12:00 PM | **Heavy rain and strong wind gusts late tonight/tomorrow morning aided by a powerful upper-level jet streak**
Paul Dorian
The “right entrance” region (circled) of an intense upper-level jet streak is favorable for strong upward motion which will contribute to strong wind gusts at the surface and heavy rainfall; courtesy NOAA, tropicaltidbits.com
Overview
Another soaking rain event is headed to the DC-to-Philly-to-NYC corridor and heavy rain tomorrow morning will be aided by a powerful upper-level jet streak. Showers will begin this evening and then evolve into a steadier and heavier rainfall after midnight and then the rain can come down heavily at times from late tonight through the morning hours on Thursday. In addition to the heavy rainfall, winds will become an important factor late tonight and on Thursday with gusts possible past 40 mph as warmer air surges northward along the eastern seaboard. Temperatures will rise in the overnight hours perhaps peaking well into the 50’s tomorrow morning, but will then drop sharply later tomorrow afternoon following the passage of a strong cold front.
The 12Z NAM surface forecast maps from 7AM on Thursday to 1PM in hourly increments with a band of heavy rain (yellow) pushing through the I-95 corridor; courtesy NOAA, tropicaltidbits.com
Details
Low pressure is pushing northeast today over the Upper Midwest with significant snow on its north side (e.g., Wisconsin, Michigan) and rain to its south and east. This low pressure system will be over Quebec, Canada by early Thursday and will drag a strong cold front through the DC-to-Philly-to-NYC corridor. There should be nothing more than a little light rain late today and scattered showers early tonight, but then the rain will become steadier and heavier after midnight. Heavy rain is likely from late tonight through tomorrow morning and there can even be a rumble or two of thunder.
In addition to the rain, another important factor in this upcoming event will be the winds as they will strengthen noticeably late tonight from a south-to-southeast direction and continue to be very gusty on Thursday morning - perhaps past 40 mph. Warmer air will surge northward along the eastern seaboard in the overnight hours and temperatures are likely to rise through the 40’s and perhaps peak well up into the 50’s tomorrow morning. Temperatures will then fall sharply later tomorrow afternoon following the passage of the strong cold front and the 30’s are quite likely by day’s end with a shift in wind direction to the northwest. It’ll be quite cold on Friday and Saturday in the Mid-Atlantic region with temperatures well below-normal for this time of year despite plenty of sunshine each day.
One of the contributing factors to the strong winds and heavy rainfall expected around here will be a powerful jet streak located in the upper part of the atmosphere (~250 millibars). The Mid-Atlantic will be located in a favorable position for strong upward motion on Thursday morning in the “right entrance” region of an intense 250-mb jet streak. The strong lifting motion in the atmosphere should be sufficient to generate locally intense rain bands along with a possible rumble or two of thunder. Rainfall amounts should exceed 1 inch in most areas on Thursday and perhaps as much as 1.5 inches with most of it coming in a brief 3-6 hour window. Given the current cold soils, months of soaking rainfall, and possible intense rain rates on Thursday morning, the potential for localized flooding seems quite high and flash flood watches have been posted by the National Weather Service for the entire DC-to-Philly-to-NYC corridor.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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