Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* beneficial, soaking rain to precede windy, chilly halloween *

11:45 a.m. Tuesday, October 28, 2025:

As expected, a sprawling high pressure system over southeastern Canada and the northeastern United States promoted mainly clear, dry and chilly conditions across the Lower Susquehanna Valley over the past few days. Despite high temperatures in the upper 50s to low 60s from Saturday-Monday, overnight lows bottomed out in the upper 20s (coldest, outlying areas) to upper 30s (urban centers) each night. In fact, the mercury fell to 31.6°F this morning at Millersville University, marking the first official freeze of the season (see below). Believe it or not, the first freeze in 2024 occurred on the exact same date (October 28).. what a coincidence!

The aforementioned high pressure system will remain centered over southeastern Canada through tonight and continue to bring similar weather conditions to northern MD and southeastern PA. High temperatures this afternoon will be similar to the last few days and generally in the mid-to-upper 50s under mostly sunny skies. However, a northeasterly breeze of 10-20 mph will give the outdoor air an added chill. Low temperatures tonight should be several degrees higher than last night but still generally in the mid-to-upper 30s. Tomorrow should still be dry and cool across the region, but clouds will increase throughout the day in advance of an approaching storm system. Once again, high temperatures will be around 5°F below average and in the mid 50s to perhaps 60°F in spots (see below). Thus, a jacket or sweatshirt will continue to be a necessity before heading out the door to work or school, and warm-weather lovers like myself may even prefer a winter coat.

From Wednesday-Friday, the storm system will track northeastward along the spine of the Appalachians. It will rapidly strengthen on its journey and become quite potent upon reaching western or central PA on Thursday. Ahead of the system, strengthening east-to-southeasterly flow will draw moisture northward from the Gulf and westward from the Atlantic, and rain should then overspread the region from southwest-to-northeast Wednesday evening. Fortunately, the rain should hold off until well after the PM commute and not arrive until the overnight hours. However, the heaviest rain may occur during the Thursday morning commute and lead to delays and slow travel on the roads. In addition, motorists should be alert for flooding of some low-lying, urban- and poor-drainage areas. The rain will then taper off from southwest-to-northeast Thursday afternoon, but not before a widespread 1-2" with locally higher amounts up to 2.5" falls across northern MD, southeastern PA and the Lower Susquehanna Valley (see below). Due to the abnormally dry and moderate drought conditions in place, the rain will be largely beneficial, but easterly winds of 12-25 mph with gusts up to 35 mph will accompany Thursday's rain and lead to absolutely miserable conditions outside (see below). Needless to say, you'll need an umbrella and rain gear throughout the day and might want to allow extra time to get to work or school. Temperatures will only bottom out in the upper 40s Wednesday night and should peak in the mid-to-upper 60s Thursday afternoon, but you definitely won't be able to get outside and enjoy the milder conditions. 

In the wake of the storm system, winds will turn westerly Thursday night and intensify on Friday. The tight pressure gradient, or difference in pressure, between the storm system and an area of high pressure over the Southern States will be the culprit for some "spookily high" wind gusts of 45-50 mph on Halloween. Sustained winds should be on the order of 20-30 mph, and high temperatures will only reach the mid-to-upper 50s. Any morning sunshine will be of the "self-destruct" variety and give way to mostly cloudy skies during the afternoon hours. Unfortunately, this Halloween will be nothing like last year's mostly sunny and record warm holiday. Instead, temperatures will drop into the upper 40s or low 50s during trick-or-treating festivities, and it may feel more like the upper 30s or low 40s outside due to the strong winds. Needless to say, anyone in light costumes will be freezing/shivering, while those in heavier ones might not feel too uncomfortable. The breezy conditions will persist from Friday night into Saturday, but wind speeds won't be quite as high with gusts only up to 30 mph. Be alert for blowing objects and debris on roadways on Friday, and keep a tight grip on the wheel on north-south oriented highways.

The high pressure system will finally reach the mid-Atlantic States by Sunday and remain centered over the region early next week. As a result, winds will subside Saturday night and not pick back up until at least Monday night or Tuesday. The large-scale subsidence, or sinking motion, associated with the high should also promote a mostly sunny and milder start to next week with highs in the upper 50s to low 60s Monday afternoon. Pesky, mid-level clouds will probably plague the Lower Susquehanna Valley both Saturday and Sunday afternoons, in particular, but high temperatures should still be similar to Friday. Due to partial cloud cover and breezy conditions, overnight lows will be higher than in recent days and generally in the low-to-mid 40s Friday night and upper 30s Saturday night. By Sunday night, they'll probably be back down in the low-to-mid 30s with the high pressure system nearby or directly overhead. Uncertainty in the forecast increases during the middle of next week, but odds favor a more tranquil and somewhat milder pattern across the Eastern States. I'll be out of the office on Halloween, so check back next week for an update! In the meantime, stay dry and hang onto your hats.. err, costumes.. on Friday.. -- Elliott