Threat of Heavy Rain Shifts as Tropical Storm Arthur Threatens Outer Banks

Tropical Storm Warnings Issued for the Outer Banks of North Carolina

Tropical Storm Arthur has now formed and the forecast for the week ahead in the Washington Area has improved substantially. However, the risk of rain has now shifted to later in the week which may also impact at least part of the upcoming Memorial Day Weekend.

The latest European Ensemble model below (courtesy Pivotal Weather) shows the blocking area of high pressure (bright red colors) holding strong over eastern Canada and nosing southward across coastal New England and the Mid-Atlantic through much of the upcoming work week.  This area of high pressure is slowing down the eastward progression of the cut-off low pressure system (blue circle over Tennessee). The key to the forecast in D.C. is how soon the area of high pressure breaks down and how quickly the cut off low pressure system weakens.

The Latest European Forecast Model

The image below shows the area of high pressure (at the surface) also holding strong across coastal areas of New England and the northern Mid-Atlantic states (NY, NJ, PA, MD, DE) through at least Wednesday. This is a significant change from yesterday’s forecast models.

However, the threat of some heavier rain may finally begin to inch its way further north and east toward the DC Area late Thursday into Friday .  In other words, we may pay for the dryer forecast (Monday through Thursday) in the short term with the threat of rain increasing Friday into at least a portion of the upcoming Holiday Weekend.

Threat of Heavy Rain Shifts South and West of Washington

The image below shows how the European Model has shifted the threat of epic rainfall totals (4 to 8″) south and west with each new run of the model.  You can see how strong the “nose of high pressure” is forecast to be across the big cities of the Northeast from Boston to Washington through Thursday.

Unfortunately flooding rains are going to still be a major problem this week from northeast Georgia to southwestern Virginia where 4 to 8 inches of rain may cause significant flooding. This is undoubtedly a tricky forecast for D.C. between Thursday and the unofficial kick off to Summer (Memorial Day Weekend).