Marine Weather and Tide Forecast for Shippensburg, PA

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
A spectacular early Autumn day is underway in Central PA and the Susquehanna Valley with plenty of sun, excellent visibility, a light north-northwest breeze, and low humidity. Afternoon highs in the mid to upper 60s across the Northern and Western Mtns and 70 to 75F elsewhere will be near to several degrees above normal for early October. Will continue to undercut NBM dewpoints based on model soundings, which show very dry air above a weak inversion. Ideal for any outdoor activities!

Look for a clear, calm and seasonably chilly night tonight with temps dipping into the low to mid 40s over most of Central and NW PA and in the upper 40s throughout the larger metro areas in the SE. A fairly large air/water delta T will yield patchy valley fog late tonight/early Sunday. The best chance for fog will be from northeast PA through south central PA underneath the ridge axis where winds go calm.

SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
Periods of broken mid level clouds will precede a warm front moving NE from the Ohio Valley Sunday morning/early afternoon. A potent cold front and increasing deep layer West-Southwesterly shear will arrive for the afternoon/evening hours across NW/Central PA with one or two lines of SHRA/SCT TSRA.

Strong upper level diffluent flow and the approaching nose of a slightly anomalous upper jet will combine with the aforementioned cfront, a 1-2 sigma WSW LLJ, and a band of 1-1.2 inch PWAT air to bring a high probability for one or two bkn lines of showers and isolated-sct TSRA (potentially containing brief strong wind gusts from a westerly direction).

05/12Z HRRR continues to MU CAPE peaking between 750-1000 J/KG across the NW Mtns during the mid to late afternoon before gradually decreasing toward dusk Sunday evening as the axis of best instability shifts SE of the Allegheny Front. SPC has upgraded Warren and the western half of Elk/McKean county to a SLGT risk of Severe weather Sunday late afternoon and evening within the unchanged MRGL risk area that extends to the I-99 corridor. Damaging straight-line winds are the primary threat, though hail and a brief tornado cannot be ruled out if storms along/ahead of the cold front can stay discrete. Best timing right now is 4-6PM in far NW PA, moving southeast to the I-99 corridor before midnight. Storms will weaken with southeastward extent and there remain some questions as to whether or not showers will stay together as they move into the Lower Susquehanna Valley. The progressive nature of storms will preclude any flood risk, with most locations getting less than a half inch of rain.

High temps Sunday afternoon will be mainly in the mid 70s or 8-13 deg F above normal. Rain will quickly come to an end behind the cold front Sunday night and skies quickly clear out for most of the area as high pressure builds in. Low temperatures by Monday morning will range from the mid 40s across the north and west, to the mid 50s in the southeast.

Enhanced northwesterly flow in the wake of the cold front will usher in a drier airmass, thus keeping Monday mostly dry.
Cyclonic flow and neutral to falling upper level heights could allow for a shower in the Alleghenies, but trends have been for drier air to filter in more quickly. High pressure builds into central PA Monday and holds some influence through much of the week, but will have to monitor the potential for a couple reinforcing fronts through midweek as an upper low near southern Hudson Bay rotates a couple of lobes of energy through the Great Lakes and toward PA. Questionable as to the degree of moisture return and associated rain chances with these at this time.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
The extended period should feature fairly benign weather lasting from the second half of next week into next weekend. An upper-level trough over the northeastern United States early in the week will gradually pull east and be replaced by zonal flow or weak upper-level ridging for the late week into the weekend.

At the surface, Canadian high pressure will build overhead during the second half of the week. This should result in a stretch of relatively cool, dry weather for central PA.
Temperatures may begin to moderate as we head into next weekend and the sfc high begins to pull to our east.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
High pressure overhead will provide VFR conditions tonight across Central PA. The best chance for fog will be in northeast PA overnight underneath the center of high pressure. Can't rule out fog developing toward daybreak at IPT, but the risk of fog elsewhere is low at this time (<30% probs from the HRRR).

Once any fog lifts in the morning, VFR conditions continue into the afternoon with high clouds streaming in from the west ahead of an approaching cold front. Winds will generally be out of the south at 5 to 10 knots with gusts to 15 knots, but BFD could see gusts of 20 to 25 knots. Most guidance shows a line of showers and thunderstorms moving into the northwest around 22Z.
The storms will continue to move eastward into the evening and timing will have to be adjusted with future TAF issuances. Brief visibility and ceiling reductions will be possible as the storms move through. Isolated damaging winds and small hail will be possible with the stronger storms as well.

Outlook...

Sun PM-Mon...Showers with CFROPA move west-to-east; isolated strong t-storm possible over the western 1/2 of the airspace.
Very brief reductions.

Tue-Thu...VFR, no sig wx.

CTP WATCHES/WARNINGS/ADVISORIES
None.