The third western system in 10 days is already over the Intermountain West and is set to drop 1-2 feet over the mountains of Utah, southern Idaho, Wyoming and Colorado over the next 24 hours. As the low swings out into the Plains and taps warm, moist air from the Gulf and cold air out of Canada, the lows will deepen and should bring another bout of snow to the Black Hills, perhaps a few inches into Rapid City.

Here’s the GFS by tomorrow.

By Tuesday the low really winds up with winds once again cranking, perhaps producing near blizzard conditions over the Dakotas for a time while we could see a line of strong storms form in the warm sector from Texas up into central Illinois.

By Wednesday a line of showers and storms steam into the Ohio Valley and eventually the Northeast late week but the cold coming south into the Plains and Great Lakes, look out! It will be easily the coldest of autumn with the first sub-32 degree lows on the way for Fargo, Minneapolis, Chicago and Detroit.

Here’s the 850mb temps by Saturday.

By Sunday strong northwest winds and temps of -5C or lower at 5,000ft will sweep down the Lakes.

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By 192 or next Monday, the cold winds continue blowing and the trough progresses east, bringing easily the coldest air mass yet into the Northeast. With this kind of air mass, we could see the first frost in Central Park with freeze warnings hoisted in the suburbs, not forgetting daytime highs stuck in the upper 40s.

As for snow. The GFS shows the snow initially over the Rockies and Dakotas.

The 120 hour chart5 shows accumulating snow over northern Minnesota.

By Saturday or 144 the snow is seen through the Lakes, perhaps in the form of Lake effect as northwest winds crank and drive colder air out of the arctic.

By 168 or next Sunday, the GFS has snow widely through the Lakes and I suspect this may well be largely lake effect. Remember the lakes remain very warm and given the amount of early season cold coming, this could be a very noteworthy event if this pans out.

Here’s the ECMWF 500mb height anomalies and notice the shift in the height field with the strongest positives shifting from Hudson Bay to the British Columbia coast along with the blacking high setting up over Greenland. This is the perfect setup for sending cold into the eastern US. Keep in mind that the AO is negative as well as the +PNA/-NAO and so don’t be surprised if the cold that comes down is pretty strong for the time of year. Also bare in mind that the arctic sea ice extent is well above the past 4-5 years. Less water means less warm feedback to the atmosphere.

Here was the 500mb heights from yesterday. Note the positioning of the blocking highs. One N of Scotland the other over Hudson Bay.

By 120 hrs you can see both blocking highs migrate and join over Greenland while a ridge shifts east onto the west coast of Canada.

By 168 or next Saturday the ridge builds over western Canada up into the arctic while the primary ridge is positioned over the Davis Straits and western Greenland. This is a setup which initially drives cold into the Plains but shifts it east and the west coast ridges strengthens and the Hudson Bay ridge becomes a trough.

Last night’s CFS showed what only could be described as a ‘block’ buster winter for eastern North America and Western Europe. Check out last night’s post to see what a brutal winter it would be if it held true.

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Tags: Cold End To October For Eastern US, Cold October, us october forecast, US Winter Forecast 2013-14