textproduct: Boise

KEY MESSAGES

- Breezy and much cooler today, with lingering showers in northeast OR and the central ID mountains.

- Warming and drying this week.

- Unsettled conditions later this week bring precipitation to higher terrain.

SHORT TERM /Through Tuesday Night/

Behind a cold front that passed through this morning, much of the region is remaining cool even in areas with clear skies. Forecast highs for this afternoon are on track to verify. Post- frontal winds continue to gust across the area, with sustained winds 10 to 15 mph and gusts up to 25 mph. Gusts this afternoon could be as high as 35 mph in the Snake Plain between Mountain Home and Twin falls. As the core of the low moves in behind the front, showers will continue across eastern and northeastern Oregon as well as Central Idaho. Light to moderate rainfall is expected out of showers, and a few may develop into thunderstorms during peak afternoon/evening instability. Precipitation dissipates overnight, and morning low temperatures on Monday will be about 10 degrees cooler than Sunday morning especially in Idaho. Cold enough for RHs to approach saturation and support fog development in higher and colder valleys, and frost in highlands. Cooler temperatures begin to warm Monday and especially Tuesday as heights rise in the region.

LONG TERM /Wednesday through Sunday/

A weak cut-off low looks to remain centered over the region through Saturday. This feature will keep temperatures slightly below seasonal normals, along with periodic chances (15-30 percent) for rain showers and isolated afternoon thunderstorms, primarily over the higher terrain of eastern Oregon and southwest Idaho. While widespread heavy precipitation is not expected due to limited moisture transport initially, moisture does look to increase later in the week as more monsoonal moisture is pulled into the low. Thus, greater potential for heavier rainfall exists, especially across the central Idaho mountains. By Sunday, ensemble clusters show increasing divergence regarding the evolution of the pattern. A subset of cluster guidance maintains a secondary longwave trough dropping out of the Gulf of Alaska, which would prolong cool temperatures and unsettled shower activity. Conversely, other deterministic solutions favor the advancement of a flat high- pressure ridge from the Great Basin, leading to a warmer and drier pattern heading into early next week. Given the high uncertainty inherent to cut-off systems, forecast confidence remains low for the Sunday period.

AVIATION /18Z Sunday through Monday/

Issued 1133 AM MDT SUN SEP 13 2026 Mainly VFR. Scattered to broken clouds today. Isolated showers and thunderstorms this afternoon and evening across Baker County into the West Central Idaho Mountains. Outflow winds to 30 kts and brief heavy rain possible. Patchy valley fog Monday morning near KBKE, KMYL, and KBNO. Surface winds: W to NW 5-15 kt, with gusts to 20-30 kt in the Magic Valley and on ridgetops. Winds aloft at 10kft MSL: SW-W 25-45 kt.

KBOI...VFR with mid level clouds. Surface winds: WNW 10-15 kt with gusts to 25 kt, decreasing to variable less than 10 kt overnight.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.