textproduct: State College

SYNOPSIS

*Widespread rainfall is expected this evening through early Friday morning, potentially heavy for a short period of time with the passage of a cold frontal rainband. *Friday will be quite windy with gusts of 40-50 mph for much of the area and locally up to 60 mph possible in the Laurels. *As colder air moves in on Friday, snow will develop in the Laurel Highlands and downwind of Lake Erie over the NW Alleghenies, with scattered now showers pushing farther inland.

NEAR TERM /THROUGH TONIGHT/

Satellite imagery and sfc obs indicate patchy freezing fog has developed in the valleys of north central PA overnight, but is generally limited in coverage. Otherwise, much of the area is clear as of 6 AM with only a few patches of altostratus/altocu. Mostly sunny skies and warm advection will allow for sfc temps to rise steadily into the 40s to near 50 this afternoon.

Skies will trend to overcast late in the day into the evening, with rain overspreading the region overnight. Despite southerly 850 mb flow increasing to 50-70 kts by midnight, a stable sfc inversion will hold sfc wind gusts to 25-35 kts. The exception may be stronger gusts in higher terrain. Stronger winds will likely mix down to the sfc with the passage of the cold front, moving through central PA between roughly 1 AM and 9 AM. Several convective allowing models also suggest a narrow cold frontal rain band (NCFR) given the strong forcing and presence of a neutral Theta-E profile above the BL. A few rumbles of thunder can not be ruled out. Rainfall totals will generally increase from west to east, ranging from near 0.25-0.50" around the Laurels, to locally 1"+ from the Susq Valley eastward as the front taps a plume of higher moisture (PWAT 1"+). The highest amounts will likely be where orographic lift of high PWAT air is maximized.

SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/

A persistent flow of colder air behind the front will result in falling temperatures through the day on Friday. A tightening pressure gradient and sfc pressure rises within broad CAA regime will deliver strong gusty winds. Max gusts in the 40-50 mph range are likely, with gusts up to 60 mph possible in the Laurel Highlands. Northwest flow at 850 mb will become strongest between 18z Fri and 00z Sat, so we expect some of the strongest wind gusts to be late in the afternoon as the diurnal BL overlaps the strong winds aloft.

After the steady rain ends Friday morning, scattered snow showers will be possible across the area through much of the day, with steadier snow across the Laurel Highlands and lake effect regions of the northwest. The lake effect snow will be shorter in duration compared to some events earlier this season. Snow accums in Warren and McKean Cos are likely to be limited to the 1-3" range. Similar amounts may also be found in the Laurel Highlands given the upslope snow there.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Arrival of sfc high ends LES by early Saturday. Model data continues to show a strong cold frontal passage with quick shot of arctic air Sunday-Sunday night along with gusty winds and lake effect snow. SNSQ risk should also be monitored.

The cold air retreats through early next week, setting up a possible overrunning mixed precip event for Tuesday. The weather for Christmas Eve looks fair and seasonable with no major travel impacts expected at this time.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Dry weather will prevail for most of the daylight hours today, with VFR conditions prevailing for most airfields. Reduced visibility at LNS (and perhaps MDT and IPT) will be slow to improve today with high pressure hindering much vertical mixing.

Conditions will deteriorate tonight as rain overspreads the area from southwest to northeast. LNS, MDT, and IPT may be the first to drop to MVFR ceilings as moisture pools along the Susquehanna Valley. Ceilings and visibilities will drop to IFR areawide overnight ahead of an approaching cold front. Gusty southerly winds ahead of the front will shift to westerly behind the front. The front will cross the western airfields (BFD and JST) around 09Z and exit east of the area (IPT/MDT/LNS) around 12Z. Winds could gust 40+ knots with the line of gusty showers as it passes through.

Temperatures will plummet during the day on Friday with rain changing over to snow. Wind gusts of 35 to 45 knots are likely Friday afternoon at all airfields, with gusts over 50 knots possible at JST and AOO. Restrictions are possible in snow showers across the west Friday as well.

Outlook...

Fri...Gusty W wind (40+ kts possible). MVFR w/SCT SHSN at JST/BFD. Mainly VFR elsewhere.

Sat-Sun...MVFR-IFR BFD in SCT -SHSN. VFR cigs favored elsewhere.

Mon...Trending drier with VFR favored. Snow enters W PA late evening with restrictions possible.

CLIMATE

Astronomical winter (solstice) begins at 10:03 a.m. on Sunday, December 21st.

CTP WATCHES/WARNINGS/ADVISORIES

Wind Advisory from 1 AM Friday to 1 AM EST Saturday for PAZ004>006-010>012-017>019-026>028-035>037-041-042-045-046- 049>053-056>059-063>066. High Wind Watch from late tonight through late Friday night for PAZ024-025-033-034.