It sure isn't a lot of snow, certainly not by last winter's standards. But the first measurable snowfall of the season is getting off to a quick start and seems poised to mess up a perfectly nice evening rush hour commute.

UPDATE, 11:20 a.m.: The snow has begun falling in downtown Baltimore. If you're out there driving around, let us know if road conditions begin to deteriorate, or if highway crews are staying ahead of it. Send us a comment and describe. Thanks!

UPDATE, 12:20 p.m.: Foot's Forecast is calling for 4 inches in Annapolis; 2.5 inches at BWI-Marshall; 2.5 inches at Bel Air; 2.8 inches in Dundalk; 2.75 inches in Reisterstown.

By 12:30 p.m. the snow was sticking - or "laying," as they say in Baltimore - to city streets, and traffic was slowing down. Starting to become a traffic issue.

UPDATE, 2:45 p.m.: The NWS says they may lift the Winter Weather Advisory early as the storm moves rapidly to the east. But even as the snow stops, the cold will remain. That means icy patches will remain a hazard into tomorrow. More snow is possible for the weekend, but the computer models disagree on that. More later. Earlier post resumes:

Forecasters at the National Weather Service are predicting "about an inch" of snow for the northern tier of counties farthest from the Virginia storm track. But places south of that, and on the Eastern Shore, could see as much as 3 inches before it all winds down this evening. Temperatures are  forecast to remain in the upper 20s, making this an all-snow event for Maryland.

Snow was already falling at 10 a.m. in Washington, D.C. Here are the Winter Weather Advisories. And here's how the forecasts break down:

1 inch: Frederick, Carroll, Baltimore, Harford counties, including the cities of Frederick, Westminster and Baltimore. Beginning around 11 a.m., contiuing through the evening rush and ending around  9 p.m. "Travel difficulties... Be prepared for slippery roads and limited visibilities and use caution while driving."

1 to 2 inches: District of Columbia, Montgomery, Howard, Prince George's, Anne Arundel counties. Beginning in late morning, continuing into the early evening, and through the evening rush hour. "Travel difficulties ... Be prepared for slippery roads and limited visibilities and use caution while driving."

1 to 3 inches: Charles, Calvert and St. Mary's counties. Schools are closed. Snow is falling, will continue through the early evening. "Travel difficulties ...Be prepared for slippery roads and limited visibilities and use caution while driving.

1 to 3 inches: Dorchester, Wicomico, Somerset counties, Maryland beaches. SNow beginning in late morning, continuing into early evening. "Travel difficulties... Be prepared for snow-covered roads and limited visibilities and use caution while driving."

1 to 3 inches:  Southern Delaware, Talbot and Caroline counties. "Largest impact should be during the evening commute from school and work. Snow will accumulate quickly on untreated roadways as the ground is cold. The first widespread snow of the season normally causes numerous accidents. Please be very careful driving later today."

Eric the Red is agreeing with one model that sets the storm's "peak intensity" between 1 and 4 p.m., "and it's pretty much done by 7. A quick-hitting 1-2 inches seems likely now in central MD, closer to an inch in northern MD, and perhaps 2-3 inches south of BWI. Northern and Central VA are still looking at 2-4 inches, perhaps more. I think this is reasonable."

Here's Foot's Forecast. And here's the storm-total radar loop.

(SUN PHOTO: Clarksville, Md., Kim Hairston, Dec. 16, 2010)