A strong Pacific cold front will sweep through southwest Idaho tonight with a widespread round of rain, gusty winds and even a chance of thunderstorms. Behind it, we get a break this weekend, but the bigger weather story may be what happens next.
A series of progressively colder storms is expected to reach Idaho next week. Snow levels will gradually fall, giving Idaho ski areas several opportunities to pick up snow before Thanksgiving.
Rain arrives tonight
Friday's unusually mild weather won't last much longer.
A strong cold front will move across the region this evening and tonight, producing widespread valley rain and mountain precipitation. In the Boise area, rain is likely tonight with a few thunderstorms possible before about 3 a.m.
Rainfall around the Treasure Valley could reach roughly 0.25 to 0.50 inch, while many lower elevations of southwest Idaho and southeast Oregon should receive around 0.10 to 0.25 inch. Mountains could receive approximately 0.30 to 0.60 inch of precipitation.
Snow levels are initially above 7,000 feet, so much of tonight's precipitation will fall as rain even fairly high into the mountains. Snow levels eventually drop into the 5,500- to 6,500-foot range behind the front.
Gusty winds are also accompanying the front. Winds around Boise could gust close to 30 mph, while considerably stronger winds are possible farther southeast. Southern Twin Falls County could experience winds approaching 50 knots.
The storm moves quickly. Precipitation should begin ending from west to east late tonight and early Saturday.
Cooler and quieter this weekend
Saturday provides a substantial break.
After some morning clouds, skies should gradually clear around the Treasure Valley. Boise's high will only reach the middle 50s, roughly 10 to 15 degrees cooler than Friday across much of the region.
Winds also become much lighter Saturday, although gusty conditions will linger across portions of the Magic Valley.
Sunday will be somewhat warmer with Boise climbing to around 61 degrees under partly sunny skies. Clouds begin increasing again later Sunday as our next weather system approaches from Oregon.
Rain associated with that system should hold off in southwest Idaho until Sunday night or early Monday.
Boise weekend forecast
| Period | Forecast |
|---|---|
| Tonight | Rain, possible thunderstorm, low near 43 |
| Saturday | Morning clouds, then clearing, high near 54 |
| Saturday night | Mostly cloudy, low near 40 |
| Sunday | Partly sunny and breezy, high near 61 |
| Sunday night | Showers possible late, low near 40 |
Powerful Pacific storms hammer the West Coast
The storm reaching Idaho is part of a much bigger and more powerful Pacific weather pattern affecting the western United States.
A series of atmospheric rivers has been directing huge amounts of Pacific moisture into Washington, Oregon and Northern California. Parts of Washington's Outer Coast received more than 8 inches of rain from Tuesday through Thursday, with additional heavy rain expected. Additional storms are raising concerns about urban and river flooding, flash flooding and landslides.
Wind has been another problem. Coastal and higher-elevation areas of southern Oregon and Northern California have faced the potential for gusts exceeding 60 mph, creating the threat of downed trees, power outages and wind damage.
The ocean has also become extremely dangerous.
Waves of 20 to 25 feet are expected along portions of the West Coast, and nearshore waves around 30 feet could become even larger as they break along favored portions of the Oregon and Northern California coast. Combined with unusually high tides, that creates the potential for coastal flooding and damaging surf.
Instead of maintaining its full strength as it reaches Idaho, tonight's system weakens considerably as it crosses the mountains. We still get rain and wind, but nothing comparable to the storm's impacts closer to the Pacific Coast.
Idaho ski areas finally have something to watch
For Idaho's ski industry, the next seven to 10 days become much more interesting.
Warm November temperatures have made natural snow accumulation difficult at lower mountain elevations and have also limited opportunities for snowmaking. Tonight's storm helps with precipitation, but snow levels begin too high for this to be a major base-building storm for most ski areas.
Next week is different.
Another storm arrives Monday into Tuesday with snow levels initially around 5,500 to 6,500 feet, falling into the 4,500- to 5,500-foot range Tuesday morning.
The National Weather Service expects some Central Idaho mountain locations and mountains near the Idaho-Nevada border to receive around 1 to 3 inches of snow by Tuesday night.
That's useful, but still not the big storm many ski areas need.
The more intriguing system arrives Wednesday night into Thursday.
Forecast models are turning colder
This is where the forecast has changed.
Forecast models have increasingly supported a deeper upper-level storm moving through the region late Wednesday into Friday. That would pull significantly colder air into Idaho while another round of precipitation moves through.
Approximately three-quarters of the GFS and European ensemble solutions favor snow levels falling all the way to valley floors by Thursday night.
If that colder solution verifies, this would be much more favorable for Idaho's ski areas because precipitation would fall primarily as snow rather than rain at mountain elevations. It could even produce the Treasure Valley's first measurable snow of the season.
There remains considerable uncertainty.
The warmer forecast solutions keep snow levels closer to 3,000 to 4,000 feet, which would maintain rain in many lower valleys. Forecast temperatures for Thursday and Friday also show a large spread, with potential highs ranging from the upper 30s into the upper 40s.
