Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* dry, quiet and pleasantly warm through early next week *

Brief 11:30 a.m. Friday, September 12, 2025, Update:

Other than mostly cloudy skies and some spotty mist/drizzle from Wednesday into Wednesday night, the weather has been absolutely spectacular this week across northern MD, southeastern PA and the Lower Susquehanna Valley. High temps from Monday-Wednesday were in the 70s with overnight lows in the comfortably cool upper 40s to mid 50s. Warmer and more seasonable conditions returned on Thursday with highs in the upper 70s to low 80s, but this morning still kicked off on a comfortably cool note with temperatures in the 50s. Better yet, the sprawling high pressure system that has been in place over eastern North America will hold its ground and move very little through the middle of next week. As a result, there is absolutely no rain in sight, and skies will generally be mainly clear through early next week with high temperatures in the 80s and overnight lows in the 50s on a day-to-day basis (see below). The large-scale subsidence, or sinking motion, associated with the high will thwart clouds and precipitation, and humidity will also be low with dewpoints in the 50s for the foreseeable future.

Quite frankly, the weather doesn't get much nicer or quieter than this across the mid-Atlantic States, so lather on the sunscreen, soak up the sun and enjoy the Great Outdoors this weekend! A subtle warming trend will take place over the next couple of days, but temperatures should still not exceed the upper 80s in the hottest spots Sunday afternoon. You'll be able to sleep comfortably with the windows open at night, as well, through at least Monday or Tuesday. High temperatures may peel back into the low 80s next Tuesday and/or Wednesday, but that's still several degrees above normal by mid-September standards. I'd deem afternoons as "pleasantly warm" and overnights as "comfortably cool" in this type of pattern, and that's a wrap! You will most likely find me somewhere on the Conewago Creek all weekend long.. it's "big bass" season! 🐟 -- Elliott

1:15 p.m. Tuesday, September 9, 2025:

In the wake of Saturday's cold frontal passage, northwesterly winds ushered a much cooler, drier and more refreshing air mass into the mid-Atlantic States on Sunday. Morning clouds gave way to afternoon sunshine, and high temperatures were about 10°F lower than Saturday. In addition, dewpoints fell into the upper 40s late Sunday afternoon and have remained in the 40s and 50s early this week. High humidity won't be making a comeback anytime soon, and the forecast through the upcoming weekend is about as quiet and straightforward as possible. A sprawling high pressure system of Canadian origin settled over the eastern Great Lakes region and southern New England on Monday, and it will essentially "camp out" over the Northeast through the middle of the month. Thus, our autumnal air mass will stick around for at least the next 5-7 days. Comfortably cool nights and pleasantly warm afternoons will be the norm through the third weekend of the month, and there will be plenty of sunshine to enjoy as well. The large-scale subsidence, or sinking motion, associated with the high will thwart clouds and precipitation and instead promote mostly sunny skies on most days. 

The only "fly in the ointment" will come in the form of a weak low pressure system currently located several hundred miles off the North Carolina coastline. It will make its closest pass to the mid-Atlantic coastline later tonight into tomorrow and cause an enhancement in cloud cover across northern MD, southeastern PA and the Lower Susquehanna Valley during that time. However, no more than a few sprinkles should reach areas north/west of I-95. Due to the clouds, high temperatures on Wednesday will likely be a few degrees lower than this afternoon and generally in the upper 60s to mid 70s from southeast-to-northwest across the region. Although 5-10F below average by mid-September standards, it's hard to complain about temperatures in this range. Better yet, clouds should gradually dissipate Wednesday night as the system moves farther out to sea, and skies will then be mostly sunny on Thursday with high temperatures back in the upper 70s to low 80s. With the aforementioned high pressure system locked in place through Sunday, the weather from Friday-Sunday will be virtually identical to Thursday and absolutely spectacular for outdoor activities and sleeping with the windows open (see below). Low temperatures will generally be in the comfortably cool low-to-mid 50s from tonight through Saturday night and not exceed the upper 50s to low 60s from Sunday night through early next week.

A more substantial warming trend may occur during the middle of next week, but that's highly uncertain at this distance. Needless to say, you really couldn't ask for a quieter or nicer stretch of weather in September. Just be sure to lather on the sunscreen as the sun angle is still equivalent to that in late March. My only real concern going forward through the rest of September is the return of abnormally dry conditions and pockets of moderate drought. Our incredibly wet July was balanced by an unusually dry August, and a second-consecutive month of extremely dry conditions could equal a return of drought. We'll see where things stand in a few weeks (see below). Until then, "enjoy the calm!"

Temperatures will be around 5°F below average through tomorrow but "near normal" from Thursday through early next week. Even as a warm-weather lover, I love these conditions and certainly won't complain about the crisp nights and cool mornings. They're a welcome change from the oppressively hot and humid conditions during July and the first half of August, and we are indeed now in meteorological fall. Welcome to the season!-- Elliott