Nor’easter Incoming followed by major Pattern Change

View of the National Mall from the Netherlands Carillon in Arlington, Virginia

A steady rain will develop late this afternoon into the evening hours arriving first in Fredericksburg and then moving northward into Washington and Baltimore.

The image above (courtesy TropicalTidbits) shows the latest North American Model “future-cast radar simulation” between 4 PM this afternoon and 4 PM Saturday.  Rain will pick up in intensity during the overnight hours before tapering off from southwest to northeast on between 6 AM and 10 AM.

How much rain could fall in your backyard?

The heaviest rainfall is expected from Fredericksburg into southern Maryland where up to 2″ could fall. A general swath of three-quarters to one inch of rain is expected elsewhere in our region.

Pattern Change

The upper-level pattern is going to flip with a ridge of high pressure building across the east and a trough digging into the west.  As a result, temperatures will climb each day next week with highs easily reaching the 90s as we head into the latter-half of the upcoming work week.

Image below is from the Global Ensemble Forecast System (GEFS) model and is showing you the atmospheric pressure anomalies at 500 millibars or about 18,000 feet above the ground.  Blue colors represent low pressure (lower heights/thinner atmosphere) and red colors represent an upper-level ridge of high pressure (thicker atmosphere & sinking air).

As you can see, temperature anomalies (departure from “average”) are easily correlated to the upper-level pattern:

As the upper-level ridge builds into the eastern United States, notice how the surface temperature anomalies (departure from “average”) soar… so as you are sweating your rear off next Thursday into the weekend… you will understand why.

On a side note, Mother’s Day is looking decent with partly sunny skies and a slight chance of an isolated shower during the afternoon.  Temperatures should make it into the lower 70s but a brisk northwesterly breeze will make it feel a bit chilly.  The good news is that it won’t be pouring down rain.  Have a fantastic weekend and Happy Mother’s Day to all the moms out there!


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