Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 312121
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
420 PM EST SAT JAN 31 2015

VALID 00Z SUN FEB 01 2015 - 00Z WED FEB 04 2015


...CENTRAL PLAINS/MID TO UPPER MISSISSIPPI VALLEY TO NORTHEAST...

QUITE POSSIBLY THE MOST EXTENSIVE WINTER STORM OF THE SEASON WILL
IMPACT PARTS OF THE MIDWEST INTO THE NORTHEAST ON SUN AND MON. THE
COMBINATION OF AN AGGRESSIVE AND SHARP SHORT WAVE TROUGH DIGGING
DOWN THE FRONT RANGE OF THE NRN ROCKIES THIS AFTN WILL TEAM WITH
SRN STREAM DYNAMICS AND ANOMALOUS MOISTURE CONTENT OVER THE
MIDWEST. THIS WILL RESULT IN A SURFACE WAVE DEVELOPING SUN MORNING
JUST SOUTH OF THE KANSAS CITY AREA. THIS LOW WILL TRACK TO EVV/SDF
BY SUN EVENING AND PIT/MGW BY MON MORNING... WHILE DEEPENING.
MEANWHILE... ANOMALOUS PWS FROM MID-HIGH LEVEL MOISTURE FROM THE
PAC/SUBTROPICAL JET AND LOW-LEVEL GULF OF MEXICO MOISTURE WILL
SURGE UP TO THE SYSTEM AND OVERRUN INTO THE EXPANDING COLD SECTOR
OR MAMMOTH POLAR/ARCTIC SURFACE RIDGE. THE TREND WITH THE GUIDANCE
OVER THE LAST FEW DAYS IS TO GRADUALLY SHIFTING NORTH THE WEST TO
EAST AXIS OF FROZEN PRECIP. THIS TREND APPEARS TO HAVE SETTLED
FINALLY FOR DAY 1... AS THE GUIDANCE HAS PINPOINTED VERY HEAVY
SNOWFALL FROM THE NE/IA BORDER TO NRN IN WITH A MDT TO HIGH PROB
OF A FOOT OR MORE FROM SERN IA THROUGH NRN IL. THE ERN EXTENT OF
THIS ZONE OF FROZEN PRECIP WILL BE MOST QUESTIONABLE WITH THE 12Z
GFS TRENDING DEEPER AND SLOWER ALLOWING AN ACTIVE LOW LEVEL JET TO
ADVECT A WARM TONGUE TO MAKE SNOWFALL AND MIX TOTALS A BIT MORE
DIFFICULT TO FORECAST.

THE SYSTEM ADVANCES DOWNSTREAM FOR MON... WITH THE UPPER DYNAMICS
TRANSFERRING FROM WRN PA/WV TO THE NORTHEAST COAST. THE STEADY
NORTHWARD TREND THAT DISAPPEARS SOME WITH THE GUIDANCE ON SUN
CONTINUES HOWEVER ON MON. THE AMPLIFICATION OF THE UPPER TROUGH
AND DOWNSTREAM SURFACE RIDGE SHIFTING OFF THE EAST COAST WILL
ALLOW THE AXIS TO MOVE NORTH AND WARM AIR TO SURGE INTO THE
REGION. THUS THE HEAVY SNOWFALL AXIS ACTUALLY SHIFTS UP TO THE ERN
LAKES AND INTERIOR PARTS OF THE NORTHEAST AND THE NEW ENGLAND
COAST. WITH A BIT MORE SPREAD AND UNCERTAINTY ON MON WITH PTYPE
AND DETAILS... ONLY A LOW TO MDT PROB OF A FOOT WILL BE ISSUED
FROM SWRN NY/NWRN PA TO EASTERN NEW ENGLAND.

OVERALL WPC FOLLOWED A BLEND OF THE GUIDANCE ON SUN... A SHIFT TO
THE GFS/ECMWF ON MON AND AS THE SYSTEM DEPARTS ON TUES... A BLEND
OF THE GFS/ECMWF.


...PACIFIC NORTHWEST TO THE NORTHERN ROCKIES...

UPPER RIDGING OVER THE PAC NW WILL GIVE WAY TO A SERIES OF LOW
AMPLITUDE SHORTWAVES ARRIVING FROM THE PAC TO RAISE THE THREAT FOR
HEAVY SNOWS. THE MAIN RISK APPEARS TO BE FROM THE NORTHERN WA
CASCADES TO THE NORTHERN ROCKIES AND POSSIBLE SPREADING OUT INTO
THE NRN PLAINS ON MON AND TUES. WPC FOLLOWED A BLEND OF THE
ECMWF/GFS FOR THE HEAVY SNOW PROBS FOR THE WRN TERRAIN INTO THE
ERN PORTION OF MT.


MUSHER

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