Area Forecast Discussion

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated to scattered showers through this afternoon.

- Widespread rain and high elevation snow tonight into Sunday. A slight chance of thunderstorms late this afternoon through this evening. - Cooler with gusty winds Sunday, and especially Sunday night, then drying and warming Monday through Wednesday. Slight chance of precipitation late week.

SHORT TERM /Through Monday Night/

Issued 332 AM MDT SAT OCT 31 2026 An upper low off the Oregon coast will slowly move inland tonight into Sunday. The track of the low and southerly flow will transport subtropical moisture over the Desert Southwest northward into our area. Shower activity will initially be isolated to scattered through the afternoon, then increase this evening and become widespread overnight as the low advances and moisture increases. A 10-20% chance of thunderstorms will develop across southern Idaho and far southeast Oregon late this afternoon through tonight with lower chances elsewhere. Brief heavy rain is possible from thunderstorms. Precipitation will continue into Sunday as moisture wraps around the low, decreasing from west to east. Showers will finally come to an end Sunday evening across south-central Idaho.

Precipitation amounts from this system will be substantial, with 0.25 to 0.50 inch likely across most of southwest Idaho and far southeast Oregon. However, there is a 10-20% chance of heavy rainfall totals in excess of 1 inch in the lower elevations of southwest Idaho. Lower amounts are expected to the west including Burns and Baker City Oregon. Totals of 0.50 to 1 inch are expected in the Boise mountains and southwest Idaho highlands, with locally higher amounts possible. Snow levels will be 6500-8000 feet today, then lower to 5500-7000 feet Sunday morning behind a cold front, lowest across southeast Oregon. This will limit significant snow accumulation to elevations above 7000-8000 feet with several inches of snow, and a dusting possible down to 6000 feet.

Temperatures today will be near normal with valley highs in the mid to upper 50s, with most areas cooling 5 to 10 degrees on Sunday behind the cold front. Winds will be breezy on Sunday with gusts 20 to 35 mph, except up to 45 mph east of Boise through the Magic Valley, strongest Sunday night. Winds will taper off on Monday as the low moves east and an upper level ridge moves overhead. This will bring dry conditions and warming temperatures at higher elevations while lower elevations see similar temperatures as a weak inversion develops.

LONG TERM /Tuesday through Saturday/

Issued 332 AM MDT SAT OCT 31 2026 An upper level ridge will remain overhead on Tuesday with continued dry and slightly warmer temperatures. Winds will become breezy ahead of a low that will weaken and move through on Wednesday. Additional troughs are expected late week, increasing precipitation chances to 10-30% late Wednesday and Thursday, and further rising to 20-50% on Friday. These systems will be weak, keeping similar, near-normal temperatures from day to day. A ridge of high pressure is likely to build overhead on Saturday with a return to dry conditions.

AVIATION /12Z Saturday through Sunday/

Issued 600 AM MDT SAT OCT 31 2026 Mainly VFR under mid to high clouds and isolated to scattered showers through the afternoon. Patchy valley fog this morning. Isolated thunderstorms across S Idaho and far SE Oregon late this afternoon through the evening. Showers becoming widespread tonight. VFR-MVFR in rain showers, IFR-LIFR in mountain snow. Mountains obscured in precipitation. Snow levels 6500-8000 ft MSL. Surface winds: SE-SW 5-10 kt, except gusts to 25 kt near heavy showers and thunderstorms. Winds aloft at 10kft MSL: S-SW 10-20 kt.

KBOI...VFR through the afternoon. Isolated showers through mid afternoon, becoming widespread tonight. MVFR ceilings and visibility during heavier showers this evening, prevailing overnight with a low chance of IFR conditions developing. Surface winds: variable to SE 4-8 kt, becoming W-NW 4-8 kt overnight.

Sunday Outlook...Precipitation gradually tapering off from W-E. VFR-MVFR in rain showers, IFR-LIFR in mountain snow. Mountains obscured in precipitation. Snow levels lowering to 5500-6500 ft MSL. Surface winds: W-NW 10-20 kt with gusts 20-35 kt behind a cold front, strongest east of KBOI through the Magic Valley.

BOI WATCHES / WARNINGS / ADVISORIES

ID...None.

OR...None.