Good Sunday morning…special edition of the blog this morning as I’m in full winter mode this week…with two waves of accumulating snows…and a massive Siberian/Arctic outbreak that will engulf most of the country from the Rockies to the East Coast. From the US/Canadian border all the way down to Florida and Texas.

I wrote a FB update yesterday that I want to start with before we go anywhere else. My feeling is that most folks, even if they’re somewhat paying attention to the weather forecasts may not fully grasp what is setting up for Thursday.

It’s frankly something that we haven’t seen in many years…and the reason I’m making that statement is because, while history says we’ve been colder, and we’ve been snowier, and we’ve been windier, it’s the fact that all these things may happen at the same time over the course of hours.

I won’t be surprised if we have near blizzard conditions on Thursday early morning. Decent falling snow with crashing temperatures and the potential of 30 MPH winds (or higher) contributing to dangerous conditions on the roads heading into Christmas weekend.

The nastiness is enhanced by the fact that we may be looking at temperatures falling below 0° during the day, which is rare. Add in the strong winds…and wind chills may drop below -20…and approach -30° at some point heading into Friday. Truly a memorable day I believe is setting up and a dangerous day.

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Forecast:

Rest of the day: Mostly sunny with increasing high clouds this afternoon. Highs well into the 30s. Not a lot of wind (for a change)

Tonight: Clouds gradually lower and thicken. Lows near 30°

Tomorrow: Snow arrives 1st thing in the morning and we should see accumulations of a dusting to 2″ on the high side. Lower amounts the farther east of KC you go. Temperatures will gradually increase into the mid 30s in the afternoon with some melting.

Tuesday: Overall not a terrible day. Cold. Highs in the upper 20s to near 30° with clouds and some sunshine.

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Discussion:

I’ve talked about this whole set-up now for almost 2 weeks…and here we are. An incredible week of weather for the KC region is about to unfold.

When I think about what may transpire, and don’t get me wrong…the brutal cold coming is a lock…we can’t avoid that…I’m trying to think of a way you can appreciate the magnitude of what’s ahead. I thought yesterday that perhaps if I say something along the lines of relating things to what happens in the Dakotas during their extreme winter scenarios might allow you to mentally paint a picture. That’s what it’s going to look like in KC on Thursday

We’ve talked about this often…and I’ll show you maps of brutal cold up towards the upper Midwest. This time that is going to happen in KC…and like I said it’s not common to have this sort of combination of snow, wind, cold, and life threatening wind chills happen so quickly and to such extremes…it’s coming. The amounts of snow are somewhat questionable, but it will be blowing around so much you won’t be able to accurately measure it anyway.

So let’s dive in because while Thursday into Christmas morning will be extreme there is a situation tomorrow that warrants attention and I don’t want that to get lost in the big picture.

After a pretty decent day today…a disturbance is going to be coming up from the SW part of the country. This disturbance isn’t particularly strong and there won’t be a ton of moisture ahead of it to work with BUT there should be enough combined with the disturbance itself and some decently strong winds above the surface to allow precipitation to break out towards the west of the region early Monday which then would move eastwards towards the area.

There are a couple of complications, as is typical with weak and somewhat disorganized waves. 1) it sort of is pieces which isn’t the greatest 2) the atmosphere, initially may actually be above freezing, if not a the surface then above us 1st thing in the morning as the snow is arriving. It should chill to support snow that with the precipitation arriving. 3) that same atmosphere is pretty dry too and while that should hold through the night we should saturate pretty quickly tomorrow at daybreak.

This all presents a challenge to road conditions…temperatures today should warm up to near 40° or so…then we’ll drop this evening with clouds slowly increasing but the low level moisture never gets here this evening…it’s still well south of here so temperatures may drop to around 30° or so. Then what comes in the morning creates some headaches since it’s really our 1st snow of the season…that that always seems to be a challenge. We should have mostly a snow event from this, perhaps some tail end raindrops as things wind down in the afternoon.

At this point a dusting to 2″ seems like a good forecast for the KC Metro, areas east of the Metro may see less because the disturbance is going to be zipping through and weakening to some extent, and encountering even more dry air that it has to fight through.

The higher accumulations, perhaps 2-4″ worth should be west of Topeka and down towards Emporia.

