textproduct: State College

WHAT HAS CHANGED

Temperatures tonight into Monday morning have trended down and will bring some concern for Cold Weather Advisories with the ridge and valley region likely the only region to experience near-zero wind chills. The mid-week system has also trended slightly drier in the most recent forecast package, mainly due to lack of moisture available for precipitation mentions.

KEY MESSAGES

1) Frigid wind chills to begin Sunday morning with one more bitterly cold night possible across central Pennsylvania tonight into Monday morning.

2) Warming trend interrupted by potential mid-week system that will bring next chances for precipitation across central Pennsylvania.

DISCUSSION

KEY MESSAGE 1: Frigid wind chills to begin Sunday morning with one more bitterly cold night possible across central Pennsylvania tonight into Monday morning.

Cold air remains in place this Sunday morning; however, wind gusts have shifted to mainly eastern Pennsylvania where a pressure gradient still remains with the departing area of low pressure across the northern Atlantic. This has allowed for wind chills across northeastern Pennsylvania to trend the coldest with recent observations at KN38/KZER outlining wind chills near -20F this morning. At this point, only see a couple more degree drop across the region ahead of sunrise before temperatures begin to increase. No changes to the Extreme Cold Warning this cycle and remains on track to expire at 10AM EST this morning.

The more interesting portion of this forecast package comes with regards to minimum temperatures/wind chill forecast tonight into Monday morning, where recent model guidance outlines some potential for radiational cooling across mainly western Pennsylvania as high pressure in the Bluegrass Region of northern Kentucky gradually shifts into northwestern Pennsylvania. Clear skies and light winds appear most likely across the western half of the CWA which typically promotes radiational cooling and undercutting of NBM model guidance. Across the eastern half, there is moderate (~50-60%) confidence in clear skies; however, a slight breeze remains possible as while the pressure gradient shifts further east, recent guidance does not outline an entirely quick eastward movement.

As alluded to above, there remains a couple failure modes with regards to radiational cooling overnight that could limit wind chills/temperatures reaching Cold Weather Advisory across much of central Pennsylvania: * The potential prospect of a scattered cloud deck that allows for less radiational cooling across NW PA that could limit radiational cooling prospects. * There remain two camps with respect to temperatures with the colder ECMWF/NAM guidance versus relatively warm GFS/HRRR model output, leading to higher uncertainty in the forecast. * Considerations on how low dewpoints get overnight, which could lead to a slightly higher temperature forecast.

Given all of the above considerations this morning and after collaboration with WFO BUF/CLE/PBZ/LWX, have decided to hold off on Cold Weather headlines this cycle to get another suite of model guidance that could limit the weight of some of these considerations. Despite having no headlines out at this time, best bet is to expect cold temperatures across central Pennsylvania for another evening, so make plans of action with respect to checking vulnerable populations, whether they are your neighbors, family, or friends given the longer duration of cold weather and make any considerations for outdoor pets into Monday morning.

KEY MESSAGE 2: Warming trend interrupted by potential mid-week and end of week system that will bring next chances for precipitation across central Pennsylvania.

A warming trend emerges on Monday, where temperatures are expected to rebound closer to climatological averages for the second week of February. This warming trend is expected to be interrupted for the middle of the week as an area of surface low pressure tracks north of the area. Recent ensemble guidance has continued to trend relatively dry as despite any forcing that will be available, the overall column remains fairly dry, effectively canceling out any chances for precipitation with respect to the middle of the week system. Recent NBM probabilities outline overall less than 20% of measurable precipitation across all of central Pennsylvania, with highest chances across the northern tier Wednesday into Thursday. Have decided to continue rolling with NBM model guidance this cycle given the remaining uncertainty, but looking closer to a drier mid-week for those across the region. Precipitation chances have trended slightly upward for the a potential system across central Pennsylvania next weekend; however, still a lot of uncertainty this far out so have rolled with NBM model guidance outlining highest chances mainly north/west of the Allegheny Front into the beginning of next week.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Ceilings will bounce between VFR and MVFR at KBFD and KJST through the remainder of the afternoon with the rest of the area good VFR. Expect all areas to go VFR early tonight. Winds will diminish through the afternoon and evening in all locations as high pressure builds into the region.

Skies will clear overnight but some signal in the high resolution models of low level moisture settling in at KBFD and KJST later tonight. Introduced a brief period of MVFR to IFR later tonight in BR. Elsewhere, VFR remains through the end of the forecast period.

Outlook...

Mon-Tue...No sig wx.

Wed-Thu...Mixed precipitation possible.

CTP WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory from 10 PM this evening to 9 AM EST Monday for PAZ004>006-010>012-017>019-024-025-033-034-037-041- 042-045-046-049>053-057>059-065-066.