Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* Burst of Remarkable warmth this weekend; severe Storms monday? *

1:00 p.m. Friday, March 28, 2025, Update:

The final week of March is ending on a mostly cloudy and milder note across the Lower Susquehanna Valley. Southwesterly winds on the backside of a high pressure system over the western Atlantic are ushering the warmer air mass into the region. A warm front will traverse the mid-Atlantic States from southwest-to-northeast later this afternoon and evening and bring a few showers to northern MD and southeastern PA between ~4-10 PM. However, the showers will be relatively light and widely separated, so rainfall totals should not exceed 0.10" in most spots. Some wet roadways and areas of light rain will be the only weather-related issues during today's PM commute (see below). Before the showers arrive, temperatures will peak in the upper 50s to mid 60s this afternoon and only fall back into the low-to-mid 50s tonight. Skies should gradually clear during the second half of the night.

With regard to the forecast through the middle of next week, I have little to add from Wednesday's discussion. Behind the warm front, a burst of unseasonably warm air will surge into the Commonwealth and Delmarva Region from Saturday-Monday on the wings of strong, southwesterly flow throughout the entire atmosphere. In addition, the Jet Stream will undergo a major reconfiguration and exhibit a large, northward bulge along the Eastern Seaboard in response to a deep trough over the Western States. All signs still point to a "blowtorch" tomorrow and the first 80°F day since November 6, 2024, across the Lower Susquehanna Valley. A quasi-stationary frontal boundary will be draped across southern New England, and west-to-southwesterly winds of 12-25 mph will "downslope" off the Appalachians and aid in compressional warming to its south. Temperatures around 5,000 feet above the ground will range from 55-60°F, and that equates to surface temperatures in the low-to-mid 80s. Partly-to-mostly sunny skies will also aid in the warming process tomorrow. If I were to pick an exact number for tomorrow's high at Millersville University, I would choose 83°F. Not since 2007 has there been a high temperature greater than 80°F at Millersville, so a high of 83°F would certainly be noteworthy and remarkable. We'll see how it plays out! Record high temperatures on March 29 and 30 are in the mid-to-upper 80s across most of northern MD and southeastern PA. Those numbers won't be challenged or broken this weekend, but I could see an 84°F or 85°F reading appear on the "warmest thermometers" tomorrow afternoon.

The persistent, south-to-southwesterly flow originating from the western Atlantic and Gulf of America will draw increasing amounts of moisture into the region from Saturday night through Monday, so more cloud cover and scattered showers should limit high temperatures to the mid 70s both Sunday and Monday. However, the clouds will also prevent temperatures from falling much at night. Thus, low temperatures both Saturday and Sunday nights will be near 60°F.. some 25°F above average by late-March standards! A weak and disorganized disturbance moving northeastward through the mid-Atlantic States may trigger more scattered showers Sunday afternoon and evening, but rainfall amounts should again be negligible and on the order of 0.10" or less. Keep an umbrella handy for outdoor activities on Sunday, but you won't need it for much of the day. In addition, shorts and t-shirts will be the attire of choice this weekend, especially with Saturday's "taste of summer" now less than 24 hours away. As a warm-weather lover, I couldn't be more excited! 

A storm system will take shape over the Central States this weekend and track northeastward into southeastern Canada or northern New England by Monday. A cold front trailing southward from the system will traverse the mid-Atlantic States from Monday into Tuesday. Ahead of the front, the stage could be set for severe weather in the form of damaging wind gusts and isolated tornadoes, but that potential still hinges on the exact timing of the frontal passage. Due to the ongoing drought and extremely dry ground, flooding of streams and creeks won't be a concern. Rainfall amounts from Monday into Tuesday should average 0.50-1.00" with locally higher amounts up to 2.00", but 6-hour flash flood guidance values range from 2-4" across the entire region. Thus, the rain will be largely beneficial with the exception of locally heavy downpours and ponding of water in low-lying and poor-drainage areas. Compared to Wednesday, it does appear more likely that the cold frontal passage will be delayed until Monday evening or night. Thus, the risk of severe weather will certainly exist, and violent thunderstorms could wreak havoc in parts of the region. With high temperatures in the 70s and dewpoints in the upper 50s to low 60s on Monday, there should be ample moisture and at least some instability available for thunderstorm development. The front will serve as the "triggering mechanism" for the storms, and there could be enough wind shear (a change in wind speed and/or direction with height) present for a few rotating supercells to develop. However, the threat is still 3 days away, so the timing could change by several hours. I'll have a complete update on Monday to "pin down" the window for thunderstorms and potentially severe weather. For now, continue to remain aware of the hazards outlined above. I'll also be tracking the storms on Twitter(X) at @MUweather Monday afternoon and evening, so give me a follow if you haven't already! 😊

Behind the front, a Canadian high pressure system will settle into the Northeast during the middle of next week, and north-to-northwesterly winds will usher much cooler, drier and more seasonable air back into the Commonwealth. Skies should clear Monday night and remain mostly sunny on Tuesday. Temperatures will likely be slightly-below normal next Tuesday and near normal on Wednesday, but that still places highs in the 50s to perhaps 60°F and lows in the 30s. Moreover, the "chill" probably won't last long, and 70- or 80-degree warmth may make a quick return late in the week. Another storm system will likely develop in the Central States from Tuesday night into Wednesday and track into southeastern Canada late in the week, so we could also face another round of showers and thunderstorms on Thursday and/or Friday. Either way you slice it, spring mode has been fully activated with warmer weather and severe thunderstorms now the "talk of the town!" -- Elliott

1:15 p.m. Wednesday, March 26, 2025:

