Low pressure passed over the Great Lakes and up the Saint Lawrence River valley from February 22 into February 23, 2021, pushing a warm front and cold front across central Pennsylvania. A narrow, north-south stripe of heavy snow (1-2 per hour) associated with the warm front passed over the Susquehanna Valley during the morning rush hour, and the heavy snowfall rates combined with the potential…
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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.
Low pressure passed over the Great Lakes and up the Saint Lawrence River valley from February 22 into February 23, 2021, pushing a warm front and cold front across central Pennsylvania. A narrow, north-south stripe of heavy snow (1-2 per hour) associated with the warm front passed over the Susquehanna Valley during the morning rush hour, and the heavy snowfall rates combined with the potential for a flash freeze prompted the issuance of snow squall warnings.
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 Feb 22, 5:10 AM EST, 3 hours 5 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 510 AM EST Mon Feb 22 2021 .SYNOPSIS... A fast moving system will produce a widespread 2-4 inch snowfall this morning and early afternoon. High pressure will bring a short break before a weak Clipper moves across on Tuesday. Temperatures will warm well above normal Wednesday. A sharp but dry front moves through later Wednesday and will drop the temperatures drastically for the second part of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The forecast is rolling along with extremely minor tweaks this morning. There is snow falling in western PA, but the dewpoints are higher there. The very dry low levels (sfc dewpoints in the lower teens at 10Z) will keep the snow currently over wrn PA from getting to the surface in most places. It will be light if it does. The dewpoints do rise as the srly wind is starting to increase now, and will get more gusty. The intensity of the snow should also pick up in the next 2-3 hrs as the orographic upslope lift into the Laurels and Allegheny Plateau adds to the forcing. Therefore, we will keep the timing of onset and the heaviest snowfall exactly the same. Latest HREF continues to show a high probability of 1+"/hr rates as the main band of snow moves through, leading to significant travel impacts in the west during the rush hour and perhaps for the end of the rush in the central mtns. The precip should hold off for places along and east of the Mainstem Susq River until 10 or 11 AM. Have held the snow amounts as is, except for a tiny increase of an inch or less over the far eastern zones, esp Sullivan and Schuylkill counties where they will likely get close to 6 inches. Have opted to keep the advy going with some uncertainty in the fluffiness of the snow. SLRs stay below 10:1 for the far srn tier of counties, but intense rates in mid-day could bring them a little more than currently forecast. On the other hand, the mid-day solar heating and marginal sfc temps could make the impacts much less than expected even if current SF totals are achieved. The roads could just stay wet in the south as temps will be right around freezing at first, then rise into the m30s when the occlusion moves in for a few hours just after the heaviest snow goes by there. The temps could actually spike this morning before falling during the heavy snowfall, then go back up well above freezing until sunset. Some mixing with rain is possible in the southern half of the area, but only after the heavy snow passes through. Transfer/jump of 850 mb jet and the best low-mid level forcing/uvvel is expected to lead to a relative minimum in snowfall between the I-99 and RT11/15 corridors, where around 2 inches appear likely. Passage of the sfc (and upper) trough will likely support some lingering snow showers this afternoon, mainly over the Allegheny Plateau. However, little any additional accumulation is likely. Strong subsidence behind departing trough will allow stronger winds aloft to mix down late in the day. Bufkit soundings support gusts near 30kts by 21Z over the Allegheny Plateau. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... Some flurries overnight for the nrn mtns. But, a Clipper arrives in the morning on Friday. It will produce a quick coating of snow Tuesday morning for the NW and Laurels. Lack of moisture, downslope and fast movement will make hardly a flurry from UNV south. SHSN will linger early Tues night for the upslope areas of the Laurels and Alleghenies. Clearing elsewhere and a quick veering of the wind on Wed will bring temps above normal. Some debate as to how hot it can get with all the snow on the ground. Still, 8H temps of +4C (S) usually get us into the 50s unless we are very stable. The GFS BUFKIT soundings Wed have us getting near at least moist adiabatic lapse rates for a few thousand feet in the central in the afternoon and evening in the south, so some very shallow convection is possible during the passage of a cold front. The meager moisture may preclude rain in the SE, though. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Medium range guidance supports fair and seasonable conditions Thursday associated with a large surface high and low pwat airmass building into the area. A shortwave and associated cold front should sweep southeast from the Grt Lks early Friday, likely accompanied by scattered snow showers over the northern mountains. The post-frontal air mass doesn't look cold enough to support lake effect. Significant changes have been made to the weekend forecast. Latest ECENS and GEFS now track a weak area of low pressure up the east coast. Although the large scale forcing looks unimpressive, the combination of the weak low and anomalous high pressure off of the New England coast should result in an increasingly moist easterly flow off of the Atlantic, resulting in a period of light precipitation. Model thermal profiles point toward light snow late Friday night, changing to light rain Saturday. The bulk of guidance indicates fair weather returns Saturday night, as weak low lifts into New England. Beyond that, plenty of model spread and forecast uncertainty. However, ECENS and GEFS point toward mild conditions with a chance of rain showers either late Sunday or Sunday night in association with low pressure tracking west of Pa. