MODELS.

ON DAY 1...THE BROAD WARM ADVECTION PATTERN AHEAD OF THE SHORTWAVE
AS IT MOVES ONSHORE WILL SEND SNOW LEVELS HIGHER DURING THE
PERIOD...CONFINING THE RISK FOR ANY HEAVY ACCUMULATIONS TO THE
HIGHER PEAKS OF THE NORTHERN CASCADES.

DURING DAY 2...AS THE SHORTWAVE MOVES ACROSS THE
NORTHWEST...DECREASING SNOW LEVELS IN THE WAKE OF THE ASSOCIATED
COLD FRONT ARE EXPECTED TO EXPAND THE HEAVY SNOW THREAT ACROSS THE
NORTHERN CASCADES AND INTO THE NORTHERN ROCKIES.  THE THE LOW TO
MID LEVEL FLOW SHOULD FOCUS THE THE MOISTURE ON THE TERRAIN OF
WA/OR...AS WELL AS THE BITTERROOTS OF ID AND THE GRAND TETONS OF
WY.

BY DAY 3...AS THE SHORTWAVE ELONGATES INTO A LONGWAVE TROUGH THAT
CROSSES THE ROCKIES INTO THE PLAINS...THE MOISTURE SUPPLY AND
REBOUNDING HEIGHTS WILL BECOME LIMITING FACTORS FOR HEAVY SNOW
ACROSS THE REGION.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA

$$





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