Flash Flooding & Severe Thunderstorms Possible Across Parts of the Mid-Atlantic on Monday

The last few runs of the high-resolution North American Model (NAM) continue to outline thunderstorms capable of dropping copious amounts of rain in a short period of time on Monday. 

The image below, courtesy TropicalTidbits is from the latest Sunday morning run of the NAM model, showing numerous showers and thunderstorms impacting the DC Region beginning during the morning rush hour and exiting the region during the late evening hours.

The Storm Prediction Center (SPC) has outlined the southern and eastern zones of the DC Region with a slight risk of Severe Thunderstorms.

Flash Flooding will be the main risk tomorrow, especially in low-lying, flood prone areas along the interstate 95 corridor.  The next two images show potential rainfall amounts (highly dependent upon where multiple rounds of convection travel over the same locations).  A general one to two inches of rain is possible with some locations possibly picking upwards of 2 to 4″ where thunderstorms train (travel over the same locations).

Wind Shear & Tornado Threat:

  • Currently the highest threat for rotating super cells is from east-central Virginia across the northern neck of Virginia. 

 

  • The tornado risk across northern Virginia, southern and eastern Maryland across the Chesapeake Bay into Delaware and southern New Jersey is not zero, but according the latest forecast models the threat in these location is relatively low.  Regardless, keep in mind that any severe thunderstorms that do develop are always capable of producing short-lived weak tornadoes with little to no warning. Pay close attention to any watches that are issued and be ready to seek shelter if a tornado warning is issued for your location.

Latest Forecast Sounding for the middle peninsula & eastern half of the northern neck of Virginia:

  • These are currently the locations with the highest CAPE, and bulk wind shear (0-6 km of 40+ knots).  The wind field in this forecast sounding also shows southerly flow rapidly becoming southwesterly and then westerly through the lower half of the troposphere.

Latest forecast sounding in Fairfax County:

  • Threat of isolated tornadoes within this sounding environment is not zero (see Psbl Haz. Type: “MRGL TOR”/marginal tornado conditions) with moderate wind shear values (0-6 km) of 34 knots.

 

  • Across Northern Virginia, DC & Suburban Maryland the main threat at this time appears to be heavy rain with the potential for flash flooding.

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