Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 060759
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EST SAT FEB 06 2016

VALID 12Z SAT FEB 06 2016 - 12Z TUE FEB 09 2016


DAYS 1 THROUGH 3...

...NORTH/SOUTH CAROLINA TO SOUTHERN NEW ENGLAND...

TO START OFF...THERE IS QUITE LOW CONFIDENCE IN MANY ASPECTS OF
THIS FORECAST.  FIRST...AN INTENSIFYING CYCLONE OFF THE SOUTHEAST
COAST IS ASSOCIATED WITH AN AMPLIFYING/NEGATIVELY TILTED UPPER
TROUGH UNUSUALLY FAR SOUTH WITH MARGINAL SUPPORT FOR
RAIN/MIXED/SNOW ALONG THE NORTHWESTERN EDGE OF THE SIGNIFICANT
PRECIPITATION WHICH IS EXPECTED TO FALL IN THE CENTRAL AND EASTERN
SOUTH CAROLINA AND POSSIBLY INTO SOUTHEASTERN NORTH CAROLINA AND
EXTREME EASTERN GEORGIA.  THE 12Z NAM IS THE MOST AGGRESSIVE AND
COLDEST OF THE OPERATIONAL RUNS BUT ALSO DEVELOPS THE QPF ON A
MORE SOUTHERN AXIS ACROSS GEORGIA AND SOUTH CAROLINA...WITH SOME
OBJECTIVE TECHNIQUES INDICATING THE POSSIBILITY OF SIGNIFICANT
SNOW NEAR THE BORDER OF SOUTHERN GEORGIA AND SOUTH CAROLINA.  WE
CONSIDER THIS ONLY A REMOTE POSSIBILITY AT THIS POINT BUT IT DOES
ADD PAUSE WITH A ONE DAY FORECAST.  THE GEFS MEANS ALSO SUGGEST
SOME LIGHT ACCUMULATIONS POSSIBLE FARTHER NORTH ACROSS NORTHEAST
SOUTH CAROLINA AND SOUTHEASTERN NORTH CAROLINA BUT THE 12Z GFS/00Z
ECMWF AND MORNING SREFMEANS KEEP NEAR ZERO SNOWFALL.
THEREFORE...WE DO NOT FORECAST GREATER THAN AN INCH OF SNOW IN OUR
DETERMINISTIC FORECAST BUT NEED TO WAIT AND SEE HOW OUR
PROBABILITIES WORK OUT INCORPORATING A LARGER ENSEMBLE SUITE.

EVEN ON DAY 2/SUNDAY INTO MONDAY MORNING...THERE IS A LOW
PROBABILITY OF EVEN 4 INCHES OF SNOW FROM THE SOUTHEAST COAST TO
NEW YORK CITY. IT SHOULD BE STRESSED THAT WHILE THERE IS A LOW
PROBABILITY...IT IS LIKELY DUE TO THE SREF MEMBERS MOSTLY ALTHOUGH
THERE ARE SOME CANADIAN AND ECMWF MEMBERS THAT ALSO KEEP SNOWFALL
ALONG THE COAST.  AT THIS TIME...THOSE PROBABILITIES APPEAR TO BE
NO MORE THAN 10 TO MAYBE 30 PERCENT.

