Marine Weather and Tide Forecast for Chester Hill, PA

NEAR TERM /THROUGH TONIGHT/
No significant changes to the near term forecast for the mid morning update. Despite a 24hr MaxTemp change of -5 to -20 degrees, expect a sunny and very pleasant last day of April with plenty of sunshine and low humidity. Highs in the 60-75F range this afternoon are very close to daily climo in the northern tier and +5-10 degrees above the historical average across the south central ridge and valley region to the MD line.

Previous Discussion Issued: 504 AM EDT Wed Apr 30 2025

Latest guidance supports warm and dry weather today, as the cold front stalls out south of the Mason-Dixon Line and high pressure noses into PA from the Great Lakes. It should be another perfect spring day with a refreshing northwest breeze, low humidity, and abundant sunshine. Good day to mow the grass with more widespread rainfall expected Thursday into Saturday.
RH does get into the 20s for much of the area. Wind not especially gusty, but without much rain in the SE, fire weather concerns are not out of mind. In Central PA, yesterday's rainfall should help mitigate major concerns across most of the area, but a Special Weather Statement is in effect until 8PM for Dauphin, Schuylkill, Lebanon, York, and Lancaster County based on a lack of notable rainfall yesterday and slightly higher winds expected today (up to 15 or 20mph at times this morning into early afternoon).

Later tonight, efficient radiational cooling will support a frost risk across the northeast zones/Endless Mtns into early Thursday morning with fcst min temperatures in the mid to upper 30s. The growing season for this area does not activate until 5/11, so no frost headlines will be issued. Meanwhile, more clouds and higher dewpoints keep lows near 50F along the PA/MD border, with lows in the 40s everywhere in between.

SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
Upper ridging will begin to erode on Thursday as a trough over the High Plains moves into the northeast US. At the surface, the quasi- stationary front south of the Mason-Dixon line will pivot and lift northward as a warm front across Central PA as a sfc low tracks from near Chicago into Lake Huron by 02/12Z.
Expect shower activity to ramp up particularly in the western/northwestern portions of the CWA through Thursday night in association with strongest 850mb moisture flux and IVT.
Sufficient instability will be in the place to support the potential for some stronger storms west of US-219 Thursday afternoon and evening as well. Thursday night looks very mild for the first night of May 2025 with min temps 55-65F or +15 to +25 degrees above climo.

LONG TERM /FRIDAY THROUGH TUESDAY/
Changes with the late evening update to the long range forecast are very minor. Still a great deal of uncertainty with the possible development of an upper low over the OH Valley over the weekend (ECMWF) vs. a progressive trough swinging thru to clear things out for the latter half of the weekend and almost all of next week (GFS). So, the forecast from the NBM is basically a wash of the two camps. Don't see a lot of reasons to have a closed low form, esp in early May. But, the low chc PoPs that now permeate the extended are an expression of the forecast uncertainty, and this solution is not (entirely) out of the question.

Prev...
Scattered convection is likely to accompany the trailing cold front on Friday with daytime highs ranging from 65-70F in the NW mtns and 75-85F in the south central/southeastern ridges and valleys. Severe storm potential remains limited based on the D4 discussion from SPC. However, WPC excessive rainfall outlooks carry a marginal risk Thu/Fri with an emerging trend toward more rain (wetter on the margin) on Saturday tied to a frontal wave.
POPs were increased vs. NBM to start the first weekend of May.

What appeared to be firm drying trend and nice stretch of wx dominated by high pressure from Sunday into early next week has now faded away -- as medium range models and ensembles show a more blocky pattern over the Lower 48 and potential cutoff low developing somewhere over the Eastern U.S. This spread keeps confidence much lower than average on sensible wx details due to very uncertain upper level flow details.

AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
IFR conditions at BFD are not expected to persist very long as dry air begins to work its way into the region and allow for widespread VFR conditions through 01/12Z with high (~90%)
confidence. The main source of uncertainty is with respect to BFD/JST/AOO where low-level clouds could remain through 30/13Z; however, this is a lower confidence solution at this time. Winds generally will range between 5-10kts today with gusts across the eastern airspace (IPT/MDT/LNS) approaching 20kts later this afternoon. Winds become light and variable to calm overnight.

Thu...Showers/t-storms return areawide, restrictions possible.

Fri...Showers with restrictions possible.

Sat...Showers early. Improving late.

Sun...Mainly VFR with a few showers possible.

CLIMATE
A high record of 82 degrees was tied in Bradford on April 29th, which ties the record set back in 2024.

A high record of 87 degrees was set in Altoona on April 29th, breaking the old record of 86 degrees set back in 2024.

CTP WATCHES/WARNINGS/ADVISORIES
None.