An intense low pressure system and sharp cold front moved across the Mid-Atlantic and Northeast states. The initial surge of precipitation with this system quickly changed from rain to snow across the Alleghenies and Central Mountains early on the 21st.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CTP wrote it up.
An intense low pressure system and sharp cold front moved across the Mid-Atlantic and Northeast states. The initial surge of precipitation with this system quickly changed from rain to snow across the Alleghenies and Central Mountains early on the 21st. The pattern transitioned to a lake effect snow regime on the backside of the departing storm system later on the 21st into the 22nd. Cold and blustery northwest winds added to the winter weather impacts causing near-blizzard conditions and significant blowing/drifting snow across the highest elevations. The heaviest snow fell across Warren and Somerset counties, given the proximity to Lake Erie and elevated terrain enhancement.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS State College, PA wrote its last area forecast discussion before the first event at Dec 20, 10:56 PM EST, 1 hour 4 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1056 PM EST THU DEC 20 2012 .SYNOPSIS... A STRONG COLD FRONT WILL MOVE EAST ACROSS THE STATE OVERNIGHT. WIDESPREAD RAIN SHOWERS...WITH SNOW AND SLEET MIXED IN...WILL MOVE ACROSS THE REGION AHEAD OF THE FRONT. WINDY AND COLDER CONDITIONS ALONG WITH FREQUENT MOUNTAIN SNOW SHOWERS AND LOCALIZED SQUALLS WILL OCCUR BEHIND THE FRONT...FRIDAY MORNING THROUGH SATURDAY NIGHT. SIGNIFICANT SNOW ACCUMULATIONS ARE LIKELY ACROSS PORTIONS OF THE LAUREL HIGHLANDS...AND THE NORTHWEST SNOW BELT HEADING INTO THIS WEEKEND. A VERY UNSETTLED PATTERN THEN CONTINUES INTO NEXT WEEK. SEVERAL CHANCES FOR SNOW AND MIXED PRECIPITATION WILL EXIST NEXT WEEK...AND A WHITE CHRISTMAS IS BEGINNING TO LOOK POSSIBLE FOR SOME PARTS OF CENTRAL PENNSYLVANIA. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... LATEST RADAR IMAGERY SHOWS THAT PCPN...STILL AHEAD OF SFC FRONT...HAS BECOME MORE SHOWERY IN NATURE. EXPECT THIS TO CONTINUE FOR THE NEXT SEVERAL HOURS...MAINLY AS RAIN...BUT WITH SLEET AND SNOW MIXED IN. SFC LOW NOW FORMING OVER SRN VA/NRN NC IS FORECAST TO LIFT NORTHWARD THROUGH EASTERN OVERNIGHT. THIS WILL HELP TO RE-INTENSIFY PCPN...AS WELL AS AID IN PTYPE CHANGEOVER WITH INCREASING UPWARD MOTION. STILL...HOWEVER...A GREAT DEAL OF UNCERTAINTY REMAINS OVERNIGHT. