We’re almost halfway done with the month and despite the turn into the colder air for awhile…we’re running about 4° above average so far for the 1st 14 days of the month. It doesn’t feel like it’s been the 35th warmest start to December but here we are.

Colder air has moved in…we got another push of it overnight, hence the stronger winds out there last night and today. We’re also seeing some very light areas of snow out there as well. No significant accumulations are expected.

This colder air will be with us through Saturday…before is briefly eases off on Sunday into early Monday.

This will be ahead of the stronger and nastier surge of Siberian air that is going to slosh over into North America…and then, eventually drain down into the Plains for mid next week. This is the air mass that I’ve been telling you about all month…and it’s still coming.

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Forecast:

Today: Mainly cloudy with a few areas of flurries or light snow. Highs in the low to mid 30s (about where we are now). Windy as well with gusts to 30 MPH possible at times.

Tonight: Variable clouds and cold. Clouds will play a role in just how cold we end up being but we may not fall below 25°

Tomorrow: Mostly cloudy, blustery and cold…highs only near 32°

Saturday: More sunshine and chilly with highs in the mid 30s

Sunday: Better with highs in the lower 40s

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Discussion:

Not the prettiest day out there and it’s not going to change a lot over the next 36 hours. We’re feeling the effects of the big storm that was moving through the Plains and early this morning is now centered south of Minneapolis, MN at 8AM

That’s a 992 millibar (mb) surface low…which equates to about around 29.30″ on the home barometer.

It’s only slowly going to move round eastern MN today…essentially it’s stalled this morning so in effect it’s going to continue to wrap moisture, around 3-5,000 feet around it’s core. If the storm is stationary…that moisture will just pinwheel around it. You can see the moisture spinning around by looking this satellite loop.


There may be an occasional break in the cloud cover…but a lot of clouds are expected for the next 36 hours it appears.

The storm should finally move far enough east, towards the Great Lakes and southern Canada to take it’s wrap around moisture with it…and allow skies to brighten up, perhaps later tomorrow or more likely on Saturday.

The colder air will also start to ease a bit as well over the weekend. It’s been quite the storm. On the cold side…there’s been a lot of snow across the upper Midwest.

The darkest blue is 4-6″…the lightest red is 18-24″…there are some 30″ maxs in there in SD.

Deadwood, SD seems to have have had the most (non mountain) snow with 3 FEET

That is on the colder side of the storm…then in the warmer side…with more Gulf moisture and a tremendous amount of shear…numerous tornadoes have ripped through the southern Plains and especially the Deep South over the last couple of days. Yesterday was a really rough day down south, especially from SE Louisiana through Mississippi.

On the 13th…the red dots represent the tornado reports.

Then yesterday…another 2 dozen plus were reported

Interestingly there were almost twice as many tornado reports as hail reports…that’s rather unique.

Today the main threats are down towards FL and up into the Carolinas.

Locally, as we look at the bigger picture we’re watching for a weak disturbance to potentially give us some precipitation on Monday although there is some conflict on whether this will be all snow or perhaps a wintery mix to snow.

The EURO model is a bit warmer, with also the ICON model…meaning it would be tough for us to keep this all snow. The GFS is colder and somewhat snowier…perhaps a couple of inches worth of snow. It may be too cold and too snowy though.

The disturbance coming towards the region on most of the model data is broken up in nature and likely it’s going to be weakening as it moves closer to the State Line region.

It’s something to watch because 1) we haven’t had really any snow in awhile and 2) if the disturbance could maintain itself and be more organized…then there would be an uptick. Although I’m not sure how much would be sticking to the pavement with temperatures potentially in the mid 30s.

So there’s that we’ll be working on.

Then there’s the main show…the colder air. For that let’s take you to Siberia…over towards northern Russia where the Siberian air is cold and there’s very little light during this time of the year.


Those temperatures are running 50 to 55° C(!) below 0. That equates to more than -60°F below 0°. Impressive cold for sure.

This air mass will sort of split in half and some of it will slosh over towards the north of Alaska and move into the northern territories of Canada over the next 3 days or so.

From there it moves into western Canada moves across the border early next week and then slowly comes into the western Plains before being unleashed southwards into the Plains and elsewhere later next Wednesday into Thursday.

As a matter of fact if we trace a bubble of air over the coming 5 days or so into northern Canada…you can see where the air is coming from.

When it gets there…then it will be draining southwards.

As I’ve suspected model data is trending colder and colder with this. I will be very aggressive with my forecasts for this heading into next Thursday -> Christmas Eve. I anticipate forecasting sub-zero cold for one or two of those days…highs may struggle to get to 10°. There will be caveats though.

  1. when exactly will the formerly Siberian air mass arrive? We may have some sort of 12AM high next Thursday morning but take a look at the EURO ensemble forecast for Thursday afternoon. The deterministic model has sub-zero temperatures in the afternoon on Thursday but I don’t want to go there at this point.

Oh and the winds may be in excess of 20-30 MPH depending on how this plays out. Wind chills will be a dangerous levels regardless.
  • 2) Then there is the issue of lower clouds. Always a concern with forecasting low temperatures. Sub-zero lows are certainly in the table. How sub-zero we get though will be connected to lower clouds and winds.
  • 3) you can see how the EURO is likely “seeing” the colder air more and more as I expected the model to react. Several days ago it was seeing lows closer to 10° for next Friday morning. Now it “sees” sub-zero.

It may not be done “seeing” what’s coming either.
  • 4) Then there is the issue of snow…which is still likely although how much I’m not convinced about. As I mentioned on Tuesday, I’d still be somewhat surprised IF we didn’t get at least 1-3″ of snow out of this transition. The probabilities on the ensembles aren’t though overly high with the overnight data although the deterministic EURO is trying to sniff out something more significant in the transition to the Siberian/arctic air mass Wednesday night into Thursday morning. We’ll see about all this. I see why it’s doing it but again there isn’t a lot of support for it’s solution at this point.

It basically comes down to the trajectory of the coldest air. There are some decent signs of a bit of “moderation” on Christmas Day. Still well below average but perhaps not as extreme.

The feature photo comes from Mary Jo Seever out in Cummings, KS in Atchison County.

Joe