So confidence is increasing that Idaho turns colder next week. Confidence is much lower concerning exactly how cold it becomes and how much snow ultimately falls.
That's an important distinction for ski-area forecasts.
What could happen at Idaho ski areas before Thanksgiving?
The outlook is improving, but one or two cold storms don't automatically translate into enough base to open an entire mountain.
Bogus Basin: Tonight's high snow levels limit the benefit initially, but colder storms next week are much more promising. Bogus has announced plans for a Nov. 21 opening. The colder temperatures are important because they would also provide much better snowmaking conditions.
Tamarack Resort: Its higher terrain should benefit increasingly as snow levels lower Monday and Tuesday. The colder Wednesday night through Friday system has better potential to produce natural snow throughout much more of the mountain.
Brundage Mountain: Brundage is particularly well positioned to take advantage of colder northwest storms. The Monday-Tuesday system could add some snow, with the late-week storm offering the more interesting opportunity for meaningful accumulation before Thanksgiving.
Sun Valley: Higher Bald Mountain terrain should see snow from colder systems next week. Sun Valley currently has a projected Thanksgiving Day opening of Nov. 26, making snowmaking temperatures and next week's colder pattern particularly important.
Soldier Mountain: Soldier should also benefit substantially from falling snow levels. The first storm offers limited accumulation, but colder air later next week could make precipitation much more likely to fall as snow across a larger portion of the mountain.
Pomerelle: Its relatively high elevation gives Pomerelle a better opportunity to see snow as the pattern cools. Monday and Tuesday could bring some accumulation, followed by another opportunity with the colder late-week storm.
Magic Mountain: Magic Mountain will also be watching snow levels closely. Tonight offers only limited snow potential, while Tuesday and especially Thursday-Friday become considerably more favorable.
Eagle Island State Park tubing and Gateway Parks: This is an entirely different situation because of the much lower elevation in the Treasure Valley. Natural snow tonight isn't a factor, but next week's colder temperatures are encouraging. If snow levels actually fall to the valley floor Thursday night, natural snow becomes possible. More importantly for snowmaking operations, colder overnight temperatures would finally create more favorable conditions heading toward Thanksgiving.
The Thanksgiving snow outlook
There isn't enough confidence yet to promise a major pre-Thanksgiving snowstorm.
But the pattern certainly looks better for Idaho skiing than it did during our recent stretch of exceptionally mild November weather.
Think of the next week as a transition.
Tonight: High snow levels with mainly rain below about 7,000 feet initially.
Monday-Tuesday: Colder, with snow levels dropping toward 4,500 to 5,500 feet and some mountain accumulation.
Wednesday: Brief break.
Wednesday night-Friday: Potentially the coldest and most significant storm of the period, with some forecast models dropping snow levels all the way to valley floors.
Next weekend into Thanksgiving week: The amount of snow left on the mountains will depend heavily on the strength, temperature and track of that late-week storm.
For Bogus Basin, Tamarack, Brundage, Sun Valley, Soldier Mountain, Pomerelle and Magic Mountain, the most important change isn't necessarily one huge snowfall total yet. It's the transition toward repeated chances for snow combined with temperatures increasingly favorable for snowmaking.
After weeks of mild November weather, that's exactly the trend Idaho ski areas have been waiting to see.
This Evening
Mostly cloudy with showers developing, with temps in the 60s. SE wind around 15 mph, with gusts as high as 26 mph.
Tonight
Showers and possibly a thunderstorm before 3am, then scattered showers. Low around 43. SE wind 10-18 mph, becoming light and variable after midnight. Winds could gust as high as 30 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.
Saturday
Mostly cloudy through mid morning, then gradual clearing, with a high near 54. WNW wind around 6 mph becoming calm in the afternoon.
Saturday Night
Mostly cloudy, with a low around 40. Light east wind becoming east southeast 5 to 9 mph in the evening.
Sunday
Partly sunny, with a high near 61. East southeast wind around 11 mph, with gusts as high as 21 mph.
Sunday Night
A 30 percent chance of showers after 11pm. Mostly cloudy, with a low around 40.
Monday
Showers likely, mainly before 11am. Mostly cloudy, with a high near 53. Chance of precipitation is 60%.
Monday Night
A 50 percent chance of showers. Patchy fog between 1am and 2am. Otherwise, mostly cloudy, with a low around 34.
Tuesday
A 20 percent chance of showers before 11am. Partly sunny, with a high near 48.
Tuesday Night
A 10 percent chance of showers after 5am. Partly cloudy, with a low around 30.
Wednesday
A chance of rain and snow showers. Partly sunny, with a high near 49. Chance of precipitation is 50%.
Wednesday Night
Rain and snow showers likely. Patchy fog. Otherwise, mostly cloudy, with a low around 32. Chance of precipitation is 60%.
Thursday
A chance of rain and snow showers. Areas of fog. Otherwise, mostly cloudy, with a high near 46. Chance of precipitation is 30%.
Thursday Night
A 20 percent chance of snow showers. Patchy fog. Otherwise, mostly cloudy, with a low around 28.
Friday
Areas of fog. Otherwise, partly sunny, with a high near 45.