The last week of March kicked off on a windy but mild note. Despite gusts up to 35 mph both Monday and Tuesday afternoons, high temperatures reached the low-to-mid 60s on Monday and upper 50s to low 60s Tuesday. However, an upper-level trough, or dip in the Jet Stream, and its associated pocket of chilly air will swing through the Northeast over the next 24 hours. As a result, northwesterly winds of 12-25 mph with gusts up to 35 mph will accompany unseasonably cool conditions this afternoon across northern MD, southeastern PA and the Lower Susquehanna Valley (see below). In fact, temperatures will be around 10°F below average this afternoon and remain nearly steady in the 40s. Factor in the blustery conditions and partly-to-mostly cloudy skies, and wind chills will only be in the 30s. Needless to say, a jacket or winter coat will be a necessity for outdoor activities. In addition, a vigorous but moisture-starved disturbance moving through PA and NY has triggered scattered rain and snow showers.. as well as some locally heavier snow squalls.. over higher-terrain regions of each state (see below). Only a few sprinkles, graupel pellets or wet snowflakes will reach areas south/east of I-78/81, and roadways should remain dry. However, don't be surprised to see a bit of the "white stuff" fly for a few minutes. Graupel pellets fell at Millersville University around 10:50 AM this morning.. "Shift+T (trace)!"

An area of high pressure will build into the mid-Atlantic States from tonight into tomorrow and cause winds to subside. The aforementioned trough will also lift into northern New England and the Canadian Maritimes late this week and give way to a gradual moderating trend. However, temperatures will first plummet below freezing (32°F) in most places tonight on account of clear skies, light winds and the abnormally dry air mass in place. In fact, temperatures may bottom out in the mid 20s in some rural/outlying areas early Thursday morning (see below). Some early-blooming trees like dogwoods and magnolia may even be damaged by the cold weather, but that seems to happen almost every year around here. 😞 Fortunately, temperatures will rebound quickly tomorrow morning under mostly sunny skies and top out in the low-to-mid 50s during the afternoon hours. Skies will stay mainly clear Thursday night, but overnight lows should remain at least a few degrees above freezing. The high pressure system will then move into the western Atlantic on Friday, and southwesterly winds on its backside will usher milder air into the region. Despite increasing clouds or a mix of clouds and sun, high temperatures should reach the upper 50s west of the South Mountain Range to mid 60s across southeastern PA Friday afternoon. Winds will also remain light throughout the day, so the final week of March should end on a relatively pleasant note. No complaints here! 

Looking ahead into the upcoming weekend, a warm front will traverse the mid-Atlantic States from southwest-to-northeast spanning Friday afternoon to Saturday morning. A few showers may accompany the frontal passage late Friday afternoon and evening, but rainfall amounts won't exceed one tenth of an inch. Behind it, a burst of unseasonably warm air will surge into the region from Saturday-Monday on the wings of strong, southwesterly flow throughout the entire atmosphere. In addition, the Jet Stream will undergo a major reconfiguration and exhibit a large, northward bulge along the Eastern Seaboard in response to a deep trough over the Western States. Temperatures will be "off to the races" under partly sunny skies on Saturday, and highs should approach or exceed the 80-degree mark for the first time since November 6, 2024. Record high temperatures on March 29 and 30 are in the mid-to-upper 80s across most of northern MD and southeastern PA. Those numbers won't be challenged or broken this weekend, but maximum temperatures could reach 82-83°F in the warmest locations Saturday afternoon. The persistent, south-to-southwesterly flow originating from the western Atlantic and Gulf of America will draw increasing amounts of moisture into the region from Saturday night through Monday, so more cloud cover and scattered showers will limit high temperatures to the upper 60s to mid 70s on Sunday. However, the clouds will also prevent temperatures from falling much at night. Thus, low temperatures both Saturday and Sunday nights could be near 60°F.. some 25°F above average by late-March standards! You'll need to keep an umbrella handy for outdoor activities on Sunday, but shorts and t-shirts will be the attire of choice this weekend. Not since 2007 has there been a high temperature above 80°F at Millersville University in March, but I expect that to change in a few short days. Bring it on!

A storm system will take shape over the Central States this weekend and track northeastward into southeastern Canada or northern New England by Monday. A cold front trailing southward from the system will traverse the mid-Atlantic States from northwest-to-southeast early next week. Ahead of the front, the stage could be set for severe weather in the form of damaging wind gusts and isolated tornadoes, but that potential will hinge on the timing of the frontal passage. If the front moves through northern MD, southeastern PA and the Lower Susquehanna Valley Monday afternoon and evening, then scattered severe thunderstorms would likely erupt and wreak havoc on the region. However, a faster (Monday morning) or slower (Monday night) frontal passage would equal a much lower risk of severe weather. With high temperatures in the 70s to perhaps 80°F and dewpoints in the upper 50s to low 60s on Monday, there should be ample moisture and instability available for thunderstorm development. The front will serve as the "triggering mechanism" for the storms, and there could be enough wind shear (a change in wind speed and/or direction with height) present for a few rotating supercells to develop. With Monday still 5 days away, there is still a lot of uncertainty in the eventual outcome. I'll have a much better handle on the threat by Friday or Saturday, so check back then for an update! For now, just remain cognizant of these potential severe weather hazards. Behind the front, a Canadian high pressure system will settle into the Northeast during the middle of next week, and north-to-northwesterly winds will usher much cooler and more seasonable air back into the Commonwealth. Temperatures will likely be slightly-below normal next Tuesday and near normal on Wednesday, but that still places highs in the 50s to perhaps 60°F and lows in the 30s. Moreover, the "chill" probably won't last long, and 70- or 80-degree warmth may make a quick return late in the week. Either way you slice it, spring mode has been fully activated! -- Elliott