UPDATE (6:20 p.m.) Power is back on at George Mason University's Fairfax campus.

(5:37 p.m.) Now about 800 customers without power according to Dominion.

(5:12 p.m.) Add your storm photos and videos to this article or email to whitney@patch.com.

(4:53 p.m.): George Mason University's Fairfax campus is experiencing power outages. Call Mason Police at 703-993-2810 if you need help.

(4:13 p.m.): Dominion Power reports just under 600 customers without power in Fairfax City. Click here to see outages in your neighborhood.

(4:09 p.m.): Now back to a thunderstorm warning. Reports suggest tornado spotted near #Fairfax moving east. Warning done for #Fairfax, but NE still in effect. Follow @FairfaxPatch on Twitter for more updates.

(3:39 p.m.) Tornado Warning in effect until 4 p.m. Take cover.

(3:20 p.m.): Watch upgraded to a warning until 4:30 p.m. From Fairfax County EMAS:

"The National Weather Service indicates the storm is expected to enter Fairfax County at 3:30PM with 60-70MPH Winds. Expected to cross through Fairfax City at 3:45. Rainfall could be up to 1"-1.5"."

National Weather Service issued a severe thunderstorm watch until 10 tonight.

Move indoors and stay away from windows to escape hail, damaging gusts and cloud to ground lightning.

Click here for storm coverage and photos.

CORRECTION: NWS was not the initial source of the tornado allegedly spotted near Fairfax. That comes from police scanners and media reports. Not confirmed.