Quantitative Precipitation Forecast
Issued by NWS

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037
FOUS11 KWBC 142103
QPFHSD

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

VALID 00Z MON FEB 15 2016 - 00Z THU FEB 18 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/FREEZING AND THEN RAIN.

MODELS CONTINUE TO CONVERGE ON A SOLUTION WITH THE EVOLUTION OF
THE UPPER TROUGH AND DEVELOPMENT OF THE SURFACE LOW...WHICH IS
EXPECTED TO FOLLOW AN INLAND TRACK EAST OF THE CENTRAL
APPALACHIANS ON TUE...REACHING THE ST LAWRENCE VALLEY BY TUE
NIGHT. HOWEVER...SLIGHT ADJUSTMENTS IN THE LOW TRACK AND SPEED IN
WHICH THE PRECEDING WARM AIR ADVECTION PRECIPITATION SPREADS
NORTH...CONTINUE TO PLAY SIGNIFICANT ROLES IN THE DETAILS OF THE
FORECAST.  THE NAM IS A BIT FASTER SPREADING WARM ADVECTION
PRECIPITATION NORTH ACROSS THE MID ATLANTIC INTO THE NORTHEAST
TONIGHT...RESULTING IN SOME HEAVIER SNOW ACCUMULATIONS BEFORE
CHANGING OVER TO MIXED PRECIPITATION ON MON.  THE 12Z ECMWF HAS
SHOWN SIMILAR TRENDS...SUGGESTING THE GFS MAY BE A BIT TOO SLOW
WITH RESPECT TO THE NORTHWARD ADVANCE OF THE WARM ADVECTION
PRECIPITATION.  OVERALL...WPC FOLLOWED A BLEND OF THE
NAM/GFS/ECMWF THROUGH DAY 1 BEFORE DISCOUNTING THE NAM BY LATE TUE
WHEN IT BECOMES A NOTABLY SLOW OUTLIER WITH THE SURFACE LOW TRACK
FROM THE MID ATLANTIC THROUGH THE NORTHEAST.  FOLLOWING A BLEND OF
THE GFS/ECMWF SUPPORTED AN AXIS FOR HEAVIER SNOW TOTALS FROM
NORTHWESTERN PA/SOUTHWESTERN NY TO THE ADIRONDACKS...WHERE A
SLIGHT RISK WHERE A SLIGHT RISK FOR 8-INCHES ON TUE IS INDICATED.
WIDESPREAD TOTALS EXCEEDING A FOOT ARE NOT EXPECTED.  LOCALLY
HEAVY ICE ACCUMULATIONS OF A QUARTER-INCH OR MORE ARE
POSSIBLE...ESPECIALLY WITHIN SOME OF THE MORE SHELTERED VALLEYS IN
THE CENTRAL TO NORTHERN APPALACHIANS.

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

PEREIRA

$$





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