The Treasure Valley will see a slight cooldown and a 20 percent chance of showers Friday as an upper-level low passes overhead, before high pressure rebuilds and delivers a stunning fall weekend with sunny skies and temperatures climbing back to the low 80s by Sunday.
A few storms ahead of a beautiful weekend in Scott Dorval's video forecast
Friday: Slight Cooldown with Limited Shower Chances
Temperatures will cool 5 to 10 degrees Friday as the low-pressure system moves overhead, with the Treasure Valley seeing a high near 76 degrees. A 20 percent chance of showers and thunderstorms will exist before 5 p.m. Friday, though coverage will be limited for the valley. Conditions will clear Friday night with mostly cloudy skies and a low around 54 degrees.
Central Idaho Mountains: Significant Storm Threat
While the Treasure Valley sees only limited shower chances, the central Idaho mountains will face a much more significant weather day. Scattered strong thunderstorms are expected over the west-central Idaho mountains, with gusty outflow winds up to 50 to 60 mph, small hail, and brief heavy rain as the main concerns. Abundant lightning is also likely with these scattered storms, and a Red Flag Warning has been issued for scattered lightning through 9 p.m. tonight due to the risk of lightning ignitions on dry fuels.
Hikers, campers, and outdoor enthusiasts in the central Idaho mountains should seek shelter immediately if thunderstorms approach and be aware of the elevated fire danger from lightning strikes.
Weekend Outlook: Outstanding Fall Conditions
After the low exits east of the region Saturday, high pressure will rebuild over the western United States, delivering a beautiful fall weekend.
Saturday: Mostly cloudy skies will gradually give way to sunny conditions with a high near 76 degrees. A pleasant day with improving conditions through the afternoon.
Sunday: Sunny skies and a high near 82 degrees. Right at seasonal normals and ideal for any outdoor activity.
Monday and Tuesday: Sunny skies and highs near 83 degrees. The warmth continues into the new work week, making for some of the finest fall weather of the season.
This weekend's conditions will be exceptional for outdoor activities across the Treasure Valley and central Idaho mountains:
- Outdoor festivals and community events: Sunday through Tuesday will be picture-perfect with sunny skies, temperatures in the low 80s, and light winds.
- Hiking and trail running: The Boise Foothills and surrounding areas will be spectacular. The recent rainfall has improved trail conditions and fall colors are beginning to emerge.
- Fall foliage viewing in the central Idaho mountains: This weekend will be an outstanding time to visit the Sawtooth Valley, Payette River corridor, and the mountains around McCall. Thursday and Friday's rainfall will further enhance the fall color change, and temperatures in the mountains will be comfortable in the mid to upper 60s Saturday and climbing to the low 70s Sunday and Monday.
- Golf and cycling: Near-perfect conditions Sunday through Tuesday with sunny skies and temperatures in the low 80s.
The official start of astronomical fall, the autumnal equinox, arrives on Tuesday, September 22 at 8:29 p.m. MDT. The Treasure Valley will be celebrating the first full day of fall Wednesday under sunny skies and a high near 81 degrees.
Looking Ahead
Late Monday through Tuesday, the area will be sandwiched between a shortwave trough steering across the lower Great Basin and a longwave Pacific trough moving into the northwest coast. This pattern will keep conditions seasonable Tuesday with a slight chance of showers near the Idaho-Nevada border. Wednesday through Thursday will bring dry conditions and temperatures 5 to 10 degrees above normal as strong southwest flow develops ahead of the approaching Pacific trough.
Tonight
A 20 percent chance of showers and thunderstorms after 4am. Increasing clouds, with a low around 56. West northwest wind 5 to 9 mph becoming calm in the evening. Winds could gust as high as 20 mph.
Friday
A 20 percent chance of showers and thunderstorms before 5pm. Partly sunny, with a high near 76. Calm wind becoming northwest 5 to 8 mph in the morning.
Friday Night
A slight chance of showers and thunderstorms between 9pm and midnight, then a slight chance of showers after midnight. Mostly cloudy, with a low around 54. North northwest wind 5 to 7 mph becoming calm in the evening. Chance of precipitation is 20%.
Saturday
Mostly cloudy, then gradually becoming sunny, with a high near 76. Calm wind becoming northwest 5 to 9 mph in the afternoon.
Saturday Night
Mostly clear, with a low around 55. Northwest wind 5 to 9 mph becoming calm in the evening. Winds could gust as high as 20 mph.
Sunday
Sunny, with a high near 82.
Sunday Night
Mostly clear, with a low around 56.
Monday
Sunny, with a high near 83.
Monday Night
Partly cloudy, with a low around 56.
Tuesday
Sunny, with a high near 82.
Tuesday Night
Mostly clear, with a low around 55.
Wednesday
Sunny, with a high near 81.
Wednesday Night
Mostly clear, with a low around 56.
Thursday
Sunny, with a high near 84.
