*Not exactly soaking rain events for the Mid-Atlantic region, but we’ll take it...a couple chances of rain in the near-term from two separate cold fronts...late Thursday and again late Saturday*
Paul Dorian
While not particularly soaking rain events, rainfall amounts of 0.25-0.50 inches are on the table for each of these upcoming cold frontal passages and will be quite welcome for those in the Mid-Atlantic region. Map courtesy NOAA, tropicaltidbits.com
Overview
The month of August was not only quite a bit cooler-than-normal in the Mid-Atlantic region (e.g., coolest in 25 years for DC, 3rd coolest in 25 for NYC), but it was also very dry as well in many areas. In fact, the DC-to-Philly-to-NYC corridor saw virtually no rain during the last ten days of August and September has started off rain-free as well. There is some hope, however, in the near-term as there are two chances for some rainfall associated with two cold frontal systems. The first chance of showers and thunderstorms will come late tomorrow and tomorrow with the first cold front and another shot at some rain will come late Saturday with a second cold front.
The month of August was very dry across much of the Mid-Atlantic region and also cooler-than-normal. In fact, it was the coolest August in 25 years across the DC metro region, 3rd coolest in NYC, and the 6th chilliest since the late 1800’s across portions of SE PA such as Chester County (courtesy @ChescoWx).
Details
We’ve experienced some very dry stretches of weather in the Mid-Atlantic region during the past year or so including an October of 2024 that managed to produce virtually no rain at all in the Philly metro region. The just ended month of August was not only quite a bit cooler than normal in the Mid-Atlantic region, but it was also very dry as well in many locations with, for example, only 0.20 inches in the DC metro area (DCA). The month of September has seen a continuation of dry, comfortable conditions in the Mid-Atlantic, but the next few days will present some changes.
An initial cold frontal system will usher in an unseasonably chilly air mass into the Northern Plains/Upper Midwest/Great Lakes and it is likely to produce some well needed rainfall in the Mid-Atlantic region and Northeast US from late Thursday into Thursday night. Map courtesy NOAA, tropicaltidbits.com
To begin with, the overall humidity, which has been exceptionally low in recent weeks, will begin to become more noticeable again during the Thursday, Friday and Saturday time period. In addition, temperatures will climb back to more uncomfortable levels with mid-to-upper 80’s on the table in some spots for afternoon highs during the next few days.
A second cold front will usher in a reinforcing unseasonably chilly air mass into the central and eastern US and it is likely to produce some well needed rainfall in the Mid-Atlantic region and Northeast US from late Saturday into Saturday night. Map courtesy NOAA, tropicaltidbits.com
The increase in warmth and humidity on Thursday will come ahead of a cold front that will cross the Great Lakes and head towards the eastern seaboard. This front has ushered in a much cooler than normal air mass to the Northern Plains and Upper Midwest with temperatures some 15 to 25 degrees the averages for early September. This front will lose some of its punch as it arrives in the Mid-Atlantic on Thursday night, but it should still be able to produce some showers and thunderstorms...perhaps even a few strong thunderstorms and brief downpours; especially, to the west of I-95. Rainfall amounts of a quarter-to-half an inch are possible with this first cold front along DC-to-Philly-to-NYC corridor which - while not a particularly soaking rainfall event - will be quite welcome in the area.
A widespread much cooler-than-normal air mass will encompass much of the eastern half of the nation by the middle of the upcoming weekend. This air mass is likely to produce numerous record or near record lows from later this week into the weekend; especially, across the Northern Plains, Upper Midwest and Great Lakes regions. Map courtesy NOAA, tropicaltidbits.com
Meanwhile, a second cold front will push across the Northern Plains/Upper Midwest from later Thursday into Friday and it’ll usher in a reinforcing blast of unseasonably chilly air for those areas. This second cold front will push into the eastern states later Saturday and increase the chance here for some PM shower and thunderstorm activity with perhaps another quarter-to-half an inch on the table. Following its passage, the unseasonably cool air mass from the Northern Plains/Upper Midwest will spread eastward on Sunday into the Mid-Atlantic region and temperatures will return to well below-normal levels to close out the weekend and for the early part of next week.
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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