Western US Daily Snow

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By Alan Smith, Meteorologist Posted 1 month ago June 17, 2024

Late Season Cold Snap with Snow for the Northern Rockies

Summary

A cold storm system is moving into the Northern Rockies early this week after bringing rain and snow to the Cascades over the weekend. Montana will be favored for the heaviest and most widespread rain/snow, with significant snow in the mountains. Freezing temps are also expected in valleys behind the storm. Late this week, subtropical moisture & t-storm chances increase over the Southwest.

Short Term Forecast

Big Picture Weather Pattern:

A deep trough of low pressure containing well below-average temperatures will move into the Northern Rockies on Monday and Tuesday, resulting in a late-season chill with snow for the mountains. Areas to the south will also see some temporary heat relief along with gusty winds. 

5-Day Precipitation Forecast:

Precipitation will favor the Northern Rockies early this week with additional light showers for the Cascades and Coast Range of British Columbia. Late this week, moisture will increase across the Southwest and Southern Rockies, leading to an uptick in thunderstorm activity.

Southern California Fires:

While northern parts of the Western U.S. are cool and wet early this week, wildfires broke out across Southern California near LA over the weekend. The most notable is the Post Fire near Gorman (north of LA) which started on Saturday and had burned over 14,000 acres as of Sunday.

Here is a view of this fire on our Active Fires Map.

Smoke from this fire and numerous other small fires are resulting in poor air quality across parts of Southern California. Strong winds early this week will also transport some of this smoke into Arizona and Southern Utah.

View → High-Res Smoke (Surface) Map

Forecast for Mon (Jun 17) to Tue (Jun 18):

The storm system on Monday and Tuesday will favor Montana and Idaho for the heaviest rain and snow, while the Cascades will see lighter showers on the backside of the storm. Mostly dry conditions are expected across the Southern Rockies. 

Taking a closer look, many of the higher elevation areas in Montana as well as the Salmon River Mountains in Idaho will pick up over an inch of precipitation (rain and liquid-equivalent snow) on Monday and Tuesday. Southwestern portions of Montana around Bozeman look to see the highest totals.

Snowfall will also be significant across higher-elevation areas of the Northern Rockies, with snow levels dipping below pass level. However, some of the higher snowfall accumulations on this map are likely overdone, as this particular model blend assumes higher snow-liquid ratios than what is typical this late in the year.

OpenSnow point forecasts are projecting 0.71 inches of rain in Bozeman on Monday and another 0.36 inches after 12 a.m. on Monday night/Tuesday morning for a storm total of 1.07 inches. For the higher terrain, our forecast calls for 7-13 inches of total snowfall at Big Sky Resort.

Forecast for Wed (Jun 19) to Thu (Jun 20):

Warmer and drier conditions will gradually take hold across the Northern Rockies, but isolated lighter showers will redevelop both afternoons. Northern Washington and British Columbia will see a few light showers as well. 

On Wednesday, moisture from the Northern Rockies storm will spill southward into the eastern ranges of Colorado and New Mexico, resulting in an uptick in showers and thunderstorms.

On Thursday, a significant surge of moisture from a tropical disturbance in the Gulf of Mexico will reach the Southwest, resulting in more numerous thunderstorms across New Mexico and Southern Colorado with the potential for locally heavy rain.

Forecast for Fri (Jun 21) to Sat (Jun 22):

A weak area of low pressure over the Southwest combined with an uptick in subtropical moisture will aid in thunderstorm development with activity spreading westward into Eastern/Southern Utah and Eastern Arizona.

Locally heavy rain will be possible with some of the highest totals expected across Northern New Mexico and the San Juans in Southwest Colorado.

To the north, a weaker disturbance tracking across Alberta and Montana will result in scattered thunderstorms east of the Continental Divide. The Olympics and Cascades near the West Coast could potentially see a few light showers as well.

Extended Forecast

Outlook for Sun (Jun 23) to Thu (Jun 27):

Above-average warmth will overtake most of the West once again, with the only exception being the Pacific Northwest (along and west of the Cascades) where temperatures will be near average. Subtropical moisture will linger over the southwest, resulting in additional thunderstorm chances with hit-or-miss rainfall. The Northwest will also see occasional light showers move through. 

Thanks so much for reading! Next update on Wednesday (June 19).

Alan Smith 

Announcements

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View the real-time lightning risk for the next 60 minutes and lightning strikes over the past hour for any area in the United States with our new "Lightning Risk" map overlay.

This overlay is incredibly useful for knowing:

  • If you should end your outdoor activity early with lightning risk ramping up.
  • If you should take shelter or get below treeline with lightning strikes nearby.

Getting Started

  1. Tap the "Maps" tab.
  2. Tap the overlay button.
  3. Tap "Lightning Risk".
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  5. Tap the map to view details.

Here's an example of the lightning risk increasing and strikes occuring across Wisconsin on June 12, 2024.

Make sure you're updated to the latest version of the OpenSnow app (App Store / Google Play > OpenSnow > Update) or visit the OpenSnow website (OpenSnow.com).

View → Lightning Risk Map

About Our Forecaster

Alan Smith

Meteorologist

Alan Smith received a B.S. in Meteorology from Metropolitan State University of Denver and has been working in the private sector since 2013. When he’s not watching the weather from the office, Alan loves to spend time outdoors skiing, hiking, and mountain biking, and of course keeping an eye on the sky for weather changes while recreating.

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