Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 270821
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
320 AM EST THU NOV 27 2014

VALID 12Z THU NOV 27 2014 - 12Z SUN NOV 30 2014

DAYS 1 TO 3...

...PACIFIC NORTHWEST/NORTHERN ROCKIES/NORTHERN PLAINS/UPPER
MIDWEST...

OVER THE NEXT 3 DAYS...THERE WILL BE QUITE A SHIFT WITH THE UPPER
LEVEL PATTERN ACROSS THE US AS THE EASTERN TROUGH LIFTS
NORTHEASTWARD AND A SERIES OF TROUGHS...SEVERAL COMING ASHORE
ACROSS THE EASTERN PACIFIC AND A STRONG SHORTWAVE TROUGH DROPPING
SOUTH AND EASTWARD ACROSS THE NORTHWEST PORTION OF THE COUNTRY
CREATE HEAVY SNOW POSSIBILITIES FOR THE NORTHWEST MOUNTAINS.

COLD AIR OVER THE NORTHERN PLAINS ON THURSDAY WILL RETREAT AS
WARMER AIR SURGES NORTHWARD. OUT AHEAD OF AN ADVANCING WARM
FRONT...A BAND OF MOSTLY LIGHT SNOW WILL DRIFT EASTWARD  ACROSS
NORTH DAKOTA WITH 1 TO 3 INCHES COMMON AND A LOW PROBABILITY THAT
A FEW AMOUNTS WILL APPROACH 4 INCHES.

WHILE A STREAM OF PACIFIC MOISTURE WILL PRODUCE SOME SIGNIFICANT
SNOW ACROSS THE CASCADES/BITTERROOTS AND NORTHWESTERN MONTANA ON
THURSDAY...THE REAL THREAT FOR HEAVY SNOW WILL BE ON FRIDAY INTO
SATURDAY/DAYS 2 TO 3. AMOUNTS OF OVER A FOOT OF SNOW WILL BE
LIKELY ACROSS THE CASCADES/BITTERROOTS AND ESPECIALLY FOR THE
ROCKIES IN NW MONTANA. THE HEAVY AMOUNT ARE RELATED TO THE
COMBINATION OF A TROUGH MOVING EASTWARD INTO THE WESTERN STATES
FROM THE EASTERN PACIFIC AND THE SEPARATE TROUGH DROPPING
SOUTHEASTWARD ACROSS SOUTHWESTERN CANADA.

MUCH COLDER AIR WILL DROP SOUTHWARD WITH THE PROGRESSION OF THE
TROUGH MOVING EASTWARD FROM SOUTHWESTERN CANADA FROM LATE FRIDAY
NIGHT INTO EARLY SUNDAY AND THE SIGNIFICANT SNOW WILL ALSO SHIFT
SOUTHEASTWARD ACROSS OREGON/PARTS OF NORTHERN CALIFORNIA/THE
SIERRA/CENTRAL IDAHO INTO SOUTHWESTERN MONTANA AND NORTHWESTERN
WYOMING. THIS SHIFT IS IN OCCURRING WITHIN THE ENTRANCE REGION OF
A DEVELOPING JET OVER THE NORTHERN ROCKIES RESPONDING TO AN
INCREASE IN CONFLUENT FLOW ACROSS THE NORTHERN TIER OF STATES.

THE PROBABILITY FOR SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

KOCIN

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