****Severe thunderstorm risk this afternoon and again later Thursday...high heat and humidity from later this weekend into at least the middle of next week with 100 degrees on the table****
Paul Dorian
There will be heavy downpours and strong-to-severe thunderstorm activity today in the Mid-Atlantic’s I-95 corridor region likely between 1pm and 8pm. The downpours can produce localized flash flooding and the some storms can generate vivid lightning and damaging wind gusts. Map courtesy NOAA, tropicaltidbits.com
Overview
It has become uncomfortably humid and warm today across much of the Mid-Atlantic region following the progression of a warm frontal system that is pushing slowly to the north. This change in atmospheric conditions comes following a cool stretch of weather that featured high temperatures on Sunday, Monday, and Tuesday that were well below-normal for the middle of June. The atmosphere will quickly destabilize this afternoon and there are likely to be downpours and strong-to-severe thunderstorms impacting the I-95 corridor somewhere between 1pm and 8pm.
A surface cold frontal system will approach the Mid-Atlantic region from the northwest on Thursday, and this will combine with an upper-air disturbance to bring another threat of severe weather threat to the DC-to-Philly-to-NYC corridor. The likely timetable for severe thunderstorm activity on Thursday will again be 1pm-8pm, and there can be damaging wind gusts, hail, and even isolated tornadoes in any spot along the I-95 corridor. The cold front clears the coast by later tomorrow night and Friday will turn out to be a rather decent day featuring warm and dry conditions to end the work week.
Looking ahead, a very strong ridge of high pressure will build into the Mid-Atlantic region by the early part of next week and this will lead to high heat and humidity in the DC-to-Philly-to-NYC corridor from later this weekend into at least the middle of next week. After a very warm day on Saturday, temperatures are likely to soar into the 90’s on Sunday and then the first half of next week will feature high heat and humidity and 100 degrees will be a possibility in the DC-to-Philly-to-NYC corridor.
There will be an enhanced threat of severe weather on Thursday afternoon and evening in the DC-to-Philly-to-NYC corridor as a strong cold front approaches from the northwest. Similar to today’s threat, there can be downpours on Thursday, vivid lightning, and localized flash flooding and damaging wind gusts are a possibility in some of the storms. Map courtesy NOAA, tropicaltidbits.com
Strong-to-severe thunderstorm threat both today and on Thursday
Low clouds continue to erode away across southern portions of the Mid-Atlantic (e.g., DC metro) at mid-day, and there can be some intervals of sun later today across Philly, NYC, and much of New Jersey as a warm front edges slowly to the north. The passage of the warm front has resulted in the influx of an uncomfortably humid (dewpoints in the 70’s) and warm air mass for the DC, Philly and NYC metro areas. A shortwave of energy will also play a role in the weather later today as it pivots across the region increasing upward motion and leading to an increasing coverage of showers and thunderstorms. Some of the rain that falls this afternoon and evening will be heavy at times and some of the thunderstorms can reach strong-to-severe levels with vivid lightning and damaging winds a possibility...timetable 1pm-8pm. Grounds are well saturated in much of the Mid-Atlantic region; especially, in and around the DC metro, and this raises the risk of flash flooding with this next round of showers and thunderstorms.
On Thursday, a surface cold front will approach from our northwest and this will combine with yet another upper-air disturbance to destabilize the atmosphere during the afternoon and evening (high CAPE values, steep low-level lapse rates, moderate shear). The main threats on Thursday will again be heavy downpours, vivid lightning, and damaging wind gusts, but large hail and even an isolated tornado cannot be ruled out. The risk of localized flash flooding will continue as well given the expected rainfall later today and the already well saturated grounds. Temperatures on Thursday are likely to climb to at least 90 degrees and humidity levels will remain at quite uncomfortable levels. Similar to today, the timetable for the severe weather on Thursday is 1pm-8pm in the DC-to-Philly-to-NYC corridor.
Very strong upper-level ridging will form in the eastern states by early next week leading to a surge of high heat and humidity in the DC-to-NYC corridor. This coming heat wave can result in temperatures reaching the 100-degree mark in the I-95 corridor during the first half of next week. Map courtesy ECMWF, Pivotal Weather
High heat and humidity on the way
While the weather has turned uncomfortably warm and humid today in the Mid-Atlantic region (and those same conditions will repeat on Thursday), the worst stretch of high heat and humidity will come in the period from later this weekend into at least the middle of next week. Very strong ridging in the upper part of the atmosphere that has been generally parked over the western states in recent days will push eastward this weekend and end up directly overhead in the Mid-Atlantic/Northeast US by the early part of next week.
A surge of heat (orange, red) reaches the eastern states during the early and middle parts of next week as strong upper-level ridging of high pressure develops overhead. Meanwhile, cooler-than-normal conditions (blue) dominate the western states as an upper-level low develops in that area. Map courtesy ECMWF, Pivotal Weather
As a result, the sweltering heat will first be felt early this weekend across the central Plains, Mississippi Valley and Great Lakes (e.g., Chicago in the middle 90’s for highs on Saturday), and then the intense heat and high humidity will reach the eastern states on Sunday (e.g., DC in the middle 90’s for highs on Sunday). That very strong ridge of high pressure aloft will be a slow-mover and likely remain located over the northeastern states into at least the middle of next week. This should translate to perhaps a 4- or 5-day period of high heat and humidity all along the DC-to-NYC corridor and 100-degrees is on the table.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com