textproduct: State College

WHAT HAS CHANGED

* The Slight Risk Severe Weather Outlook for Saturday has been expanded to include all of central PA; increased wind threat. * Introduced a mention of patchy fog late Saturday night into early Sunday morning.

KEY MESSAGES

1) Ongoing dry spell precedes surge of midsummer heat for the first weekend of June

2) Scattered strong to severe thunderstorms are possible Saturday afternoon and evening

3) Warmth surges again next week with a classic summerlike pattern expected - though uncertainty remains.

DISCUSSION

KEY MESSAGE 1: Ongoing dry spell precedes surge of midsummer heat for the first weekend of June

The 8-10 day stretch of dry weather continues today. Max temps climb +5-15F above climo into the 80-90F range today and Saturday. Dewpoints will be in the 50s today and 60s on Saturday, which will bring noticeable humidity back to the region. Tonight and Saturday night will also be noticeably warmer than recent nights, with lows generally in the 60s.

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KEY MESSAGE 2: Scattered strong to severe thunderstorms are possible Saturday afternoon and evening

A cold front sliding southeastward from the Great Lakes will bring an increasing chance for showers/t-storms Saturday through Saturday night. SPC continues to expand the level 2/5 (SLGT) severe t-storm risk, which now includes all of central PA. Latest hires guidance shows considerable uncertainty with respect to the number and timing of convective elements through the day Saturday, with some of the guidance showing showers and leftover thunderstorms rolling into the NW zones as early as Saturday morning. However, the highest chance for severe weather will be in the afternoon and evening, as SBCAPE climbs to near 1500 J/kg and an approaching shortwave trough provides broad scale ascent and increasing wind shear. Damaging winds and large hail will be the primary severe hazards, but a tornado can not be ruled out particularly in western zones where there is a little more turning in the low levels of the atmosphere. The latest outlook from SPC increased the chance of damaging winds for much of the region as well.

Model data has reduced odds for rain on Sunday, with much of the precip ending around midnight Sat night. Rainfall totals are expected to be highest in the west and northwest, with storms producing less rainfall over the southeast as the evening wears on and daytime heating is lost. This pattern does not bode well for ongoing drought conditions. Patchy fog will be possible late Saturday night into Sunday morning as clouds clear out behind the cold front and the wet ground allows for sfc RH near 100 pct in spots. Key limiting factor will be how quickly the winds diminish as skies clear out.

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KEY MESSAGE 3: Warmth surges again next week with a classic summerlike pattern expected - though uncertainty remains.

Following a modest cool down on Monday, emerging model data continues to signal dry precip pattern with above normal temperatures for the rest of next week. Even the cool down on Monday will see above normal high temperatures for most of the area. Long range models diverge on potential solutions toward the end of next week. A prevailing ridge in place over the eastern US will ensure above normal temperatures (80s and 90s), but an upper level closed low could develop. Such a solution would bring cool temperatures aloft steepening lapse rates and leading to daily afternoon pulse thunderstorms. If the upper level low does not form, very warm and drier conditions would be more likely.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Ridging across the Mid-Atlantic ahead of a shortwave trough moving across the Great Lakes will maintain VFR with rain-free conditions through early Saturday morning (07Z-10Z). WSW wind gusts around 15 kts across west-central PA (KBFD/KJST/KAOO/KUNV) will diminish between 22Z Friday - 00Z Saturday as the boundary layer decouples, leaving light/variable winds with a SW tendency overnight. A borderline LLWS signal emerges between 05Z-12Z Saturday over west-central PA, characterized by 0-2 kft shear at 240 deg ~30 kts, though no mentions were added at this time given sub-threshold shear on guidance + higher LLWS probabilities over the Ohio Valley closer to the trough.

Cloud bases will gradually lower with sky cover trending BKN- OVC overnight as moisture advection continues ahead of the approaching shortwave, with shower activity increasing through the morning as well (currently handled by PROB30s due to low certainty in -SHRA prevailing at any one terminal). Nevertheless, restrictions remain unlikely through the end of the 18Z TAF for most outside of KBFD, where greater low-level moisture may be in place. Similar to the previous discussion, an NBM/HREF/LAMP blend was used to handle MVFR timing and likelihood (30-50% chance). Otherwise, SW winds increase to 10-15 kts gusting to 20-25 kts midday, with -TSRA chances appearing more probable (>30% chance) after 18Z as the right side of a cyclonic jet streak begins moving overhead.

Outlook...

Sat...VFR conds favored early, brief restrictions possible in late-day -SHRA/TSRA.

Sun-Tue...VFR favored outside of isolated morning fog. Restrictions possible in -SHRA/-TSRA early Sun & again on Tue.

Wed...Restrictions possible in -SHRA/-TSRA.

CTP WATCHES/WARNINGS/ADVISORIES

None.