Low pressure moved through the Eastern Great Lakes and Upper Ohio Valley and produced a wintry mix of snow, sleet and freezing rain across southwest Pennsylvania. The heaviest wintry precipitation fell from late on the 20th into the overnight and early morning hours on the 21st.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
Low pressure moved through the Eastern Great Lakes and Upper Ohio Valley and produced a wintry mix of snow, sleet and freezing rain across southwest Pennsylvania. The heaviest wintry precipitation fell from late on the 20th into the overnight and early morning hours on the 21st. Moderate accumulations of snow and ice were observed in Somerset, Cambria, Bedford and Fulton Counties.
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 Jan 20, 10:51 PM EST, 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1051 PM EST FRI JAN 20 2012 .SYNOPSIS... A LOW PRESSURE SYSTEM OVER THE MIDWEST WILL PASS SOUTH OF PENNSYLVANIA EARLY SATURDAY...BRINGING MORE WINTRY WEATHER TO THE REGION TONIGHT AND EARLY SATURDAY. AN UNSETTLED WEATHER PATTERN IS THEN IN STORE FOR NEXT WEEK...WITH GENERALLY MILD TEMPERATURES AND ONLY BRIEF PERIODS OF COLD. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... LGT SNOW HAS OVERSPREAD THE WESTERN HALF OF THE STATE AS OF 04Z AND CHARACTER OF RADAR ECHOES OVER SOMERSET CO SUGGEST MIXED PRECIP. RADAR TRENDS AND 4KM NAM INDICATE SNOW WILL SPREAD EAST...REACHING THE REST OF CENTRAL PA ARND OR SHORTLY AFTER MIDNIGHT. LOOKS LIKE WE ARE IN FOR A SHORT PERIOD OF ROBUST FORCING AND PRECIPITATION AS A SURFACE WAVE RACES OFF JUST TO OUR SOUTH UNDER A POTENT LEFT JET ENTRANCE REGION ALOFT. THE STRONG THERMALLY DIRECT CIRCULATION HELPS SUPPORT AN AREA OF DEEP LAYERED FRONTOGENETIC FORCING TRACKING ACROSS THE REGION OVERNIGHT. OPERATIONAL MODEL AND SREF PLUME QPF/S ARE IN THE .30 TO .60 INCH RANGE FOR THE EVENT...WITH THE HEAVIEST NUMBERS EXPECTED TO FALL OVER THE SRN TIER. ALL MDL DATA CONTINUES TO INDICATE ENOUGH WARM AIR WORKS IN ALOFT TO CHANGE CREATE MAINLY ZR/IP ACROSS SOMERSET AND ADJACENT COUNTIES. FOR THE REST OF SOUTHERN PA...SNOW SHOULD LIKELY CHANGE TO A WINTRY MIX BEFORE ENDING LATE SAT MORNING. ELSEWHERE...THE NORTHERN 2/3 OF THE STATE SHOULD REMAIN COLD ENOUGH FOR ALL SNOW. AT THIS TIME THE WARNING AREA LOOKS PRETTY WELL REPRESENTED WITH THE BEST CHANCE OF SEEING SIG ICING...WITH LESSER AMOUNTS OF SLEET/FRZ RAIN LIKELY ALONG THE SRN TIER INTO THE LOWER SUSQ VALLEY. FURTHER NORTH QPF IS EXPECTED TO DROP OFF A BIT BUT BE MAINLY SNOW. MDLS INDICATE PRECIP-PRODUCING CLOUD LAYER WILL CONTAIN A SIG AMT OF SUPERCOOLED LIQUID...RESULTING IN RIMING AND SNOW/WATER RATIOS CLOSE TO 12 TO 1. OVERALL THE NEW GUIDANCE IS STILL WELL IN LINE WITH A GENERALIZED 4-6 SNOWFALL FOR THE BULK OF MY FCST AREA...WITH A SLOPPY MIX ALONG THE S TIER. SOMERSET CO STILL STANDS OUT AS THE AREA MOST SUSCEPTIBLE TO SIG FZRA. MDL SOUNDINGS INDICATE MOST OF THE PRECIP DOWN THERE WILL BE EITHER FZRA OR IP. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... THE SHORT WAVE IS EXPECTED TO ALREADY BE MAKING A HASTY RETREAT BY 12-15Z WHICH WILL BRING AN END TO THE STEADIER PRECIP. FCST SOUNDINGS SUGGEST THINGS MAY TAPER OFF AS A PERIOD OF FRZ DRIZZLE...ESPECIALLY OVER THE LAURELS BEFORE DRIER AIR WORKS IN ON A NORTHERLY BREEZE. WITH SOME CLEARING LIKELY BY AFTERNOON...IT COULD TURN OUT TO BE A DECENT AFTERNOON WITH TEMPS A FEW DEGS MILDER THAN TODAY...NOT FAR FROM SEASONAL NORMALS. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... HIGH PRESSURE CENTERED OVER THE LOWER LAKES AT THE START OF THE PERIOD WILL SHIFT ENE TO THE CANADIAN MARITIMES BY 23/00Z. SAT NIGHT WILL BE CHILLY WITH DRIER AIR IN LOWER LEVELS ALONG WITH CLEARING SKIES AND FRESH SNOW COVER. AN INCREASING WARM ADVECTION PATTERN WILL DOMINATE SUN-MON. AS HIGH RETREATS...MODELS BECOMING MORE CONSISTENT IN DEVELOPING A BAND OF LIGHT OVERRUNNING PRECIP SUNDAY AFT/NIGHT EAST OF THE ALLEGHENY FRONT AS LOW LEVEL WINDS REMAIN EASTERLY. QPF LOOKS TO BE JUST A FEW HUNDREDTHS...BUT MAIN CONCERN IS PRECIP TYPE. A COLD START TO THE DAY WITH CLOUDS INCREASING WILL MAKE IT A STRUGGLE TO REACH FREEZING...AND THIS LIGHT PRECIP COULD FALL AS A COATING OF FREEZING DRIZZLE/RAIN ACROSS THE SUSQ VALLEY. WILL HAVE