The first accumulating snow of the season has arrived in the DC metro region and it will move into the Philly metro region by late morning or early afternoon and then reach New York City by late afternoon or early evening. The general scenario at all three metro regions will be for a several hour period of accumulating snow followed by a several hour period with icing (i.e., sleet and/or freezing rain) and this will add a layer of ice on top of the snow. Finally, enough milder air will move in to change all of the precipitation to plain rain later tonight and early Monday from the immediate I-95 corridor to the coast. Areas north and west of I-95 will see a longer period of frozen precipitation perhaps into the early morning hours on Monday.
Snow accumulations of 2-4 inches can be expected across the DC metro region and I believe this 2-4 inch range, perhaps even isolated 6" amounts, will extend northward to the region between Philly and New York City based on current radar observations which suggest a heavier band of snow will set up later today in that region. Travel conditions will deteriorate for an extended period of time into the overnight hours in all three metro regions given the accumulating snow and ice and with surface temperatures holding at or below the freezing mark. By tomorrow morning, plain rain should help to improve travel conditions along I-95 and to the coast. Stay tuned, tricky forecast.
One final note, there will be snow and/or bitter cold across the board today for the NFL in places like Philly, Baltimore, DC, Green Bay, Denver, etc., etc.
The average temperature at 9am this morning across the continental US was 18.0°F which was nearly a degree colder than the lowest average CONUS temperature recorded all of last winter – and winter hasn’t even begun yet. While much of the nation has been in a deep freeze, the Mid-Atlantic region has been quite mild for the past couple of days, but colder air is now oozing into this part of the country following the passage of an Arctic front. Around here, our temperatures will continue to gradually drop this afternoon and evening as rain continues to fall from one wave of low pressure riding along the stalling Arctic frontal boundary zone. By late tonight and early Saturday, it could get just cold enough in the northern and western suburbs for the rain to mix with or change to ice and/or snow before ending early Saturday. More significant snow will fall later tonight across places like central and northeastern Pennsylvania and skiers will be happy for that.
After a break in the action on Saturday, a classic “cold air damming” event will take place on Sunday and Sunday night in the Mid-Atlantic region where cold air funnels southward from high pressure situated to the north. Snow is likely to break out in the morning across the DC metro region, then by mid-afternoon in Philly, and by early evening in the NYC metro region. The DC region could see snow accumulate in the 2-4 inch range before a changeover to sleet and freezing rain adds a singificant layer of ice on top of the snow. The Philly and NYC metro regions could see snow accumulations on the order of ½ to 2 inches before a changeover to sleet and freezing rain adds a significant layer of ice on top of the snow in those locations. Travel conditions will no doubt be adversely affected for an extended period of time during this event in much of the Mid-Atlantic region from Virginia to New York as temperatures hold at or below the freezing mark and significant icing results. Ultimately, by late Sunday night/early Monday, the wintry precipitation changes to plain rain along the immediate I-95 corridor and to points south and east, but it is still a pretty close call and frozen precipitation will very likely last into early Monday just to the north and west of the big cities.
Cloudy with periods of rain, after peaking early in the day temperatures will fall through the afternoon reaching the mid 40’s by day’s end
Cloudy with periods of rain, there is a small chance that the rain could mix with or change to sleet and/or snow after midnight well to the N and W of the District before winding down, lows by morning in the low-to-mid 30’s
Becoming partly sunny, cold, breezy, low 40’s
Mostly cloudy, colder, upper 20’s
Cloudy with snow arriving during the morning hours then mixing with or changing to sleet and freezing rain, up to a couple inches of snow and ice accumulations are possible on Sunday with tricky travel conditions for awhile, mid 30’s
Mostly cloudy, cold, rain likely, mid 40’s
Mostly cloudy, windy, cold, chance for some rain or snow early in the day, mid 30’s
Partly sunny, very cold, near 30
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 periods of rain around here today and tonight 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 far 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 on Sunday that will continue into Sunday night before changing to plain rain. The current thinking on the timetable and precipitation type is as follows (subject to change): snow is likely to arrive during the morning hours and then it should mix with or change to sleet and/or freezing rain before a change to plain rain later Sunday night. Accumulations of up to a couple of inches of snow and ice are possible on Sunday and travel can get tricky for awhile as there is likely to be an extended period with temperatures near the freezing mark. By 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.
1:45 PM | **Amazing weather across the western 2/3 of the nation; two chances for wintry precipitation in the Mid-Atlantic region this weekend**
Quite an incredible weather pattern across the western two-thirds of the nation during the past couple of days and some of the fun will spread to the eastern states this weekend. From California to Texas to the Great Lakes, there has already been an influx of brutal Arctic air and some of these areas have received a boat load of snow to go along with it. In addition, one of the worst ice storms in years is now unfolding in the region between Texas and Kentucky and icing problems are likely to hit the Mid-Atlantic I-95 big cities later this weekend…more on that threat below. Here are a few of the highlights of this amazing winter weather across the nation in the last 48 hours or so:
1) West Yellowstone, Montana reached 31 degrees below zero
2) Denver set a record low on Wednesday of 13 degrees below zero which shattered the old record by a whopping 8 degrees. Denver bottomed out at 15 degrees below zero this morning which is the coldest ever this early in the season. All of this bitter cold was accompanied by several inches of snow in the metro region.
3) Record low temperatures, frost and hard freezes hit California this morning and will again early tomorrow. Also, significant snow will fall in some of the California higher elevations later today and tonight.
4) More than 30 inches of snow fell in some areas between the Colorado Rockies and upstate Minnesota.
There are two shots at wintry precipitation in the I-95 corridor between DC and NYC during the upcoming weekend. The first shot will come late Friday night/early Saturday morning as rain winds down from one low pressure system. Temperatures will likely peak tomorrow morning and then will drop during the afternoon and evening hours on Friday in this region. By late tomorrow night, just as the precipitation is ending, it is possible that the rain mixes with or changes to sleet and/or snow in the northern and western suburbs of the big cities.
The second threat comes on Sunday and this one is a more significant threat than the first one. This appears to be setting up as a classic "cold air damming" event with very strong Arctic high pressure system situated in the Northeast US by Sunday that will act as an anchor for dense, cold low-level air which will be able to penetrate southward on the eastern side of the Appalachian Mountains. Snow, sleet and freezing rain is likely to reach the DC metro region on Sunday morning, and then Philly by Sunday afternoon, and New York City by Sunday evening. The snow will likely not be a big player in these areas during this upcoming event; however, the icing could last for an extended period as temperatures will only grudgingly rise above the freezing mark. By late Sunday night or early Monday, enough milder air should move into the big cities to change the precipitation to plain rain, but it is still a close call, and areas just to the N and W of I-95 may hold onto frozen precipitation for awhile longer on Monday. More Arctic air moves into the Mid-Atlantic region for Tuesday and Wednesday.
Finally, it is not often one sees a 6-10 day temperature forecast by NOAA (above) with colder-than-normal weather (blue) expected from coast-to-coast.