Low pressure moved from the Ohio Valley into the eastern Great Lakes on Monday, December 27, 2021, producing 1 to 2 inches of snow, before changing over to a wintry mix and eventually plain rain from southwest to northeast across the area. A burst of moderate snow at the onset of the precipitation quickly slickened roads, and I-80 westbound was closed at mile marker 140 in Rush Township, Centre…
Every event with a place to put it; 1 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 from the Ohio Valley into the eastern Great Lakes on Monday, December 27, 2021, producing 1 to 2 inches of snow, before changing over to a wintry mix and eventually plain rain from southwest to northeast across the area. A burst of moderate snow at the onset of the precipitation quickly slickened roads, and I-80 westbound was closed at mile marker 140 in Rush Township, Centre County due to multiple accidents.
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 27, 6:48 AM EST, 3 hours 17 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 648 AM EST Mon Dec 27 2021 .SYNOPSIS... Mixed precipitation and rain are expected across central Pennsylvania today into tonight. Another disturbance will bring mixed precipitation and rain Tuesday afternoon and evening, followed by yet another weather system bringing mainly rain for Thursday into Friday. Another warm surge will be possible at the start of next weekend, before colder weather follows for late next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ...6:45 AM Update... Snow/sleet breaking out over the Alleghenies at this hour, poised to push into the WC and NW Mountains shortly. Near term hi-res models indicate a quick burst of moderate snow and sleet is in store for much of central and north central PA. Current 1-2" amounts given mix with sleet are on track for no changes here at sunrise. ...Previous discussion... Clouds are lowering and thickening this morning in advance of warm front lifting NE thru the OH Vally. WAA has increased early this morning as the nose of a 50KT LLJet arrived into wrn PA. Current temps range from the upper 20s to the lower 30s with dewpoints from the mid to upper 20s, setting the stage for wintry precip to start in the pre dawn hours over the SW. Timing is very similar to the last few runs, arriving before sunrise in the Laurels, but wait until after sunrise elsewhere. Moderate precipitation rates advertised from latest HRRR/HREF runs with prob 1"/hr rates ticking up for an hour or two near UNV. Mix with sleet should occur fairly quickly so not overly concerned with snow totals and have stayed close to previous. Overall, we expect 1-2 inches of snow/sleet in the Alleghenies and Blair/Hunt counties...and less than an inch elsewhere. Snow breaks out between 12z and 15z, so deteriorating conds possible during morning rush across central and western sections. Most areas will see 2-4 hours of mixed light to moderate precipitation, with a changeover to patchy freezing drizzle and then plain r-- or drizzle later this afternoon or even lasting into this evening far northeast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Precipitation tapers early tonight with still some residual drizzle or areas of very light rain into the overnight. Temps remain mild, and should remain above freezing. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Fast moving systems this week will make for chances for mixed precipitation again by Tuesday afternoon and night, with 00z Monday guidance going colder with more S/IP chances Tuesday PM. Timing of systems every 36 hours means great changeability in model solutions and resulting forecasts mid to late week. Next weekend is trending milder to begin, followed by colder air late next weekend. By then, it may end up not being quite as significant of cool down as some models have it. Earlier discussion below. Another system will quickly follow on the heels of Monday's, with precipitation arriving Tuesday morning into the afternoon as a warm front approaches central PA. Given the lack of a cold antecedent airmass before the arrival of the precipitation, not currently expecting significant wintry precipitation. Transient/weak surface ridging will not have much residence time across the Commonwealth prior to warm/moist advection filtering in from the southwest on Tuesday, so have opted to keep the prevailing weather grids comprised of only rain/snow at this time. Very possible that we could see a brief period of light freezing rain/sleet as wet-bulb cooling takes place, but again, the lack of a deeper and more significant cold dome should preclude greater concerns. Could see up to 1-2 inches of