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... AS THE UPPER AND SFC LOWS PULL AWAY...PRECIP WILL TAPER OFF OVER MOST OF THE REGION...HOWEVER LAKE AND OROGRAPHIC SNOWS ARE EXPECTED TO BE REVITALIZED BEFORE THE DAY IS OUT. SO DESPITE WHAT COULD VERY WELL BE A SEVERAL HOUR LULL...THE STORM WILL BE FAR FROM OVER IN WESTERN AND NORTHERN AREAS. IN FACT IT COULD BE WORSE AS LAKE EFFECT COMBINES WITH A GUSTY WEST-NORTHWEST WIND POSSIBLY CREATING NEAR BLIZZARD CONDITIONS OVER THE LAURELS UP INTO THE NORMAL LAKE SNOW BELTS AREAS OF THE NW. WEST TO NW WIND GUSTS OF 50 MPH APPEAR LIKELY ACROSS THE LAURELS/WESTERN MTNS...AND PERHAPS THE SCENT MTNS FRIDAY AFTERNOON INTO SATURDAY AS THE NRN EDGE OF A 3 SIGMA 925-850 MB WIND MAX SLIDES ACROSS THAT PART OF THE STATE. AS THE SFC/UPPER LOW CONSOLIDATES AND REMAINS NEARLY STATIONARY OVER NY ON SATURDAY...SNOW WILL TRANSITION FROM BEING DYNAMICALLY DRIVEN TO BEING CAUSED BY STG CAA OVER THE RELATIVELY WARM/OPEN WATERS OF THE GREAT LAKES...AND UPSLOPE ENHANCEMENT INTO THE HIGHER TERRAIN. ALTHOUGH LAKE INDUCED INSTABILITY IS NOT ALL THAT IMPRESSIVE WITH 850MB TEMPS ESSENTIALLY NORMAL FOR MID-LATE DECEMBER...EXPECT BROAD AND RELATIVELY MOIST CYCLONIC/UPSLOPE FLOW TO LEAD TO A PROTRACTED LAKE EFFECT SNOW EVENT INTO THE WEEKEND...WITH SIGNIFICANT SNOWS PILING UP OVER THE NW SNOWBELT...ALLEGHENY RIDGES AND LAUREL HIGHLANDS. WILL CONTINUE TO RIDE WITH THE WINTER STORM WATCH...AS OPPOSED TO LAKE EFFECT HEADLINES AS LAKE EFFECT APPEARS SECONDARY TO INITIAL PERIOD OF SYNOPTIC/DEFORMATION SNOWS...ALONG WITH IMPACTS ASSOC WITH GUSTY WINDS AND FIRST SIGNIFICANT/PLOWABLE SNOW OF THE SEASON. CONFIDENCE IN ADVISORY SNFL AMTS IS HIGH ALONG THE ALLEGHENIES...WITH WARNING CONFIDENCE ABV AVERAGE OVER THE NW SNOWBELT AND HIGHEST ELEVATIONS OF THE LAURELS GIVEN 1-2 PUNCH OF SYNOPTIC + LAKE EFFECT/OROGRAPHIC SNOWS. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... COMPLICATED AND BUSY WEATHER PATTERN STARTS BEFORE THE PERIOD AND RUNS RIGHT THROUGH DAY 8. LAKE EFFECT AND BLUSTERY CONDITIONS START UP FRIDAY NIGHT AND WINDS MAY INCREASE TO ADVY LEVELS LATE FRI NIGHT AND THROUGH ALL THE DAY SAT...MAINLY OVER SRN PA. THE WELL-ALIGNED FLOW WILL MAKE MIXING VERY POSSIBLE AND EFFICIENT. WITH 925/850MB WINDS UP TO 50KTS ON MOST MDLS...WE COULD SEE GUSTS NEAR WARNING CRITERIA. BUT THE MORE-LIKELY OUTCOME IS ADVY WINDS. TOO MUCH CONFUSION WOULD BE ADDED TO THE FCST IF WE STARTED TO INCLUDE ANY WIND WATCHES/ADVYS AT THIS POINT IN THE GAME. ADVYS ARE MORE A 1ST/2ND PD THING AS WELL DUE TO THE LOW POTENTIAL FOR DAMAGE. THE LAKE EFFECT IS THE MORE-SURE THING. THE FLOW IS FAVORABLE AND LAKES STILL WARM...SO A LONG-DURATION EVENT IS LIKELY. WHILE EACH INDIV 12-HR PD MAY NOT HOLD >3 INCHES IN THE SNOW BELT/NRN MTS AND IN THE UPSLOPE AREAS OF THE LAURELS...WE WILL HAVE FREQUENT SHSN AND OCNL SQUALLS INTO SAT EVENING. THUS...THE ADVY/WARNINGS WILL STAY IN PLACE THROUGH THEN...BUT THE CENTRAL MTS MAY BE ABLE TO BE DROPPED EARLY AS FLOW BECOMES A BIT MORE WRLY ON SAT. 8H TEMPS DO NOT REALLY RISE UNTIL SAT NIGHT...SO EXPECT STRATO CU AND SCT MTN SHSN