Quantitative Precipitation Forecast
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QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
332 PM EST SUN FEB 12 2017

VALID 00Z MON FEB 13 2017 - 00Z THU FEB 16 2017

DAY 1...

...NORTHEAST...

A DEVELOPING CYCLONE CURRENTLY ACROSS THE MIDDLE ATLANTIC STATES
WILL MOVE NORTHEASTWARD AND DEEPEN EXPLOSIVELY THROUGH MONDAY
AFTERNOON.

FORECAST CONFIDENCE REMAINS HIGH FOR A RAPIDLY INTENSIFYING
CYCLONE OVER THE NORTHEAST THAT IS EXPECTED TO PRODUCE WIDESPREAD
MODERATE TO HEAVY SNOWS OVER A LARGE PORTION OF UPSTATE NY AND
CENTRAL AND NORTHERN NEW ENGLAND. AS AN EXAMPLE...THE CURRENT 12Z
ECMWF HAS THE SYSTEM DEEPENING FROM 1000 MB AT 00Z TO 964 MB IN
ONLY 18 HOURS THROUGH MONDAY AFTERNOON.  THESE DEEPENING RATES ARE
INDICATIVE OF A STORM THAT WILL PRODUCE HEAVY SNOW/HIGH
WINDS/MESOSCALE BANDING IN PORTIONS OF EASTERN AND NORTHERN NEW
ENGLAND.  THE STORM WILL MOVE JUST OFF THE NEW ENGLAND COAST AND
SLOW ITS FORWARD MOVEMENT AS IT INTENSIFIES WHILE IT MOVES TO A
POSITION OFF THE COAST OF SOUTHERN MAINE ON EARLY MONDAY...BEFORE
RESUMING A MORE EASTERLY TRACK BY MONDAY EVENING.  AS SUCH THIS
WILL PRODUCE IN SOME AREAS QUITE A LONG PERIOD OF SNOWFALL
ESPECIALLY ACROSS NEW HAMPSHIRE AND MAINE WHERE SNOW MAY LAST FROM
24 TO OVER 30 HOURS.

FARTHER SOUTH...A PRONOUNCED DRY SLOT ASSOCIATED WITH THE DIVING
UPPER JET WILL MAKE ITS WAY RAPIDLY EASTWARD...ENDING SNOWFALL FOR
THE MOST PART ACROSS SOUTHERN NEW ENGLAND. THE TRICKY PART IS
TRYING TO FIGURE OUT WHERE THE BORDER BETWEEN ENDING SNOWFALL AND
REDEVELOPING SNOWFALL OCCURS WITHIN THE DEVELOPING COMMA HEAD AS
THE CYCLONE CONTINUES TO INTENSIFY.  AND THERE LIES THE DIFFERENCE
BETWEEN 6 TO 12 HOURS OF SNOW VS 24 HOURS OR GREATER.  THAT
DILEMMA COULD OCCUR NEAR OR WITHIN THE BOSTON METROPOLITAN AREA
WHERE IT DOES APPEAR THAT THE DRY SLOT WILL LIKELY CAUSE TO SNOW
TO DIMINISH FOR A NUMBER OF HOURS BEFORE STARTING UP AGAIN.  THE
CONSENSUS OF THE OPERATIONAL RUNS SEEMS TO POINT THIS OUT...BUT
THERE IS INHERENT UNCERTAINTY HOW THIS WILL ULTIMATELY PLAY OUT.
INTERESTING TO WATCH THOUGH.  SMALL CHANGES COULD PRODUCE LARGE
CHANGES IN IMPACT BOTH WITH LESS VS MORE SNOW.

HOWEVER...THE FOCUS OF THE STORM APPEARS TO BE CENTERED ACROSS NEW
HAMPSHIRE AND MAINE WHICH WILL BEAR THE BRUNT OF BLIZZARD
CONDITIONS ESPECIALLY ALONG THE COAST BUT THE
POSSIBILITY...ACTUALLY LIKELHOOD OF MESOSCALE BANDING ESPECIALLY
ON MONDAY COULD RESULT IN DIFFERENCES BETWEEN FORECAST AND ACTUAL
SNOW TOTALS.  ACCUMULATIONS OF MORE THAN 2 FEET IN LOCATIONS IS
LIKELY WITH A STORM OF THIS INTENSITY/DURATION. WHILE SNOWFALL
FORECASTS AROUND BOSTON ARE SOMEWHAT UNCERTAIN...CONFIDENCE
INCREASES NORTH OF THERE WHERE MOST GUIDANCE SHOWS HIGH
PROBABILITIES OF 1 TO 2 FEET OF SNOW. SNOWFALL ACROSS INERIOR NEW
YORK WILL CONTINUE OR REDEVELOP ESPECIALLY IN UPSLOPE LOCATIONS IN
THE NORTHERN HALF OF THE STATE AS WELL AS ACROSS THE LAKE EFFECT
AREAS DOWNWIND OF LAKES ERIE AND ONTARIO.

DAYS 1 TO 3...

...SOUTHERN ROCKIES/SOUTHERN PLAINS...

AN UPPER LOW OVER NORTHWESTERN MEXICO WILL MOVE EAST NORTHEASTWARD
ACROSS SOUTHERN NEW MEXICO INTO TEXAS BY TUESDAY.  DIFFLUENT FLOW
NORTH AND EAST OF THE CENTER IS EXPECTED TO SUPPORT RAIN AND
SHOWERS WITH HIGHER ELEVATION SNOWS ACROSS THE SOUTHERN COLORADO
AND NORTHERN TO THE MOUNTAINS OF NEW MEXICO.  DECREASING MOISTURE
AVAILABILITY IS EXPECTED TO LIMIT AMOUNTS...WITH GENERAL AREAS OF
ACCUMULATIONS OF 4 TO 8 INCHES WITH SOME OF THE GREATEST TOTALS
POSSIBLE ACROSS THE MOUNTAINS OF THE SOUTH CLOSER TO THE UPPER LOW
CENTER.   SOME LIGHT SNOW AND FREEZING RAIN ARE POSSIBLE IN AREAS
ACROSS NORTH TEXAS AND EASTERN NEW MEXICO AS WELL.

DAY 3...NORTHEAST...

ANOTHER DIGGING TROUGH WILL MOVE SOUTHEASTWARD FROM NORTH CENTRAL
CANADA TO NEW ENGLAND BY WEDNESDAY.  LOW PRESSURE WILL MOVE
SOUTHEASTWARD WITH THIS SYSTEM WHILE ANOTHER SECONDARY LOW MAY
DEVELOP AGAIN IN THE GULF OF ALASKA.  AT PRESENT...THERE IS STILL
QUITE A BIT OF SPREAD WITH THIS SYSTEM SINCE ITS AT THE END OF THE
FORECAST PERIOD...BUT THERE COULD AGAIN BE SOME SIGNIFICANT SNOW
ACROSS PORTIONS OF NORTHERN NEW YORK AND NEW ENGLAND.  AT PRESENT
THERE IS A LOW TO MODERATE PROBABILITY OF GREATER THAN 4 INCHES OF
SNOW ACROSS NORTHERN NEW YORK AND PORTIONS OF MAINE.

KOCIN

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