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... The leading, northern edge of a potent south-southwesterly 60-70 kt low-level jet will bring LLWS to all airfields through this morning. Light snow will overspread central PA this morning and continue through mid morning, producing widespread restrictions, especially during some 60-90 minute periods, when the snow could fall at a rate of nearly 1 inch per hour, which would equate to around 1/2SM vsby and cigs below 1000 FT AGL. Conditions should improve to mainly VFR across the Central and Eastern parts of PA during the afternoon, while upslope flow and moderately strong cooling aloft pushes in via a deep west- northwest flow keeping Western section of the airspace sub-VFR. Outlook... Mon afternoon and Mon night...Lingering MVFR to IFR Cigs and light snow showers across mainly the Western PA Mtn airfields of KBFD, south through KFIG and KJST. Periods of MVFR cigs at KAOO and KUNV. Susq airfields should transition to mainly VFR with brief MVFR possible. Tues...Scattered -SHSN to bring reductions to primarily the northern and western highlands. Wed...VFR conds. Wed night-Thu...Restrictions possible mainly N/W in light rain/snow showers. Friday...Looking at dry conditions with mainly VFR conditions. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 3 PM EST this afternoon for PAZ042-051>053-057>059-065-066. Winter Weather Advisory until 1 PM EST this afternoon for PAZ004-005-010-011-017-024-033. Winter Weather Advisory until 1 PM EST this afternoon for PAZ006-012-018-019-025>028-034>037-041-045-046-049-050-056-063- 064. && SYNOPSIS...Dangelo NEAR TERM...Fitzgerald/Dangelo SHORT TERM...Dangelo/Martin LONG TERM...Fitzgerald AVIATION...Gartner/Travis
Hazardous Weather Outlook National Weather Service State College PA 426 AM EST Mon Feb 22 2021 PAZ006-012-018-019-025>028-034>037-041-045-046-049-050-056-063-064- 230930- Potter-Northern Clinton-Northern Centre-Southern Centre-Blair- Huntingdon-Mifflin-Juniata-Bedford-Fulton-Franklin-Tioga- Northern Lycoming-Southern Clinton-Southern Lycoming-Union-Snyder- Perry-Cumberland-Adams- 426 AM EST Mon Feb 22 2021 ...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EST THIS AFTERNOON... 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...Tuesday through Sunday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report snowfall accumulations. PAZ042-051>053-057>059-065-066-230930- Sullivan-Montour-Northumberland-Columbia-Dauphin-Schuylkill-Lebanon- York-Lancaster- 426 AM EST Mon Feb 22 2021 ...WINTER WEATHER ADVISORY IN EFFECT FROM 8 AM THIS MORNING TO 3 PM EST THIS AFTERNOON... 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...Tuesday through Sunday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report snowfall accumulations. PAZ004-005-010-011-017-024-033-230930- Warren-McKean-Elk-Cameron-Clearfield-Cambria-Somerset- 426 AM EST Mon Feb 22 2021 ...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EST THIS AFTERNOON... 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...Tuesday through Sunday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report snowfall accumulations.
The national radar mosaic for the moment the first event began.
19 winter weather. Local standard time, as filed.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in northwestern Lancaster County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Northumberland County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Dauphin County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in eastern Synder County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Columbia County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Union County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in southeastern Tioga County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in eastern Cumberland County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in northeastern Perry County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Schuylkill County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in northwestern York County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Montour County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in northern Lycoming County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in southern Lycoming County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Sullivan County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Lebanon County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in Lancaster County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in southeastern Adams County.
SNOW SQUALL. A snow squall on the leading edge of a mesoscale band of heavy snow briefly dropped visibility to under one quarter mile in and produced flash-freeze conditions in York County.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2021Every state in 2021This day in weather historyWarnings in Pennsylvania, February 2021
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: 944723, 944724, 944725, 944726, 944727, 944728, 944729, 944730, 944731, 944732, 944733, 944734, 944735, 944736, 944737, 944738, 944741, 944742, 944743.