****Atmosphere about to "re-ignite"...another round of showers and thunderstorms on the way with flooding downpours on the table (again)...break in the humidity from Friday into Saturday****
Paul Dorian
One measure of atmospheric instability is known as the Convective Available Potential Energy (CAPE) and it is quite high in the Mid-Atlantic region raising the chance of flooding downpours and strong-to-severe thunderstorm activity. Map courtesy NOAA/SPC
Overview
The combination of a tropical air mass, a stalled-out frontal boundary zone, and an upper-level disturbance will “re-ignite” the atmosphere this afternoon and the result is very likely to be yet another round of heavy showers and strong thunderstorms for the DC-to-Philly-to-NYC corridor. With the likelihood of flooding downpours and the well saturated grounds, flash flood watches have been issued throughout the Mid-Atlantic region by the National Weather Service. This stalled-out front system will turn around by tomorrow and push to the north as a warm front and the heat and humidity should reach a peak in the afternoon with highs well up in the 90’s in many places. A cold front then crosses the Mid-Atlantic region from tomorrow night into early Friday – potentially with another round of showers and thunderstorms – and its passage will pave the way for much more comfortable conditions from later Friday into Saturday. The humidity does build back up again for the second half of the weekend and the chance of showers and thunderstorms will also make a return.
Showers and thunderstorms are likely in the I-95 corridor during the 5-11pm time period and flooding downpours are on the table. Map courtesy NOAA, tropicaltidbits.com
Details
Here we go again...the atmosphere is very moist and quite unstable and the arrival of an upper-level “short-wave” this afternoon will be the catalyst for the development of clusters of showers and thunderstorms. These showers and thunderstorms will first form across the central and western Mid-Atlantic regions and then slide slowly east to the DC-to-Philly-to-NYC corridor with a timetable in the I-95 corridor from around 5pm to midnight (an isolated shower or thunderstorm possible beforehand). Given the entrenched high humidity and the expectation of strengthening upward motion, heavy downpours will once again be on the table and flash-flooding will be of high concern. Any thunderstorm that forms later today can produce an inch or two of rainfall in just an hour or so and local amounts of 3-4 inches are certainly on the table in the Mid-Atlantic region.
Flash-flooding is on the table once again with another round of showers and thunderstorms on the way to the DC-to-Philly-to-NYC corridor. Map courtesy NOAA/SPC
The stalled-out frontal system that plays an important role in the destabilization of the atmosphere later today will turn around and advance northward as a warm front by later tonight and early Thursday. On the back side of the warm front, Thursday afternoon is likely to see the peak of the heat and humidity for the week with many spots featuring high temperatures well up in the 90’s. The next front to deal with will be a strong cold front that approaches and then crosses the area from later tomorrow night into early Friday…possibly bringing us yet another round of showers and thunderstorms.
Much more comfortable conditions are headed to the Mid-Atlantic region for the Friday into Saturday time period…humidity will rise again quite noticeably for the second half of the weekend. Map courtesy NOAA, tropicaltidbits.com
That cold front should have enough push behind it (a strong Canadian-born high pressure system) to clear the east coast on Friday morning paving the way for much more comfortable conditions in the Mid-Atlantic region lasting from later Friday into Saturday. The humidity will tend to build back up again on Saturday night and Sunday and the chance of showers and thunderstorms will also return as another frontal system approaches the area. One final note, there continues to be no intense heat in sight for the Mid-Atlantic region.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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