* Flash flood watch until 10 p.m. | Rainfall totals from NWS *

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Already 1-2 inches of rain have drenched the heart of the D.C. metro region, and we’ve only gotten started. Tropical storm Andrea’s heaviest rains still lie to our south, and are poised to deluge us late this morning through mid-evening.

The afternoon commute may be very slow and messy, with ponding of water on roads, and possible flooding of roads in low lying areas and near creeks and streams.

We expect the rain to taper off between 8 p.m. and midnight from southwest to northeast.

An additional one to three inches of rain is likely today, with locally heavier amounts.  Storm totals are now likely to be in the 3-6 inch range particularly along and east of I-95.  West of I-95 totals may be closer to 1-4 inches.

Additional rainfall predicted by the National Weather Service (on top of 1-2 inches which has fallen in the immediate D.C. metro area).

Flash flooding is a strong possibility, particularly in areas that tend to flood during heavy rain events in the area.  This includes low lying urban areas like Bloomingdale, and streams and creeks (e.g. Rock Creek).

Tropical storm Andrea is currently centered in northeast South Carolina and is trucking northeast at about 30 mph. Maximum sustained winds are around 45 mph mainly near and just east/southeast of the center.

Satellite view of tropical storm Andrea Friday morning (NASA)

Andrea should cross the mouth of Chesapeake Bay  late this afternoon and then zip northeastward paralleling the Delmarva coast before reaching a position off the central Jersey shore around 2 a.m. tonight.

Winds should not be a major factor for most of the D.C. area, with maximum gusts in the 20 mph range late this afternoon. Some stronger winds are possible closer to the storm center on the Delmarva Peninsula. See coastal impacts below.

Flood safety

Fairfax County’s emergency information blog features some excellent flood safety tips:

* Parents are reminded to keep children away from streams and rivers as they may overflow very quickly and with saturated river banks, playing near moving water is a dangerous situation.

Doppler estimated rainfall totals so far (through 9:30 a.m.) in the D.C. area.

* If you are in your car, remember “Turn Around; Don’t Drown.”  Water may be much deeper than you think, causing your car to stall or even get stuck in hidden debris; road beds may be washed out under flood waters. Just six inches of swiftly moving water can knock someone off their feet and approximately two feet of swift water can move or float most vehicles, including SUV’s and pickup trucks. Don’t get trapped in flood waters – find an alternative route.

Coastal impacts

Generally, the impacts from Andrea will worsen as you head east of Washington.  Rainfall amounts will tend to be a bit higher and winds will be stronger, especially in coastal areas – with some gusts reaching 35-45 mph.

Minor coastal flooding is expected with water levels 1-2 feet above normal.

Here’s a good infographic from the National Weather Service office serving southeast Virginia, the Maryland and Virginia beaches:

For those of you interested in effects in Delaware and New Jersey, follow this link: Andrea briefing for coastal Delaware and New Jersey