521
FOUS11 KWBC 212034
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
333 PM EST FRI NOV 21 2008
VALID 00Z SAT NOV 22 2008 - 00Z TUE NOV 25 2008
DAY 1...
..GREAT LAKES/APPALACHIANS
FAVORABLE CONDITIONS FOR LAKE EFFECT SNOW WILL BE IN PLACE THROUGH
ONLY THE FIRST HALF OF DAY 1 AS THE RESPONSIBLE UPPER LOW FINALLY
SWINGS NORTH AND EAST BACKING THE SURFACE WINDS MORE WESTERLY.
EARLY PERIOD LL WIND TRAJECTORIES FAVOR AREAS SE OF LAKES
SUPERIOR...MICHIGAN AND ERIE FOR LOCALIZED 2 TO 4 INCHES MOSTLY
OVERNIGHT INTO EARLY SATURDAY MORNING. IN ADDITION...SOME HEAVY
SNOW TOTALS ARE ALSO LIKELY ALONG THE WRN SLOPES OF THE
APPALACHIANS WHERE THE STRONG NWLY UPSLOPE FLOW WILL AIM INTO WV
AND WRN MD. ALL OF THE SNOW SHOWER ACTIVITY SHOULD BE TAPERING
DOWN SAT NIGHT AS A RIDGE OF HIGH PRESSURE MOVES OVER THE REGION.
..NORTHWEST
ANOTHER SHORT BURST OF PACIFIC MOISTURE WILL IMPACT THE PACIFIC NW
AT THE ONSET OF DAY 1...WITH A SURFACE COLD FROPA OVERNIGHT
LOWERING SNOW LEVELS TO ABOUT 3000 FEET. WA CASCADES WILL SQUEEZE
OUT MOST OF THE MOISTURE IN THE FORM OF 6 TO 8 INCHES OF
SNOW...ALTHOUGH SOME MOISTURE WILL SPILL OVER INTO THE SAWTOOTH
AND TETONS DROPPING A COUPLE INCHES. DRY RIDGING WILL TAKE HOLD
BY SATURDAY AFTERNOON.
THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.
DAYS 2 AND 3...
..NORTHEAST
THE NEXT SIGNIFICANT SYSTEM WILL DROP OUT OF CANADA THROUGH THE
GREAT LAKES BY DAY 3 AS A DEEPENING CYCLONE. ANY SIGNIFICANT
WINTER-TYPE WEATHER WILL OCCUR AFTER THE VALID TIME OF THIS
FORECAST...BUT BARELY. MOISTURE SURGING FROM THE GULF WILL
EVENTUALLY MAKE IT ALL THE WAY UP TO THE COLD AIR IN THE NRN OHIO
VALLEY THROUGH NEW ENGLAND CREATING SNOWFALL POTENTIAL. AT THE
VERY LEAST...BACK-SIDE CAA WILL INITIATE ANOTHER ROUND OF
LAKE-EFFECT SNOW BY THE END OF DAY THREE TO THE NRN GREAT LAKES.
THE PROBABILITY OF SIGNIFICANT SNOW AND/OR ICING IS LESS THAN 10
PERCENT.
SOWKO
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