An early season nor’easter will impact much of the Mid-Atlantic region and Northeast US and likely have its greatest affects on coastal sections where tidal flooding and beach erosion are big concerns. The time period for impact by this developing storm system for the northeastern states will be from Friday night through Sunday…a prolonged event. The combination of strong high pressure centered over southeastern Canada and intensifying low-pressure over the western Atlantic Ocean will result in an extended period of onshore flow along coastal sections leading to the tidal flooding and beach erosion issues; especially, at times of high tide - and a full moon on Saturday won’t help the situation. As the Atlantic low intensifies and slowly pushes to the north, it will become increasingly under the influence of the strong high pressure ridging to its north, and this will lead to a slowdown and then likely a loop back to the coast. Rain and wind will extend inland back to the big cities in the I-95 corridor during the Friday night through Sunday time period.
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The combination of strong high pressure to the north and multiple low-pressure systems to the east will result in a prolonged period of onshore flow along coastal sections from the Delmarva Peninsula to New England. This extended period of onshore flow will increase the chance for tidal flooding at times of high tide right through the upcoming weekend and a full moon on Saturday will not help the situation. Low pressure will intensify over the weekend as it climbs northward over the western Atlantic Ocean and then it’ll run into a brick wall in the atmosphere with strong riding to its north. As a result, the strong low will slow down, perhaps loop back around towards the coast, and produce rain and wind along coastal sections into early next week.
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Temperatures have been consistently peaking well up in the 80’s in recent days along the DC-to-Philly-to-NYC corridor, but there can be quite a change by the middle of next week. An unusually strong “cold air damming” setup is looking likely with deep high pressure centered over southeastern Canada and this could limit temperatures to the 60’s along the I-95 corridor. In addition to the high-pressure system to the north, this scenario will feature a slow-moving frontal boundary zone that will allow multiple low pressure systems to ride along bringing plenty of moisture into the Mid-Atlantic region. And there is the chance that one of these low pressure systems intensifies just off the Mid-Atlantic coastline in “nor’easter” fashion. The bottom line…occasional rain is likely from Sunday into the middle of next week and some of the rain can be heavy at times to go along with much cooler-than-normal temperatures.
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We have now reached rare territory for the Atlantic Basin due to the lack of hurricanes at this stage of the tropical season. In fact, this is the latest time without an Atlantic hurricane during the satellite era which began in 1966 and there is likelihood that one has to go all the way back to 1941 though confidence in the tracking of hurricanes is far less certain in the pre-satellite era. Having said that, an extremely quiet first half of the tropical season does not guarantee an uneventful second half…indeed, there are some signals that activity will pick up later this month.
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The peripheral region of an intense upper-level ridge can often be quite an active area for thunderstorms this time of year and this summer has been no exception. Specifically, the northeastern quadrant of an intense upper-level ridge where northwesterly flow dominates in the overall clockwise circulation around high pressure can often contain numerous bands of thunderstorms, complexes of thunderstorms and even long-lasting lines known as derechos. This “ring of fire” region in the outer peripheral of high pressure with northwesterly flow aloft has been repeatedly showing up this summer extending from the Great Lakes to the Mid-Atlantic and numerous severe weather outbreaks have been the result. A repeat performance is on the table during the next few days with Tuesday, Wednesday and Thursday likely to feature numerous bands of strong-to-severe thunderstorms that will potentially impact the DC-to-Philly-to-NYC corridor.
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Labor Day is still two weeks away and that puts this outlook in the “speculation” phase; however, there are interesting and somewhat consistent signs of an “omega” blocking pattern in the upper atmosphere over North America which is more typical of winter or spring seasons. An “omega” blocking pattern typically features an upper-level ridge sandwiched in between two upper-level troughs and these systems tend to linger for several days. If indeed this pattern unfolds with an upper-level trough centered over the Northeast US, then any chance for sustained heat for summer’s unofficial end would be quite low in that part of the nation. However, if the ridge sets up over the Northeast US then 90+ degree heat would certainly remain on the table in those urban areas along the I-95 corridor.
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Our active weather pattern in the Mid-Atlantic region continues for the next several days with multiple chances of heavy showers and severe thunderstorms that can produce damaging wind gusts and even isolated tornadoes. In a similar pattern to recent severe weather outbreaks, a strong wave of energy will drop southeastward into the Mid-Atlantic region later today riding along a northwesterly flow of air on the peripheral of strong high pressure centered over the western states.
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It is rather warm and humid today in the DC-to-Philly-to-NYC corridor and it looks like we better get used to these conditions as a “Bermuda-high” weather pattern is setting up for the eastern states. An upper-level trough of low pressure over the eastern US here at the beginning of the week will dissipate shortly and strong ridging will form over the western Atlantic by mid-week. As such, a broad southwesterly flow of air will develop along the Atlantic Seaboard and likely persist for several days bringing warm and humid conditions to the I-95 corridor and moisture levels will be high enough to produce a daily shot of showers and thunderstorms.
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While not everyone will get hit, the atmosphere is fueling up to produce numerous showers and thunderstorms during the afternoon and evening hours in the Mid-Atlantic region. Strong-to-severe thunderstorms are on the table as well as torrential rainfall from this significant system with the greatest chance of flash flooding likely in the northern Mid-Atlantic (e.g., E PA, N NJ, NYC) and the greatest chance of severe weather likely in the southern Mid-Atlantic (e.g., DC, Delmarva). Multiple ingredients are coming together to raise the likelihood of this very active weather pattern for later today and tonight.
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Numerous ingredients will come together during the next couple of days to raise the possibility of severe thunderstorms and heavy rainfall in the Mid-Atlantic region. In an overall pattern quite similar to a week ago, strong upper-level ridging is currently centered over the Rocky Mountain States, and the outer periphery of this system features northwesterly flow over the Great Lakes. Embedded within this northwesterly flow will be an intensifying upper-level jet streak on Tuesday that’ll drop to the south and east enhancing upper motion in the Mid-Atlantic region. Meanwhile, an upper-level trough of low pressure is currently positioned over the southeastern part of Canada, and it will add fuel to the fire by sending spokes of energy into the northeastern states during the next couple of days. Finally, not to be outdone by its upper-level counterparts, the surface level will get involved as low pressure will deepen over the Delmarva Peninsula on Tuesday and there will be a secondary surface low unfolding over western NY State.
All of these ingredients can result in severe thunderstorm activity during the next couple of days with a focus on Tuesday afternoon and evening and there can be torrential rainfall in portions of the Mid-Atlantic region with 3+ inches on the table. The best chance of severe weather on Tuesday will likely be across the southern Mid-Atlantic (e.g., DC, Delmarva), and the best chance of soaking rainfall will likely be across the northern Mid-Atlantic (e.g., eastern PA, NJ, NYC), but some of these details still have to be worked out.
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