7:00 AM | **Wintry precipitation likely to arrive by Sunday evening with snow/ice accumulations possible**
Cloudy with periods of rain, after peaking early this morning, temperatures will fall through the afternoon hours
Cloudy with periods of rain and there is a small chance that the rain could mix with or change to sleet and/or snow after midnight before winding down to the N and W of the metro region, lows by morning in the low-to-mid 30’s
Becoming partly sunny, cold, breezy, low 40’s
Mostly cloudy, colder, upper 20’s
Becoming cloudy with snow arriving late in the day or early at night and then it'll mix with or change to sleet and/or freezing rain in the overnight hours, cold, upper 30’s
Mostly cloudy, cold, rain likely, mid-to-upper 40’s
Mostly cloudy, windy, cold, maybe some rain or snow early, upper 30’s
Partly sunny, very cold, low 30’s
An Arctic front that has been progressively sweeping across the nation will slow down and then stall out today in a southwest-to-northeast fashion near the east coast allowing for a couple waves of low pressure to ride along its temperature gradient boundary zone. The first wave will generate showers around here today, and as the colder air continues to filter into the region in the overnight hours, there is a small chance that the rain could mix with or change to sleet and/or snow in the northern and western suburbs before ending.
After a break in the action on Saturday, a classic "cold air damming" event will take place on Sunday and Sunday night. Another wave of low pressure will spread wintry precipitation into the region by Sunday night that should change to plain rain by Monday. The current thinking on the timetable and precipitation type is as follows (subject to change): snow is likely to arrive by early evening and then it should mix with or change to sleet and/or freezing rain later Sunday night before a change to plain rain early Monday. Accumulations of up to a couple of inches of snow and ice are possible on Sunday night and travel can get tricky for awhile as there is likely to be an extended period with temperatures near the freezing mark. By early Monday, milder air should win out along the I-95 corridor where the precipitation is likely to fall as plain rain, but not too far to the north and west of the big cities, frozen precipitation could linger. By Tuesday, the next Arctic invasion will begin and very cold conditions will persist through the mid-week in the Mid-Atlantic region as well as across much of the country. [A detailed video description of "cold air damming" is available on our "Meteorology 101" page].
One final interesting tidbit: there is a report this morning that the 8am average temperature across the continental US was 18.1 deg F which is colder than at any time during last winter. According to weatherbell.com, the lowest average CONUS temperature at any time last winter was 18.9 deg F.