Cold northwesterly flow with an arctic intrusion brought the first significant lake-effect snow of the season to Warren County in northwestern Pennsylvania, with 8 to 16 inches of new snowfall across northern and western Warren County.
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The episode as NWS CTP wrote it up.
Cold northwesterly flow with an arctic intrusion brought the first significant lake-effect snow of the season to Warren County in northwestern Pennsylvania, with 8 to 16 inches of new snowfall across northern and western Warren County.
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 12, 6:34 AM EST, 26 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 634 AM EST Tue Dec 12 2017 .SYNOPSIS... An alberta clipper will track over northwestern PA early today with a trailing arctic cold front sweeping through the area during the mid to late morning afternoon. A deep upper level trough will remain over the eastern conus through the rest of this week with another weak clipper likely affecting the area Thursday. The upper trough will likely lift out by next weekend. A low pressure system lifting northeast from the Great Plains will bring a southwest flow of milder air for the weekend. && .NEAR TERM /UNTIL NOON TODAY/... A compact, but quite potent mid/upr level vort max moving ENE across the WRN Mtns attm will bring a brief period of rain/snow showers as mean 925-850mb temps are near to slightly above freezing across the southern tier with sfc temps in the mid-upr 30s. Near and to the north of the RT 22 corridor in Scent PA boundary layer wet bulb temps are a few deg C below freezing, which will support a few periods of primarily snow showers through 14Z. Short range, high res RAP and HRRR consensus brings a batch of warm advection snowfall to the NRN mtns during the mid morning hours with a coating to the lower terrain, and 1 to 3 inches across the Mtns north of a KDUJ to KIPT line. The mid level shear axis will be across the Susq Valley and points east between 12-14Z...accompanied by a band or two of light rain and snow showers. QPF and snowfall amounts near and to the SE of the I-99/Route 220 corridor look to be light with a few to svrl hundredths of an inch of LEQ at most and perhaps a ground coating of snow (mainly across the higher terrain near and to the north of I-80, which will be along of just to the north of the track of the aforementioned compact mid/upr level short wave. The main impacts from this system will come as the cold front ushers in the coldest air of the season into PA later today, after the arctic FROPA later this morning. Temps peak between 35 and 40 deg F late this morning/early this afternoon across the SE half of the CWA, while highs today across the western mtns (in the low-mid 30s) will occur within the next few hours, followed by falling steadily through the 20s and into the mid teens around dusk. West to northwest winds will pick up drastically in the wake of the shortwave and closely trailing arctic front, with gusts of 35 to 45 mph likely across the western mtns beginning late this morning, then developing across the central and eastern parts of the CWA this afternoon. Lake Effect Snow Warning is in effect for Warren County beginning at 12Z today, while a Winter Weather Advisory extends south from McKean County through the Laurel Highlands in Cambria and Somerset County. && .SHORT TERM /NOON TODAY THROUGH 6 PM WEDNESDAY/... The coldest air of the season is forecast to arrive behind trailing arctic cold front this afternoon and tonight with more lake effect snow lasting through midweek. Northwest Warren County should get into some of the more robust lake effect banding later Today and continuing into Wednesday. Lake Effect Snow Warning in effect for this, per collaboration with BGM, for widespread 10 to 15 inches, with local amounts up to 18 inches over extreme northwest Warren County. Model blended qpf supports a long duration advisory over Elk/Mckean counties, as well as Clearfield/Cambria/Somerset Counties where 4 to 8 inches are expected from 12z Tuesday through 18z Wednesday. Still some concern about snow squalls accompanying cold front passage between 12Z-18Z today with the best values of the snow squall parameter noted across the Lower Susq Valley for an hour or two this afternoon. However, boundary layer temps appear borderline for signif impacts from snow showers/squalls and surface temps are likely to be between 35 and 40F during the time of the best dynamics for squalls. Gusty northwest winds and snow showers will be the main issue Tonight into Wed. Warnings and advisories in effect until 18Z Wed. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Models show another system for Thursday. This system looks weak and EC a little further south, as been the case. Thus just have very light amts in. Maybe more of an impact for the far southeast, than system for Tue into Wed. After this the pattern supports a deep low tracking northeast from the Great Plains for the weekend, which will result in milder conditions. As been the case, the Gulf of Mexico is not really open, so looking at a mainly dry weekend. Complex pattern for Monday, perhaps a little light snow, but nothing major. Minor changes to the extended package. