Timing Greatest Risk of Tornadoes on Monday

A strong low-level jet stream will be responsible for sustained southerly winds of 25 to 35 mph throughout the day on Monday with gusts over 50 mph (even outside of thunderstorms) which is why the National Weather Service has issued a Wind Advisory and/or High Wind Warning for portions of our area.

The latest high-resolution North American Model (image below) shows the first line of showers and embedded stronger thunderstorms crossing the interstate 95 corridor from Baltimore to DC to Fredericksburg at 09z (5am). The main threat from these storms will be damaging wind gusts but an isolated spin up tornado can’t be ruled out.

By 12z (8am) the next, stronger line of storms will be moving through the Shenandoah Valley and will be poised to cross the Washington Area around 15z (11am). The model indicates a potential break in the action around 16z (12pm) before the cold front crosses the region from west to east between 17z and 19z (1-3pm).  The thunderstorms along the cold front will coincide with the highest levels of EHI (Energy-Helicity Index), potentially spawning several longer tracking tornadoes across our region.

Note in the image above, the highest Energy Helicity Index (EHI) values are forecast to occur between 17z and 20z (1pm and 4pm) on Monday afternoon as the cold front is crossing our region.