The Treasure Valley will enjoy another warm and sunny day Wednesday before an upper-level low brings the potential for isolated strong thunderstorms Thursday afternoon, followed by a clearing and warming trend that will deliver an outstanding weekend just in time for the official start of fall.
Spectacular weather gives way to isolated storms ahead of a nice weekend in Scott Dorval's video forecast
Wednesday: Near-Perfect Fall Conditions
Wednesday will bring sunny skies and a high near 82 degrees, right at the normal high for mid-September in Boise. Light winds and dry conditions will make for an ideal day outdoors. This will be the last fully dry day before the next weather system arrives, so make the most of it.
The official start of astronomical fall, the autumnal equinox, arrives on Tuesday, September 22 at 8:29 p.m. MDT. The Treasure Valley is already experiencing the kind of crisp, clear, and comfortable weather that defines the best of the fall season, with temperatures right at seasonal normals and low humidity.
Thursday: Isolated Strong Thunderstorms Possible
The weather pattern will become more active Thursday as an upper-level low shifts eastward and moves inland from the Oregon coast. An associated jet streak will position itself across southwest Idaho, providing favorable dynamics for broad-scale ascent and increasing instability.
A 20 percent chance of showers and thunderstorms will develop Thursday afternoon in the Treasure Valley. While coverage will be limited, some of the storms that do develop could be strong, capable of producing heavy rain, gusty winds, and small hail. Thunderstorm parameters suggest a marginal threat for organized convection, with the highest potential for robust thunderstorm development focused across southeast Oregon and eastern Idaho depending on the exact placement of the mid-level dry slot.
Temperatures Thursday will remain mild near 81 degrees, though cloud cover and shower activity will moderate afternoon highs slightly compared to Wednesday.
Friday: Lingering Shower Chances Before Clearing
Friday will bring a 20 percent chance of showers before noon, mainly across the west-central Idaho mountains and Baker County, before mostly sunny skies develop in the afternoon. Temperatures will be slightly cooler at 76 degrees before the warming trend resumes heading into the weekend.
Weekend Recreation Forecast: Outstanding Conditions
After the midweek weather system clears out, an upper-level ridge will build into the Northwest, delivering an outstanding weekend for outdoor activities.
Saturday: Sunny skies and a high near 79 degrees. Excellent conditions for any outdoor activity.
Sunday: Sunny skies and a high near 83 degrees. One of the warmest and most beautiful days of the fall season so far.
This weekend's weather will be exceptional for popular fall events and outdoor activities:
- Outdoor festivals and community events: Saturday and Sunday will be picture-perfect with sunny skies, temperatures in the upper 70s to low 80s, and light winds. Any outdoor event scheduled this weekend will benefit from near-ideal conditions.
- Hiking and trail running: The Boise Foothills, Table Rock, and Camel's Back Park will be spectacular. The recent rainfall has improved trail conditions and the 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. The combination of recent cold fronts and significant rainfall has accelerated 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 Saturday through Monday with sunny skies and temperatures in the upper 70s to mid-80s.
Tonight: Mostly clear during the early evening, then becoming mostly cloudy, with a low around 51. Light wind.
Wednesday: Sunny, with a high near 82. Light wind.
Wednesday Night: A 30 percent chance of showers and thunderstorms after midnight. Partly cloudy, with a low around 57. Light wind.
Thursday: A 20 percent chance of showers and thunderstorms after noon. Mostly sunny, with a high near 81. Light wind becoming south 5-10 mph. Winds could gust as high as 20 mph.
Thursday Night: A 20 percent chance of showers after midnight. Partly cloudy, with a low around 57. Diminishing wind.
Friday: A 20 percent chance of showers before noon. Mostly sunny & pleasant, with a high near 76.
Friday Night: Mostly clear, with a low around 52.
Saturday: Sunny & pleasant, with a high near 79.
Saturday Night: Mostly clear, with a low around 52.
Sunday: Sunny & warmer, with a high near 83.
Sunday Night: Partly cloudy, with a low around 54.
Monday: Mostly sunny & warnm, with a high near 85.
Monday Night: Partly cloudy, with a low around 54.
Tuesday: Mostly sunny, with a high near 81.
