Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 022113
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 PM EST FRI DEC 02 2016

VALID 00Z SAT DEC 03 2016 - 00Z TUE DEC 06 2016

DAY 1 TO 3...

...PACIFIC NORTHWEST TO THE NORTHERN ROCKIES/NORTHERN PLAINS...

A DEEPENING TROUGH OVER THE WESTERN UNITED STATES IS EXPECTED TO
BRING HEAVY SNOW SPREADING ACROSS MANY REGIONS OF THE
NORTHWESTERN/GREAT BASIN AND NORTHERN ROCKIES INTO THE NORTHERN
PLAINS. WHILE SIGNIFICANT SNOW WILL BE CONFINED TO THE THE
WASHINGTON CASCADES AND THE MOUNTAINS OF NORTHERN IDAHO INTO
WESTERN MONTANA ON DAY 1/FRIDAY EVENING INTO SATURDAY...SNOW WILL
BECOME HEAVIER AND MORE WIDESPREAD ON DAY 2/SATURDAY EVENING INTO
SUNDAY AND MORE WIDESPREAD OVER THE WESTERN HALF OF THE NATION ON
DAY 3/SUNDAY EVENING INTO MONDAY. THERE IS A MODERATE TO HIGH
PROBABILITY OF 6 TO 12 INCHES OF SNOW AND GREATER ON DAY 2 ACROSS
THE WASHINGTON AND OREGON CASCADES AS WELL AS THE BITTERROOTS IN
NORTHERN IDAHO AND ACROSS THE HIGHER ELEVATION OF NORTHWESTERN
MONTANA.  THE MORE WIDESPREAD SNOW ON DAY 3 IS EXPECTED FROM THE
CASCADES ACROSS THE MOUNTAINS OF IDAHO IN WESTERN MONTANA/THE
MOUNTAINS OF WESTERN AND NORTHERN WYOMING AND ACROSS THE
WASATCH/UINTA IN UTAH.

THE COLDEST AIRMASS OF THE SEASON IS EXPECTED TO PLUNGE SOUTH AND
EASTWARD ACROSS THE NORTHWEST INTO THE NORTHERN ROCKIES AND
NORTHERN PLAINS SO THE SNOW WILL BE ACCOMPANIED BY STRONG WINDS
AND VERY LOW TEMPERATURES.  EVEN ACROSS THE LOWER ELEVATIONS OF
COASTAL OREGON AND WASHINGTON...RAIN IS EXPECTED TO CHANGE TO SNOW
WHERE AN INCH OR TWO IS CURRENTLY POSSIBLE.

DAYS 1 TO 2...

...SOUTHERN ROCKIES/SOUTHERN PLAINS...

AN UPPER LEVEL LOW CENTER WITHIN A SPLIT FLOW REGIME OVER THE WEST
WILL CLOSE OFF ON SATURDAY OVER NORTHWESTERN MEXICO.   LOWER
TROPOSPHERIC SOUTHEASTERLY FLOW WILL TRANSPORT MOISTURE ACROSS
EASTERN NEW MEXICO INTO THE TEXAS AND OKLAHOMA PANHANDLES INTO
PORTIONS OF KANSAS ON FRIDAY INTO SATURDAY MORNING  WITH
TEMPERATURES COLD ENOUGH TO SNOW ALONG THE NORTHWESTERN FRINGE OF
A WIDESPREAD PRECIPITATION SHIELD.  THE NORTHERN EXTENSION OF THE
SNOWFALL OVER THE ROCKIES WILL BE LIMITED BY THE OTHER PORTION OF
THE SPLIT FLOW AS A TROUGH MOVES TO THE NORTH OF THE UPPER LOW
CENTER.  HOWEVER...THIS IS THE TROUGH THAT COULD AFFECT THE
MIDWEST AND NORTHEAST ON DAYS 2 TO 3 AS MOISTURE IS BROUGHT
NORTHWARD EAST OF THE NORTHERN TROUGH AXIS.

WHILE THERE IS A RELATIVELY LOW PROBABILITY OF SNOW EXCEEDING 4
INCHES ACROSS PORTIONS OF NEW MEXICO INTO THE TEXAS AND OKLAHOMA
PANHANDLES BUT A 50 TO 70 PERCENT CHANCE OF GREATER THAN 4 INCHES
ACROSS THE SACRAMENTO AND BLACK RANGE MOUNTAINS IN SOUTHERN NEW
MEXICO.

DAYS 2 TO 3...

...MID MISSISSIPPI VALLEY/MIDWEST/NORTHEAST...

THE NORTHERN STREAM TROUGH MENTIONED EARLIER IS A LITTLE BIT OF
FORECAST PROBLEM AS VARIOUS MODEL SOLUTIONS MOSTLY INDICATE A WEAK
SYSTEM.  HOWEVER...THE 12Z ECMWF HAS IT A BIT STRONGER...WITH
POSSIBLY GREATER SNOWFALL AMOUNTS.  AT PRESENT...THERE IS A
MODERATE TO HIGH PROBABILITY OF LIGHT SNOW...MOSTLY OF THE 1 TO 2
INCH VARIETY FROM IOWA/NORTHERN ILLINOIS/WISCONSIN/EASTERN
MINNESOTA/MICHIGAN ON DAY 2/SATURDAY EVENING INTO SUNDAY SPREADING
INTO PORTIONS OF PENNSYLVANIA AND NEW YORK ON DAY 3/SUNDAY EVENING
INTO MONDAY. CURRENTLY...PROBABILITIES FOR GREATER THAN 4 INCHES
OF SNOW IN THESE AREAS IS LESS THAN 10 PERCENT.  THIS IS A PORTION
OF THE FORECAST THAT MAY HAVE RELATIVELY LOW RELIABILITY GIVEN
SOME OF THE LATEST MODELS SUGGESTING THAT 3 TO  4 INCH SNOW IS NOT
OUT OF THE QUESTION.


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA



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