Capital Weather Gang's Angela Fritz has your forecast and snow accumulation predictions as D.C. enters a state of emergency in response to a major storm heading toward the District and the Mid-Atlantic region. (Ashleigh Joplin,Angela Fritz/The Washington Post)

Blizzard warning starts at 3 p.m., federal government closes at noon

Concluding thoughts: Tonight’s models mostly cemented the idea that an extreme snowstorm is about to occur in the region. The way in which the system is presently developing also argues for the unbelievably-high totals to occur somewhere in this event. That somewhere could be here or very close by.

[Blizzard Warning: High winds, about two feet of snow forecast for D.C. area]

Arguably the main takeaway from tonight’s information is to prepare for an earlier than previously advertised onset with snow. It may be into the immediate area by noon or so, give or take an hour. Across the entire area, we’re looking at the potential of generally a near noon to 2 p.m. start time. Snow sticks quick, and intensity picks up as well. Plan on being where you need to be by mid-afternoon or so.


Our eventual blizzard beginning to take shape this evening over the southern United States. (NASA)

Snow piles up into the night and may become supercharged for a time early Saturday. Then it just keeps snowing into Saturday night. Temperatures may stay in the 20s tomorrow, and through the storm for most spots. A greater chance of near-freezing and perhaps a mix comes in further southeast. We’ll need to watch the potential of a “dry slot” that could cut off precipitation for a time.

All signs continue to point toward a snowstorm that has the potential to be extremely dangerous and even life threatening. Please do plan on the potential of both power outages and being stuck at home for several days at minimum.

At various grocery and hardware stores, it's better to be safe than sorry as D.C. residents fill up on winter storm essentials. For some, that means everything from bread and beer to rock salt and firewood. (Jorge Ribas/The Washington Post)

Overview: As a winter storm begins to take shape over the Gulf states, the blizzard that is expected to focus on our region becomes increasingly real. Blizzard warnings go active in the D.C. area at 3 p.m. Friday and run through 6 a.m. Sunday. Blizzard conditions are also possible across a broader part of the northeast that includes Philadelphia and New York City. The coming snow and wind are just parts of the concern up and down the coast in this historic event.

[Poll: Help us name this winter storm!]

Snow totals in our area are forecast to be at least 16 inches, with 24 to 30 inches or so possible in some spots, especially north and west of the District. Lesser amounts are likely in southern Maryland where snow is more likely to change to a wintry mix for a time. Please see our detailed storm post for all the key timing and impact information.

Over the next few hours we’ll examine the upcoming blizzard. Since it’s beginning to take shape, in addition to weather models that roll through about midnight, we’ll take a look at some of the current happenings. At conclusion we will post updated thoughts as we continue to fine tune the forecast for what will likely be an extreme snowstorm.

11:50 p.m. update: Precipitation is already approaching parts of the Mid-Atlantic as the low strengthens over the South.


(NOAA)

In addition to the NAM and GFS hinting at an earlier start time, the short range HRRR and RAP models are doing so as well. Both of these models simulate snow rapidly moving through the area at noon.


(Weatherbell.com)

(Weatherbell.com)

Temperatures are forecast to struggle to freezing tomorrow, staying in the 20s most spots.

This storm should be considerably colder at onset than Snowmageddon (Feb 5-6, 2010) especially in the city. More like the December storm that year which had powdery snow from the start. Rather than flakes that struggle to stick for a while, everyone should see conditions deteriorate fairly rapidly once snow begins.


GGEM snowfall forecast. (Weatherbell.com)

11:35 p.m. update: We’re starting to run out of “early” evening models. Another is in though. This time, the Canadian GGEM (it’s a cousin to the shorter range RGEM below). They’re all showing the same crippling event that’s been advertised. At this point it seems to be a matter of how far up the yard stick the snow will fall. Someone might need more than a yardstick.

If you’re still with us, a quick update on where the storm is in a few, then some thoughts to wrap up.

11:20 p.m. update: Since it might have gotten lost with the other rapid-fire updates on the mega snow shown on the GFS, it’s worth reiterating start time. The newest set of modeling suggests accumulating snow is in the region in the noon to 2 p.m. timeframe. Please strongly consider that as a possibility when making plans. If anything it seems storm onset is often quicker than anticipated. Not a hard rule, but it often works.


GFS simulation of the upcoming snowstorm. (Weatherbell.com)

11:05 p.m. update: Since the GFS depiction is perhaps the most extreme model snowstorm we’ll ever see, you might want to save the loop above to your archives. It’s somewhat hard to buy the widespread mega totals in entirety but most signs continue to point toward a top 5 type of snowstorm in D.C., at the least. There’s certainly a signal for a generational or greater snow event starting tomorrow.


