Quantitative Precipitation Forecast
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FOUS11 KWBC 302049
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 PM EST WED NOV 30 2016

VALID 00Z THU DEC 01 2016 - 00Z SUN DEC 04 2016

DAY 1 TO 3...

...PACIFIC NORTHWEST/NORTHERN INTER-MOUNTAIN WEST...

A SHORTWAVE TROUGH CROSSING THE PACIFIC NORTHWEST ON WEDNESDAY
WILL BE FOLLOWED BY ANOTHER TROUGH THAT WILL APPROACH THE BRITISH
COLUMBIA COAST ON THURSDAY AND SHEAR OUT AS ONE PORTION TAKES THE
NORTHWESTERN TROUGH AND AMPLIFIES IT OVER THE WESTERN UNITED
STATES.  ONLY MODEST MOISTURE WILL BE ASSOCIATED WITH THESE
SYSTEMS WHILE THE BEST CHANCES FOR SIGNIFICANT SNOW WILL BE FOUND
ACROSS THE BITTERROOTS AND THE ROCKIES OF WESTERN MONTANA.
MODERATE TO HIGH PROBABILITIES FOR 4 TO 8 INCHES ARE INDICATED
OVER THESE AREAS AS WELL AS PORTIONS OF THE WASHINGTON CASCADES ON
DAY 1/WEDNESDAY NIGHT INTO THURSDAY.  WHILE SNOW WILL CONTINUE
ESPECIALLY ACROSS THE WASHINGTON CASCADES ON DAYS 2 INTO
3/THURSDAY NIGHT INTO SATURDAY...MOST OF THE HEAVY SNOW WILL
REMAIN NORTH ACROSS THE BORDER IN THE MOUNTAINS OF BRITISH
COLUMBIA.

...NORTHERN MAINE/EASTERN GREAT LAKES...

STRONG DIFFLUENT UPPER FLOW AHEAD OF A SIGNIFICANT TROUGH
APPROACHING THE EAST COAST WILL GENERATE THE DEVELOPMENT OF A
SECONDARY AREA OF LOW PRESSURE OVER SOUTHERN NEW ENGLAND OVERNIGHT
WITH LOW PRESSURE THEN MOVING ALONG THE MAINE COAST INTO NOVA
SCOTIA BY THURSDAY EVENING.  A SECOND ROUND OF HEAVY SNOW IS
EXPECTED TO DEVELOP OVERNIGHT INTO THURSDAY MORNING AS A STRONG
LOW LEVEL JET BRINGS SIGNIFICANT MOISTURE AGAIN ACROSS NORTHERN
MAINE WHERE TEMPERATURES WILL BE COLD ENOUGH FOR SNOW.  THERE ARE
HIGH PROBABILITIES FOR 8 OR MORE INCHES OF SNOW WITH SNOWFALL
FALLING OFF QUICKLY FARTHER SOUTH WHERE MOSTLY RAIN IS LIKELY TO
FALL...EVEN OVER CENTRAL MAINE.  HOWEVER...THERE IS AT LEAST A 50
PERCENT CHANCE THAT GREATER THAN 12 INCHES OF SNOW WILL FALL NEAR
THE NORTHERN MAINE BORDER.

MODERATELY COLD AIR ASSOCIATED WITH CYCLONIC FLOW AROUND THE
DEPARTING STORM SYSTEM WILL GENERATE SOME LAKE EFFECT SNOW WITH
ONLY GENERALLY LIGHT ACCUMULATIONS EXPECTED DOWNWIND OF LAKES
SUPERIOR/MICHIGAN AND HURON ALTHOUGH LOCALLY HEAVY AMOUNTS ARE
LIKELY.  MORE SIGNIFICANT SNOW IS FORECAST TO FALL DOWNWIND OF
LAKES ERIE AND ONTARIO WHERE THE GREATEST PROBABILITIES OF GREATER
THAN 4 INCHES OF SNOW IS EXPECTED OVER THE TUG HILL PLATEAU IN NEW
YORK.  HOWEVER...TWO DAY TOTALS GREATER THAN 4 INCHES ARE POSSIBLE
EAST OF LAKE ERIE AS WELL.

DAY 3...

...SOUTHERN ROCKIES/SOUTHERN PLAINS...

A DEEP UPPER TROUGH IS EXPECTED TO DEVELOP OVER THE WEST ON
SATURDAY AS A LARGE RIDGE BUILDS OVER THE EASTERN PACIFIC.
PRESENTLY...LITTLE WINTER WEATHER IS FORECAST BUT THERE ARE
DIFFERENT MODEL CAMPS SUGGESTING DIFFERENT SOLUTIONS...SO
UNCERTAINTY IS RELATIVELY HIGH.  THE 12Z GFS/NAM MINIMIZED THE
THREAT OF SIGNIFICANT SNOWFALL AS THE PRECIPITATION SHIELD
FORECAST BY THESE MODEL SYSTEMS REMAINS MOSTLY TOO FAR EAST FOR
TEMPERATURES COLD ENOUGH FOR FROZEN PRECIPITATION.  HOWEVER...
FORECASTS BY THE 00Z/12Z ECMWF/12Z UKMET/CANADIAN AND UKMET SEEMED
MORE SUGGESTIVE THAT SNOW COULD BE A CONCERN...ESPECIALLY ACROSS
NORTHERN TEXAS INTO PORTIONS OF EASTERN NEW MEXICO.  WHILE THE
DETERMINISTIC FORECAST FAVORED THE GFS AT THIS TIME...THE ENSEMBLE
PROBABILITIES SHOW A 20 TO 40 PERCENT CHANCE OF GREATER THAN 4
INCHES OF SNOW ACROSS THIS REGION.  THEREFORE...THERE IS STILL A
COMPELLING CHANCE FOR SNOWFALL ACROSS THIS REGION EVEN THOUGH
PROBABILITIES ARE CURRENTLY LESS THAN 50 PERCENT.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

KOCIN

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