Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* Record-challenging heat to arrive early next week *

1:00 p.m. Friday, May 15, 2026, Update:

The second full week of May has been rather cool across the mid-Atlantic States, but a quick flip to "sudden summer" is about to take place early next week. In fact, the year's first official heatwave.. defined as three or more consecutive days with high temperatures at or above 90°F.. may unfold across parts of northern MD, southeastern PA and the Lower Susquehanna Valley from Monday-Wednesday. Beforehand, the week will end on a partly sunny, breezy and seasonable note this afternoon with highs in the upper 60s to perhaps 70°F in spots. An upper-level low off the East Coast is still in close enough proximity to the region to cause a continuation of the breezy and relatively cool conditions, but there won't be a drop of rain in sight (see below). Northwesterly winds will be sustained at 10-20 mph through 5-6 PM before subsiding by sunset. 

A sprawling high pressure system currently over the southeastern United States will shift into the western Atlantic over the weekend. On its backside, strengthening west-to-southwesterly flow will pump unseasonably and increasingly warm air into the region through early next week (see below). After a mainly clear and comfortably cool Friday night with lows in the mid-to-upper 40s, high temperatures will soar into the low-to-mid 80s on Saturday. Clouds will increase during the afternoon hours in advance of a weak disturbance, but they shouldn't hold temperatures back at all. The disturbance will move through the Commonwealth Saturday night and bring isolated showers to the Lower Susquehanna Valley, but its overnight timing will be unfavorable for any thunderstorm activity. As a result, the showers should generally be light and widely-separated in nature and fail to produce more than 0.10-0.20" of rain in the hardest-hit locations (see below). Behind the disturbance, clouds will give way to sunshine Sunday morning, and the afternoon should then turn out mostly sunny and pleasantly warm with highs in the low-to-mid 80s once again. Needless to say, it will be a great weekend for outdoor activities in lightweight clothing/attire. Enjoy!

Looking ahead into early next week, an upper-level, Jet Stream ridge will amplify and flex northward along the Eastern Seaboard from Monday-Wednesday in response to a deep trough over the Intermountain West and northern Plains. The large-scale subsidence, or sinking motion, beneath the ridge will support mostly sunny skies and efficient, compressional warming both Monday and Tuesday. Thus, high temperatures should soar into the upper 80s to perhaps low 90s Monday afternoon and then approach record levels on Tuesday. In fact, the May 19th record high temperature of 95°F from 1962 at Millersville University may be tied. I suspect Tuesday's eventual high temperature comes up 1-2°F short of tying the record, but it's definitely going to be close. Fortunately, high humidity will not accompany the early-season heat, and dewpoints should be no higher than the upper 50s to low 60s both Monday and Tuesday afternoons. Thus, the heat index should essentially be the same as the actual air temperature. That being said, most people have had virtually no time to acclimate to the heat yet, so it will be imperative to drink plenty of non-alcoholic beverages, take frequent breaks from the heat, and wear loose-fitting/lightweight clothing early next week. Never leave children or pets unattended in a vehicle, either, as its internal temperature can reach 120°F in just 10-15 minutes on a 95-degree day. Despite mainly clear skies at night, overnight lows will also be way above average from Saturday-Wednesday and generally around 60°F on Saturday and Sunday nights and between 62-68°F both Monday and Tuesday nights. 

By the middle of next week, a cold front will sag southeastward from the Great Lakes region and "beat down" the Jet Stream ridge along the East Coast. It will likely traverse northern MD and southeastern PA from northwest-to-southeast spanning Wednesday to Thursday morning and be accompanied by scattered showers and thunderstorms. Its exact timing will determine whether high temperatures reach 90°F again on Wednesday or fall well short of the milestone. In addition, thunderstorms could turn strong-to-severe in the event of an afternoon/evening frontal passage. It's far too early to finesse those details, so check back Wednesday for an update! Regardless of the exact outcome, a Canadian high pressure system should settle into the eastern Great Lakes region and Northeast late next week and put an end to the heat. In fact, the week may end on a mostly sunny and beautiful note with highs in the low-to-mid 70s on Thursday and/or Friday, and it could be a week or two before 90-degree heat returns. With that being said, I certainly don't expect the last 10 days of May to be "cool." Instead, I foresee high temperatures in the 70s/80s most days with overnight lows in the 50s. We'll see what happens.. -- Elliott

