There are two parts to this approaching storm. The first part is overspreading the state Sunday afternoon/evening. The second one is still hanging back over the Ohio Valley. Since the atmosphere was so dry to start (dewpoints in the 20s), a lot of this first part is simply reinforcing clouds, while moistening up the atmosphere but not supporting a lot of rain or snow–yet. That will change.
A Winter Storm Warning is now in effect for Garrett and Allegany Counties through Monday at 6 p.m. That’s where this storm may mix at times, but will mainly be snow with a few inches accumulating.
A Winter Weather Advisory is in effect through 6 p.m. Monday for Washington County. A second Winter Weather Advisory goes into effect for Carroll and Frederick Counties at midnight, and a third for northern Baltimore, Harford, Montgomery, and Howard Counties at 4 a.m. In these areas, the rain/snow mix will change to snow overnight. A slushy 1-2″ is possible, primarily on unpaved surfaces. When the sun comes up Monday, any road that did get a coating will become more wet than anything–even with some snow still coming down.
Closer to Baltimore, temperatures were in the 40s Sunday afternoon and are only going down to about freezing (maybe even stopping short a degree or so). So the rain/snow mix that will go to snow for a time will only create wet roads. There is the chance that we could see a slushy coating or maybe up to an inch in northern Baltimore County by the morning, but that would be on the non-paved surfaces. Then, the rain/snow/maybe sleet mix will continue to fluctuate over the metro area into Monday before this storm moves away Monday evening. And even though it will be a raw, chilly day, highs will be in the upper 30s – enough above freezing.
The rain will mix with snow south and east of the city, but it will mainly only create wet roads.
Winds out of the north will turn around to the northwest Monday night. Gusty winds will keep temperatures below average (with highs in the 40s) Tuesday and Wednesday, but it will be milder than Monday. There will still be a lot of clouds overall, with times of sunshine. Expect more sunshine as highs continue to climb closer to 50 Thursday, and then to the low 50s Friday.