textproduct: State College

SYNOPSIS

* Sun followed by increasing high clouds today with light wind * Trending milder with periods of rain Tuesday and Wednesday * Becoming windy beginning Wednesday night and turning much colder with lake effect snow Thanksgiving Day through Black Friday

NEAR TERM /UNTIL 6 PM THIS EVENING/

Shallow and warm lake effect stratocu clouds extended from the North-Central Mtns of PA SE to the North Branch Susq Valley, which was helping to keep temps relatively warmer and in the upper 30s to low 40s, while clear skies and light wind elsewhere allowed temps to cool to between 25-30F in some locations from the NW Mtns to the Middle Susq Valley near KSEG.

Nice travel conditions today with abundant morning sunshine followed by an increase in high clouds from the west this afternoon and tonight. A ridge of high pressure slides east from the Ohio Valley and crests over the Commonwealth during the midday and afternoon hours today.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/

Cloud cover will be overcast tonight and bases will gradually lower through the mid cloud range overnight, keeping min temps mainly in the 30s. Wind will continue to be light in most places, though the slight increase in the llvl p-gradient across the Western Mtns could result in a 10-15 kt breeze developing on the ridge tops there.

Light rain or mixed precip could reach the southwest mtns as early as 12Z Tuesday, although the probability is low at this time. Latest model runs suggest that wet bulb temps will only dip as low as +1-2 C across the NW Mtns early Tuesday morning as the leading edge of stratiform precip moves in, so there is higher confidence in the PTYPE being plain rain rather than a mix at, and shortly after the onset.

Overcast skies and periods of rain/showers for Tuesday with temps anywhere from several, to as much as 10F above normal with the greatest departures occurring across the Laurel Highlands in SW PA.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Cloudy with a few round of showers and/or areas of drizzle for Tuesday night. Low temps will range through the 40s.

The mild trend continues through midweek with max temps peaking on Wednesday in the 50-60F range. Temp departures Tuesday night and Wed will average 14-18F above normal for late November.

Periods of rain are expected to move over the area Tuesday and Wednesday which could slow holiday travel. Overall NBM has 0.25-0.50 inch of rain in the Tue-Wed period, but it is worth noting that the NBM 75th pctl has as much as 0.50 inch of rain falling in just a 6 hour period from 1-7 PM Tuesday across potions of south central PA. Rain on Wednesday will likely be less widespread and more confined to the cold FROPA.

Conditions turn breezy by Wednesday afternoon ahead of a well- defined cold front poised to plow through PA Wednesday night.

Blustery post-frontal flow with gusts 30-40 mph Thursday and Friday is expected to deliver much colder temperatures for Thanksgiving Day. 40 KT wind contour occupies the upper 1/3 to 1/2 of the well-mixed layer as the cold air deepens Thursday into Friday (and will be as low as ~1000 FT AGL Thursday night). This will create a likelihood of Wind Advisory criteria developing for much of the Region Thursday into Friday.

This pattern shift to cold/blustery WSW to WNW flow will trigger lake effect snow - initially targeting the LE shoreline into SW NY early Thursday before before pivoting into the NW PA snowbelts Thursday night into Friday. Several inches of snow accumulation and significant travel disruptions are possible Thu-Sat across the NW mtns. We added the potential wind and lake effect snow hazards to the HWO which will likely become key messages heading into peak Thanksgiving holiday travel and Black Friday. Some heavier snow showers are possible all the way down to Interstate 80 on Friday.

Models diverge over the weekend but general idea is a break in the lake effect snow Saturday, followed by warm advection into Sunday/Monday with potential for a deep, slow moving storm system.

AVIATION /12Z MONDAY THROUGH FRIDAY/

VFR conditions will prevail areawide through the TAF period as high pressure builds in. There could be some brief fog in a few valleys of northern/central PA early, but restrictions appear unlikely at this time.

VFR continues through tonight before next system arrives on Tue bringing thickening/lowering clouds and eventually restrictions to the NW half as rain overspreads the state with winds turning around to the S/SE.

Outlook...

Mon...VFR.

Tue...Breezy with periods of rain.

Wed...Breezy with rain showers, mixing with and changing to snow after sunset.

Thu-Fri...Breezy with SHSN for northwest PA.

CTP WATCHES/WARNINGS/ADVISORIES

None.