textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Dry with gradually warming temps through Monday morning. Frost and/or freezing temps in agricultural valleys this morning.

- Light rain and mountain snow Monday afternoon through Tuesday morning.

- Cooler and unsettled again Tuesday.

SHORT TERM /Through Tuesday Night/

Issued 1230 AM MDT SUN OCT 25 2026 Another chilly morning is in store today with minimum temperatures of 15-25 degrees in E-Oregon and higher SW-Idaho basins, and then mid-20s to mid-30s elsewhere. Southwesterly flow aloft today will bring increasing high clouds and warmer temperatures; with high temps climbing to around 5 degrees above normal (generally mid 60s in lower elevations and mid 50s in mountain valleys).

Come Monday into Tuesday a closed upper level low will move inland across the Northern Rockies. Ahead of this system, breezy west- southwest winds will set in Monday afternoon, with gusts to 20-30 mph, strongest south and west of the Snake River Plain. These winds will transition to be west-northwest following a west to east moving cold front Monday afternoon into Monday night. While this system is not as wet as the previous one, showers will increase Monday afternoon into Monday night, especially over the Central Idaho Mountains. Over the course of Monday and Tuesday, precipitation amounts of 0.15-0.35 inches are forecast for the Central Idaho Mountains, with elsewhere remaining under 0.15 inches. While surface temperatures will be cool (highs across lower elevations a few degrees cooler than Monday, and higher terrain 5-10 degrees cooler), cooling aloft will support weak instability across higher terrain; this instability will lead to a slight chance of thunderstorms over terrain come Monday afternoon. Lowering snow levels will allow for a dusting to a few inches of snow for elevations above 6kft MSL.

Isolated to scattered showers will continue across higher terrain north through Tuesday. Following the cold frontal passage, high temperatures on Tuesday will be back near normal if not a few degrees below, with breezy conditions tapering off.

LONG TERM /Wednesday through Sunday/

Issued 1230 AM MDT SUN OCT 25 2026 The seasonably cool and unsettled pattern will continue through the long-term period. With zonal flow aloft offering multiple opportunity for shortwave passages. The next notable system will approach the area late this week, although uncertainty remains on exact location, magnitude, and timing. Precipitation chances will increase Late Thursday into Friday to 20-60% (highest north and east of the Snake River Plain) as the low digs down into the northwest (which there is good ensemble agreement on). The question becomes whether or not the low aloft rejoins the main flow or breaks off to the south. The former of the two would keep showers over our area through Sunday, with the later offering a brief period of drying come late Saturday before bringing more widespread precipitation Sunday. With that uncertainty, elevated precipitation chances will be carried through Sunday.

AVIATION /18Z Sunday through Monday/

Issued 1229 PM MDT SUN OCT 25 2026 Generally VFR with increasing mid/high clouds through the remainder of today. Exception will be the Long Valley of Idaho and KMYL which will experience IFR/LIFR into early afternoon before improving to VFR, then dropping back to IFR/LIFR overnight in low ceilings and fog. Showers are expected to impact the region and all terminals mid day Monday through Tuesday. Snow levels dropping to 5000-6000 feet. Surface winds: favoring ESE 10-15 kt with gusts to 20+ kts at times this afternoon. Winds aloft at 10kft: WSW 20-30 kt.

KBOI...VFR with mid/high clouds. Increasing clouds and potential for showers after 16Z Monday. Surface winds: ESE 10-15 kt with higher gusts. Winds aloft at 10kft: WSW 20-30 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.