Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* warmth, humidity and storms to return late this week *

11:00 a.m. Tuesday, August 25, 2026:

The last week of August kicked off on a partly-to-mostly sunny, cooler and less humid note. In the wake of Sunday's cold frontal passage, northwesterly winds of 8-16 mph ushered a refreshing and even fall-like air mass into the Commonwealth. High temperatures were around 5°F below average Monday afternoon, and dewpoints bottomed out in the low-to-mid 50s. This morning then kicked off on a comfortably cool note with lows in the mid 50s (outlying areas) to low 60s (urban centers), and we'll be treated to a "repeat performance" of Monday's weather today and tonight. A trough, or dip in the Jet Stream, over the Northeast will continue to promote partly-to-mostly sunny and beautiful conditions this afternoon with high temperatures in the upper 70s to perhaps 80°F for most. Dewpoints will remain between 55-60°F through tonight, and minimum temperatures early Wednesday morning should be similar to this morning (see below). Needless to say, it'll be a perfect day to get outside after work or school and ideal night for sleeping with the windows open! 

A sprawling high pressure system will settle into the mid-Atlantic States on Wednesday, but it will quickly shift into the western Atlantic later Wednesday into Thursday. On its backside, a persistent, southerly breeze will draw warmer and more seasonable air into northern MD and southeastern PA. As a result, high temperatures should be back in the mid 80s Wednesday afternoon under mostly sunny skies, but dewpoints won't rise much if at all until Wednesday evening. That being said, they'll jump dramatically during the overnight hours and peak in the upper 60s to low 70s on Thursday. Due to increasing clouds and the higher humidity, Wednesday night will feel more oppressive again with low temperatures in the upper 60s to perhaps 70°F. Most of you will probably want to turn the air conditioning back on before going to bed and then keep it running through the end of the week. 

The threat for showers and locally heavy, drenching thunderstorms will return on Thursday and stick around through Friday. Broad, south-to-southwesterly flow both at the surface and aloft will draw ample amounts of moisture back into the mid-Atlantic States, and multiple, upper-level disturbances will interact with the unstable air mass to trigger the storms (see below). Wind shear, or a change in wind speed and/or direction with increasing height above the ground, will be relatively low, but the strongest storms may still be capable of producing frequent lightning, torrential downpours and wind gusts up to 50 mph Thursday afternoon and evening. Ahead of the storms, high temperatures should reach the low-to-mid 80s with peak heat indices around 90°F. The storms should weaken during the mid-to-late evening hours, but a second round may erupt on Friday. A weak cold front sagging southeastward through the Commonwealth will spark Friday's storms, but they should be far more isolated and also weaker than Thursday despite similar temperatures and dewpoints. Be alert for flooding of low-lying, urban- and poor-drainage areas during the Thursday afternoon commute, as well as minor debris on some roadways. Any similar issues on Friday will be far more localized and the exception rather than the rule.

Behind the front, a large high pressure system will settle into the eastern Great Lakes region and Northeast this weekend. The Lower Susquehanna Valley will be on the southern periphery of the high pressure's area of influence, so temperatures and humidity may be similar to or just slightly lower than Thursday and Friday. However, the large-scale subsidence, or sinking motion, beneath the high should promote a partly-to-mostly sunny and generally dry weekend well suited for outdoor activities. Noticeably hotter and even more humid air may then return early next week on the backside of the high pressure system, but to what extent is relatively uncertain. Meteorological summer ends on Monday, August 31, but it certainly looks like more 90-degree days lie ahead in September. Stay tuned! -- Elliott