Western US Daily Snow
By Alan Smith, Meteorologist Posted 3 years ago September 10, 2021
Unsettled weekend ahead with showers and thunderstorms
Summary
A Pacific storm system will bring showers and thunderstorms to a large portion of the West from Friday through Sunday along with a cooling trend. Smoke will continue to impact portions of the Far West and Northern Rockies, while other areas will see improvement. A cool and wet pattern will take aim at the Pacific Northwest later next week.
Short Term Forecast
As of Friday afternoon, a trough of low pressure is located over Oregon and moving eastward. This feature will be responsible for more unsettled conditions throughout the West over the next few days.
Welcome rain has been falling throughout the Northwest, heaviest over Oregon, but even Northern California including Tahoe saw a nice round of showers earlier on Friday.
Here is the radar image from early Friday afternoon.
Showers will spread eastward across the Northern Rockies on Friday night as a cold front moves through.
On Saturday, the cold front will slowly progress south and east with showers and thunderstorms developing during the afternoon and evening hours across Utah, Southern Wyoming, and Northwest Colorado.
Smoke conditions have been fluctuating quite a bit this week and that trend will continue into the weekend. This can largely be explained by a more active but variable jet stream and resulting winds aloft since we are undergoing a transition from a summer weather pattern to a fall weather pattern.
In addition to wind direction influencing smoke transport, fire behavior has also been fluctuating significantly due to frequent changes in temperature, winds, precipitation, and relative humidity.
On Friday afternoon, smoke will be heaviest across the Interior Northwest and far Northern Rockies, courtesy of both Northern California fires as well as Idaho/Montana fires. Fortunately, progresses has been made on the Caldor Fire near Tahoe and this one is not burning as intensely as it once was.
On Saturday, the main smoke "plume" will start to shift southward with Utah and Colorado experiencing minimal smoke issues.
For the remainder of the short-term period, smoke conditions will be more variable throughout the West, so be sure to check our smoke maps each day for the latest conditions and keep your outdoor plans as flexible as possible.
Temperature-wise, most areas of the West will be cooler over the next 5 days compared to the previous 5 days. Most regions will still be warmer than average between now and Tuesday, except for the Pacific Northwest, but keep in mind that "average" is quickly decreasing at this time of year.
Forecast for Friday, September 10th
The heaviest rain totals (much of which has already fallen as of this writing) on Friday will occur over Central Oregon as well as Northeast Washington, the Idaho Panhandle, and Northwest Montana. This rain is certainly welcome, though the fire areas in Idaho and Montana will see lighter amounts.
Farther south, Northern California already picked up some needed rain and Nevada, Utah, and Western Wyoming are or will be experiencing an uptick in showers Friday afternoon and Friday night.
Forecast for Saturday, September 11th
As a cold front moves south and east, scattered afternoon and evening shower/thunderstorms will develop across Utah and Colorado. Lingering showers can also be expected across the Northern Rockies on Saturday, especially for areas along and east of the Continental Divide.
Showers will also arrive over the Olympics and Northern Cascades late Saturday afternoon and Saturday night as the next system approaches.
Forecast for Sunday, September 12th
Lingering moisture and instability will contribute to afternoon thunderstorms developing over Colorado and Southern Wyoming on Sunday, favoring areas near the Continental Divide.
Farther west, a storm system will split apart as it moves inland with the heaviest showers expected north of the Canadian border. Showers will also be possible across Northern Utah, Southeast Idaho, Western Wyoming, and Southwest Montana.
Forecast for Monday, September 13th
Showers and thunderstorms will be most numerous across the Northern and Central Rockies on Monday as the second system moves through. Areas along and east of the Continental Divide in Wyoming will likely see the most widespread shower activity. Drier conditions are expected elsewhere, though the Olympic Peninsula could see some showers arrive on Monday night.
Forecast for Tuesday, September 14th
Another round of showers and thunderstorms is likely along and east of the Continental Divide in Colorado and Wyoming. The next Pacific disturbance will primarily impact the Olympics and Washington Cascades with showers, while areas farther south and east should remain dry.
Extended Forecast
Outlook for Wed, Sept 15th - Sun, Sept 19th
The pattern for late next week is looking more interesting and fall-like as a large trough of low pressure is projected to become the dominant feature across the Northwest.
Late next week and into the weekend of September 18th-19th, rain potential will increase across the Olympics, Cascades, BC Coast Range, and Northern Rockies. Cooler temperatures are also expected for this region, meaning snow is a strong possibility across the higher elevations of these mountain ranges.
Farther south, ideal hiking and peak-bagging conditions should be expected, at least to some extent, across Utah and Colorado with the obvious caveat being the smoke.
Thanks so much for reading! Next update on Monday (9/13).
ALAN SMITH
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