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... A compact yet potent mid level shortwave sliding across the CWA early this morning (dragging a weak occluded front along with it) will bring brief reductions in snow showers before it moves off to the NE by 13z. Then attention turns to an arctic cold front sweeping through the area during the mid to late morning afternoon. Between now and then, generally IFR reductions will persist across the NW mountains in snow showers. with reductions arriving at JST by 13z and AOO/UNV/IPT by 15z. The western sections will remain IFR for much of the day as upslope westerly flow increases and snow showers become more widespread, with MVFR spilling into the central mountains with lighter snow showers likely. Winds also increase with FROPA with gusts to 30-40 mph becoming more common by midday over the west, and 25-35 mph gusts for this afternoon over the east. There remains some concern for localized snow squalls accompanying cold front passage over NW half of CWA. Reductions continue tonight into Wed across NW half, with mainly IFR at BFD and MVFR at JST. Winds remain very gusty as well. Outlook... Wed...Snow showers with IFR NW Mtns. Sct snow showers with MVFR NW half. Otherwise VFR. Wed night...Alberta Clipper could bring light snow and more widespread reductions. Thu-Fri...Sct snow showers NW. Reductions west. Sat...Mainly VFR. Perhaps a snow shower north. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 1 PM EST Wednesday for PAZ005- 010-017-024-033. Lake Effect Snow Warning until 1 PM EST Wednesday for PAZ004. && SYNOPSIS...Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Lambert LONG TERM...Martin AVIATION...RXR
Hazardous Weather Outlook National Weather Service State College PA 538 AM EST Tue Dec 12 2017 PAZ004-131045- Warren- 538 AM EST Tue Dec 12 2017 ...LAKE EFFECT SNOW WARNING IN EFFECT UNTIL 1 PM EST WEDNESDAY... 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. Lake Effect Snow Warning. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Please listen to NOAA Weather Radio or go to weather.gov/StateCollege on the internet for more information about the following hazards. Lake Effect Snow Warning. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather. PAZ005-010-131045- McKean-Elk- 538 AM EST Tue Dec 12 2017 ...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EST WEDNESDAY... 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...Wednesday through Monday. 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... Spotters are encouraged to report significant hazardous weather. PAZ017-024-033-131045- Clearfield-Cambria-Somerset- 538 AM EST Tue Dec 12 2017 ...WINTER WEATHER ADVISORY IN EFFECT UNTIL 1 PM EST WEDNESDAY... 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...Wednesday through Monday. 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... Spotters are encouraged to report significant hazardous weather. PAZ006-011-012-018-037-041-042-131045- Potter-Cameron-Northern Clinton-Northern Centre-Tioga- Northern Lycoming-Sullivan- 538 AM EST Tue Dec 12 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. Snow showers will bring an inch or two of snow accumulation to many locations. West to northwest winds will increase to 15 to 25 mph with frequent gusts of 35 to 40 mph this afternoon into tonight. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Additional snow showers and gusty winds will occur tonight and Wednesday with light accumulations. Winds will lighten up and a few periods of steadier light snow will occur Wednesday night into Thursday with another 1 to 2 inches likely. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather. PAZ019-025>028-034>036-045-046-049>053-056>059-063>066-131045- Southern Centre-Blair-Huntingdon-Mifflin-Juniata-Bedford-Fulton- Franklin-Southern Clinton-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Perry-Dauphin-Schuylkill-Lebanon-Cumberland- Adams-York-Lancaster- 538 AM EST Tue Dec 12 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. Scattered snow showers will occur today and tonight with the chance for a few briefly heavier squalls. West to northwest winds will increase to 15 to 25 mph with frequent gusts of 35 to 40 mph this afternoon into tonight. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Additional scattered snow showers and gusty winds will occur tonight and Wednesday with light accumulations in some locations. Winds will lighten up and a few periods of steadier light snow will occur Wednesday night into Thursday with a coating to one inch of snow likely. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather.
The national radar mosaic for the moment the first event began.
1 lake-effect snow. Local standard time, as filed.
Lake-effect snow produced 8 to 16 inches of snowfall across northern and western Warren County.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2017Every state in 2017This day in weather historyWarnings in Pennsylvania, December 2017
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: 727453.