snow in spots across the northern tier by the time warm air advection sweeps through all of PA into Tuesday night. Look for mainly rain Tuesday night, with portions of the northeast continuing to see a mix with some snow. Conditions should dry out through the day on Wednesday as a frontal boundary slowly sags off to the south of PA. Southwest flow aloft, in response to troughing to our west, will keep things unsettled for late week as temperatures remain above normal. An embedded disturbance should knock temperatures down a bit for Thursday, but still expecting above normal readings in the upper 30s north to upper 40s south. Passing rain/snow showers with no real impact will therefore be possible Thursday/Friday, before a potentially more significant precipitation event sets up for later New Year's Day into the second half of next weekend. Still a great deal of uncertainty in all aspects of this system's development at this time. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Low clouds over the northern tier earlier tonight have been eroding over the past few hours, with BFD recently trending from MVFR to VFR. All TAF sites should continue to see VFR conditions until just before daybreak. Wintry precip will overspread central PA from west to east through Monday morning, starting in JST and the Laurel highlands around 12z. Much of the precip will be a mix of snow, sleet, and freezing rain, with northern and eastern areas seeing more in the way of sleet and snow. As warmer air arrives aloft, the precip will change over to freezing rain and then to plain light rain during the afternoon. Restrictions will accompany the precip, with conditions deteriorating to IFR or lower for most of central PA by Mon afternoon. LLWS will begin over western areas (BFD, JST) starting Mon morning as southerly flow increases at 2kft. Lingering light rain will gradually taper off Monday evening into Mon night. Winds at 2kft will turn to the SW Mon evening as LLWS expands to cover more of central PA. Outlook... Mon night...IFR early, improvement late. Tues-Tues night...Another round of rain and restrictions will overspread the area, and a wintry mix is possible north. Wed...Improvement thru the day. Wed night-Thurs...Light rain (wintry mix possible north) and restrictions return. Fri...Becoming VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 AM this morning to midnight EST tonight for PAZ037-041-042-053-058. Winter Weather Advisory until 3 PM EST this afternoon for PAZ005-010-011-017>019-025>028-034-035-056-057-059. Winter Weather Advisory until 1 PM EST this afternoon for PAZ024-033. Winter Weather Advisory until 6 PM EST this evening for PAZ006- 012-045-046-049>052. && SYNOPSIS...DeVoir/Martin NEAR TERM...DeVoir SHORT TERM...DeVoir LONG TERM...Guseman/Martin AVIATION...Evanego/Colbert
Hazardous Weather Outlook National Weather Service State College PA 357 AM EST Mon Dec 27 2021 PAZ004-036-063>066-280900- Warren-Franklin-Cumberland-Adams-York-Lancaster- 357 AM EST Mon Dec 27 2021 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ037-041-042-053-058-280900- Tioga-Northern Lycoming-Sullivan-Columbia-Schuylkill- 357 AM EST Mon Dec 27 2021 ...WINTER WEATHER ADVISORY IN EFFECT FROM 11 AM THIS MORNING TO MIDNIGHT EST TONIGHT... 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... Spotter activation is not expected at this time. PAZ024-033-280900- Cambria-Somerset- 357 AM EST Mon Dec 27 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... Spotter activation is not expected at this time. PAZ006-012-045-046-049>052-280900- Potter-Northern Clinton-Southern Clinton-Southern Lycoming-Union- Snyder-Montour-Northumberland- 357 AM EST Mon Dec 27 2021 ...WINTER WEATHER ADVISORY IN EFFECT FROM 9 AM THIS MORNING TO 6 PM EST THIS EVENING... 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... Spotter activation is not expected at this time. PAZ005-010-011-017>019-025>028-034-035-056-057-059-280900- McKean-Elk-Cameron-Clearfield-Northern Centre-Southern Centre-Blair- Huntingdon-Mifflin-Juniata-Bedford-Fulton-Perry-Dauphin-Lebanon- 357 AM EST Mon Dec 27 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... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
1 winter weather. Local standard time, as filed.
A burst of moderate snow produced a quick 1 to 2 inches of snow that quickly slickened roads, and I-80 westbound was closed at mile marker 140 in Rush Township, Centre County due to multiple accidents. The westbound lanes were closed for nearly three and a half hours.
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, December 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: 990269.