textproduct: State College

WHAT HAS CHANGED

* Frost Advisory issued tonight for the western and northern Alleghenies

KEY MESSAGES

1) Seasonably cool and mainly dry end to the week with areas of frost tonight into early Friday morning

2) Wet weather - but not a total washout - for Mother's Day weekend; monitoring frost freeze risk Monday night/AM Tuesday

DISCUSSION

KEY MESSAGE 1: Seasonably cool and mainly dry end to the week with areas of frost tonight into early Friday morning

Most locations stay dry through the end of the week with a couple of passing showers or sprinkles over the northern portion of the forecast area. Daytime highs Thu/Fri are 5-10F below the historical average for early May. Diurnal/instability cu field should fade this evening and give way to initial clearing before some clouds try to return by the predawn hours Friday. The cloud coverage could limit areas of frost which are most likely to be found across the western and northern Alleghenies where min temps are fcst in the low-mid 30s. Patchy frost is also possible farther to the east/downwind of the Allegheny Front especially in the usually colder sheltered rural valleys between I99/US220 and I81.

KEY MESSAGE 2: Wet weather - but not a total washout - for Mother's Day weekend; monitoring frost freeze risk Monday night/AM Tuesday

Model signals point toward a wet start to Mother's Day weekend with zone of steady light rain early Saturday tapering to showers by Saturday night. Hires output suggests a WSW-ENE oriented band of rain focusing over the northern half of the CWA Saturday morning. Additional showers are likely Sunday into Sunday night although the exact timing is still unclear. Initial read favors late Sunday through Sunday night/early Monday with more rain breaks or intermittent periods of rain/showers for the second half of Mother's Day weekend. Daytime highs this weekend are projected to warmup a bit into the 60-75F range Sunday afternoon. While we have high confidence for rain at times this weekend, we don't expect a total washout. Total rainfall amounts through Sunday evening are generally 0.25" or less in most places. A dry-out period likely follows as rain exits CPA by Monday night with another frost/freeze risk to manage into early Tuesday morning.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Scattered showers have developed over northwestern PA and will continue to expand eastward through the rest of the evening. These showers are most likely to impact BFD and IPT, though they could make a close approach to UNV. VFR conditions are favored over all of Central PA for much of the night, though MVFR ceilings likely develop at BFD close to sunrise. VFR conditions should return area-wide by early afternoon.

Expect additional showers to develop during the morning over western PA. These should increase in coverage through the afternoon, potentially bringing light rain to most of the region. At this point all airfields except MDT and LNS have at least a 30 percent chance of seeing showers on Friday. While no restrictions have been included in the TAFs for now, brief visibility drops to MVFR will be possible with the rain. Model soundings shows some weak instability during the afternoon, so a lightning strike cannot be completely ruled out.

Outlook...

Sat...Restrictions possible in rain and fog.

Sun...VFR favored early, with restrictions becoming more likely in the afternoon as another cold front moves SE. SHRA with isolated TSRA possible as cold front passes through.

Mon-Tue...VFR conditions expected to prevail.

CTP WATCHES/WARNINGS/ADVISORIES

Frost Advisory from 11 PM this evening to 8 AM EDT Friday for PAZ004>006-010>012-017-018-024-033-037-041-042.