TO LAST INTO THEN. THE NEXT SYSTEM IS MORE-VAGUE...BUT A SHORT BREAK SHOULD EXIST IN PRECIP CHCS SUN NIGHT-MON NIGHT WITH HIGH PRESSURE OVERHEAD. A WEAK SECONDARY BOUNDARY MIGHT KEEP IT CLOUDIER IN THE NORTH...THOUGH. CHRISTMAS EVE MAY BE AN INTERESTING NIGHT WITH BOTH GFS AND ECMWF PLOTTING A SFC LOW RIDING SOMEWHERE WITHIN 100MI OF THE CWA. BUT CERTAINTY IS VERY LOW AT THIS POINT ON THE TRACK OF THIS MINOR AND FAST-MOVING WAVE. WILL PLAY IT WITH MID-CHC POPS. BUT IT LOOKS LIKE COLD/SNOW PROFILES. SO A WHITE CHRISTMAS IS POSSIBLE...BUT NOT LIKELY YET. UPPER FLOW BUCKLES WITH A TROUGH DEVELOPING OVER THE CENTRAL STATES...AND A SIGNIFICANT LOW MOVING INTO THE AREA FROM THE SW. PLENTY OF MOISTURE AND A STORM TRACK WHICH IS GENERALLY HERE OR TO THE EAST - AT THIS POINT ON DAYS6/7 - WOULD BE FAVORABLE FOR SNOW. THE NEAR TO SUB-NORMAL TEMPS FOR THE ENTIRE PERIOD WILL ALSO BE A POSITIVE FOR SNOW VS RAIN. BUT AT THIS RANGE...CERTAINTY IS RARELY ABOVE 50 PCT OF PRECIP IN ANY ONE 12 HR PERIOD. WILL HANG WITH HIGH CHC POPS BEYOND WED. THE TROUGH MOVES OVERHEAD FOR THE LATTER PART OF THE LONG RANGE. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... BATTLE CONTINUES BETWEEN WARM ADVECTION AND PRECIPITATION RATES OVER CENTRAL PENNSYLVANIA THIS EVENING. OBSERVATIONS CONTINUE TO TRANSITION FROM RAIN TO SNOW AND BACK AGAIN AT MOST TAF LOCATIONS. RADAR ENHANCEMENT OVER WESTERN AREAS WOULD TEND TO SUPPORT MORE SNOW OVER BFD...WITH RAIN ELSEWHERE UNTIL AFTER 07-09Z WHEN TRUE COLD ADVECTION MAKES IT INTO THE AREA. MVFR TO IFR CONDITIONS WILL PREVAIL OVERNIGHT. EXPECTING WIND SHIFT AND FROPA AROUND 07Z KBFD/KJST...09Z CENTRAL LOCATIONS...AND 11Z IN THE EASTERN AREAS. WITH LLJ WEAKENING...WILL DROP LLWS MENTION IN TAFS AFTER 07/08Z. SURFACE WINDS WILL BEGIN TO AGAIN GET GUSTY AFTER 11-12Z BEHIND THE FRONT. SHORT RANGE MODELS INDICATE THAT FLOW DOES NOT REALLY BECOME NW UNTIL LATER FRIDAY....WITH A 230-250 FLOW MOST OF THE DAY. THAT WOULD SUPPORT LESS ORGANIZED PRECIPITATION...MAINLY CONFINED TO OROGRAPHIC UPLIFT AREAS OF WESTERN MOUNTAINS. STRONGEST WINDS DEVELOP LATER FRIDAY INTO FRIDAY NIGHT...WITH MORE CONCENTRATED LAKE SNOWS DEVELOPING OVER THE NW MOUNTAINS AND LAUREL HIGHLANDS. OUTLOOK... FRI...MVFR/IFR OVER MOUNTAINS OF THE WEST WITH SNOW SHOWERS...MVFR/VFR CENTRAL AND EASTERN TERMINALS WITH OCCASIONAL SNOW SHOWERS/FLURRIES. FRI NIGHT...IFR/LIFR OVER WESTERN MOUNTAINS IN SNOW SQUALLS...MVFR TO VFR ELSEWHERE. SAT...BREEZY. LAKE EFFECT SNOWS CONTINUE IN N AND WEST MTNS WITH IFR/MVFR CONDITIONS. MVFR IN SNOW SHOWERS CENTRAL. VFR SE. SUN...MVFR NW. VFR ELSEWHERE. MON...GENERALLY VFR. TUES...SOME MVFR POSS...WITH LIGHT RAIN/SNOW DEVELOPING. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 7 PM EST SATURDAY FOR PAZ004-005- 010. WINTER WEATHER ADVISORY UNTIL 7 PM EST SATURDAY FOR PAZ006-011- 012-017>019-024-025-034-037-041-042-045-046. WINTER STORM WARNING UNTIL 7 PM EST SATURDAY FOR PAZ033. && SYNOPSIS...LA CORTE/GARTNER NEAR TERM...GARTNER SHORT TERM...LAMBERT/GARTNER LONG TERM...DANGELO AVIATION...JUNG/LA CORTE/EVANEGO