TO KEEP AN EYE ON THIS AS TIME FRAME APPROACHES. TEMPS SHOULD BE SLOWLY WARMING LATER SUN NIGHT-MON AS UPPER LOW LIFTS INTO THE GLAKES...SPREADING PLAIN RAIN ACROSS THE REGION DURING THAT PERIOD...EXCEPT ENDING AS SCT LAKE EFFECT SNOW SHOWERS MIDWEEK. LOW CONTINUES TO PULL AWAY TO THE NE TUE AS FLOW AGAIN TURNS ZONAL...KEEPING TEMPERATURES ABOVE NORMAL FOR MUCH OF THE WEEK...THOUGH TUE NIGHT WILL BE CHILLY WITH CLEARING SKIES. FOR LATER NEXT WEEK...MODELS AGREE IN DROPPING A CYCLONE INTO TEXAS BY THU...BUT THEN THE GUIDANCE DIVERGES HEADING INTO NEXT WEEKEND. EVENTUALLY THE LOW GETS PICKED UP IN MAIN FLOW AND WEAKENS AS IT LIFTS TO THE NE WITH SHORTWAVES SLIDING THROUGH NORTHERN STREAM TOWARD PA. LARGE TIMING DIFFERENCES MAKE THIS A DIFFICULT FORECAST...AND HAD TO SPREAD CHANCE POPS ACROSS A COUPLE DAYS - THOUGH TRENDED TO THE ECMWF. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... SNOW WILL QUICKLY DEVELOP OVER THE AREA THIS EVENING...AS AN INTENSE TEMPERATURE GRAIDENT SETS UP...AND IN COMBINATION WITH STRONG DYNAMICS WILL RESULT IN INTENSE UPWARD MOTION. EXPECT MODERATE SNOW AT TIMES BY LATE EVENING. SOME SLEET AND FREEZING RAIN WILL MOX WITH THE SNOW...MAINLY ACROSS THE SOUTHERN PART OF THE STATE. EXPECT WIDESPREAD IFR/LIFR CONDITIONS. CONDITIONS SLOWLY IMPROVE ON SATURDAY...AS A FAST MOVING LOW NEAR THE PA...MD BORDER MOVES EASTWARD. EXPECT VFR CONDITIONS BY EARLY TO MID AFT. COLD NIGHT IN STORE FOR THE AREA SATURDAY NIGHT. TIMING OF THE NEXT SYSTEM FOR LATER SUNDAY INTO MONDAY MAY HAVE A LARGE INFLUENCE ON THE TYPE OF PRECIPITATION...AS COLD...DRY AIR MAY REMAIN NEAR THE SFC...BEFORE TEMPPERATURES MODERATE SOME. OUTLOOK... SUN...NO SIG WX. SUN NGT-MON...MVFR-IFR. LGT MIXED PCPN CHANGING TO RA CENTRAL AND EAST. LLWS. SHARP COLD FROPA/GUSTY WIND SHIFT MON. TUES...MVFR IN -SHSN N/W...VFR E OF MTNS. WED...NO SIG WX. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR PAZ004>006-010>012-017>019-025>028-036-037-041-042-045-046- 049>053-056>059-063>066. WINTER STORM WARNING UNTIL 10 AM EST SATURDAY FOR PAZ024- 033>035. && SYNOPSIS...LA CORTE NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD/LA CORTE LONG TERM...RXR AVIATION...LA CORTE/MARTIN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE STATE COLLEGE PA 428 AM EST FRI JAN 20 2012 PAZ004>006-010>012-017>019-025>028-036-037-041-042-045-046-049>053- 056>059-063>066-210930- WARREN-MCKEAN-POTTER-ELK-CAMERON-NORTHERN CLINTON-CLEARFIELD- NORTHERN CENTRE-SOUTHERN CENTRE-BLAIR-HUNTINGDON-MIFFLIN-JUNIATA- FRANKLIN-TIOGA-NORTHERN LYCOMING-SULLIVAN-SOUTHERN CLINTON- SOUTHERN LYCOMING-UNION-SNYDER-MONTOUR-NORTHUMBERLAND-COLUMBIA-PERRY- DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND-ADAMS-YORK-LANCASTER- 428 AM EST FRI JAN 20 2012 ...WINTER WEATHER ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO 10 AM EST SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TODAY AND 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...SATURDAY THROUGH THURSDAY. 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. PAZ024-033>035-210930- CAMBRIA-SOMERSET-BEDFORD-FULTON- 428 AM EST FRI JAN 20 2012 ...WINTER STORM WARNING IN EFFECT FROM 7 PM THIS EVENING TO 10 AM EST SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TODAY AND 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...SATURDAY THROUGH THURSDAY. 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.
The national radar mosaic for the moment the first event began.
4 winter storm. Local standard time, as filed.
Widespread snow and sleet accumulation between 2 and 4 inches and ice accumulation of less than one-tenth of an inch were observed across the county.
Widespread snow and sleet accumulation between 3 and 6 inches and ice accumulation of less than one-tenth of an inch were observed across the county.
Widespread snow and sleet accumulation between 3 and 6 inches and ice accumulation of less than one-tenth of an inch were observed across the county.
Widespread snow and sleet accumulation between 2 and 4 inches and ice accumulation of less than one-tenth of an inch were observed across the county.
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, January 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: 355208, 355209, 355210, 355211.