May gets underway on Friday, and it looks like a cooler-than-normal pattern will dominate in the eastern half of the nation to at least the middle of the new month. Multiple cooler than normal air masses are likely to push into the north-central states from central Canada during those next couple of weeks and these will ultimately spread to the south and east and encompass the Great Lakes, Mid-Atlantic, and Northeast US. A favorable pattern for the transport of cooler-than-normal air masses from Canada into the US will feature a persistent upper-level trough centered near the Great Lakes as well as some “high-latitude blocking” up across northeastern Canada and Greenland. In addition to the expected cooler conditions, multiple rain events are on the table during the next couple of weeks beginning with one from later today into early Thursday which will impact the Mid-Atlantic region.
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A combination of ingredients will come together later today and tonight to enhance the risk of severe weather in the Middle Mississippi Valley region with a focus on the region from Arkansas to Indiana. One of the contributing factors in today’s severe weather threat is an active jet stream that has intensified in recent days across the central and southern US in an atmospheric response to the initial phase of El Nino in the tropical Pacific. The threat of severe weather will shift slightly to the south and east on Tuesday mainly to the Middle and Lower Mississippi Valley regions. In fact, the threat of severe weather will likely continue well into the month of May as additional cold air masses are destined to drop southeastward from central Canada into the northern US. This evolving weather pattern will produce below-normal temperatures across much of the eastern half of the nation from late April into at least the middle of May and multiple rain events are likely to be included from the Rockies to the eastern seaboard.
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As noted in the 2026 Tropical Outlook, El Nino is likely to be a major player with respect to the upcoming tropical season in the Atlantic Basin and all signs continue to point to the increase of water temperatures in the equatorial Pacific Ocean. Not only have surface water temperatures climbed dramatically in the tropical Pacific Ocean in recent days, but some very warm water lurks just beneath the surface, and it is “bubbling” up to the top.
The development of El Nino in the tropical Pacific is actually having some current effects on the upper air flow across the continental US with a more favorable environment for severe weather outbreaks and better opportunities for rain from the Rocky Mountain States to the Mid-Atlantic region. Looking ahead, the combination of an El Nino episode in the Pacific Ocean and an area of cooler-than-normal water in the Atlantic’s Main Development Region may result in below-normal tropical activity in the Atlantic Basin during the summer and fall seasons. Should El Nino continue into the 2026-2027 winter season - and odds are good - it would also have big implications for the weather across the continental US...something we’ll monitor in the months to come.
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The unseasonably warm conditions in the Mid-Atlantic region will continue for one more day and many spots today will challenge their daily high temperature record. It’ll remain on the warm side on Friday and Saturday, but not quite the record-challenging warmth experienced here during the past couple of days. The warmer weather pattern breaks down over the weekend as a strong surface cold front heads toward the eastern states at the same time intense high pressure ridging along the coast slides to the east.
The front will bring with it a good chance of much-needed shower activity late Saturday night and Sunday morning and it’ll usher in a much cooler air mass to close out the weekend and start the new work week. In fact, temperatures late Monday night/early Tuesday are likely to drop way down to freezing or below in much of the Mid-Atlantic region which could prompt widespread frost and freeze warnings. Temperatures rebound noticeably by mid-week, but an overall pattern change will bring additional colder-than-normal air masses to the central and eastern states during late April/early May.
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Most have been waiting for this kind of warmup in the eastern states following several false starts this season, but this may end up being a little too much on the extreme side. Not only are daily high temperature records in jeopardy this week in the Mid-Atlantic region with 90+ degrees on the table, but a few spots could experience their highest April temperatures ever recorded although it will be tough to beat the heat wave of April 1976. This warmup should last well into the upcoming weekend, but there are strong signs that another chilly air outbreak is destined to reach the northeastern part of the country by early next week. In fact, there are signs that additional colder-than-normal air masses will impact the central and eastern states during the last week of April at the same time a teleconnection index known as the Madden-Julian Oscillation or MJO shifts into a colder-than-normal phase for this time of year.
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Strong upper-level ridging that was parked over the Four Corner states in recent days has shifted to the east and this re-positioning will allow warm, moist air from the Gulf region to flow northward into the nation’s mid-section. One result of this changing weather pattern will be a much-increased chance of significant precipitation all the from Texas to the Great Lakes, and this can include strong-to-severe thunderstorms at mid-week. Farther north, there will be another influx of cold, Canadian air and this can lead to accumulating snow and perhaps significant icing across portions of the Northern Plains and Great Lakes later in the week.
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Below-normal sea surface temperatures continue this month across much of the equatorial part of the Pacific Ocean, but there are signs that this La Nina episode is about to enter “ENSO-neutral” status, and then likely flip to El Nino conditions by the early part of the summer (tropical) season. A change from La Nina to El Nino across the equatorial Pacific Ocean can have big implications for the upcoming Atlantic Basin tropical season. Indeed, warmer-than-normal water associated with an El Nino episode in the tropical Pacific is often an inhibiting factor for tropical activity in the Atlantic Basin. This is due to increased wind shear in the atmosphere; especially over the Caribbean Sea during typical El Nino summer seasons, and this inhibits the development and intensification of tropical storms. A second potential inhibiting factor for tropical activity in the Atlantic Basin this summer is the chance that colder-than-normal water will develop across much of the tropical Atlantic Ocean according to some longer-range forecast models.
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There is an unusually high risk of severe weather in parts of the Mid-Atlantic region from today into the late evening hours with numerous ingredients coming together. The severe weather risk will include all the following weather parameters: downpours, localized flooding, damaging winds, lightning, hail, isolated tornadoes and power outages are all on the table. Multiple rounds of showers and thunderstorms are likely into the late evening hours and severe weather can develop with any of these bands from mid-day on through the late evening. Much colder air pours into the Mid-Atlantic region in the overnight hours and temperatures will be well below normal on Tuesday and lows tomorrow night can bottom out near the 20-degree mark in some suburban locations. The Great Lakes “snow machine” will be turned on as well on Tuesday with numerous snow bands likely just downstream and a few snow showers can make it into the I-95 corridor.
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An intense storm system will develop later this weekend, and it will have an impact over a large part of the nation in the Sunday/Monday/Tuesday time period ranging from blizzard conditions to severe weather including the risk of tornadoes. The risk of severe weather in the Mid-Atlantic region will be unusually high from Monday into Monday night. The heaviest snow band is likely to extend from Minnesota to Wisconsin to the upper part of Michigan where 1-2 feet can fall and the severe weather threat will exist on Sunday/Sunday night across the MS, TN, Ohio Valleys and then shift east on Monday/Monday night from the Mid-Atlantic region to the Carolinas. Arctic air with well below-normal temperatures will pour into the northeastern states by Tuesday and lake-effect snow bands are likely to set up just downstream of the Great Lakes.
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An intense cold front barreled through the Mid-Atlantic region earlier today and temperatures have dropped sharply from early day highs in the 60’s and should reach the middle 30’s by early-to-mid afternoon. Rain is abundant on the back side of the front and - as colder air becomes better established - a changeover to snow is going to take place in many of the same areas of the Mid-Atlantic region that experienced 80-degree high temperatures during the past couple of days. Any snow that falls this afternoon will be of the heavy, wet variety and can certainly cling easily to grassy surfaces.
Over the weekend, another strong cold front will enter the weather picture as it moves to the nation’s midsection with a widespread colder-than-normal air mass on its backside and charging to the south and east. A strong storm system is likely to form along the frontal boundary zone as upper-level support arrives, and the Great Lakes may end up with an all-out blizzard come Sunday night and Monday with plenty of snow and powerful winds. In fact, there can be accumulating snow and strong winds in this same Great Lakes region on Friday from a clipper-system and this would precede the potential blizzard. The intense cold front will bring heavy rain and strong winds to the Mid-Atlantic region/Northeast US on Monday and there can be strong-to-severe thunderstorm activity…much colder air will follow for Tuesday and Wednesday.
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