12:00 p.m. Tuesday, May 11, 2026:

In terms of the weather, Mother's Day turned out to be just what you might expect this year. Partly-to-mostly cloudy skies and scattered afternoon showers accompanied high temperatures in the low-to-mid 70s across northern MD, southeastern PA and the Lower Susquehanna Valley. The showers were associated with a weak cold front that moved through the region last night, and the second week of May is kicking off on a mostly cloudy and unseasonably cool note today. A disturbance moving northeastward along the boundary in the southern mid-Atlantic States is responsible for today's thick cloud cover, but no rain will reach areas north/west of the I-95 corridor this afternoon. High temperatures will be around 10°F below average and only reach the low-to-mid 60s, so grab a light jacket or sweatshirt before heading outside (see below). A Canadian high pressure system over the western Great Lakes region at the time of this writing will build into the Commonwealth later tonight into Tuesday. As a result, skies will clear this evening, and Tuesday will turn out mostly sunny and pleasant with light winds and high temperatures in the mid-to-upper 60s. Temperatures will bottom out in the mid-to-upper 30s in the deepest valleys and most outlying areas tonight and low-to-mid 40s in urban centers, but that's fortunately not quite low enough for frost formation. Phew!

Clouds will return Tuesday night in advance of an approaching storm system, and showers are then expected to arrive on Wednesday. A few thunderstorms containing locally heavy downpours and wind gusts up to 40 mph may also erupt Wednesday evening, but I don't anticipate any severe weather in areas east of the Appalachians (see below). The actual storm system responsible for the showers and storms will track from the Great Lakes region into southeastern Canada from Wednesday into Thursday morning before re-developing along the mid-Atlantic or southern New England coastline later Thursday into Thursday night. Unfortunately, this will be our lone chance for rain through at least Friday night and perhaps even into early next week. While beneficial, the midweek showers and storms won't be heavy enough to put even the slightest dent in the moderate-to-severe drought across northern MD, southeastern PA and most of the Lower Susquehanna Valley. Rainfall amounts will only average 0.25-0.50" through early Thursday morning with locally higher amounts up to 0.75" (see below). Be alert for areas of slow travel and reduced visibility, as well as standing water on some roadways, during the Wednesday afternoon commute, but I really don't anticipate too many travel concerns with this one. Due to the clouds and wet weather, high temperatures on Wednesday will be similar to Tuesday and generally in the 60s. 

Behind the system, northwesterly winds of 10-20 mph with gusts up to 30 mph will usher a reinforcing shot of chilly air into the mid-Atlantic States late this week. In addition, skies will likely remain mostly cloudy on Thursday with a stray shower or two still possible throughout the day. Thus, you'll certainly want to keep a light jacket or sweatshirt handy through Friday. Overnight lows from Tuesday night through Friday night will be "near normal" by mid-May standards and generally in the upper 40s to low 50s, but high temperatures may struggle to reach the mid 60s on Thursday and upper 60s Friday. I've seen much damper and chillier conditions during the middle of May, but this week's weather certainly won't be ideal for warm-weather lovers like myself. However, that should change over the weekend..

The aforementioned storm system will finally lift into the Canadian Maritimes this weekend and be replaced by an area of high pressure over the southwestern Atlantic. To its north and west, winds will turn southwesterly by Saturday and usher warmer air back into the Commonwealth. There's still some uncertainty as to how fast the warmer air returns and whether clouds/showers accompany its arrival, but odds favor a partly sunny and dry start to the weekend with high temperatures in the mid 70s to perhaps 80°F Saturday afternoon. The warming trend should then continue into early next week, and high temperatures may be back in the mid-to-upper 80s both Sunday and Monday afternoons under partly-to-mostly sunny skies. An upper-level, Jet Stream ridge should amplify and flex northward along the Eastern Seaboard from Sunday-Tuesday in response to an upper-level low over the northern Rockies and northern Plains. Thus, the southwesterly flow should strengthen during that time and promote a stretch of unseasonably warm conditions after this week's relative chill. An eventual peel back to "near normal conditions" is a virtual guarantee by the middle-to-latter part of next week, but I don't expect any future bouts of "cool" weather to be as pointed or prolonged as the current one. After all, the start of Meteorological Summer is only three weeks away, so days with high temperatures in the 60s and 70s will be numbered after this week.. and I'm more than OK with that! -- Elliott