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September 8, 2011

Somebody turn off the rain machine!

The epic rainfall that has hosed Central Maryland since Monday continued overnight. And it's not over yet.

Doppler radar rain estimateThe three-day total at BWI had reached 6.67 inches by midnight. We've had 5.74 inches here on the WeatherDeck in Cockeysville. But some locations have seen even more than that in just the past 24 hours.

The map at left is's Doppler radar estimate of rain totals for the 24 hours ending at 6 a.m. Thursday. No scale was provided, but you get the idea. 

Somehow, it was not a record. BWI reported 3.40 inches of rain Wednesday. The Baltimore record for a Sept. 7 is 3.84 inches, set in 1934.

Many roads are closed this morning by high water or fallen trees. The WeatherDeck, and the four developments around us, were an island last night, blocked by high water from all directions. I - and perhaps 100 of my neighbors - didn't get home to our families and pets until the waters receded at 10 p.m. And I'm told by police that at least one of the exits is blocked again this morning by a fallen tree.

And forecasters say the relatively narrow plume of tropical moisture being channeled our way from Florida by the remnants of Tropical Storm Lee is still aimed right for us. (That's Hurricane Katia swirling off the coast.)

Here are some 24-hour rain totals reported this morning by the CoCoRaHS Network:

Waldorf, Charles County:  8.71 inches

Catonsville, Baltimore County:  7.87 inches

Ellicott City, Howard: 8.49 inches

Crofton, Anne Arundel:  7.00 inches

Elkridge, Howard:  6.78 inches

Severn, Arundel:  4.12 inches

Towson, Baltimore County:  3.74 inches

Mt. Airy, Carroll: 2.08 inches

Here's another tally from the National Weather Service, showing an unofficial Parkville station with a storm total of 9.42 inches.

The rain totals map above shows the heaviest amounts smack on top of the Susquehanna River watershed, so we can expect to see historic flooding in Harrisburg, and serious worries for communities as far downstream at Port Deposit in Maryland. Here's some of the thinking from AccuWeather.

Posted by Frank Roylance at 6:52 AM | | Comments (5)
Categories: Flooding


I left the house yesterday am at 10:45 with about 3/4 inch rain showing on my rain gauge. Got home at 2pm to see it standing at 4.25 inches. Unreal.

My back deck registered 6.06 inches total for yesterday, and over an inch already this morning. Fortunately, no problems getting in and out of our neighborhood, and so far, no power problems either.

We've emptied our rain gauge twice in the past 36 hours in Riesterstown and it stops at 4 inches, meaning we've gotten at least 8 inches!

At least all this precipitation is not snow!!!!

The official CoCoRaHS total for Reisterstown through 7am this morning was 6.64". I'm inclined to think that is low for the area.

Frank. I'm looking at picking up some equipment and setting it up in my backyard so that I can make official measurements. I've looked at Oregon Tech and Davis Instruments. Do you have any recommendations? (I think I've asked this before) And is there a process for becoming an official station for the NWS?

FR REPLIES: I can only tell you that I use the Davis Vantage Pro2 station on the WeatherDeck and here at the paper. They have both done very well for five or six years. They can be set up to report to WeatherUnderground, making our data available online. The only glitch I've found is that the temperature and humidity sensors on the Sun's unit tend to wig out in major rain events (as they have this week) That hasn't happened at home. And I was unable to put the anemometers in sufficiently open spaces. Surrounding buildings shelter the spinning cups and reduce wind readings. But that's a siting issue, not a knock on the unit. You can read about the NWS Cooperative Observer Program here:

All you up there be glad temperatures are NOT at freezing or below.

1 inch of rain = 10 inches of snow.

This rain would be one heck of mega, mega, mega blizzard.

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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