THE FORECAST CONTINUES TO REMAIN UNCERTAIN LATER ON DAY 3 AS THIS
STORM SYSTEM MAY INTERACT WITH A DEEPENING TROUGH OVER THE CENTER
OF THE COUNTRY THAT WILL INFLUENCE HOW THIS SYSTEM AFFECTS THE
EASTERN SEABOARD PARTICULARLY ON DAY 3/MONDAY INTO TUESDAY.  THERE
IS QUITE A BIT OF SPREAD REGARDING WHETHER THIS STORM SYSTEM
REMAINS FAR ENOUGH WEST TO GIVE PORTIONS OF THE NORTHEAST SOME
SIGNIFICANT SNOW OR IF IT STAYS FARTHER EAST.  THE VERDICT IS NOT
CLEAR.  THE MOST RECENT GEFS/SREF/CANADIAN AND ECMWF ENSEMBLES
STILL AVERAGE OUT TO SOME INFLUENCE OVER NEW ENGLAND IN
PARTICULAR...WITH THE 12Z ECMWF/00Z NAM/00Z CANADIAN RUNS IN SOME
DEGREE OF AGREEMENT...WHILE THE 00 GFS/ECMWF AND UKMET ARE BOTH
FARTHER EAST WITH MUCH LESS INFLUENCE.  IT IS SUSPECTED THAT SUCH
DIFFERENCES WILL ALSO PLAY OUT IN HOW THE FOLLOWING DIGGING TROUGH
DEVELOPS ALONG THE EAST COAST ON DAY 3 AND LATER OR IS MORE
PROGRESSIVE IF THE FIRST STORM REMAINS CLOSER TO NEW ENGLAND.
THESE FACTORS CANNOT BE ASCERTAINED WITH ANY DEGREE OF CONFIDENCE
AT THIS POINT.


...NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY/UPPER MIDWEST TO
OHIO/TENNESSEE VALLEYS AND APPALACHIANS/MIDDLE ATLANTIC STATES...

A SHORTWAVE TROUGH CROSSING THE PACIFIC NORTHWEST WILL AMPLIFY AS
AN UPPER RIDGE BUILDS ACROSS THE WESTERN UNITED STATES.  THE
AMPLIFICATION OF THIS TROUGH WILL INFLUENCE THE WEATHER ACROSS THE
EASTERN TWO THIRDS OF THE US DURING MOSTLY THE LATTER HALF OF THE
FORECAST.  LIGHT TO MODERATE SNOWFALL AMOUNTS ARE FORECAST WITH
THIS SYSTEM AS IT MOVES ACROSS THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY WITH SOME PROBABILITIES FOR GREATER THAN 4
INCHES OF SNOW ESPECIALLY ACROSS NORTHEASTERN MINNESOTA ON DAY
2/SUNDAY INTO MONDAY MORNING.  IN ADDITION TO THE SNOW...STRONG
NORTHWESTERLY WINDS WILL CAUSE BLOWING AND DRIFTING
SNOW...CREATING POSSIBLE BLIZZARD CONDITIONS EVEN WHERE SNOWFALL
AMOUNTS ARE EXPECTED TO BE GENERALLY LIGHT.  THE AMPLIFICATION OF
THIS SYSTEM WILL BE RESPONSIBLE FOR THE WIDESPREAD INCREASE IN
WIND SPEEDS THAT WILL LIKELY BE A SIGNIFICANT FORECAST ISSUE FOR
THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY.

ON DAY 3/MONDAY INTO TUESDAY MORNING...THERE STILL IS CONSIDERABLE
UNCERTAINTY IN THE FORECAST BUT AS THE TROUGH CONTINUES TO
AMPLIFY...THERE IS AN INCREASING LIKELY PROBABILITY FOR SOME
POSSIBLE SIGNIFICANT SNOW CONTINUING ACROSS PORTIONS OF THE GREAT
LAKES INTO THE EASTERN OHIO VALLEY/THE APPALACHIANS AND INTO THE
MIDDLE ATLANTIC STATES.  AT PRESENT...THERE IS ONLY A LOW TO
MODERATE PROBABILITY FOR GREATER THAN 4 INCHES OF SNOW DOWNWIND OF
LAKE SUPERIOR AS WELL AS ACROSS THE APPALACHIANS NEAR WEST
VIRGINIA...THERE ALSO COULD SOME SIGNIFICANT ACCUMULATIONS IN
PORTIONS OF OHIO/PENNSYLVANIA/MARYLAND AND NORTHERN VIRGINIA
ALTHOUGH THE FORECAST REMAINS QUITE UNCERTAIN.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

KOCIN


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