textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Strong to severe thunderstorms today capable of wind gusts to 70 mph, blowing dust, hail, and heavy rain, with the highest potential across southeast Oregon and the west-central Idaho mountains.

- Breezy south winds this afternoon with gusts 25 to 40 mph.

- Showers and weaker thunderstorms persist on Friday, then decrease on Saturday with mostly dry conditions returning next week.

- Temperatures cool to slightly below normal on Saturday, then warm to 10-15 degrees above normal by the middle of next week.

SHORT TERM /Through Saturday Night/

Issued 349 AM MDT THU MAY 28 2026 Another active day is in store today with strong to severe thunderstorms expected this afternoon and evening across parts of our area. The upper level pattern will feature a nearly stationary upper level low over northern California. This morning, isolated showers and thunderstorms will develop across southeast Oregon with dry conditions elsewhere. Activity will increase dramatically this afternoon and evening as a shortwave trough rotates around the low across far southwest Idaho and southeast Oregon, providing lift for showers and thunderstorms. Instability will be high for our area (surface CAPE > 1000 J/kg) across northern and western areas, and the low will also provide ample wind shear for organized thunderstorms. Strong to severe thunderstorms will develop across Oregon and far western Idaho near the Nevada border early this afternoon and lift north-northwest, exiting our northern and western borders early this evening.

CAM guidance indicates organized lines of showers and thunderstorms may develop (which often occurs with the passage of a shortwave), increasing the threat for strong to severe outflow gusts 40-60 mph, with isolated gusts to 70 mph possible. Confidence in outflow gusts over 40 mph is highest across southeast Oregon and west-central Idaho, with moderate confidence across far southwest Idaho (including the Treasure Valley) and lower confidence across the Magic Valley and the central Idaho mountains. Large hail will also be possible where instability is highest across east-central Oregon and the west- central Idaho mountains. Heavy rain and blowing dust will also be possible from storms.

Outside of thunderstorms, it will be breezy this afternoon with gusts 25-40 mph from the south. Temperatures today will be around 10 degrees above normal, except near normal along the Nevada border closer to the low center. On Friday, the upper low will lift northeast as an upper trough approaches the Pacific Northwest. The center of the low will remain to our southeast, but broad troughing overhead combined with daytime heating will bring a 20-50% chance of showers and thunderstorms, with the highest chance in the mountains. Temperatures will cool by 5-10 degrees, and winds outside of thunderstorms will not be as breezy as previous days. The low will continue to lift north on Saturday, leaving our area mostly dry except across the central Idaho mountains closer to the low center where showers and thunderstorms will continue. Temperatures will cool another 5 degrees and winds will pick back up with afternoon gusts 20-35 mph across the area.

LONG TERM /Sunday through Thursday/

Issued 349 AM MDT THU MAY 28 2026 Sunday will mark the start of a warming and drying trend as the upper-low exits our area. A weak shortwave will immediately follow this exiting low, but it looks inconsequential for our area. The best chance of precipitation throughout the long term will come Sunday in our far northeastern zones, where isolated showers may persist across higher terrain on the back side of the exiting low. Ridging will begin to build into the area come Monday, supporting a warming trend through the week. Temperatures on Sunday will sit right around normal, warming to 10-15 degrees above normal by Wednesday.

AVIATION /12Z Thursday through Friday/

Issued 448 AM MDT THU MAY 28 2026

Generally VFR. Scattered showers and thunderstorms developing early this afternoon, with the strongest storms in E-Oregon. Storms will be capable of outflows of 35-45 kt, up to 60 kt possible near the strongest storms, hail, and brief heavy rain. Showers and thunder tapering off in the evening. Surface winds outside of storms: Variable up to 12 kt this morning, then SW-SE 10-20 kt with gusts to 20-35 kt this afternoon. Winds aloft at 10kft MSL: E-SE 15-30 kt.

KBOI...VFR. A 15% chance of thunder at the terminal between Thu/21z-Fri/00z. Thunder capable of small hail, brief heavy rain, and outflows to 40-50 kt. Outflows may travel from distant storms. Surface winds outside of storms: Favoring NW under 10 kt this morning, becoming S-SE 10-15 kt with gusts to 25 kt around 18z.

Weekend Outlook...Generally VFR. Scattered rain showers and isolated thunderstorms Friday. Showers and thunder decreasing in coverage Saturday, mainly over the central ID mountains. Then generally dry Sunday. Gusty erratic winds and brief heavy rain in storms. Surface winds: W-NW 5-15 kt each day with afternoon gusts to 20-25 kt, except W-NW 10-20 kt with afternoon gusts to 30-35 kt near KMUO/KTWF/KJER.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.