(Storm Vista Weather Models)

10:50 p.m. update: When crazy forecasts get crazier. Meteorologists and weather watchers around the region are left in awe by the new GFS run. Our winter weather expert Wes Junker says, “I’ve never seen a run like this ever.” I have a lot less experience than him, but I agree wholeheartedly.


10:45 p.m. update: As the GFS run, it’s has a quick commonality in the NAM with the idea of a somewhat early start time. There’s accumulation into D.C. by 1 p.m., which is very similar to the NAM. It seems reasonable to bump start time up to the noon to 2 p.m. zone. Given that the federal government has announced a closure at noon, strongly consider that early onset in your decision to go into work.

10:35 p.m. update: GFS will be out through the storm shortly. In the meantime, here’s the RGEM. It’s a Canadian short-range model. High end of model precipitation (and thus snowfall), but it tends to do OK with events like this.


RGEM snowfall forecast. (Tropical Tidbits)

10:25 p.m. update: The next model, the Global Forecast System (GFS) is getting underway. It’ll run much quicker than the NAM so we’ll have thoughts on it shortly. In the interim, let’s again highlight the NAM quickly because it shows the idea of a major snow pummeling in the near midnight to near dawn range on Saturday in particular. It shows as much as a foot of snow in that period alone.


Extreme snowfall rates up to 8 to 12 inches in 6 hours as shown on the NAM in the pre-dawn hours on Saturday. (Storm Vista Weather Models)

In the period after, there’s been some question about the “dry slot” on the NAM. A dry slot is basically a big stream of dry air that tends to wrap into the biggest of winter storms. It does enter parts of the region on this run, and it is a risk which could cut off precipitation for a time. We’ve considered it. The dry slot came very close during our major winter storms in 2009-2010. Often to get the best snow you need to be near the dry slot because the mid-level dry air helps aid development of heavy snow nearby.


Infrared satellite of storm developing over the South. (NASA)

10:05 p.m. update: I opened with an image of the storm because it’s quickly become a beauty. The infrared loop above shows it beginning to take shape quite nicely. There has been a regional severe weather episode associated with this storm today over parts of the mid-South. Recent analysis shows the surface low to the north of the New Orleans region. Classic early development zone for our big ones.


Snowfall forecast from the NAM. (Weatherbell.com)

9:45 p.m. update: The snow map from the NAM shows what most have in recent days. A major snow event for the region. The details are more or less the same compared to prior. One interesting thing with the NAM is it’s kind of on its own with the snow north of the New York City area. And it’s got a lot. Really tough forecast up there.


NAM simulated radar loop for the majority of the upcoming storm. (Weatherbell.com)

9:35 p.m. update: The NAM is out for the storm. It shows snow from midday on Friday and deep into Saturday night. CWG’s Wes Junker notes that thundersnow remains possible on this run. He said, “there’s a distinct unstable layer, which means there’s a real good chance of having convection.” The best chance for that comes in the overnight Friday into early morning Saturday period, perhaps focused on the pre-dawn period.

9:23 p.m. update: While snow may initially start rather friendly, it will pick up in intensity fast. About 3-4 hours after onset, the NAM already has about 3 inches of snow on the ground in D.C. That total would be by 6 p.m. Friday, with even more intense activity coming in from the south at the same time. Snow gets very heavy heading into the night.

9:15 p.m. update: If you’re looking for some expert talk to go with the information here, CWG’s Wes Junker is again joining AmericanWx.com radio to talk snow. Always worth a listen. I’m tuning in myself.


(Storm Vista Weather Models)

9:10 p.m. update: The NAM runs rather slow. So let’s look at timing again a bit. It has measurable precipitation by 3 p.m. through the immediate area, and this is after snow begins in the hour or two prior. Not heavy yet, but it’ll stick quick given it’s been so cold and will likely stay near or below freezing on Friday.


SREF total precipitation, current run compared to previous run. (Storm Vista Weather Models)

9:00 p.m. update: The evening’s models are underway. Our usual starting point while we wait for the North American Model (NAM) to complete is the short range ensemble forecast (SREF). A The main takeaway here is that there’s no significant change from prior runs, and it aligns quite with what we’ve seen from other modeling recently. Big snow for everyone. The NAM is running, it brings snow into the area by about noon tomorrow which is on the early side of current expectations. We’ll be back with details as it gets through the storm.