Quantitative Precipitation Forecast
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FOUS11 KWBC 292110
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
409 PM EST THU JAN 29 2015

VALID 00Z FRI JAN 30 2015 - 00Z MON FEB 02 2015


DAYS 1 AND 2...

...APPALACHIANS/NORTHEAST...

AN AMPLIFYING TROUGH WILL BECOME NEGATIVELY TILTED ACROSS THE
NORTHEAST US ON FRIDAY. A RELATIVELY WEAK AREA OF LOW PRESSURE
CROSSING THE GREAT LAKES WILL FEATURE A REDEVELOPING AREA OF LOW
PRESSURE NEAR THE COAST OF SOUTHEAST NEW ENGLAND THAT WILL THEN
INTENSIFY INTO ANOTHER SIGNIFICANT SNOWSTORM FOR PORTIONS OF
NORTHERN AND NORTHEAST NEW ENGLAND. IN PARTICULAR...MAINE WILL BE
THE PRIMARY FOCUS WITH ACCUMULATIONS LIKELY TO EXCEED A FOOT IN A
NUMBER OF PLACES.

THE MORNING MODELS STILL SUGGEST THE DEVELOPMENT OF A WELL DEFINED
COMMA HEAD WITH THIS SYSTEM WITH A BAND OF HEAVY SNOW ROTATING
WEST AND SOUTHWARD AROUND A SIGNIFICANT LOWER TO MIDDLE
TROPOSPHERIC CENTER. AS A RESULT...HEAVY SNOW IS LIKELY FOR A GOOD
PORTION OF MAINE WITH MORE MODERATE SNOWFALLS ACROSS THE REST OF
NEW ENGLAND AND NEW YORK EXCEPT THE SOUTHERN COAST. IN
ADDITION...STRONG NORTHWESTERLY FLOW AND FALLING TEMPERATURES WILL
CREATE LAKE EFFECT SNOWFALL ESPECIALLY DOWNWIND OF LAKE ERIE AS
WELL AS UPSLOPE SNOW ALONG THE LEE SIDE OF THE APPALACHIANS WITH A
LOW TO MODERATE PROBABILITY OF 4 OR MORE INCHES FROM SOUTHWEST
PENNSYLVANIA INTO THE HIGHLANDS OF WEST VIRGINIA.

THE FORECAST WAS BASED PRIMARILY OFF A COMBINATION OF THE 00Z
ECMWF AND THE 12Z GFS ALTHOUGH THERE WAS RELATIVELY GOOD AGREEMENT
AMONGST MANY OPERATIONAL MODELS.


...SOUTHWEST/SOUTHERN ROCKIES...

A LONGWAVE TROUGH WILL BECOME BETTER ORGANIZED AS IT MOVES
EASTWARD ACROSS THE CALIFORNIA COAST AND OVER THE SOUTHWEST ON
FRIDAY INTO SATURDAY BEFORE RETREATING SOUTHWARD INTO NORTHERN
MEXICO ON SUNDAY. SEVERAL SHORTWAVE FEATURES CAN BE SEEN ROTATING
ABOUT THE DEVELOPING NEAR CUTOFF SYSTEM BEFORE THE MAIN TROUGH
BEGINS TO EDGE SOUTHWARD SOUTH OF THE BORDER.  A MULTI MODEL BLEND
APPROACH WAS USED TO HELP FINE TUNE SNOWFALL AMOUNTS ACROSS THE
DIVERSE TOPOGRAPHY OF THE REGION. HEAVIEST SNOW IS EXPECTED TO
AFFECT THE HIGHER ELEVATIONS OF NEW MEXICO AND THE SAN JUAN/SANGRE
DE CRISTO PEAKS ACROSS SOUTHERN COLORADO. PORTIONS OF THE SOUTHERN
WASATCH IN UTAH CAN EXPECT SOME SIGNIFICANT SNOWFALL AS WELL.

