Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* unseasonably cool pattern in early may after beneficial rain this evening *

1:15 p.m. Wednesday, April 29, 2026:

The last week of April kicked off on a sunny and beautiful note across northern MD, southeastern PA and the Lower Susquehanna Valley with high temperatures in the upper 60s to low 70s Monday afternoon. Unfortunately, those kind of days will be "few and far between" through the first 7-10 days of May. A large trough, or dip in the Jet Stream, will continue to develop over southeastern Canada and the eastern United States through the end of this week, and it will essentially become detached, or break off, from the Jet Stream and remain locked in place over the next 1-2 weeks. The upper-level low associated with it will spiral and pinwheel around southeastern Canada in early May, and weaker disturbances will rotate around its base and bring bouts of isolated-to-scattered showers, breezy and cool conditions to the mid-Atlantic States. As a warm-weather lover, the upcoming pattern is the very antithesis of what I'd like to see in May. 

In the short term, a storm system tracking from the eastern Ohio Valley into New England through Thursday morning will bring periods of rain to the Lower Susquehanna Valley this afternoon and evening. At the time of this writing, isolated showers containing locally heavy downpours have already erupted across south-central PA, but steadier rain won't arrive until the late-afternoon and early-evening hours between ~6-10 PM. The rain will then taper off from southwest-to-northeast tonight between ~10 PM and 2 AM (see below). Keep an umbrella handy and remain alert for areas of standing water in some low-lying and poor drainage areas during this evening's commute. Additionally, expect areas of slow travel and reduce speed in any heavier downpours to minimize the risk of hydroplaning. However, the rain will be largely beneficial due to the moderate-to-severe drought in place. Most areas will receive 1/3 to 2/3 of an inch of rain with locally higher amounts of 0.75-1.00" (see below). Due to the clouds and wet weather, high temperatures will be around 5-10°F below average this afternoon and generally in the upper 50s to mid 60s from NW-to-SE across the region. 

Behind the system, clouds will linger tonight, but northwesterly winds of 10-20 mph with gusts up to 30 mph will usher much drier air into the Commonwealth on Thursday and cause skies to clear during the morning hours. The rest of the day should then turn out partly-to-mostly sunny and pleasantly cool with high temperatures in the low-to-mid 60s (see below). After a mainly clear and chilly Thursday night with lows in the mid 30s (outlying areas) to low 40s (urban centers), a weak disturbance rotating around the base of the aforementioned upper-level low will zip through the Commonwealth from Friday afternoon into Friday night. As a result, clouds will increase Friday morning, and isolated showers may dot parts of the Lower Susquehanna Valley Friday afternoon and evening. However, the air mass will be very dry and the disturbance starved for moisture, so much of the rain on radar may actually be "virga," or precipitation that falls from clouds but evaporates before reaching the ground. High temperatures Friday afternoon should be several degrees lower than tomorrow, or in the upper 50s to low 60s, on account of more cloud cover and the stray showers. 

In the wake of Friday's disturbance, northwesterly winds of 10-20 mph will usher a reinforcing shot of chilly air into the mid-Atlantic States this weekend. At the same time, a storm system is expected to track from the Deep South to the Carolina coastline spanning Friday night to Saturday evening. Fortunately, the system should remain too far south for any rain to reach areas north/west of the I-95 corridor, but Saturday will likely be a mostly cloudy and chilly day with highs in the mid-to-upper 50s.. about 10-15°F below average in early May. The system will zip into the open waters of the western Atlantic from Saturday night into Sunday. However, high temperatures on Sunday may only be a degree or two higher than Saturday despite the return of more sunshine. Needless to say, you'll need to grab a jacket or sweatshirt for outdoor activities this weekend, and there may be patchy frost in the deepest valleys and most outlying areas of south-central PA Saturday and/or Sunday mornings. I don't anticipate sub-freezing temperatures or widespread frost, but a few of you may have to cover tender plants/vegetation Friday and/or Saturday evenings before going to bed.

Another disturbance will rotate around the base of the upper low early next week, but this one should track from the Great Lakes region into southeastern Canada or northern New England by Tuesday. Thus, winds will turn south-to-southwesterly across the mid-Atlantic States on Monday and usher more seasonable air back into the region. In stark contrast to the weekend, high temperatures should reach the mid 60s to perhaps 70°F Monday afternoon under partly sunny skies. A weak cold front trailing southward from the system will likely traverse the Commonwealth from northwest-to-southeast spanning Monday night into Tuesday, and it may be accompanied by a few showers. However, timing of the front currently looks unfavorable for meaningful rain, and most areas will likely receive 0.20" or less from the showers. A high pressure system may briefly settle over the mid-Atlantic States during the middle of next week and promote mostly sunny, drier and more seasonable conditions with high and low temperatures in the upper 60s and 40s, respectively, but discrepancies in the timing of various disturbances makes the long-range quite uncertain. So, it's best to check back on Friday for an update! One thing's for certain: I have no clue when the mercury will hit the 80-degree mark again.. 🙁 -- Elliott