The week is ending on a wet (and snowy) note across much of the West. Heavy rain and high elevation snow fell on Thursday & Thursday night along and east of the Continental Divide, including Glacier National Park.

The Bitterroots, Cascades, and Sierras also have picked up new snow as of Friday morning, including snow all the way down to lake level at Tahoe.

Forecast for Friday, May 21

A powerful low-pressure system is centered along the California/Nevada border as of Friday morning after slowly shifting south over the previous 24 hours.

Taking a look at visible satellite, we can clearly see this storm system and the moisture/cloud cover associated with it. 

As of late Friday morning, showers were picking up in coverage and intensity across the Great Basin and the Central Rockies, with an overall southward shift in rain (and high elevation snow) compared to Thursday.

The heaviest and most widespread rain on Friday & Friday night will fall across the Sierras, Great Basin, the Uintas in Utah, the San Juans, Tetons, and the Madison/Gallatin Ranges in Montana. Thunderstorms will be possible on Friday afternoon as well, especially in Western Colorado and Western Wyoming. 

Southern Utah and Arizona will remain dry, but with the added benefit of cooler temperatures. For example, highs will be in the 70s at the Zion Visitor Center, as opposed to the 90s experienced in recent days. The only downside is that winds will also be strong across the desert on Friday. 

With colder temperatures taking hold across the West, mountain snow can be expected from the Sierras to the Rockies through Friday night. The higher elevations of the San Juans in Colorado will see some of the heavier snow totals, along with portions of Nevada and Southwest Montana.

Forecast for Saturday, May 22

The low-pressure system will slowly begin to move east on Saturday. Showers will continue across the Sierras, Great Basin, and north into Eastern Oregon and Western Idaho.

Meanwhile, thunderstorm potential will increase across Colorado and New Mexico on Saturday afternoon, especially along and east of the Continental Divide including the Front Range and Sangre de Christos where stronger storms are possible. 

On Saturday night, the Low will begin to move northeast with heavy rain and high elevation snow spreading into Northern Utah, Western Wyoming, and Southwest Montana. Once again, the desert regions will hold onto the most favorable weather conditions including lighter winds, though some light showers couldn't be ruled out as far south as Bryce Canyon or so. 

Below are the projected precipitation amounts for Saturday & Saturday night.

Forecast for Sunday, May 23

Colder than average temperatures will prevail across much of the West on Sunday, with wet conditions for the Wasatch, Tetons, Yellowstone, Wind Rivers, and a large portion of Montana and Idaho.

Heavy snow is also expected at the mid to upper elevations of the Northern Rockies on Sunday & Sunday night.

The Sierras and Colorado Rockies will both see improving weather conditions on Sunday to help salvage the weekend, while Southern Utah and Arizona will continue to enjoy outstanding conditions. 

Forecast for Monday, May 24

Showers and cooler than average temperatures will linger across the Northern Rockies on Monday, especially in and near Glacier National Park, and to a lesser extent, in the Tetons and Yellowstone.

Meanwhile, another storm system will reach the Pacific Northwest with showers developing across Washington and Oregon.

Outlook for Tue, May 25 – Thu, May 27

The pattern for the middle of next week will feature cooler and wetter weather across the Northwest and drier weather across the Southwest.

A series of disturbances will bring daily rounds of showers to the Cascades and the Northern Rockies while the Wasatch and Northern Colorado Front Range could get in on the action at some point as well. 

Southern Utah and Arizona will remain in a dry pattern, but temperatures will start to heat back up. Farther west, California will experience drier conditions as well with only light rain chances in the northern part of the state.

Outlook for Fri, May 28 – Mon, May 31 (Memorial Day Weekend):

The overall trend for the holiday weekend is for temperatures to warm up throughout the West to above-average levels.

Rain chances are more uncertain at this time, though there are some indications that the Northern Rockies and perhaps the Colorado Front Range would be more favored for showers/thunderstorms, with drier conditions farther west and south.

Thanks so much for reading and check back for my next forecast on Monday, May 24th!

ALAN SMITH

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