Model data shows roughly 1/10″-2/10″ of liquid equivalent to fall. This should be a pretty standard 10:1 type snow for us so I do want to have some high side coverage to 2″ just in case, especially for the west side of the Metro towards Lawrence.

There should some melting as the afternoon happens so let’s hope there’s noticeable road improvement in the afternoon. Be aware though the morning is going to be impacted by the snow. Another thought as well is IF things are still wet or slushy towards evening, and as the temperatures fall back into the 20s…refreezing may occur.

Tuesday and Wednesday won’t be too eventful. Just cold with clouds and perhaps some sunshine at times.

Now to the “show”

By tomorrow morning temperatures in western Canada will be in the 20-40° BELOW range. Here is the Canadian model forecast.

By Tuesday morning…that cold air is moving/oozing through the northern Rockies and the upper Midwest…you can see it clearly in the temperature anomalies up at 5,000 feet or so. See all that purple…that is bitterly cold air.

What does this look like at the surface…something like this.

That’s the leading edge of the brutal air mass that gets colder the farther north you go.

Usually this extreme cold, and with nothing to stop that bitter cold from pouring over the border, would drain towards us in a much weaker state. We’d get cold but we’ve been cold before.

This time though there is an important atmospheric feature that will be the driving force to extreme cold in the region and other things as well. That is a developing soon to be very strong upper level storm that will be moving down through the upper Midwest into the Ohio Valley region later in the week. That allows this brutal air mass to flow unimpeded into the Plains.

When it arrives it will literally be a wall of bitterly cold air. Cold air at the surface and cold air being brought down from the mid levels of the atmosphere…an impressive combination.

So I have a mantra that when extreme events occur in the atmosphere extreme things can happen on the ground. By winter standards this is a VERY potent developing upper level system and while there may be some adjustments with timing on the arriving cold…when it gets here it will be potent.

The cold comes with strong winds…check out this surface map for Thursday night off the latest GFS model…

The black lines are isobars or lines of equal pressure. Air flows OUT of high pressure and INTO LOW pressure…the more lines you see the stronger the surface winds are…the more tightly the isobars are packed together shows a big change of air pressure in a short distance. Hence…wind…lots of it.

So we have the wind…we have sub-zero cold pouring south through the MO River Valley…and now we have to contend with snow.

This front won’t come through dry (although there is still a remote chance of that happening). Again back to the mantra…extreme weather set-ups do extreme things.

Model data, while somewhat fluctuating in how much wind blown snow we may get has been consistent in cranking out some snow. The new GFS run is over 1/2″ equivalent, which when combined with the ridiculously high snow ratios…perhaps more than 20:1…would yield A LOT of snow. I’m not all in on that amount though.

The GFS does love to crank out the moisture…it’s a bias of the model and I expect that liquid equivalent to come down over the coming days…perhaps more towards 1/4″-4/10″. Still though that would be a significant snow…perhaps over 3″. Again with 20-40 MPH gusts though it will be impossible to measure.

All this happens in the morning Thursday and ends in the afternoon at some point. The EURO model takes temperatures down to an incredible -11° DURING THE DAY. Unheard of for us. It’s extreme…perhaps too extreme but you get the point…sub-zero falling temperatures are on the table for Thursday. The new GFS has areas N/W of I-35 marginally below 0° by the end of the day Thursday. Wind chills near 30 BELOW! Hence the dangerous combination all aligning for Thursday.

Then the issue after the event moves through is how cold we get after the fact. Sub-zero for sure I think Friday…perhaps -10° (winds and clouds could impact that) and again on Saturday morning. That game on Saturday will be cold! Winds should be fading though.

Fascinatingly though…the seeds of warmer changes start to erode the cold air mass over the holiday weekend and we’ll see moderation to some extent on Christmas Day but especially early for New Years Week.

Again what preparations that could be taken should be. Being out on Thursday is not going to be good…and depending on the amount of snow…perhaps not safe for many. Think of the pets…any elderly that may be on their own…make sure they have heat…farmers should prepare as much as possible for roughly 6-7 straight days of sub freezing cold. Watch the use of space heaters…and other heating ways that may be dangerous, especially for the inner city area.

More tomorrow…but I need to get this out to the masses.

Joe