Quantitative Precipitation Forecast
Issued by NWS

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724
FOUS11 KWBC 120959
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
458 AM EST THU JAN 12 2017

VALID 12Z THU JAN 12 2017 - 12Z SUN JAN 15 2017


...WESTERN U.S....

AN UPPER LEVEL TROUGH OVER THE NORTHWEST COAST WILL DROP
SOUTHEASTWARD SHIFTING THE AXIS OF WINTER WEATHER FARTHER TO THE
SOUTH AND EAST OVER THE NEXT DAY OR SO IN THE WESTERN US..  HEAVY
SNOW FALLING OVER THE SIERRA NEVADA RANGE TODAY WILL EVENTUALLY
TAPER OFF AS THE BEST DYNAMICS WITH THIS SYSTEM MOVE OUT OF THE
AREA.  SNOW FALLING OVER THE HIGHER ELEVATIONS OF NEVADA/UTAH AND
WESTERN COLORADO TODAY WILL ALSO GRADUALLY SAG SOUTH AND EAST WITH
TIME.

...SOUTHERN CALIFORNIA MOUNTAINS...

A CLOSED LOW ALONG THE WESTERN COAST OF THE U.S. /PART OF THE SAME
SYSTEM MENTIONED ABOVE/ WILL EVENTUALLY MAKE ITS INTO SOUTHERN CA
TONIGHT AND ON FRIDAY.  AS THE LOW AND ASSOCIATED TROUGH AXIS
PASSES THE AREA...LOW LEVEL THICKNESS VALUES DROP SUFFICIENTLY TO
ALLOW PRECIPITATION TO FALL AS SNOW AT THE HIGHER ELEVATIONS OF
THE MOUNTAINS IN SANTA BARBARA/VENTURA COUNTY SOUTH AND EAST TO
THE SAN BERNADINO AND SAN JACINTO RANGES.  SNOW LEVELS COULD BE AS
LOW AS 4500 FEET TO 5000 FEET...BUT THE AMOUNTS IN EXCESS OF 8
INCHES SHOULD GENERALLY BE AT OR ABOVE 6500 FT.


...SOUTHERN PLAINS/MID MISSISSIPPI AND LOWER OHIO VALLEYS/MID
ATLANTIC...

A SIGNIFICANT POTENTIAL ICING EVENT IS SHAPING UP ESPECIALLY
ACROSS THE SOUTHERN PLAINS AND MID MISSISSIPPI VALLEY FROM LATE
FRIDAY THROUGH INTO EARLY SUNDAY AND BEYOND.

A LARGE SCALE UPPER CONFLUENT FLOW PATTERN WITH A PERSISTENT JET
ENTRANCE REGION WILL ALLOW COLD AIR TO MOVE SOUTHWARD TOWARD THE
SOUTHERN PLAINS.  THIS PATTERN IS BEING FORCED BY A STRONG UPPER
LEVEL RIDGE OVER THE SOUTHEAST U.S. IN COMBINATION WITH BITTERLY
COLD TEMPERATURES MOVING SOUTH AND EASTWARD ACROSS THE NORTHERN
TIER OF STATES...AND THEN REINFORCED BY A SHORTWAVE TROUGH OVER
CENTRAL CANADA THAT WILL MOVE RAPIDLY EASTWARD ACROSS THE
US/CANADIAN BORDER FOLLOWED BY THE MOVEMENT OF A BUILDING HIGH
PRESSURE SYSTEM.  THESE FEATURES WILL PRODUCE A LOW LEVEL FLOW OF
COLD AIR SOUTHWARD THAT WILL BE SHALLOW AND HELP GENERATE
CONDITIONS RIPE FOR SIGNIFICANT FREEZING RAIN.

WHILE SOME LOCALIZED AREAS OF LIGHT FREEZING RAIN MAY DEVELOP
ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS BY EARLY FRIDAY
MORNING...THE THREAT FOR SIGNIFICANT ICING TAKES SHAPE DURING THE
DAY ON FRIDAY AND FRIDAY NIGHT FROM THE SOUTHERN PLAINS TO THE
LOWER OHIO VALLEY...WITH THE GREATEST LIKELIHOOD FOR AMOUNTS
GREATER THAN .25 INCHES ACROSS SOUTH CENTRAL MISSOURI.  ON DAY
3/SATURDAY ...THE AREA EXPERIENCING FREEZING RAIN CONTINUES OVER
MANY OF THE SAME AREAS BUT AMOUNTS ARE EXPECTED TO INCREASE WITH
MODERATE TO HIGH CHANCES FOR AMOUNTS GREATER THAN .5 INCHES ACROSS
THE NORTHEAST PANHANDLE OF TEXAS INTO OKLAHOMA WITH PROBABILITIES
ABOVE 50 PERCENT FOR AMOUNTS EXCEEDING .25 INCHES OVER A WIDER
AREA FROM THE PANHANDLE OF TEXAS ACROSS OKLAHOMA INTO SOUTHERN
KANSAS INTO CENTRAL MISSOURI.

SOME LIGHT SNOW IS EXPECTED ALONG THE NORTHERN PERIPHERY OF THE
PRECIPITATION ACROSS PARTS IN THE APPALACHIANS AND MID ATLANTIC
REGION...BUT ANY AMOUNTS ARE CURRENTLY EXPECTED TO REMAIN BELOW 4
INCHES.

WHAT IS PARTICULARLY SERIOUS ABOUT THIS EVENT IS THAT IT APPEARS
THAT CONDITIONS MAY CONTINUE TO DETERIORATE AFTER THE 3 DAY
FORECAST PERIOD...POTENTIALLY RESULTING IN A VERY SIGNIFICANT AND
LONG LASTING ICING EVENT.

BANN

$$





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