The complex snow, ice, rain and cold pattern talked about here since way back early last week is now well underway with big snows already fallen and continue to fall over the Cascades and particularly over the Northern Rockies east across the Dakotas into the western Great Lakes. That’s thanks to a low crossing the top of the country and is tugging on some bitterly cold arctic air.

There has been upwards of 20-40″ already over parts of Idaho, Wyoming and Montana and these snow get going big time tonight and tomorrow over the Colorado Rockies. While we’ve already seen several inches of snow across the Dakotas and particularly northeast Minnesota around the Duluth area, we’re going to see the main event for the Dakotas through tomorrow with an additional 4-8, locally 12 inches and as winds crank on the backside of the low as it moves into the Great Lakes, watch for zero visibility on those open roads. Tomorrow will see the main batch of arctic air begin to drive south as the low pushes through the Lakes.

Here’s a look at the additional snow through the next 72 hours off the ECMWF.

Rockies and Plains

The floodgates to the arctic air and it’s really Wednesday night through Thursday and Friday that it turns really bitter with highs dropping into -0 territory across a broad area stretching from west Montana to northern Wisconsin.

Southern Mess

As the plunge of arctic air reaches the Southern Plains, we have a secondary low develop and this will be a real troublemaker for Texas, Oklahoma east into Arkansas, even northern Louisiana, Mississippi and Alabama through this weekend. A real ice risk will be had for some, while it’s major snow for others depending upon where you are.

Surface chart for Friday and notice the fine line in the thickness values with warm, moist air running up and over the low level cold air. Will be hard to pinpoint where exactly gets rain, sleet, freezing rain or snow.

ECMWF snow chart through 96 hrs.

In terms of snow, Dallas looks likely to see a mix of rain and some freezing rain, perhaps snow on the north burbs with 1-3 inch accumulations from Lubbock up through OKC and Tulsa with 6+ inches through St Louis.

Check out the ice threat chart from TWC.

Southwest Surprise

Now, let’s not forget that while the arctic air sinks south through the second half of this week, there’s another system pushes into California and this will produce rare snow across potentially many parts of California including the mountains surrounding both San Francisco and Los Angeles. Such routes as I-5 through the Grapevine north of LA and the passes along I-15 to the east will be seriously affected. SNOW is also expected to impact Las Vegas too with this system. Expect major frosts and freezes to accompany this snow.

Check out the ECMWF surface chart for Saturday and notice two things, the system pushing through with moisture and more strikingly, the thickness values. You don’t often see this level of cold air in this part of the world. While snow is going to be noteworthy, for many more across typically mild or warm, Southern and Central California, the COLD will be worst with record lows a given.

ECMWF snow chart through 120 hrs.

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Here’s a graphic from AccuWeather which shows their forecasted low temperatures Wed/Thu nights, these lows are before the system arrives this weekend.

Just How Cold?

Check out the projected temperature drops between today and tomorrow for highs according to the NWS of Boulder.

Forecasted highs tomorrow.

Check out the thermal gradient between Dallas and OKC!!

Remember by Wed night, the northern system is into the Lakes and the door is open…

Wed night lows.

Thursday highs

With cold daytime base temperatures, the knife really cuts Thursday night, don’t be surprised to see -30s start to show up over Montana, perhaps western ND. This for some, will be the coldest night in a few years.

Thu night lows.

Note the 27 in Dallas following tomorrow’s projected 80! What a turnaround. Also notice the 20s for Vegas and likely throughout the Central Valley of CA. First -0 for Twin Cities also.

By Friday, highs are impressively cold. Note the -10 in Billings, coldest in several years here and we’ll likely see widespread highs into the -10s across Montana.

Fri highs

By Friday night, the southern system is out of the region and so skies clear and the cold air rushes over the snow covered ground. Lows drop below 10 for the first time in several years in OKC, could get into the 10s as far south as Dallas while the Panhandle goes below 0.

Fri night lows.

 

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Tags: arctic blast, arctic outbreak, blizzard, cold, snow, snowstorm