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September 20, 2009

Coldest morning since ...

The National Weather Service thermometer at Baltimore-Washington International Thurgood Marshall Airport dropped to an official 47 degrees this morning. You can credit clear skies amid dry Canadian high pressure, and radiational cooling. All the warmth we built up under Saturday's WeatherDeckperfect blue skies just radiated back out into space overnight.

Lows in the 40s felt pretty darn cold if you went to bed with the windows open last night. But it was still 5 degrees short of the record. The coldest morning for Baltimore on a Sept. 20 is 42 degrees, last reached on this date in 1959.

The last time we were this cold at the airport was back on June 1, when the mercury touched 46 degrees.

We reached 44 degrees out here on the WeatherDeck in Cockeysville (left). And there were some even colder readings across the region - as low as 41 degrees just over the Pennsylvania line. Sunshine today will bring us back into the 70s. Another fine late-summer afternoon; of course, it can't last.

The high pressure system is moving off the coast today, and we will come into the return flow of the clockwise circulation around the center, bringing us increasingly warm and moist air.

That will mean more clouds, and eventually rising chances for rain and showers as the week rolls along. 

Posted by Frank Roylance at 9:54 AM | | Comments (1)
Categories: By the numbers


You may have addressed this before. If so I apologize for missing it.


I'm sure that your weather fans would like to know about all of the equipment that went into creating the WeatherDeck in Cockeysville.

Each time you mention your WeatherDeck, your weather followers get just a tad bit jealous.

Let us know all about the big WeatherDeck package and how we could create a WeatherTerrace, a WeatherRoof, or better a WeatherWindowLedge.


FR: Sure. The WeatherDeck is my rear deck, overlooking the scenic Cockeysville Swale. Back in 2004, I installed a Davis Instruments Vantage Pro 2 wireless weather station. It consists of a tipping bucket rain gauge, thermometer, barometer, hygrometer, wind vane and anemometer. The solar-powered outdoor unit transmits every few seconds to the C-cell-powered indoor console, which also measures indoor temperature and humidity.

The console displays all this information, and calculates relative humidity and dew point. It also records the data and displays it in a graphic display, along with moon phase, current-weather icons, and some pretty comical crawls, such as "It's raining cats and dogs!" (Meteorologist humor...)

It is also capable of forecasting the weather based on changing conditions, but I've never thought much of that feature. And, you can set up a number of alarms that will alert you to excessive rain or wind or whatever.

Davis also offers a cabled data logger that will dump all the information from the indoor console onto your PC, where it is displayed in a very good set of graphic environments. We use that feature at The Sun, which uses identical equipment that is automatically downloaded to Weather Underground (go to, but I have never seen the need for it on The WeatherDeck. (I'm also too cheap to spring for the data logger.)

These units run about $600 for the basic features, and can be enhanced with a variety of add-ons. There are other makes and models out there, but these have worked well for me for a number of years. For more on The Vantage Pro 2, go to

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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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