* Winter weather advisory Frederick, Howard, Carroll, and Baltimore counties tonight *

After reviewing this morning’s model data, our general ideas for tonight’s snow event haven’t changed.  Here’s the basic story:

* Patchy areas of rain, sleet, and/or snow begin between mid-to-late afternoon and early this evening (snow is more likely initially in colder areas to the west and northwest, with rain more likely in the city and south and east).

* The mix of precipitation changes to light snow everywhere this evening with little or no accumulation through 8 to 10 p.m. as temperatures will mostly be above freezing. The possible exception is colder areas to the west and northwest of the District, where some slick spots may develop.

* A brief period of accumulating snow is possible, mainly between 10 p.m. and 2 a.m. tonight, possibly continuing until around 4 a.m. in east and northeast suburbs.  Temperatures will fall into the 20s during this time, causing roads to freeze.

* In terms of accumulation, the general forecast range for the D.C. area  is a dusting to 2″. Best chance for 2″ is northeast of D.C. as you get into the Baltimore suburbs. From around downtown and to the west and southwest accumulations are more likely around 1″ and could be as little as a dusting.

Snowfall forecast map issued 10:45 a.m. Thursday morning. (Version 3 The main change from earlier versions is to orient the increasing snowfall from west to east rather than south to north.

* Very small changes in the storm development could change totals upwards or downwards.  The cutoff in accumulating snow is expected to be sharp, so the highest bust potential is in northern Virginia – which could get accumulating snow, or next to nothing.

* Heading out the door Friday morning it will be extremely cold with temps in the teens to near 20, winds gusting to 30-40 mph, and wind chills in the single digits and even below zero in spots.

Wes Junker, Capital Weather Gang’s winter weather expert, summarizes the event this way:

We’re still leaning towards a dusting to 2″ inches across the DC area with heaviest likely northeast of the city and the lightest amounts to the south and west of the city. This remains a tricky forecast for the city and points east as the amount of snow that accumulates will depend on how quickly the temperatures drop as the snow is falling tonight. While this will not be a big storm in terms of accumulations, it will likely produce enough snow to make the roads and sidewalks slick late tonight into tomorrow morning because of the sharp drop in temperatures expected across the region.