A Winter Weather Advisory has been posted for counties west of Baltimore, starting at midnight. It will be in effect through 2 p.m. Monday for Howard and Montgomery Counties, while it continues through 6 p.m. farther north in Carroll, Frederick, and Washington Counties. Farther west, it’s a Winter Storm Warning for Garrett and Allegany Counties that’s already in effect and will continue through Monday evening.
The next storm is already breaking out across Maryland. It’s a very long, strung out storm with a precipitation shield that extends from the driving low pressure system over Missouri all the way out to the Atlantic. This storm is picking up more moisture as it moves our way. At the same time, colder air is making a push down from New England. The real cold air (supporting snow) will cover New England down into Pa. However, cold enough air will make it into Maryland for the mixing battle zone to set up right over us once again. Basically, it’s going to be a messy mix for most of us – more or less, just a nuisance.
Like the last storm, the mixing line between wintry weather and rain will meander over Maryland right into Monday before all rain takes over from south to north during the day. A rain/snow mix will overspread the Baltimore region starting Sunday night, mixing with sleet and changing to more snow overnight. Then, it will mix with sleet again early Monday and eventually change to all rain during the day Monday. This process will happen quicker over the D.C. region, but will take longer the farther north and west you go. That’s why advisories and warnings have been posted, and are in effect through later in the day Monday the farther north and west you go.
The roads and paved surfaces have been significantly above freezing for a while. So there could be a slushy coating around Baltimore on the grass, cars, and houses. Where the colder air hangs on longer, 1-2″ is possible in Carroll and Frederick Counties. Again, most of that will be on the non-paved surfaces. Those amounts jump to 3-6″ in western Maryland with local areas of up to 8″ possible in some of the mountainous areas.
When the center of the storm gets closer Monday, it’s what will get the warmer push of air up and over the state – changing everything to rain. Rain will continue into the early morning hours of Tuesday before the front races off to the east. Temperatures will jump to the 50s Tuesday with sunshine returning behind the front. However, a new round of cold air will follow on Wednesday. It will create spotty late-day showers as it rushes in from the northwest. Highs will stop in the upper 40s/near 50 on Wednesday but only recover to the low 40s Thursday and stay in the 40s on Friday.