textproduct: State College

WHAT HAS CHANGED

* Updated rainfall forecast for this evening and continued to increase wind gust forecast. * Slight decrease in rainfall totals over the next 48 hours, with highest rainfall across Lancaster and Sullivan Counties.

KEY MESSAGES

1) Nor'easter continues to bring gusty winds and periods of rain to central Pennsylvania this weekend.

2) Tranquil conditions expected for the first half of next week with a slight warming trend emerging across the region.

DISCUSSION

KEY MESSAGE 1: Nor'easter continues to bring gusty winds and periods of rain to central Pennsylvania this weekend.

A strong Nor'easter (988 mb) off the coast of Delaware coupled with a broad area of high pressure stationed to the north will continue to bring gusty winds and periods of rain throughout the weekend across central Pennsylvania. So far across central Pennsylvania gusts have remained largely below 30 mph; however, there have been some gusts that have briefly gusted above that threshold such as Lancaster Airport (KLNS), where a 33 mph wind gust was observed this morning. In terms of precipitation, periods of rain likely continue across portions of eastern Pennsylvania, with a brief area of relatively dry conditions beginning to fill in behind this precipitation. Guidance continues to outline a general trend in continued periods of rain through the evening hours before a brief lull in precipitation is observed later this evening and ahead of sunrise on Sunday. Further west, low-level dry air continues to erode rainfall as it dived southwestward. This trend likely continues with recent observations at JST/AOO/HMZ outlining 30-40% RH values although slightly more saturation is projected based on all model guidance to occur this evening.

As the nor'easter tracks closer to the NJ Coast, an increase in winds is expected to occur across much of the forecast area, with widespread 25-30 mph gusts on Sunday. Some locations across eastern Pennsylvania, especially areas with more complex terrain will likely push closer to 35-40 mph with localized gusts pushing close to Wind Advisory criteria. In terms of Wind Advisories, there was some consideration on hoisting flags for Sullivan, Schuylkill, Lebanon, and Lancaster Counties; however, confidence remains too low at this time with NBM 24-hr Max Gusts only showing a 20-40% chance for exceeding criteria. That being said, with leaves remaining on trees across the region this time of year, cannot rule out some tree damage and isolated power outages on Sunday. Another aspect of the closer track of the storm will be more widespread rainfall; however, no flooding concerns are expected with the stratiform nature of this rain as storm-total rainfall approaches one inch across Sullivan and Lancaster Counties.

KEY MESSAGE 2: Tranquil conditions expected for the first half of next week with a slight warming trend emerging across the region.

As the aforementioned nor'easter shifts further north and east of the region, the bulk of precipitation is expected to end by Monday morning outside of some lingering showers across eastern Pennsylvania. Once these lingering showers begin to diminish, fairly high (~70-80%) confidence in dry conditions prevailing through Wednesday. All model guidance trends towards a warming trend in this timeframe, with above-average temperatures prevailing area wide by Tuesday. Unsettled pattern begins to emerge towards the end of the week with a return of rain chances; however, model differences bring low confidence to the forecast this far out in the game.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Periods of rain will bring brief restrictions to MDT/LNS over the next couple of hours with low-level dry air eroding away precipitation as it approaches all of the other airfields across central Pennsylvania. Current thinking is that MDT/LNS will likely experience some rain chances through ~22-23Z Saturday before slightly less moisture will be in play to keep showers in the forecast. Overnight, it appears that for the majority dry conditions will prevail overnight with the bulk of model guidance keeping ceilings above VFR. Thus, have penciled in VFR conditions with moderate-to-high (~60-70%) confidence. There will also be a period overnight where winds will decrease, with maximum wind gusts likely dropping below 10kts in the 00Z-10Z timeframe across all of central Pennsylvania. With these winds decreasing, some LLWS concerns overnight but slightly less than this morning's TAF package due to the bulk of these concerns coming above 2,000 ft AGL.

Rainfall appears to be more widespread on Sunday, especially after 12Z with the proximity of the nor'easter closer to the NJ Coast. This will bring a higher potential for lower ceilings and visibilities across much of the region. The highest confidence in MVFR and below restrictions will be at MDT/LNS where a couple-hour period of IFR conditions have been outlined in recent GLAMP guidance with NBM/HREF guidance also suggesting this is a plausible scenario between 15-18Z. Elsewhere, MVFR likely prevails as the lowest flight category with JST/BFD potentially prevailing VFR at worst. This system placement will also lead to wind gusts exceeding 20-25kts across all of central Pennsylvania; however, based on recent HREf/NBM guidance have trended towards a slightly stronger wind forecast with MDT/LNS pushing closer to 30kts towards the end of the TAF period.

Outlook...

Mon-Wed...Some showers early Monday AM; otherwise, trending towards VFR conditions.

Thu...Chance of showers late PM, some restrictions possible.

CTP WATCHES/WARNINGS/ADVISORIES

None.