Any long-time weather forecaster in the northeastern part of the nation knows quite well to be fearful of the “back door” cool front this time of year as it can make a forecast of summer-like temperatures look rather foolish with winter-like reality instead. Indeed, the “back door” cool front is rather common in the northeastern part of the US during the months of March and April, and it can mean the difference of 30-40 degrees over a short distance, and the difference between summer and winter weather conditions over a short period of time.
In fact, there can be winter-like temperatures this Saturday in Boston, Massachusetts while a summer-like feel is as close by as Harford, Connecticut, and summer-like temperatures in New York City on Saturday can drop significantly by Sunday after the passage of a “back door” cool front from northeast-to-southwest. The key factor in the potential dramatic impact of the passage of a “back door” cool front this time of year is that the western Atlantic Ocean is still quite cold so a switch of low-level flow of air from a warmer continental direction to an ocean flow can result in substantial temperature swings.
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The “boys of summer” are back in town...big-league baseball gets underway on Thursday with home openers in New York City (Yankees vs. Brewers) and Washington, D.C. (Nationals vs Phillies) where there should be loads of sunshine and dry, cool conditions. High pressure will be in control of the weather in the Mid-Atlantic region on Thursday resulting in the dry, cool conditions with highs likely in the lower 50’s across New York City and the upper 50’s in the D.C. metro. After a warm frontal passage on Friday night, a major-league warmup is coming on Saturday with 80 degrees on the table in at least parts of the Mid-Atlantic region.
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An on-going stratospheric warming event that began in late February increases the chance for additional cold air outbreaks as we wind down the month of March from the Great Lakes/Midwest to the Mid-Atlantic/Northeast US. In fact, the typical lag time between a stratospheric warming event over the polar region and its impact on US temperature patterns suggests there may very well be cold air outbreaks to deal with in this part of the country at least until the middle of April. As it turns out, big-league baseball gets underway in earnest in one week’s time on Thursday, March 27th, and the early part of the season may feature plenty of cold weather games thanks in large part to the on-going big-league stratospheric warming event. In addition, the influx of colder-than-normal air masses in coming weeks keeps hope alive across the northern states for those wishing for more snow...yes, even though spring season is now officially underway.
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Numerous ingredients are coming together for what is likely to be a multi-day severe weather event from the central US to the east coast during the period from later Friday to Sunday night. These ingredients include not just one, but two strong upper-level lows, powerful jet streaks at multiple levels of the atmosphere, an influx of warm, humid air on the storm’s front side, and a surface low pressure system that will deepen to rarely ever seen barometric pressure levels as it moves from the central Plains to the western Great Lakes. All severe weather parameters are on the table during this multi-day event including swaths of intense and damaging winds, strong tornadoes, hail, and torrential rainfall that can result in flash flooding.
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The combination of an intense upper-level low, powerful jet streaks at multiple levels of the atmosphere, strong southerly low-level flow of warm, moist air, and a deepening surface low pressure system will likely lead to a severe weather outbreak from later Friday into Friday night. Indeed, this threat of severe weather may continue right through the upcoming weekend as it shifts slowly to the east reaching the Atlantic seaboard by the latter part of the weekend. The deepening surface low pressure system may reach central pressures not often seen in this part of the nation which will result in a very strong pressure gradient potentially leading to widespread damaging winds. In addition, this unfolding atmospheric setup can lead to some strong tornado activity from later Friday into Saturday across portions of the central and eastern US.
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The month of March is now underway and it certainly can feature multiple severe weather outbreaks as the air becomes increasingly warm and humid across the southern states at the same time colder-than-normal air masses continue to push south and east from Canada into the US. The ingredients are falling into place for severe weather during each of the next three days as indeed colder-than-normal air from the western states will push eastward into a warmer-than-normal air mass that today will be centered over the central states. The main threat zone for severe weather today is likely to extend from Texas-to-Oklahoma-to-Kansas and then an enhanced risk is likely on Tuesday centered over the Lower and Middle Mississippi Valley region. Spring-like storm conditions will reach the eastern states on Wednesday with windy, warmer weather, soaking rainfall, and the potential of strong-to-severe thunderstorm activity.
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Today’s weather features above-normal temperatures across much of the nation and the next couple of days will remain on the mild side in the Mid-Atlantic region with high temperatures approaching 60 degrees in some areas. We are about to flip the calendar from February to March and it appears quite likely that there will be occasional cold air intrusions from Canada into the US during the next few weeks. Supporting evidence for additional cold air outbreaks during the month of March include the strong likelihood of a “disrupted” stratospheric polar vortex with significant warming near the North Pole by the middle of March and the movement of a tropical disturbance known as the Madden-Julian Oscillation (MJO). These occasional cold air outbreaks will contribute to an overall active weather pattern in the month of March and likely set the stage multiple severe weather outbreaks. In addition, the continuing cold air intrusions will certainly keep hope alive for snow lovers with multiple upcoming chances; especially, across interior higher elevation locations of the northern Mid-Atlantic and Northeast US.
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Today’s weather features above-normal temperatures across much of the nation and the remainder of the week will be generally on the mild side including in the Mid-Atlantic region where high temperatures of 60+ degrees will be commonplace. As nice as it may feel during the next few days, it appears likely that additional cold air outbreaks will make their way from Canada into the US during the next few weeks and this “back and forth” in temperatures could set the stage for multiple severe weather outbreaks during the month of March perhaps with a focus in the region from the Gulf coast to the Tennessee Valley. As the new month progresses, increasing strength of the sun will allow for warmer air masses to develop down across the southern states and any incoming cold air mass from Canada can produce “clash zones” with the prospects of severe weather. One such threat could take place next week somewhere in the middle of the nation with cold air from the north and west pushing towards warm, humid air to the south and east and there can be a repeat performance in the week to follow.
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Arctic air covers much of the nation again today with a continuing tight grip on the central states where numerous daily low temperature records have been set all the way from the Dakotas to Texas and, in a few cases, monthly low temperature records have been challenged. The average temperature across the continental US earlier today was 15.0°F below the average for this time of year and, in a few spots, temperatures were between 45 and 50 degrees below the average (e.g., Nebraska, SW Missouri). Temperatures will gradually moderate over the upcoming weekend and next week promises to feature above-normal temperatures across a wide part of the nation. It is, however, quite likely that additional very cold air masses will be able to make their way from northern Canada into the central and eastern US as the month of March gets underway.
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Arctic air covers much of the nation today with a particularly tight grip on the central states where numerous daily low temperature records have been set all the way from the Dakotas to the Rio Grande Valley region of southern Texas. The average temperature across the continental US earlier today was 15.4°F which is well below normal for this time of year and only the state of Florida could boast about warm weather conditions.
In addition to the widespread cold, accumulating snow fell yesterday across portions of the Middle Mississippi Valley and significant snow today will spread from the Tennessee Valley to the southern Mid-Atlantic region. The DC metro area will be on the northern edge of today’s “southern stream” system and can receive a coating to an inch or so; especially, across the southern suburbs. On Thursday, a “northern stream” wave in the upper atmosphere will pass right over the Mid-Atlantic region and likely result in some snow or snow shower activity in the DC-to-Philly-to-NYC corridor. The week ends with yet another very cold and windy day on Friday in the Mid-Atlantic region with well below normal temperatures and even lower wind chill values.
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