Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* some beneficial rain through wednesday, then warm and dry again *

1:30 p.m. Tuesday, September 16, 2025:

The weather during the second weekend of September was nothing short of spectacular across the Lower Susquehanna Valley. High temperatures reached the pleasantly warm low-to-mid 80s both Saturday and Sunday with overnight lows in the crisp mid-to-upper 50s. The comfortable conditions were accompanied by mainly clear skies, light winds and low humidity, and the week started on an equally pleasant note with highs in the low 80s under partly sunny skies Monday afternoon. However, clouds moved back into the region Monday night and will stick around through the middle of the week. A low pressure system currently centered just east of the VA/NC border will move onshore into southeastern VA later tonight but then slowly drift back into the open waters of the Atlantic from Wednesday evening into Thursday morning. The steadiest and heaviest rain from the system is expected to stay south/east of the I-95 corridor over the next 24-36 hours, but bands of lighter showers will rotate westward through northern MD and southeastern PA from this afternoon through early Wednesday evening. Showers should be most widespread and intense from tonight through the mid-afternoon hours tomorrow before ending around or shortly after sunset. Rainfall amounts should generally remain below 0.50" north/west of I-95 (see below). Due to the stretch of exceptionally dry conditions since early August, any rain will be highly beneficial. "Moderate drought" has not yet crept back into the region but is encroaching on our northern, western and southern flanks. Keep an umbrella handy and be prepared for some areas of slow travel on wet roadways through tomorrow evening, but the benefits of this event far outweigh its impacts. Due to the clouds and showers, high temperatures will be lower than the last few days and generally in the 70s this afternoon and around 70°F on Wednesday. However, overnights will be rather warm by mid-September standards with lows around 60°F tonight and in the low 60s Wednesday night. 

The storm system will accelerate eastward and move back out-to-sea late this week. In its wake, an area of high pressure will settle into the Ohio Valley, central Appalachians and Southeast and promote brighter and warmer conditions. Morning clouds should give way to sunshine by Thursday afternoon, and skies will then stay mainly clear through the first half of the weekend. Due to the sunshine and downsloping, northwesterly flow off the Appalachians, high temperatures should be around 5-8°F above average Thursday/Friday and back in the low-to-mid 80s. However, overnight lows will fall back into the comfortable mid-to-upper 50s on account of efficient, radiational cooling after sunset. A subtle cold front will drop southward out of New England and push through the Commonwealth Friday night, but there won't be many clouds or a drop of rain associated with it. The only noticeable impact will be a downturn in high temperatures over the weekend. However, they'll still be "near normal" and probably in the mid-to-upper 70s both Saturday and Sunday. Behind the front, a high pressure system of Canadian origin will settle over the Northeast on Saturday and shift into the western Atlantic by Sunday. East-to-southeasterly flow on its southwestern periphery will draw Atlantic moisture back into the region from Saturday night into Sunday, so I expect low clouds to develop east of the Appalachians during this time and hang tough through Sunday night. However, no more than patchy mist or drizzle should fall from the overcast skies.

The wind should slowly lose its easterly component and turn due-southerly early next week. As a result, low clouds should break for sunshine by Monday afternoon, and another major warming trend will ensue. High temperatures will likely be back in the upper 70s to low 80s Monday afternoon, and they could make a run into the mid-to-upper 80s during the middle of next week. Needless to say, there are no signs of any "early-autumn chill" on the horizon, and we'll be treated to yet another extended period of dry weather from this Thursday into the middle of next week. Astronomical fall officially begins on Monday, September 22, at 2:19 PM EDT, but the first week or more of the season may feel more like a continuation or extension of summer. As a warm-weather lover, I'm perfectly OK with that! I'll be out of the office this Friday, so check back next week for an update. In the meantime, enjoy the next stretch of quiet weather! -- Elliott