Quantitative Precipitation Forecast
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FOUS11 KWBC 052110
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
409 PM EST MON DEC 05 2016

VALID 00Z TUE DEC 06 2016 - 00Z FRI DEC 09 2016


DAYS 1-3...

...UPPER MIDWEST AND GREAT LAKES...

A DYNAMIC UPPER JET STREAK ARRIVING INTO THE DAKOTAS THIS AFTN IS
ALLOWING A TRIPLE POINT LOW TO FORM OVER ERN SD. THIS AREA OF LOW
PRESSURE WILL DEEPEN RAPIDLY WHILE LIFTING INTO ERN ND... AS A MID
TO UPPER LOW CLOSES OFF AND THE ENTIRE SHORT WAVE TROUGH TAKES A
NEG TILT ON TUES. THE RESULTANT WILL BE A STRONG DYNAMIC COOLING
FOR A ROBUST DEFORMATION ZONE... THIS IS ALREADY STARTING TO
APPEAR WITH THE BURST OF HEAVY SNOW NEAR BIS THIS AFTN. THE MODEL
CONSENSUS IS SUGGESTING VERY HEAVY SNOWFALL OVER THE NEXT 24 HRS
FROM ERN/NERN ND INTO NWRN AND NORTHERN MN. THIS POTENT SYSTEM
WILL THEN SHIFT DOWNSTREAM INTO ONTARIO AND QUEBEC ON WED AND
THURS... WHILE AN INFLUX OF ARCTIC AIR SWEEPS ACROSS THE GREAT
LAKES. THE RESULTANT WILL BE IDEAL LAKE EFFECT SNOW DOWNWIND OF
THE GREAT LAKES ON LATE WED THROUGH THURS.

...PAC NW TO CENTRAL ROCKIES/PLAINS...

A PAC SHORT WAVE ARRIVING INTO THE PAC NW THIS AFTN AND ON THE
HEELS OF THE DEVELOPING STRONG SYSTEM DOWNSTREAM OVER THE UPPER
MIDWEST WILL DIVE SOUTH AND EAST FROM THE NW THROUGH THE CENTRAL
ROCKIES TUES/WED. THIS FEATURE ALOFT WILL PRODUCE A SWATH OF HEAVY
OROGRAPHIC SNOW EACH DAY... TUES ACROSS THE OR CASCADES INTO THE
NERN OR BLUE MTNS AND ON TUES NIGHT THROUGH WED FOR THE UT
WASATCH/UINTAS INTO THE CO ROCKIES AND ATTEMPT TO SPREAD OUT INTO
THE CENTRAL PLAINS.

...CENTRAL APPALACHIANS AND INTERIOR NORTHEAST...

A RATHER IMPRESSIVE SRN STREAM SHORT WAVE TROUGH OVER SOUTHEAST TX
WILL LIFT TOWARD THE MID-ATL REGION OVER THE NEXT 24 HRS. MOISTURE
WITH THIS SYSTEM WILL BECOME MORE ROBUST AND WIDESPREAD AND BEGIN
TO OVERRUN INTO A WEDGING SURFACE RIDGE. IT IS THE NRN PERIPHERY
OF THIS PRECIP SHIELD WHERE TEMPS WILL BE NEAR OR BELOW FREEZING
FOR A VARIETY OF PRECIP TYPE ON TUES... FREEZING RAIN IN THE
CENTRAL APPALACHIANS AND POSSIBLE ACCUMULATING SNOW IN SOUTH
CENTRAL AND NORTH CENTRAL PA. THEN ON WED... MORE LIGHT TO
MODERATE SNOW WILL BE POSSIBLE FROM NRN/NERN PA INTO INTERIOR
PARTS OF THE NORTHEAST. A COASTAL LOW WILL FORM NEAR THE MID-ATL
REGION BUT ADVANCE DOWNSTREAM. HOWEVER... ENOUGH OF AN WEAKNESS
AND INVERTED TROUGH AXIS WILL BE PRESENT FROM THIS SYSTEM FOR
LOCALLY HEAVY SNOW ACROSS THE POCONOS/CATSKILLS INTO THE HUDSON
VALLEY.

...PAC NW/CA...

AN UPPER LOW NEAR THE ALEUTIANS WILL STEER A SHORT WAVE IMPULSE
TOWARD THE WEST COAST ON THURS. THIS PROGRESSIVE FEATURE WILL
FEATURE ANOMALOUS/ABOVE AVG 700-850 MB MOISTURE FLUX FOR A STEADY
SURGE OF PAC MOISTURE... AS AN EXTREMELY CHILLY AIR MASS AND
SURFACE RIDGE DOMINATES EAST OF THE CASCADES AND ATTEMPTS TO
FILTER WEST OF THE MTNS. THERE IS A FAIR AMOUNT OF SPREAD WITH THE
GFS AND ECMWF ON THE ARRIVAL AND PROGRESSION OF THIS FEATURE WHICH
REALLY IMPACTS POTENTIAL QPF ACROSS THE NW. WPC STAYED A BIT
CLOSER TO THE SLOWER SOLUTION OF THE ECMWF AND INTRODUCED A
VARIETY OF PTYPES AND SNOW PROBS FROM THE CASCADES TO SIERRA.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

MUSHER

$$





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