Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* unseasonably cool pattern to persist into mid-may *

11:15 a.m. Friday, May 1, 2026, Update:

As expected, Wednesday's storm system dumped a general 1/3 to 2/3 of an inch of rain across southeastern PA and the Lower Susquehanna Valley with locally higher amounts up to 0.85" (see below). Due to the ongoing moderate-to-severe drought, the rain was highly beneficial but not enough to put a meaningful dent in it. Behind the system, northwesterly winds of 12-25 mph ushered drier and slightly cooler air into the Commonwealth on Thursday, but April still ended on a relatively pleasant note with highs in the low-to-mid 60s under partly-to-mostly cloudy skies. Speaking of April, it concluded as the 6th-warmest on record at Millersville University due primarily to the early- and mid-month spurts of record warmth (see below). In keeping with the general trend since last autumn, monthly rainfall was slightly below average. 

May will kick off on a pleasantly cool note across northern MD, southeastern PA and the Lower Susquehanna Valley following a chilly start this morning. Clouds will increase, lower and thicken this afternoon in advance of a weak disturbance, but high temperatures should still reach the low-to-mid 60s and only be around 5°F below average. The disturbance will spark isolated showers later this afternoon into tonight, but it will be starved for moisture and passing through a very dry air mass. Thus, rainfall amounts will be negligible and on the order of 0.10" or less (see below). Due to the clouds and showers, minimum temperatures will likely be "near normal" tonight, or generally in the low-to-mid 40s. 

A storm system will then track from the Deep South into the western Atlantic on Saturday. The system will be too suppressed for any rain across southeastern PA, but Saturday will turn out mostly cloudy and cool with highs in the mid-to-upper 50s. The system will then move farther out-to-sea from Saturday night into Sunday, and northwesterly winds of 12-25 mph will usher a reinforcing shot of chilly air into the Commonwealth in its wake. Skies will clear Saturday night, and high temperatures Sunday afternoon will be similar to Saturday (~10-15°F below normal) despite more sunshine (see below). Low temperatures Saturday night may bottom out in the mid 30s in the most rural and outlying areas of south-central PA, but minimum temperatures should remain at or above 35°F in most spots. Thus, any early-morning frost will be patchy, at worst. However, you'll certainly need to grab a jacket or sweatshirt before heading outside this weekend, and it will feel more like late March than early May. Low temperatures Sunday night will bottom out around 40°F yet again.

Looking ahead into early next week, I do foresee a significant moderating trend and brief reprieve from the unseasonably cool weather. A sprawling high pressure system over the Southeast on Sunday will shift into the western Atlantic by Monday and hold its ground through the middle of the week. On its backside, broad, south-to-southwesterly flow will usher increasingly warm air into the Lower Susquehanna Valley from Monday into Tuesday and perhaps even Wednesday. At the same time, a clipper-type system will zip through southern Canada and enhance the south-to-southwesterly flow across the mid-Atlantic States. In stark contrast to this weekend, high temperatures Monday afternoon should be back around average for early May and in the upper 60s to low 70s under partly sunny skies. Monday night will also be noticeably milder with lows in the low-to-mid 50s. Tuesday and/or Wednesday may then end up being the warmest day(s) through at least the first 10-12 days of the month. A cold front trailing southwestward from the aforementioned clipper system will attempt to sag southeastward through the Commonwealth during the middle of the week, but it will run into some resistance from the high pressure system over the western Atlantic. Thus, it may ultimately stall over the eastern Great Lakes region or western NY/PA for 24-36 hours. Thereafter, a wave of low pressure developing along the front should finally drag it through the I-81 and I-95 corridors later Wednesday into Thursday. Numerical computer models differ significantly in the timing of the frontal passage, its southeastward progression, and placement/strength of "waves" along it, and all of these factors will play key roles in temperature and precipitation forecasts from Tuesday night through Thursday. At this time, I suspect that both Tuesday and Wednesday end up being partly sunny, breezy, warm and generally dry with high temperatures around 80°F. Afterward, I foresee a Wednesday night-Thursday frontal passage accompanied by scattered showers and perhaps a few thunderstorms prior to a dramatic cooldown from Friday through next weekend. I'll be out of town next Tuesday-Thursday and then participating in a charity golf tournament on Friday, May 8, so check back in about 10 days for an update. -- Elliott

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