Forecast Discussion from the National Weather Service Headquarters - Note Concern About Heavy Snow, High Winds & Downed Trees Causing Power Outages

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
457 AM EDT FRI OCT 28 2011

VALID 12Z FRI OCT 28 2011 - 12Z SUN OCT 30 2011

...SIGNIFICANT EARLY SEASON SNOW STORM EXPECTED FOR THE CENTRAL
APPALACHIANS INTO NEW ENGLAND BEGINNING TONIGHT...

...IT WILL BE MUCH COLDER THAN AVERAGE FROM THE SOUTHERN PLAINS
INTO THE MID ATLANTIC AND NORTHEAST TODAY AND SATURDAY...

A STRONG COLD FRONT HAS CLEARED MOST OF THE SOUTHERN PLAINS AND
DEEP SOUTH WITH COOL HIGH PRESSURE IN PLACE BEHIND THE FRONT
EXTENDING FROM THE CENTRAL ROCKIES TO THE OHIO VALLEY. THE
SOUTHERN HALF OF FLORIDA WILL REMAIN IN DEEP TROPICAL MOISTURE
AHEAD OF THIS FRONT WHICH WILL SUPPORT THUNDERSTORMS AND HEAVY
RAIN TODAY INTO THE WEEKEND. FAST MOVING NORTHWEST FLOW ALOFT IS
EXPECTED TO CARVE OUT AN UPPER LEVEL TROUGH BY THIS EVENING OVER
THE UPPER MISSISSIPPI VALLEY...WHICH SHOULD DEEPEN AND TRACK
EASTWARD ACROSS THE APPALACHIANS AND NEW ENGLAND THIS WEEKEND. LOW
PRESSURE SHOULD ORGANIZE ALONG THE COLD FRONT JUST OFF OF THE
SOUTHEAST COAST...AND TRACK NORTHWARD JUST OFF OF THE MID-ATLANTIC
AND NORTHEAST COASTLINE...DEEPENING AS IT GAINS LATITUDE. ENOUGH
COLD AIR IS IN PLACE BEHIND THE COLD FRONT TO SUPPORT SNOW IN THE
CENTRAL APPALACHIANS TONIGHT WITH RAIN CHANGING TO SNOW FOR
NORTHERN MARYLAND INTO EASTERN PENNSYLVANIA AND SOUTHERN NEW
ENGLAND.

THE TRACK OF THE SURFACE LOW IS CRUCIAL IN EXACTLY WHERE THE
RAIN/SNOW LINE SETS UP BUT AT THIS TIME...IT APPEARS I-95 WILL
DEMARCATE THE DIFFERENCE BETWEEN RAIN POSSIBLY ENDING AS WET SNOW
WITH ZERO TO MINOR ACCUMULATIONS FROM A HEAVIER SNOW WHICH COULD
POSE MAJOR PROBLEMS. AS THE LOW DEEPENS DURING THE DAY ON
SATURDAY...BANDS OF MODERATE TO HEAVY SNOW ARE POSSIBLE ON THE
WEST END OF THE PRECIPITATION SHIELD WITH POWER OUTAGES BECOMING A
CONCERN DUE TO THE FACT THAT MANY TREES HAVE YET TO LOSE THEIR
LEAVES. WITH GROUND TEMPERATURES STILL WARM...SNOW WILL INITIALLY
STRUGGLE TO STICK...HOWEVER THAT WILL CHANGE WHERE HIGH SNOWFALL
RATES SET UP. PLEASE NOTE THAT THIS FORECAST CAN CHANGE WITH
CHANGES TO THE EXPECTED LOW TRACK. PLEASE SEE PRODUCTS ISSUED BY
THE HPC WINTER WEATHER DESK FOR MORE DETAILS ON SNOWFALL
POTENTIAL. WHERE LOW LEVEL TEMPERATURES WILL BE TOO WARM FOR SNOW
ALONG THE COAST...PERIODS OF HEAVY RAIN AND STRONG WINDS CAN BE
EXPECTED AS THIS STORM SYSTEM GETS GOING LATE SATURDAY INTO
SUNDAY.

OUT WEST...AN UPPER LEVEL TROUGH WILL MOVE ASHORE THE PACIFIC
NORTHWEST THIS AFTERNOON ALONG WITH A COLD FRONT. A 6 TO 12 HOUR
PERIOD OF STEADY RAIN IS EXPECTED AS THE FRONT MOVES
THROUGH...FOLLOWED BY RAIN SHOWERS AND HIGHER ELEVATION SNOW IN
THE NORTHERN CASCADES AND NORTHERN ROCKIES. THE FAST MOVING NATURE
OF THIS SYSTEM SHOULD LIMIT PRECIPITATION TOTALS TO ABOUT .5 TO 1
INCHES FOR THE COASTAL RANGES AND CASCADES. LIMITED MOISTURE
AVAILABILITY WILL KEEP RAIN/SNOW AMOUNTS TO A MINIMUM AS THE
SYSTEM REACHES THE NORTHERN PLAINS ON SATURDAY.

OTTO


GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV