Much of the week ahead will be rather cool and unsettled across the northeastern part of the nation with a persistent upper-level trough of low pressure sitting nearby. This upper air pattern will keep temperatures generally suppressed to below-normal levels in the Great Lakes, Mid-Atlantic and Northeast US and there will be a shower threat from time-to-time. By the weekend, important changes will take place as the upper-level trough over the northeastern US retreats off to the northeast and an upper-level ridge of high pressure edges its way into the area from the western states. This ridge will intensify early next week, and the result could be 90+ degrees in the Sunday/Monday/Tuesday time period in places along the I-95 corridor. Looking beyond, it appears that the big-time warm up early next week will not last too much longer as a frontal system next mid-week is likely to return temperatures to more seasonal levels.
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As noted in the 2026 Tropical Outlook, El Nino is going to be a major player with respect to the upcoming tropical season in the Atlantic Basin and signs are increasingly pointing to one of the strongest episodes in the last 50 years. The most powerful El Nino events in recent history took place in 1982-1983, 1997-1998, and during 2015-2016, and this upcoming occurrence could rival all of them in terms of its magnitude. Not only have surface water temperatures climbed dramatically in recent days across the tropical Pacific Ocean, but some very warm water relative-to-normal lurks just beneath the surface…and it is “bubbling” up to the top. El Nino will have worldwide impacts during the summer and fall seasons and likely be a big inhibiting factor to the Atlantic Basin tropical season due to increased subsidence and wind shear (hostile conditions for tropical systems). Should El Nino continue into the first part of 2027 - and odds are quite good from this vantage point - it could have big implications on the winter season across the continental US...something we’ll monitor in the months to come.
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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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