The snows are beginning to pile up as forecast over the mountains of Wyoming, Montana and Idaho as a storm system pushes in plenty of moisture as well as cold air out of the Gulf of Alaska.

It should continue snowing in these areas through the rest of tonight and much of tomorrow and tomorrow night before taping off as the trough continues to deepen over the Great Basin and Rockies. This is by far the deepest trough yet.

Check out this rather snowy webcam shot capturing the heavy snows over northwest Wyoming earlier today. Wow!

Here’s the latest GFS snow forecast through the next 48 hours which takes us to Friday and you can see a few pockets in excess of 1 foot. With orographic lift etc, I expect some mountain locales to pick up 24 to 36 inches of snow and that is sure to break some records perhaps for the month of September even those these areas aren’t unaccustomed to seeing September snow.

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By Friday, we have a very amplified pattern across the US with the trough maxing out so to speak, reaching it’s deepest levels while the ridge out ahead of it is pumping warm air pretty much all the way to James Bay.

Here’s the ECMWF 500mb chart

I suspect Friday afternoon will have a large temperature spread with highs struggling to get out of the mid to upper 30s over the snow plastered mountains of WY, MT and ID but with strong SW winds, sun and warm mid levels along with dried out ground, such cities as Kansas City and Minneapolis will warm into the mid-80s as you can see from the below chart. That’s 20-30 below normal over the Rockies to 10-20 above normal over the Plains, Upper Midwest and a big temperature turnaround.

Check out the forecasted highs off weather.com for Friday.

We could see see a few record cold maxes and lows over the next few days.

As for the East Coast storm threat. Pretty much all modelling takes the developing low that’s part of the entity now crossing Florida, further east off the coast. Yes it looks to wind up pretty good offshore and should generate large onshore waves from the Carolinas to Maine but as for ‘bad weather’, this thing appears to stay offshore and so inland areas shouldn’t see much impact from this.

Here’s the GFS by Monday

This model shows this position as the closest it gets to the coast.

Here’s the ECMWF early next Tuesday at it’s closest approach.

This is it’s closest approach and sure closer to New England with wind and rain along the coast but nothing more than that.

Canadian model is considerably deeper and always has been but likewise is even further east than the GFS.

Looking at the US pattern through next week, the upper flow appears to turn zonal for a time before a late week trough begins to drop into the Upper Midwest. Doesn’t look particularly deep just now and while winds scream in off the Pacific, no real cold air can be tapped out of northern Canada, it will be interesting to see if any ARCTIC air can get tapped later next week as the western ridge begins to build.

Here’s the setup by Sunday and note the flow becomes more west-east and also notice the high doesn’t appear to build as much over eastern Canada and more importantly the Maritimes which would trap the offshore coastal feature. That’s a lot of the reason now why this won’t get captured as the ridge isn’t as strong and the trough is positively tilted.

By next Thursday the trough initially digs into the N Plains and so the ridge and warmth spreads east. Could see 80s return to the DC-Boston corridor.

Here comes the trough by next Saturday. Doesn’t look like particularly cold air gets into the trough but time will tell.

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Tags: East Coast storm threat, Rockies snowstorm