Quantitative Precipitation Forecast
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FOUS11 KWBC 041928
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
227 PM EST SUN DEC 04 2016

VALID 00Z MON DEC 05 2016 - 00Z THU DEC 08 2016


DAYS 1-2...

...GREAT LAKES/NORTHEAST...

THE NEGATIVELY TILTED TROUGH THAT HAS PANNED OUT WITH HIGHER SNOW
TOTALS THAN EARLIER FORECAST OVER THE MIDWEST WILL CONTINUE TO
LIFT AND WEAKEN ALTHOUGH SNOWFALL AMOUNTS WILL BE SLIGHTLY HIGHER
THAN EARLIER FORECASTS ON DAY 1/SUNDAY NIGHT INTO MONDAY.  THE
WEAKENING TREND SHOULD PREVENT SNOWFALL TOTALS TO INCREASE FROM
WHAT HAS BEEN REPORTED BUT THERE IS GENERALLY LESS THAN A 50
PERCENT CHANCE THAT SNOWFALL TOTALS WILL BE 4 INCHES OR GREATER
ACROSS NORTHERN PENNSYLVANIA INTO NEW YORK AND WESTERN NEW
ENGLAND...AS PER THE LATEST ENSEMBLES.  FAIRLY WIDESPREAD 2 TO 4
INCH AMOUNTS COULD FALL ACROSS PARTS OF THESE AREAS AS THE SYSTEM
MOVES THROUGH ON MONDAY. AND...INDIVIDUAL MODELS SHOW A HIGHER
POTENTIAL FOR GREATER THAN 4 INCHES IN NORTHERN NEW YORK.

DAYS 2 TO 3...

...MIDDLE ATLANTIC STATES/APPALACHIANS/NORTHEAST...

A DEEP LOW OVER NORTHWESTERN MEXICO WILL LIFT NORTHEASTWARD AND
BECOME A PROGRESSIVE SHORTWAVE TROUGH THAT MOVES ACROSS THE
SOUTHEAST US TO THE MID ATLANTIC COAST ON TUESDAY. A SLOW MOVING
UPPER LOW SOUTH OF GREENLAND THAT MAINTAINS AN AREA OF UPPER
CONFLUENCE OVER SOUTHEASTERN CANADA AND THE NORTHEAST US NOT ONLY
WILL HELP WEAKEN THE TROUGH CURRENTLY MOVING TOWARD THE NORTHEAST
TONIGHT BUT WILL ALSO  MAINTAIN THE CONFLUENT FLOW AS A WEAK AREA
OF HIGH PRESSURE BEHIND THE TROUGH EXITING NEW ENGLAND BUILDS
NORTHWARD ACROSS NORTHERN NEW ENGLAND.  THE COMBINATION OF THE
LIFTING SHORTWAVE TROUGH AND THE BUILDING HIGH WILL ALLOW A
SURFACE LOW TO MOVE NORTHEASTWARD FROM THE GULF TO THE OHIO VALLEY
AND A SECONDARY LOW TO FORM NEAR THE CAROLINAS.  WHILE THIS SYSTEM
IS NOT PRESENTLY EXPECTED TO BECOME A MAJOR STORM SINCE THE
SHORTWAVE SYSTEM WILL BE WEAKENING AS IT MOVES TOWARD THE EAST
COAST...SNOW/SLEET AND FREEZING RAIN WILL DEVELOP OVER THE
APPALACHIANS ON TUESDAY WITH WET SNOW FALLING ACROSS CENTRAL AND
NORTHERN PENNSYLVANIA INTO CENTRAL NEW YORK BY TUESDAY NIGHT.  LOW
TO MODERATE PROBABILITIES OF GREATER THAN 4 INCHES OF SNOW ARE
FORECAST OVER NORTH CENTRAL PENNSYLVANIA INTO SOUTHWESTERN TO
SOUTH CENTRAL NEW YORK ON DAY 2/TUESDAY INTO TUESDAY NIGHT WITH
PROBABILITIES LESS THAN 50 PERCENT ACROSS EASTERN NEW YORK AND
WESTERN NEW ENGLAND ON DAY 3/WEDNESDAY SINCE THE SYSTEM DOES NOT
APPEAR TO INTENSIFY.

DAY 1 TO 3...

...PACIFIC NORTHWEST/NORTHERN AND CENTRAL ROCKIES/CENTRAL PLAINS...

