Tuesday, August 31, 2021

Ida's Remnants to Impact Region

 Hurricane Ida battered portions of the Gulf Coast (particularly Louisiana) over the weekend and into the early parts of the work week. While the actual storm system is no longer a hurricane (or even a tropical storm)...the threat to life and property will continue into portions of the Mid-Atlantic and Northeast. 

The most substantial and widespread threat from Ida's remnants will be the flooding risk. There is a very large area with a high risk of excessive rainfall outlined by the WPC. Rainfall amounts of 6+ inches (locally even higher) will occur. The biggest risk for flooding will lie well north and west of the DC/Baltimore corridor. However, some risk for flash flooding will still be present due to the tropical airmass. 

A high risk of excessive rainfall is in place in portions of Pennsylvania and into the NE US.

Regardless of the placement of the heaviest rain...many areas have been receiving significant rainfall over the past few weeks. This may lead to flooding even in areas that do not get the highest totals.

Significant river flooding will become likely in the regions that receive significant rainfall. Big rivers like the Potomac may take a day or two (or longer) to crest. Therefore, flooding will remain a risk even after the rainfall ends. 

The next threat will be from tornadoes. The shear profile and instability will be conducive for bands of storms to form in the warm sector. Unfortunately, these parameters may line up just right for an elevated threat of tornadoes centered in the DC/Baltimore area and then over to the Eastern Shore. 

While 10% may not sound like a big risk - these are severe weather probabilities based on the background probability of a tornado within 25 miles of a point. Therefore, a 10% risk represents a SUBSTANTIALLY higher than normal probability of a tornado. This also is equivalent to the "enhanced" category of tiers from the Storm Prediction Center (SPC). 

A risk for tornadoes will exist in portions of the Mid-Atlantic tomorrow.

Synoptic (non-thunderstorm) winds may also be fairly gusty tomorrow. Some places may gust to 30-40mph at times. Places with saturated ground could see downed trees and power lines even in the absences of damage from storms. 

Updates will be provided as needed - be sure you and your family has a severe weather action plan in place.