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE STATE COLLEGE PA 703 PM EST THU DEC 20 2012 PAZ006-011-012-017>019-024-025-034-037-041-042-045-046-220015- POTTER-CAMERON-NORTHERN CLINTON-CLEARFIELD-NORTHERN CENTRE- SOUTHERN CENTRE-CAMBRIA-BLAIR-BEDFORD-TIOGA-NORTHERN LYCOMING- SULLIVAN-SOUTHERN CLINTON-SOUTHERN LYCOMING- 703 PM EST THU DEC 20 2012 ...WINTER WEATHER ADVISORY IN EFFECT FROM 1 AM FRIDAY TO 7 PM EST SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TONIGHT. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER WEATHER ADVISORY. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER WEATHER ADVISORY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. PAZ004-005-010-220015- WARREN-MCKEAN-ELK- 703 PM EST THU DEC 20 2012 ...WINTER STORM WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 7 PM EST SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TONIGHT. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER STORM WARNING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER STORM WARNING. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. PAZ033-220015- SOMERSET- 703 PM EST THU DEC 20 2012 ...WINTER STORM WARNING IN EFFECT UNTIL 7 PM EST SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TONIGHT. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER STORM WARNING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WINTER STORM WARNING. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. PAZ026>028-035-036-049>053-056>059-063>066-220015- HUNTINGDON-MIFFLIN-JUNIATA-FULTON-FRANKLIN-UNION-SNYDER-MONTOUR- NORTHUMBERLAND-COLUMBIA-PERRY-DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND- ADAMS-YORK-LANCASTER- 703 PM EST THU DEC 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TONIGHT. RAIN WILL BE MIXED WITH SLEET AND SNOW AT TIMES THIS EVENING...AND CHANGE TO SNOW LATE TONIGHT AND EARLY FRIDAY. A QUICK COATING TO AN INCH OF SNOW IS POSSIBLE...AND MAY CAUSE SLIPPERY TRAVEL IN THE HOURS AROUND SUNRISE THROUGH THE FRIDAY MORNING COMMUTE. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY. THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. GARTNER/JUNG
The national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
Storm total snow accumulations ranged from 6 to 10 inches.
Storm total snow accumulations ranged from 6 to 8 inches.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2012Every state in 2012This day in weather historyWarnings in Pennsylvania, December 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 419644, 419645.