Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 132130
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
429 PM EST SAT FEB 13 2016

VALID 00Z SUN FEB 14 2016 - 00Z WED FEB 17 2016

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

PERSISTENT ONSHORE FLOW...COMBINED WITH WEAK IMPULSES OF ENERGY
ALOFT...SHOULD CONTINUE TO SUPPORT MODERATE TO LOCALLY HEAVY SNOW
ACROSS THE NORTHERN CASCADES AND THE NORTHERN ROCKIES THROUGH
SUNDAY AND MONDAY.  HOWEVER...AS A RIDGE BEGINS TO SLOWLY BUILD
ONCE AGAIN...THE POTENTIAL FOR HEAVY ACCUMULATIONS WILL GRADUALLY
DECREASE.   GUIDANCE WAS IN FAIRLY GOOD AGREEMENT ACROSS THE
REGION...SO THE FORECAST WAS BASED ON A MULTI-MODEL CONSENSUS.

...NORTHERN PLAINS/MIDWEST...

WARM AIR/MOISTURE ADVECTION AHEAD OF A SHORTWAVE TROUGH SLIDING
OUT OUT OF THE NORTHERN ROCKIES WILL SUPPORT A SWATH OF LIGHT TO
MODERATE SNOWS FROM THE DAKOTAS TO THE MID MS AND LOWER OH VALLEYS
SATURDAY NIGHT INTO SUNDAY.  THE WPC FORECAST FOR HIGHER
PROBABILITIES OF HEAVIER AMOUNTS EXTENDING SOUTHEASTWARD FROM
SOUTHEASTERN ND/NORTHEASTERN SD TO CENTRAL IL IS A REFLECTION OF
WPC QPF AND A BLEND OF GFS..GEFS AND ECMWF THERMAL PROFILES.

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

INGREDIENTS ARE COMING TOGETHER FOR A POTENTIALLY HIGH-IMPACT
WINTER WEATHER EVENT ACROSS PORTIONS OF THE MIDWEST-EASTERN U.S.
EARLY NEXT WEEK...HOWEVER DETAILS OF THE FORECAST REMAIN UNCERTAIN.

MODELS CONTINUE TO SHOW A LOW AMPLITUDE SHORTWAVE SLIDING OFF OF
THE WESTERN U.S. RIDGE INTO THE BASE OF A BROAD TROUGH CENTERED
OVER THE MS VALLEY ON MONDAY.  STRONG ISENTROPIC LIFT IN ADVANCE
OF THE WAVE WILL FOCUS PRECIPITATION ACROSS THE TENNESSEE VALLEY
AND LOWER OHIO VALLEY SUNDAY NIGHT...WHICH SHOULD INTENSIFY AND
SPREAD NORTH AND EAST INTO THE MID-ATLANTIC AND NORTHEAST ON
MONDAY AS THE UPPER TROUGH SHARPENS AND ASSUMES A NEGATIVE TILT
OVER THE MID-ATLANTIC AND A SURFACE LOW BEGINS TO DEEPEN WHILE
TRACKING EAST OF THE APPALACHIANS.  MOST AREAS ARE EXPECTED TO
TRANSITION FROM SNOW...TO SLEET AND/OR FREEZING RAIN...TO RAIN AS
WARM MOIST AIR MOVES OVER THE TOP OF A STRONG...BUT
RETREATING...ARCTIC AIRMASS.  MODELS CONTINUE TO DIFFER ON THE
SURFACE LOW TRACK OF THIS SYSTEM.  WPC PREFERRED A TRACK SIMILAR
TO THE GFS...DISCOUNTING THE ECMWF WHICH REMAINS A MORE WESTERLY
OUTLIER.  THIS TRACK WOULD SUPPORT A HIGHER PROBABILITY FOR HEAVY
SNOWS ACROSS THE ADIRONDACKS INTO THE MOUNTAINS OF NORTHERN NEW
ENGLAND...WHERE FAVORABLE UPPER JET DYNAMICS AND LOW-MID LEVEL
FRONTOGENESIS WOULD SUPPORT HEAVY SNOWFALL RATES BEFORE A
CHANGEOVER TO MIXED PRECIPITATION MAY OCCUR.  SIGNIFICANT ICE
ACCUMULATIONS OF A QUARTER-INCH OR MORE ARE POSSIBLE AS
WELL...PARTICULARLY WITHIN SOME OF THE MORE SHELTERED VALLEYS OF
THE CENTRAL TO NORTHERN APPALACHIANS...WHERE THE LOW LEVEL COLD
AIR MAY BE SLOW TO SCOUR OUT.

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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