The National Weather Service issued a Flood Watch for all of Fairfax County, including Vienna, warning that storms on Thursday could dump rain at 2 to 3 inches per hour and trigger flash flooding on roads, in low-lying areas and near creeks and streams.
The watch runs from 2 p.m. to 11 p.m. EDT.
A warm, moist air mass the NWS described as "tropical air" is sitting over the Washington, D.C., region, and forecasters say it could fuel torrential downpours and scattered severe thunderstorms. In a forecast released around 4 a.m. on Thursday, the NWS Baltimore-Washington office rated the severe storm risk as "slight" but warned that frequent lightning and damaging wind gusts are possible threats.
Damaging winds are the primary severe weather concern beyond flooding, according to Fairfax County Emergency Information.
Why it matters now
Fairfax County has absorbed multiple severe storms in recent weeks. In June, a microburst near Lake Royal in the Burke area produced winds the NWS confirmed at about 90 mph, snapping and uprooting trees that fell on homes, cars, roads and power lines. Nine families lost their homes in that storm, according to FFXnow reporting, though no injuries were reported. Then on Monday, another thunderstorm knocked out electricity for thousands of residents in Reston and Herndon and uprooted trees that crushed vehicles.
That recent rainfall also means the ground is already saturated heading into Thursday's storm window, raising the flash flood risk for urbanized areas along the I-95 corridor.
What to do
Fairfax County Emergency Information urges residents to:
- Turn around at flooded roads. Just one foot of moving water can carry away a car.
- Treat any downed power line as live and keep pets and children away.
- Charge phones and have a flashlight ready.
- Bring in loose outdoor items such as patio furniture, trash cans, and grills.
- Bring pets indoors.
- Go inside if you hear thunder.
The NWS advises residents to monitor forecasts throughout the afternoon and be prepared to act if Flash Flood Warnings are issued, which represent a step up in severity from the current watch.
How to report and stay informed
For life-threatening emergencies, call or text 911. Residents can report power outages, downed trees, or storm damage through the Fairfax County Storm Center at fairfaxcounty.gov/emergency/stormcenter. To receive future storm warnings and flood watches by phone or email, sign up for Fairfax Alerts at fairfaxcounty.gov/alerts.
