Winter Weather Pattern Headed For The West | First Snow Likely For The Sierra [Powderchasers]

Winter Weather Pattern Headed For The West | First Snow Likely For The Sierra [Powderchasers]


Winter Weather Pattern Headed For The West | First Snow Likely For The Sierra [Powderchasers]


Ullr is woke | Image: WXBell

[Forecast courtesy of Powderchasers]

Short Term:

The next few weeks could have you feeling like it’s mid-winter in parts of the Western US. Although early season snowfall may not be the best thing for long term snow stability, we still love seeing snow in the forecast.

We’ve seen several rounds of snow for the Northern Rockies in Alberta over the last few weeks and in the past few days, Winter paid a visit to Montana and Wyoming with significant snow. Six inches was measured on a snotel site somewhere in the mid elevations of the Bighorn Mountains, and an even larger storm is currently aimed at Northwest Montana this weekend into early next week. The southern Sierra above 9k could see its first accumulations of the year as well. Some much needed rain associated with Hurricane Rosa will bring relief to the drought stricken Southwest early next week too. After the trough moves through early next week the upper level pattern looks favorable for continued chances of snow and below normal temperatures.


The next 5 days will feature 2 chances for accumulating snow in NW Montana. The first round of snow will begin on Saturday and last through Sunday. Snow levels will lower to around 4500 feet and winds will be very strong. A large area from Glacier National Park East and SE into the plains of Central Montana will see 2-4 inches below 4500, around 6 inches above 4500, while the higher elevations along the continental divide in NW Montana could see as much as 6-10 inches by Monday morning. The next round of snow could arrive as soon as Tuesday, but the models diverge on the exact timing. This could be another solid storm, perhaps focusing a little more on far NW Montana, with another 6+ inches not out of the question. While these systems won’t bring significant snow to most Montana ski resorts, Whitefish, Montana Snowbowl, and Big Sky could see small accumulations down to the base. We will fine tune the details for the second round of snow in a later post. Later next week will remain active and the resorts could get a more significant snowfall.

24 hour snowfall ending Sunday at 6 am | Image: WXBell

Alberta/British Columbia:

The eastern front of the Rockies in Alberta always seem to get snow in September and October, and this year is no different. Resorts like Lake Louise, Sunshine Village, and Norquay have already seen several rounds of accumulating snow, and this will continue during the next 5 days, with BC getting in on the action as well.

48 hour snowfall forecast from the ECMWF | Image: WXBEll

The first round this weekend will mainly be light to moderate snow, with just a few inches possible. Snow showers could linger on and off until Tuesday, when a stronger storm is possible. We are still ironing out the details for the second round but 6-12 inches is definitely possible. Interior BC could see accumulating snow as well as a colder airmass moves in.


The southern Sierra could see its first accumulating snow of the season next week. A storm will move in from the Pacific bringing the first real rain in the valley since April, and with it a chance of high elevation snow. Upper elevations of the southern Sierra, especially Mammoth Mountain, above 9k feet, could see 2-4 inches of snow midweek.

Long Range:

After the midweek storm that will bring snow to Alberta, Montana, and California moves through, the pattern will quickly become favorable once again for below normal temperatures and chances for snow during the second week of October. An upper level trough will likely move through the Western US during this time that could provide wintry weather to many states. We will update you on this situation as time goes on, as it bears close monitoring. You can see in the two images below, both the European and North American Ensemble Models agree that a strong upper level trough could impact the Western US in the second week of October. This could bring the first snow of the season to Utah, as well as accumulating snow to several other parts of the West.

Image: WXBell

Image: Tropical Tidbits

You can also see in the image below that the temperatures will be below average during this period. This map shows the 5 day average temperature departure from normal. The entire Western US should see below normal temps during this period in the second week of October.

Image: WXBell

Some additional good news for the Southwest US as well. Remnants from Tropical Storm Rosa will bring much needed rainfall to this drought stricken region. Several inches of rain could fall in Arizona, while Utah, New Mexico, Nevada, and Southern California could see impacts from Rosa as well depending on the track.

Drought Monitor | Image: USDA

As you can see from this US Drought Monitor map, much of the Western US is experiencing extreme to exceptional drought. However flash flooding and landslides are possible with the amount of rain the models are showing.

–Powderchaser Luke

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