Some light snow and bitter cold appear likely this week as winter finally arrives en force — if only for a while. Travel impacts are possible on Tuesday as much colder air pushes into the region.
A cold front will bring light snow to the Mid-South region overnight Monday into Tuesday morning. Minor accumulations are possible, though the trend is away from the more significant accumulations that once looked possible.
The Setup: There are two major features that are going to influence our weather going forward. The first is that area of low pressure off the coast of Florida. The second is the low pressure storm system that is diving southeast out of Canada.
That Canadian system will produce blizzard conditions across the Dakotas today, and winter storm warnings have been issued for much of the Great Lakes region. As it moves across the upper Midwest, it’s going to drag an attendant cold front behind it. That cold front will reach the Cumberland Plateau region Monday night.
Meanwhile, the low pressure system off the coast of Florida will track northeast through the Atlantic, and will be off the coast of North Carolina by late tomorrow. It’ll help influence the speed of that cold front as it races southeast towards the coast.
Ahead of all this, a southerly flow has kicked in here at home. That’s helping to drive up temperatures (we were at 42 degrees at 11 a.m., and will easily exceed forecast highs today) and we could hit 50 degrees on Monday. But it’s also going to help funnel moisture into the region; precipitable water values are modeled to go from around 0.4″ today to about 0.6″ late tomorrow night.
As temperatures crash behind the cold front, the forcing that results will turn that precipitable water into precipitation — first in the form of rain, as temperature profiles will initially be too warm for anything frozen — but quickly changing over to snow.
Impacts: When I last posted on Friday, I said this: “As of right now, the best guess is for 3-5 inches of snow here on the Cumberland Plateau. It wouldn’t surprise me to see more than that, if this system develops as forecast models are currently indicating it might . . . but, of course, this is still the Mid-South, so it also wouldn’t surprise me too much to see things change and cause us to wind up with less than that.” I also said that things would become clearer in the next 48 hours.
Well, 48 hours later, things have cleared up quite a bit — and, unfortunately for snow-lovers, the resulting picture isn’t a particularly pretty one if you’re looking for enough snow to get out and play in.
That low pressure system that is going to be off the coast of the Carolinas by late tomorrow just isn’t close enough to slow down the cold front enough for a significant snow event here on the Cumberland Plateau and points west. The progressive setup narrows the window for frozen precipitation, as everything moves out of the region by late morning on Tuesday.
The cold front will be slowing down as it approaches the mountains, which means that the East Tennessee valley, east of the plateau and towards the mountains, currently has greater potential for snow accumulation that is measured in inches than we do here on the plateau and west of the plateau.
That doesn’t mean that minor accumulations aren’t going to occur; it just means that significant accumulation isn’t expected. The best-guess for snow accumulation here on the northern plateau is currently 1-2″, but I’m currently of the opinion that 2″ might be on the high side. (Keep in mind that we’re still ~36 hours away from the onset of precipitation, so there’s still time for further changes.) Winds will be gusting, so blowing snow will likely occur. That snowfall could impact road conditions, because temperatures will rapidly drop to well below freezing. However, the impacts should be relatively minor, allowing for quick improvement as main roads are treated on Tuesday.
The drop in temperatures will be rapid. We may be near 40 degrees at midnight Monday night, dropping through the 30s and the 20s between midnight and 7 a.m. Temperatures in the upper teens to around 20 will persist through the morning before rebounding somewhat as the day progresses. Then, another cold front arrives on Wednesday to deliver even colder air. We may not get out of the teens on Wednesday afternoon, with lows dropping well into the single digits Wednesday night into Thursday morning. Sub-zero temperatures don’t currently look as likely as they did a few days ago, but it’s going to be quite cold.
Then, we rebound quickly. Thursday afternoon will see temps near or just above freezing, with temperatures pushing to 40 degrees on Friday and to near 50 degrees by Saturday!
Further out: Many meteorologists felt that Winter 2018-2019 was going to be a cold one in the eastern U.S., with potential for above-average snowfall throughout the Mid-South. Indeed, it became apparent in late December that the stratospheric warming was going to distort the polar vortex and send cold arctic air into lower latitudes.
As recently as a couple of weeks ago, it appeared the pattern we were moving into was one that was going to deliver cold conditions and multiple opportunities for snow into our region.
However, as I pointed out in a recent blog post, the lack of blocking in the northern Atlantic region, along with unfavorable phases of the Madden-Julian Oscillation (warm air that circles the globe in the tropics) was preventing winter from really tightening its grip on our region.
And that remains the case. The North Atlantic Oscillation, a measure of storminess in the northern Atlantic, remains neutral to slightly positive, which helps keep the pattern progressive. The Pacific North American ridge index, a measure of ridging in the eastern Pacific, is also neutral, indicating a lack of ridging that would help send cold air into the Southeast.
The overall result is that cold air isn’t getting locked into place, and the storm track isn’t getting shoved southeast. As a result, we’re seeing mostly seasonal temperatures here in the Mid-South, with rain instead of snow.
The wave of arctic air that’s coming this week has been obvious for a couple of weeks. But it isn’t going to stick around long because of that lack of blocking and the progressive pattern, which is why we rebound into the 40s and 50s by the weekend.
And the northwest storm track means we see more rain next week with a couple more storm systems that track north of us. We’re even looking at a warm spell as we get into February; we may see temps hit 60 degrees several days next week.
The true warmth won’t last; seasonal temps will return. But there doesn’t appear to be any more arctic air intrusions on tap for the next couple of weeks.
It’s impossible to say where things go after that. Famed winter meteorologist Joe Bastardi still feels that mid-to-late February will be brutal for the Mid-South. However, after we get through this two-week period, we’ll be knocking on the door of Valentines Day. By mid February, the sun angle is much higher in the sky, and accumulating snow has much less staying power. Warm air intrusions are becoming more common and winter is waning.
I’m not saying it’s going to be an early spring, by any means, but what once looked like a cold and snowy winter overall is starting to look as though it’s going to be a very bland, if wet, winter. I’m starting to believe that local school systems will end the winter season with a lot of their built-in snow days still in the bank.