Quantitative Precipitation Forecast
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FOUS11 KWBC 250510
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1209 AM EST THU DEC 25 2014

VALID 12Z THU DEC 25 2014 - 12Z SUN DEC 28 2014

PACIFIC NORTHWEST...

USED AN INTERMEDIATE SOLUTION INVOLVING THE 00Z GFS/12Z ECMWF FOR
THE LIQUID EQUIVALENT AMOUNTS AND THERMAL PROFILES FOR SNOW
DEVELOPING ACROSS THE CASCADES INTO THE BITTERROOTS/SAWTOOTH
RANGE/NRN. TETONS SATURDAY NIGHT INTO SUNDAY...WITH THE FASTER NAM
DISCOUNTED DUE TO ITS FAST POSITION WITHIN THE SOLUTION ENVELOPE.
THE MODEST ONSHORE FLOW AND OROGRAPHIC ASCENT FAVOR MODERATE AND
HIGH PROBABILITIES OF 8 INCHES FOR THE HIGHER ELEVATIONS ALONG
WITH SLIGHT PROBABILITIES FOR 12 INCHES.  USED ABOUT 20 PERCENT OF
THE 18Z GEFS MEAN AND 12Z ECMWF ENSEMBLE MEAN TO ADDRESS THE
GROWING SOLUTION SPREAD.

THE PROBABILITY OF 0.25 INCHES OF ICE IS LESS THAN 10 PERCENT.

INTERMOUNTAIN WEST/CNTRL-SRN ROCKIES/HIGH PLAINS...

MODEL AGREEMENT IS QUITE GOOD CONCERNING THE
TRAJECTORY/SPEED/INTENSITY OF THE SHORTWAVE TROUGH CROSSING THE
INTERMOUNTAIN WEST TODAY AND THE CENTRAL-SOUTHERN ROCKIES ON
FRIDAY BEFORE WEAKENING ACROSS THE PLAINS.  USED ABOUT 1/3 OF THE
00Z NAM/00Z GFS/12Z ECMWF FOR THE LIQUID EQUIVALENT AMOUNTS AND
THERMAL PROFILES TO DERIVE THE SNOW PROBABILITIES FOR THE REGION.
EXPECT THE WASATCH/TETONS/CENTRAL ROCKIES/SAN JUANS/SANGRE DE
CRISTOS...EXTENDING SLIGHTLY INTO THE HIGH PLAINS OF COLORADO AND
WYOMING TO RECEIVE THE HIGHEST SNOW TOTALS...WITH SOME MOUNTAIN
LOCATIONS RECEIVING 6 TO 12 INCHES...POSSIBLY MORE LOCALLY.  A
NARROW REGION OF LIGHT FREEZING RAIN MAY ALSO DEVELOP ACROSS
WESTERN TEXAS AND WESTERN OKLAHOMA FRIDAY NIGHT...ALTHOUGH THE
LIGHT AMOUNTS PROJECTED BY GUIDANCE AS WELL AS THE MODERATE
SOLUTION SPREAD PRODUCE PROBABILITIES OF 0.25 INCHES OF ICE THAT
ARE BELOW 10 PERCENT.

JAMES

$$




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