A SUCCESSION OF SHORTWAVE SYSTEMS WILL BRING FAIRLY WIDESPREAD
SNOW TO THE NORTHWEST AND THE ROCKIES AND LATER INTO THE PLAINS AS
THE MOST SIGNIFICANT PUSH OF WINTER WEATHER GRIPS MUCH OF THE
NORTHWESTERN TO CENTRAL US OVER THE NEXT SEVERAL DAYS.  WITH THE
SURGE OF ARCTIC AIR...MUCH OF THE NORTHWESTERN STATES OF
WASHINGTON/OREGON/IDAHO WYOMING AND WESTERN MONTANA WILL SEE COLD
AIR AND SNOW EVEN TO VALLEY LOCATIONS.  BY THE END OF THE FORECAST
PERIOD...SUBFREEZING TEMPERATURES WILL COVER A VAST AREA OF THE
NATION INCLUDING MUCH OF THE WEST/THE PLAINS STATES AND INTO THE
MIDWEST.

THE FIRST SHORTWAVE TROUGH WILL PUSH PACIFIC MOISTURE INLAND AS A
STRONG COLD FRONT MOVES EAST AND SOUTHWARD ACROSS THE NORTHWEST.
SNOW LEVELS WILL BE FALLING ACROSS THE NORTHWEST AS SNOW FALLS
FROM WESTERN WASHINGTON AND OREGON INTO MUCH OF THE NORTHWEST
QUARTER OF THE COUNTRY ON DAY 1/SUNDAY INTO MONDAY.  SNOWFALL
AMOUNTS WILL NOT BE EXCESSIVE BUT WILL BE SIGNIFICANT ENOUGH
ACROSS THE CASCADES WITH ACCUMULATIONS IN SOME OF THE COASTAL
RANGES BUT WILL ALSO BE WIDESPREAD ESPECIALLY ACROSS THE MOUNTAINS
OF IDAHO/WESTERN MONTANA/WYOMING/THE WASATCH AND NORTH CENTRAL
COLORADO...WHERE GREATER THAN 4 INCHES ARE LIKELY.
HOWEVER...AMOUNTS EXCEEDING 8 INCHES WILL NOT BE WIDESPREAD.  THIS
SHORTWAVE TROUGH EVENTUALLY SPAWNS A DEVELOPING SURFACE LOW ALONG
THE EASTERN SEGMENT OF THE COLD FRONT OVER THE NORTHERN PLAINS.
MOST OF THE HEAVIER SNOW WITH THIS SYSTEM IS EXPECTED NORTH OF THE
NORTH DAKOTA/CANADIAN BORDER ESPECIALLY ON DAY 2/MONDAY NIGHT INTO
TUESDAY.  HOWEVER...THERE IS A MODERATE PROBABILITY OF GREATER
THAN 4 INCHES NEAR THE EXTREME NORTHEAST NORTH DAKOTA/NORTHWEST
MINNESOTA BORDER.

THE NEXT SHORTWAVE TROUGH WILL BRING SNOW FARTHER SOUTH AS IT
MOVES ALONG THE SOUTHWARD EDGE OF THE COLD AIR OUTBREAK. there
SNOW COULD BE HEAVY ACROSS WESTERN OREGON...ESPECIALLY IN THE
MOUNTAINS OF SOUTHWESTERN OREGON INTO NORTHERN CALIFORNIA.
SNOWFALL FARTHER EASTWARD WILL BE MOSTLY RELATIVELY LIGHT ACROSS
THE INTERMOUNTAIN WEST BUT WILL AGAIN PICK UP OVER THE MOUNTAINS
OF NORTHERN COLORADO.  HEAVIEST SNOW IS LIKELY ACROSS THE SOUTHERN
OREGON CASCADES WHERE A MODERATE TO HIGH PROBABILITY OF 4 TO 8
INCHES OF SNOW IS EXPECTED WITH A LOW PROBABILITY OF GREATER THAN
8 INCHES OF SNOW.  A SIGNIFICANT WINTER STORM BEGINS TO MOVE OUT
OF THE ROCKIES ON DAY 3/TUESDAY EVENING INTO WEDNESDAY WITH A
CONTINUATION OF SNOW ACROSS MUCH OF CENTRAL AND EASTERN COLORADO
WITH THE HEAVIEST SNOW SPREADING FROM THE NORTHERN MOUNTAINS
ACROSS THE NORTHEAST PLAINS INTO SOUTHERN NEBRASKA AND KANSAS.
RAPIDLY FALLING TEMPERATURES AND INCREASING NORTHERLY WINDS
ACCOMPANIED BY A MODERATE LIKELIHOOD OF GREATER THAN 4 INCHES OF
SNOW WILL BE FOUND ACROSS THESE AREAS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

KOCIN

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