Quantitative Precipitation Forecast
Issued by NWS

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000 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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