Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 141011
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
510 AM EST SUN FEB 14 2016

VALID 12Z SUN FEB 14 2016 - 12Z WED FEB 17 2016

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

THE COMBINATION OF WEAK IMPULSES OF ENERGY ALOFT AND PERSISTENT
ONSHORE FLOW WILL ALLOW SNOW TO CONTINUE TO ACCUMULATE ALONG THE
NORTHERN WASHINGTON CASCADES AND NORTHERN TO CENTRAL ROCKIES
SUNDAY AND MONDAY.  HOWEVER...AS A RIDGE BEGINS TO SLOWLY BUILD IN
OVER THE WESTERN U.S. EARLY NEXT WEEK...SNOW ACTIVITY SHOULD
GRADUALLY COME TO AN END.   GUIDANCE WAS IN FAIRLY GOOD AGREEMENT
ACROSS THE REGION...AND MINIMAL ADJUSTMENTS WERE MADE TO
CONTINUITY.


...OHIO/TENNESSEE VALLEYS TO THE MID-ATLANTIC/NORTHEAST...

A STRONG ARCTIC AIRMASS IN PLACE OVER THE EASTERN HALF OF THE
NATION WILL SET THE STAGE FOR A POTENTIALLY HAZARDOUS WINTER
WINTER EVENT EARLY THIS WEEK.  ISENTROPIC LIFT IN ADVANCE OF A
SHORTWAVE DIVING INTO THE BASE OF A BROAD TROUGH CENTERED OVER THE
MISSISSIPPI VALLEY WILL FOCUS PRECIPITATION ACROSS THE TENNESSEE
VALLEY AND LOWER OHIO VALLEY SUNDAY NIGHT INTO MONDAY.  WARM MOIST
AIR MOVING OVER TOP OF THE RETREATING ARCTIC AIRMASS SHOULD RESULT
IN SEVERAL LOCATIONS TRANSITIONING FROM SNOW...TO SLEET AND/OR
FREEZING RAIN...TO RAIN.  MONDAY INTO TUESDAY...PRECIPITATION WILL
INTENSIFY AND SPREAD NORTH AND EAST INTO THE MID-ATLANTIC AND
NORTHEAST AS THE UPPER TROUGH BECOMES NEGATIVELY TILTED AND A
SURFACE LOW BEGINS TO DEEPEN WHILE TRACKING EAST OF THE
APPALACHIANS.  AGAIN...SEVERAL AREAS STARTING AS SNOW WILL
CHANGEOVER TO SLEET/ICE AND THEN RAIN.

MODELS ARE BEGINNING TO CONVERGE ON A SOLUTION WITH THE EVOLUTION
OF THE UPPER TROUGH AND DEVELOPMENT OF THE SURFACE LOW.
HOWEVER...EVEN THE SLIGHTEST ADJUSTMENTS IN THE LOW TRACK WILL
HAVE A LARGE ROLE IN THE DETAILS OF THE FORECAST...ESPECIALLY WITH
THE LOCATION OF THE HEAVIEST SNOWFALL AND TIMING OF THE CHANGEOVER
TO SLEET/ICE/RAIN.  THE LATEST WPC FORECAST WAS BASED ON A
COMPROMISE BETWEEN THE GFS/ECMWF...WITH SLIGHTLY MORE WEIGHT
TOWARDS THE GFS.  THIS RESULTED IN GENERAL NORTHWESTWARD SHIFT IN
SNOWFALL ACCUMULATIONS OVER WESTERN PENNSYLVANIA AND NEW YORK.

PLEASE REFER TO THE PMDHMD FOR MORE DETAILS ON MODEL DIFFERENCES
AND THE QPFPFD FOR DETAILS ON THE HEAVY RAIN THREAT WITH THIS
EVENT.


GERHARDT

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