10:00 AM (Wed.) | *Upper-level low spinning over the Carolinas finally edges north and brings a wet pattern to much of the Mid-Atlantic…another significant upper-level low to have an impact next week*

A loop of GOES-16 satellite imagery in the “natural color” RGB band is a great way to distinguish between low and high-level clouds. As a result, it is quite easy to see the upper-level low spinning over the central part of North Carolina. Images courtesy NOAA, College of DuPage

Overview

There is a surface low pressure system this morning near the Outer Banks of North Carolina and satellite imagery clearly shows an upper-level low spinning over the central part of the same state. This upper-level has resulted in substantial rainfall in recent days across the Carolinas and westward to West Virginia and southwestern Virginia and it is about to finally make a move to the next.  As a result of this movement, showers will move into the DC metro region later today and likely edge into Philly later tonight or early Thursday and once the threat of rain arrives, it’ll likely stick around all the way into next week.  In fact, another significant upper-level trough of low pressure is likely to push into the Great Lakes/Mid-Atlantic/NE US by the middle of next week and this will more than likely continue the wet pattern that is unfolding for this part of the nation.

The upper-level low that has been “cut off” over the Carolinas in recent days will finally make a move to the north over the next 48 hours. Another significant upper-level low will likely drop into the Great Lakes/Mid-Atlantic/NE US by the middle of next week. Maps courtesy NOAA, tropicaltidbits.com

Discussion

High pressure stretches this morning from the Great Lakes to New England and it has resulted in a very comfortable stretch of weather for these two areas and also for the Mid-Atlantic region from around DC north and east.  Meanwhile, an upper-level low has been spinning over the Carolinas in recent days producing copious amounts of rainfall for the Carolinas, southern Virginia, and portions of West Virginia and this nearly stationary system is finally going to make a move to the north.  As a result, a wet weather pattern will develop for the Mid-Atlantic region from DC north and east which has largely escaped any rainfall in recent days.  As the upper-level low will only slowly edge to the north, the shower threat will first increase markedly in DC later today then later tonight/early tomorrow in the Philly metro region.  The threat of showers is likely to arrive in NYC tomorrow night and Friday. 

Once the shower threat arrives in the DC-to-Philly-to-NYC corridor it looks like it’ll stick around into next week. In terms of rainfall, showers and thunderstorms will be “diurnally-driven” and more likely to form in the afternoon and evening hours over this time stretch as daytime heating will be needed to destabilize the atmosphere.  Given the expected increase in overall moisture, the threat for some moderate-to-heavy rainfall will be pat of this unsettled weather pattern and we’ll have to monitor the prospects for flash flooding over the next few days in areas where there is potential of “repeated” rainfall (e.g., central Virginia). 

A wetter pattern is unfolding for much of the Mid-Atlantic region that has experienced generally rain-free conditions and cool weather in recent days. Forecast map of total rainfall amounts next 7 days courtesy NOAA, tropicaltidbits.com

In terms of temperatures, at the same time the shower chances increase in the I-95 corridor, a warming trend will take place and the overall humidity levels will rise noticeably. Temperatures have been cooler-than-normal for the past several days in DC, Philly and NYC and they should hold again at below-normal levels this afternoon; especially, where clouds will dominate the skies such as in DC and Philly. The warming trend that is coming to the I-95 corridor will likely result in highs well up in the 80’s by the latter stages of the weekend. 

The recent stretch of colder-than-normal weather continues today across the Southeast US and much of the Mid-Atlantic. Another colder-than-normal air mass dominates the interior northwestern part of the nation where snow has fallen in states like Idaho, Wyoming and Utah. [Map courtesy NOAA, weathermodels.com, Twitter Chris Martz Weather]

By the middle of next week, another vigorous upper-level low pressure system will drop southeastward from southern Canada and head towards the Great Lakes.  This system is likely to be another slow mover, but it’ll likely expand to the Mid-Atlantic and Northeast US by next Wednesday or Thursday.  The effect of another upper-level low will be to extend the unsettled weather conditions from the Great Lakes to the Northeast US and southward to the Mid-Atlantic region and temperatures could return back to below-normal levels for a few days.  The bottom line with respect to temperatures is that no sustained hot weather (i.e., 3 or more days of 90+ degrees) is yet in sight for the DC-to-Philly-to-NYC corridor.     

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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