Marine Weather and Tide Forecast for Shippensburg, PA

NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
Zonal flow prevailing aloft with flat upper ridging building eastward from the Ohio Valley overnight. H8 high parked over the mid Atlantic region with sfc ridge axis extending from Quebec southward to the Delmarva region. Mostly clear skies will prevail overnight, with just high thin clouds increasing after midnight as deep layer moisture increases as the upper ridge axis shifts eastward. Mins will generally range from 45-50F, which is +5 to +15 degrees above late April climo (largest departures over the western Alleghenies).

SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/
Moderation to the west of the aforementioned ridge axis moving off of the eastern seaboard will bring a warmer day throughout central PA on Thursday. Highs will generally range from 75-80F which is +10 to +20 over the historical average.

The overall synoptic pattern and forecast soundings support typical pre-greenup pattern of reduced sfc Td adding a few degrees to sfc T, and lowering sfc minimum RH. Hires data suggests minRH could drop into the teens across the southwest and south central parts of the forecast area. Winds gradually increase from the south, but likely stay low enough to preclude an elevated wildfire risk (see fire wx section).

Warm air/theta-e advection pattern ramps up Thursday night into Friday downstream of sfc low moving into the Mississippi Valley with increasing clouds and rain probs from west to east. Models show the low strengthening as it tracks across the Lower Great Lakes Friday night into northern New England by Saturday night.
The parent h5 trough and attendant/trailing cold front will drive widespread rainfall and a few t-storms across the area with max POPs in the Friday evening through Saturday afternoon timeframe.

PWATs >1.00 inch, relatively strong IWT and some elevated instability suggests the potential for heavy rainfall particularly across the northwest part of the forecast area.
This area has been wet relative to the southeast zones and may be susceptible to some minor flooding concerns. WPC will maintain the D3 MRGL ERO with increased soil saturation and lower FFGs.

Influx cooler and drier air via gusty NWly post frontal flow will spelling drying conditions from NW to SE late Saturday through Saturday night. Min temps Saturday night/AM Sunday will be 10 to 20 degrees lower vs. Friday night/AM Saturday.

LONG TERM /SUNDAY THROUGH WEDNESDAY/
Breezy start on Sunday with perhaps some low clouds lingering downwind of Lake Erie. Otherwise, another nice stretch of weather setting up heading into month end.

Key callouts and playbook moves for early next week include lowering min temps Sunday night-AM Monday given strong PWAT and MSLP signals. This introduces a frost/freeze risk that should be monitored in the days ahead.

After bottoming Monday morning, expect another warming trend into the middle of next week with highs climbing back into the 75-80F range. Models show 500mb ridge cresting the region Tuesday which should open the door for increasing rain chances by the end of the period.

AVIATION /04Z THURSDAY THROUGH MONDAY/
Very high confidence in widespread VFR flying with light/calm winds through the 24/00Z TAF period.

Outlook...

Thu...No sig wx expected.

Fri...Showers developing during the afternoon and spreading to the east Friday night with sub-VFR restrictions likely.

Sat...Sub-VFR likely with rain showers and possibly a t-storm.
Wind gusts 20-25kt from 280-310 degrees behind the front Saturday night.

Sun-Mon...VFR/No sig wx expected.

FIRE WEATHER
MinRH expected to drop into the 20-30% range again Thursday afternoon with downside risk into the teens across the southwest and south central districts. Winds will begin to increase from the south, but should remain below critical thresholds. Fuels are sufficiently dry to the south of I80 per 4/23 collaboration with PA DCNR/BOF patterns; so would not completely rule out a SPS for elevated wildfire risk.

CTP WATCHES/WARNINGS/ADVISORIES
None.