In for another soaking

Looks like Central Maryland will be in the chute again as stalled weather systems to our east and west conspire to channel a few more days of tropical moisture, showers, rain and thunderstorms this way.

With nearly 20 inches of rain in the bucket since the beginning of August, forecasters are saying we should prepare for as much as another 3 to 6 inches in the next few days. And the I-95 corridor could see the worst of it, if you can believe some of the forecast models.

"The model consensus for the axis of heavy rain fall is near the I-95 corridor, with west to east variability of this axis ranging from just east of the Blue Ridge to the Chesapeake Bay. Rainfall totals of 2 to 3 inches with isolated amounts of 4 to 5 inches are possible within this band, which is enough to produce flash flooding," said National Weather Service forecasters in Sterling, Va., in this morning's forecast discussion.

Flash Flood Watches are in effect for the entire Western Shore, from Frederick County east to the bay and south to the Potomac. "The best chance for the heaviest rain will be near and east of the I-95 corridor," the watch said.

UPDATE, 11:30 a.m.: A Flash Flood Warning was issued for portions fo Frederick and western Carroll counties as heavy rains crossed the area with rain rates of up to an inch an hour.

Eric the Red, a professional meteorologist in Baltimore and frequent contributor here, said this rain event won't compare with that from remnants of Tropical Storm Lee earlier this month, but he had this analysis to offer:

"Stalled upper-air low to our west and a stationary high to our east puts us between two spinning pinwheels, pulling all sorts of tropical moisture into our area. The problem with this forecast is there is no easy-to-identify trigger mechanism (no stalled front or tropical storm) ... so we're left with a ton of moisture, high rainfall potential, but nothing to grasp in terms of where this rain will fall. This is readily apparent in the models, which all have heavy rain falling, but they are all over the place as to where."

Wherever is falls, he said, "This rain will come down in torrents ... so be prepared to deal with street flooding and all the other fun that comes with this. Throw in the 10-15" of rain that has fallen over the past 2-3 weeks, and you can see why we're under a Flash Flood Watch."

Here's's take on what's ahead.

For the record, August ended with 10.38 inches of rain at BWI-Marshall Airport, the fifth-wettest on record for the city. Through midnight last night, the airport had received 9.57 inches. Three more inches this weekend would make this the wettest September on record for Baltimore, beating the 12.41 inches in 1934. 

We've had more than a foot of surplus (above average) rain since Aug. 1.

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