textproduct: State College

WHAT HAS CHANGED

* Increased NW wind gusts by 5-7 mph for about 4-6 hours late this morning into the early afternoon following the passage of a cold front.

* Decreased max temps by 2-3 deg F across the Higher Terrain of Northern and Western PA where the highest confidence exists for thick cloud cover and wintry precip

KEY MESSAGES

1) Windy start to the week with numerous rain showers across the Northern Mountains of PA

2) First accumulating snow of the season is likely for late Thursday night through Friday Night - mainly across the Northern and Western Mtns of PA

DISCUSSION

KEY MESSAGE 1: Windy start to the week with numerous rain showers across the Northern Mountains of PA

A fast-moving upper level trough and weak sfc cold front will bring occasional rain showers, mainly to the Northern Mountains of PA through the rest of this morning. A few of the showers will sneak a layer or two of counties to the South of Interstate 80.

Rainfall amounts will be just 0.01-0.02 of an inch near I-80, with up to one-tenth of an inch in spots across the Northern Mtns. no measurable rain is expected to the south of a line from Altoona to Lewistown, Selinsgrove and Pottsville, where significant downsloping and a period of strong subsidence beneath the right exit, then left entrance regions of a 120 kt speed max will occur.

The periods of deep subsidence and increased vertical mixing throughout the boundary layer later this morning and early this afternoon will focus the strongest wind gusts - likely around 40 mph from the NW.

Breezy conditions will continue through the first part of the week with temperatures rebounding modestly higher by Tuesday. No additional precip is forecast through midweek.

KEY MESSAGE 2: First accumulating snow of the season is likely for late Thursday night through Friday Night - mainly across the Northern and Western Mtns of PA

A drastic turn to winter-like weather will occur late this week as a large and slow moving upper low becomes carved out across the NE US and SE Canada by several rounds of digging jet energy and associated surges of progressively colder air.

As a result of the upper low becoming so expansive and several areas of low pressure at the sfc trying to consolidate into a single coastal low, a significant anchoring high to our NE capable of pumping in colder llvl air and steep ascent associated with favorable couple jet structure overhead looks to be lacking at this point.

Still, ample deep layer moisture and 850 mb in the highly favorable -2 to -5C range will lead to periods of rain Thursday/Thursday evening transitioning to snow before midnight across the NW Mtns and Laurel Highlands. More uncertainty in precip type and amounts (after the daylight hours Thursday) exists across our Central Ridge and Valley zones depending on the exact shape/and track of the mid-upper level low and individual pieces of jet energy pivoting around its core(s).

09/00Z EC and its ENS members are a more southern/colder solution for more snow across our Central CWA.

Cold air expanding southward behind an increasing NW wind could drive lake effect and upslope precip Friday night into the weekend. Friday and Saturday are fcst to be the coldest days with temperatures 5-15 degrees below normal.

AVIATION /09Z MONDAY THROUGH FRIDAY/

Pockets of low clouds (mainly VFR) will continue to move over much of central Pennsylvania as a low pressure system swings across the Northeastern US. MVFR restrictions are most likely at KBFD, closer to the moisture fetch off the Great Lakes, where -SHRA will also be likely through early Monday afternoon. MVFR restrictions are also expected at KJST, though with less persistence compared to KBFD. Downsloping effects from gusty westerly winds will favor VFR conditions at KAOO/KUNV/KIPT and especially KMDT/KLNS, though intermittent MVFR ceilings remain possible.

Winds from 280 to 310 degrees will gust to around 25-30 kts regionwide during the daytime on Monday, with periods of MVFR becoming less likely through the afternoon as drier air filters in across our area. Gusts will subside after sunset with stratocumulus giving way to high clouds through the night.

Outlook...

Tue-Wed...Mainly VFR with wind from 240-270 deg gusting around 15-25 kts during the daytime.

Thu-Fri...Leaning sub-VFR with rain and/or snow possible.

CTP WATCHES/WARNINGS/ADVISORIES

None.