FOR INFORMATION PURPOSES...THE NAM/SREF FORECASTS GENERATED SOME
SIGNIFICANT FREEZING RAIN ACCUMULATIONS ESPECIALLY ACROSS PORTIONS
OF NEW MEXICO. WHILE THERE WAS COLLABORATION WITH LOCAL FORECAST
OFFICES...THERE WAS NO ICE INPUT FROM THE WPC DETERMINISTIC
FORECAST BUT WILL STILL LIKELY CREEP INTO THE PROBABILISTIC
FORECASTS.

FOR DAY 1/THURSDAY EVENING THRU FRIDAY...THERE IS A MODERATE TO
HIGH PROBABILITY OF 4 TO 8 INCHES OF SNOW ESPECIALLY ACROSS
NORTHEAST NEW MEXICO AS WELL AS ACROSS THE SOUTHERN WASATCH.  ON
DAY 2/FRIDAY EVENING INTO SATURDAY...MUCH OF THE SAME AREAS OF NEW
MEXICO NOW HAVE A LOW TO MODERATE PROBABILITY OF GREATER THAN 4
INCHES OF SNOW...WHILE THE MOUNTAINS OF SOUTHWESTERN COLORADO ALSO
HAVE A MODERATE PROBABILITY OF 4 OR MORE INCHES. WHILE EITHER DAY
APPEARS TO HAVE ONLY LOW PROBABILITIES OF GREATER THAN 12 INCHES
OF SNOW...TWO DAY TOTALS OF 12 OR MORE INCHES ACROSS THE HIGHER
PEAKS OF NEW MEXICO SHOULD BE COMMON.

...DAYS 2 AND 3...

...MID MISSISSIPPI VALLEY/OHIO VALLEY/LOWER GREAT LAKES...

WHILE THE SOUTHWEST TROUGH HEADS SOUTHWARD INTO MEXICO...ENERGY
AND MOISTURE EJECTING EASTWARD ACROSS THE PLAINS AND MISSISSIPPI
VALLEY WILL COMBINE WITH A SHARPLY AMPLIFYING TROUGH MOVING
SOUTHEASTWARD ACROSS THE NORTHERN ROCKIES ON SATURDAY NIGHT AND
BECOMING A SIGNIFICANT TROUGH OVER THE MISSISSIPPI VALLEY BY
SUNDAY. THE CONSOLIDATION OF THESE SYSTEMS APPEAR TO PRODUCE AN
EXPANDING AREA OF SIGNIFICANT SNOW WITH MODERATE TO HIGH
PROBABILITIES OF GREATER THAN 4 INCHES OF SNOW ACROSS
MISSOURI/ILLINOIS/INDIANA AND OHIO ON DAY 3/SATURDAY EVENING INTO
SUNDAY WITH A LOW PROBABILITY OF GREATER THAN 8 INCHES OF SNOW.
AS THIS STORM DEVELOPS MUCH COLDER AIR WILL BUILD NOT ONLY BEHIND
THE SYSTEM AS A LARGE ARCTIC ANTICYCLONE HEADS SOUTHWARD INTO THE
NORTHERN PLAINS BUT COLDER AIR WILL ALSO BLEED EASTWARD AS
PRESSURES RISE OVER SOUTHEASTERN CANADA AND NORTHERN NEW ENGLAND
IN ASSOCIATION WITH A PRONOUNCED UPPER CONFLUENCE ZONE.  THE
COMBINATION OF THESE TWO SYSTEMS WILL HELP GENERATE A INCREASINGLY
BAROCLINIC ZONE UPON WHICH THE DEVELOPING SURFACE WILL MOVE ALONG.

WHILE THIS SYSTEM APPEARED TO BE MORE SUPPRESSED YESTERDAY...THE
MODELS APPEAR TO HAVE TURNED AROUND AND KEPT THIS SYSTEM STRONGER.
 A BLEND OF THE 12Z GFS AND ECMWF WERE USED FOR THE INITIAL
FORECAST AND THEN EDITED BUT BOTH THE ECMWF AND GFS HAVE SIMILAR
QPF ORIENTATIONS DESPITE A WETTER/WHITER FORECAST FROM THE ECMWF.

KOCIN

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