textproduct: State College

WHAT HAS CHANGED

* Frost Advy expanded to include McKean and Potter Co

KEY MESSAGES

1) Extended stretch of dry weather with minor wind impacts from Nor'easter this weekend

DISCUSSION

KEY MESSAGE 1: Extended stretch of dry weather with minor wind impacts from Nor'easter this weekend

Another chilly late September night particularly across the northern and western Alleghenies where patchy frost is likely in the usual cold spots. Coordinated with PBZ and LWX on a frost advisory for Somerset County. Added McKean and Potter Counties to the frost advisory this evening with temps already falling into the upper 30s to mid 40s at 8 PM, increasing the likelihood of frost later tonight.

A much needed break from the rain (following one of the wettest mid to late summer patterns on record) is expected over the next 7 days across the majority of central PA.

A Nor'easter developing offshore NJ/Long Island/southern New England could bring some light rain to the eastern third of the CWA (mainly east of US-15) later this weekend (20-40 PoPs Sat, 40-60 PoPs Sun). Breezy conditions are expected Saturday and Sunday with max gusts 30-35 mph over the higher terrain in the northeast portion of the forecast area.

As the Nor'Easter moves toward the Canadian Maritimes, temperatures are projected to rebound and climb several degrees above the historical average by the middle and latter part of the week.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

VFR will prevail across much of central Pennsylvania through the rest of the night, though patchy valley fog will continue to expand in coverage. Confidence on impacts at any TAF sites is low, but a few hours of IFR are possible around sunrise at IPT and possibly BFD and UNV. A few hours of LLWS are possible prior to sunrise at MDT and LNS as winds at 2000 feet increases to 35 to 40 knots.

Fog quickly dissipates through the morning and VFR conditions are expected for the rest of the day under mainly clear skies, though high clouds will begin to move in from the east as the developing nor'easter slowly moves northward off the coast. The tightening pressure gradient between high pressure to our north and the developing storm to our south and east will allow for northeast surface winds between 10 and 15 knots with gusts to 20 knots possible. A few gusts may reach 25 knots at MDT and LNS.

LLWS becomes a bigger concern for eastern TAF sites after 00Z Saturday as a 45 to 60 knot 850 mb low-level jet moves into the area as the nor'easter deepens and continues to track northward. Wind shear will first develop at MDT and LNS, with the threat moving north and west after 06Z. Some guidance shows light rain beginning to approach the eastern TAF sites by 12Z, though confidence is low as it will depend on the just how far west the surface low ends up.

Outlook...

Sat-Sun...MVFR and periods of -RA possible far eastern airfields.

Mon-Tue...VFR.

CTP WATCHES/WARNINGS/ADVISORIES

Frost Advisory until 8 AM EDT this morning for PAZ005-006-033.