textproduct: State College

WHAT HAS CHANGED

* Increased wind gusts in the far north for later tonight

KEY MESSAGES

1) Periods of rain Tuesday and Wednesday

2) Pattern shifts to cold later this week with below average temperatures into early May

DISCUSSION

KEY MESSAGE 1: Periods of rain Tuesday and Wednesday

Minor change to add up to 10MPH onto the wind gusts for later tonight as the 50KT LLJet dips very close to the sfc (around 1kft up). The light showers/evap cooling aloft moving in could help transport some portion of that momentum down to the sfc. However, we didn't go to 40KT with them, as the stability should be enough to mitigate/diminish the threat of anything >40KT/wind advy. This is a regular trouble to have in the forecast. Locations along the Erie lakeshore can tap that higher momentum thanks to the downslope to help it mix down. But, our place on the broader Allegheny Plateau usually makes it more difficult for those faster S/SErly winds aloft to mix down.

Previous... The preponderance of model data supports two periods of wet weather Tuesday and Wednesday. QPF amounts are more robust on Wednesday tied to stronger frontal wave with 48-hr totals in the 0.75-1.50" range ending 12Z Thursday. This rain will continue to add to surpluses over the NW half of the area while helping to reduce rainfall deficits in the southern 1/3 of CPA where D1-D2 drought areas have been persistent. However like we've seen time and time again so far this year, the highest totals are expected in the northwest.

SPC D3 MRGL risk valid Wednesday clips the Laurels as a 1003 mb sfc low swings through the area. Guidance seems to suggest only limited amounts of instability, confined to SW PA. NBM has 70-80% chc of at least 200 J/kg SBCAPE in SW PA but only a 30% chc of 750+ J/kg. Storm motions would be to the northeast, so storms would be moving into a less favorable environment as they move into PA. Large scale forcing will be favorable for ascent for 6-12 hours across all of central PA as we'll be beneath the left exit region of an upper jet max.

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KEY MESSAGE 2: Pattern shifts to cold later this week with below average temperatures into early May

Latest guidance has a good handle on the mid-larger scale pattern evolution from late week into the weekend (end of April into early May) showing a broad upper trough/low over the Great Lakes into the Northeast. This unseasonably cool cyclonic flow pattern will deliver below normal temps (5-15 degrees) and maintain daily shower chances with breezy conditions (wind gusts 25-35 mph) Thursday through Sunday. Odds favor advective freeze over frost risk with wind and cloud cover playing a key factor.

AVIATION /01Z TUESDAY THROUGH SATURDAY/

VFR conditions continue through the evening and overnight with increasing high and mid level clouds ahead of an area of rain that will move through late tonight and into the morning. The main concern tonight will be LLWS at BFD, JST, AOO, and UNV as a 40 to 50 knot low-level jet moves in from the west. Some of this wind will likely mix down to the surface with wind gusts of 20 to 30 knots possible, particularly at BFD and JST after 06Z. There is some uncertainty regarding just how strong the winds get though, with some guidance indicating the potential for gusts as strong as 40 knots at BFD and JST in the 10Z to 14Z timeframe.

Ceilings lower through the morning from west to east, likely falling to MVFR everywhere except MDT and LNS by the afternoon. IFR ceilings will also be possible at BFD and JST after 18Z. Rain chances decrease through the afternoon, but isolated showers will remain possible into the early evening.

Outlook...

Wed...MVFR/IFR favored due to low cloud ceilings & rain overspreading the region.

Thu...VFR/MVFR overnight as rain ends west to east, becoming VFR in the afternoon.

Fri-Sat...Mainly VFR with brief restrictions possible in showers.

CTP WATCHES/WARNINGS/ADVISORIES

None.