textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Much cooler temperatures Saturday. Sunday and Monday will see temperatures 5 to 10 degrees below normal.

- Active pattern bringing precipitation chances Saturday through Tuesday. Snow showers in elevations above 6000-8000 feet this weekend.

- Significant rainfall possible in south-central and southeast Idaho late Saturday through Tuesday.

- Return of warmer and drier conditions Wednesday through late week.

SHORT TERM /Through Monday Night/

Issued 312 AM MDT SAT OCT 10 2026 The closed upper low will dig further into the northwest region today through Sunday, with the low center slowly moving into central OR. Much cooler conditions, along with some breezy northwest winds, are expected throughout the weekend. The low's east side will steer abundant moisture from the remnants of Tropical Storm Rachel into the Great Basin and Upper Rockies regions, with the bulk of the moisture expected to arrive over eastern/central ID late Saturday and continuing through Monday. The heaviest precipitation is still expected over the easternmost portions of our CWA, mainly over the western Magic Valley, the Boise mountains, and the southern ID highlands in particular. From Saturday to late Monday, the aforementioned areas will potentially see total rainfalls of 0.70- 0.90 inches. With snow levels expected to drop into the 4000-5500 ft MSL range in eastern OR and the 6000-8500 ft MSL range in southwest ID by Sunday, snow/wintry mix showers are still expected over high terrain areas mainly on the ID side, with accumulations heavily limited to high peaks.

Late Sunday into early Monday, there remains some guidance uncertainty over the upper low's movement pattern, but it will generally dig further down into the Great Basin as it treks east. Both Sunday and Monday will see temperatures 5 to 10 degrees below normal from this pattern. The upper low's moisture advection will gradually weaken through Monday. The Magic Valley and the south-central ID mountains will generally see lower precipitation chances (30-40%) by late Monday.

LONG TERM /Tuesday through Saturday/

Issued 312 AM MDT SAT OCT 10 2026 Come Tuesday, the closed upper low will sit just south of our area over the Great Basin as it slowly steers out east. There is some uncertainty to the extent of remnant moisture carried by the shifting low, but Tuesday will generally see a 15-35% chance of precipitation across the western Magic Valley, Boise Mountains, and Southern Idaho Highlands as it moves off to the east. Thanks to the southerly flow aloft, higher snow levels will limit any dusting of snow to elevations above 7000 feet, with little accumulation anticipated.

A warming and drying trend will set in beyond Tuesday as a following ridge builds into the area. A shortwave trough from British Columbia will dig north of our area late Wednesday through Thursday, but keep our area on the dry side. Thursday through Saturday, a highly amplified Pacific ridge will build in and return a slow warming trend. Temperatures 5 to 10 degrees above normal will be possible Friday and Saturday.

AVIATION /18Z Saturday through Sunday/

Issued 1130 AM MDT SAT OCT 10 2026

Generally VFR. Isolated showers this afternoon in SW-Idaho, with isolated thunder mainly S-E of KTWF. Precipitation increasing from SE to NW Sun/AM into Sun/PM, mainly east and south of a KMYL/KONO/KBNO line. MVFR and mtn obscuration possible in precip. Surface winds: W-NW 5-15 kt with gusts to 20-25 kt. Winds aloft at 10 kft MSL: SW 20-30 kt.

KBOI...VFR under FEW to SCT clouds this afternoon, clouds increasing this evening. A 30% chance of rain this evening. Surface winds: NW 5-15 kt through the period, with gusts to around 22 kt this afternoon.

Sunday Outlook...Precipitation expanding from the ID-NV border through S-central and central Idaho Sunday. Periods of snow/wintry mix over higher terrain. MVFR/IFR conditions and mountain obscuration possible in precip. Snow levels: 6-9 kft MSL in SW Idaho. Surface winds: Surface winds: W-N 5-15 kt with gusts 20-30 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.