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October 29, 2010

Freeze Watch tonight west of I-95

After a week that saw two record-warm overnight lows, autumn will come rushing back to Baltimore tonight as clear skies and diminishing winds allow radiational cooling to drop temperatures into the 30s.

NOAA/NWSForecasters at the National Weather Service's forecast office in Sterling, Va. have posted Freeze Watches (dark blue areas on the map) for Maryland west of the I-95 corridor (and east of counties that have already seen a freeze this fall):


UPDATE, 4 p.m.: The NWS has bumped the Freeze Watch to a Freeze Warning tonight (light blue) for Washington, Frederick and Carroll counties in Maryland, with overnight lows expected to reach 30 to 32 degrees. Earlier post resumes below:)

The forecast low for BWI-Marshall Airport overnight is 35 degrees. Westminster could see 34 degrees and Hagerstown's forecast shows a low of 32. It could get colder in the usual rural locations and low spots, producing the first freezing temperatures since last spring. Freeze Warnings and Frost Advisories may be issued for some locations later today.

The cooler weather is coming to us with high pressure that is drawing cold air out of the northwest on brisk winds. As the high moves to our south, winds will shift to the west and calm, allowing whatever solar heating we manage today to radiate back into space tonight. 

The weekend should continue sunny and seasonably cool with highs in the low 60s and overnight lows near 40 degrees.

Posted by Frank Roylance at 10:41 AM | | Comments (3)
Categories: Watches and warnings


"...the first freezing temperatures since last spring." Huh?!?!? Well, I woke up to frost last Saturday in Manchester, MD.

FR: A frost is not necessarily a freeze. Frost can occur when air temperatures are above freezing. We're also talking about Baltimore, which has the latest average freeze date in the state, thanks to the urban heat island effect..

Had frost right next to the pepper plants last Saturday morning; yet they still survived. I expect today is their last.......... Oh, my eggplants!

FR: Which reminds me of a song with the line, "You're standing in my kumquats!" Can anyone name the off-Broadway musical ? (No fair Googling it!)

The intermediancy and unpredictability of wind are two factors that negatively effect the ability of wind to become a constant reliable source for producing electricity. I have heard it quoted that the National Weather Service with its current meteorological data is unable to reliably predict wind velocity in an area more than two hours in the future. Can you comment on the accuracy of that report? Thank you

FR: Off the top of my head? Sure. Common sense would suggest that wind in any given location is not a constant source of power that one would want to bank on for reliable current. But it can supply the grid with supplemental power (as it is doing today on a large scale in many place in Europe), and can be useful in small, free-standing applications that don't require constant power, such as water pumps. Recently announced plans to connect offshore windfarms along the mid-Atlantic coast with a transmission "backbone" could also provide a way to harvest electrical power from a far-flung network of turbines that would be more reliable in the aggregate than any individual farm. Finally, I would challenge the accuracy of that (unsourced) statement about the NWS. Forecasters routinely make local wind speed forecasts two days in advance. But it's not clear to me why wind energy producers would need precise forecasts. The siting decisions are made based on long-term, empirical data on wind speed averages.

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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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