textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Cool with temperatures 10 to 15 degrees below normal and gusty winds on Sunday.

- Rain and snow tonight across SE Oregon with accumulations above 5000 feet.

- Patchy frost possible Monday morning in the Snake Plain mainly east of Mountain Home.

SHORT TERM /Through Monday Night/

Issued 236 PM MDT SAT MAY 16 2026 Showers and isolated thunderstorms this evening over e-central Oregon and w-central ID mtns will scale back this evening with sunset. A minor trough off the BC coast this afternoon will deepen as it drops through the Pac NW overnight. It's a more impressive wave as it pushes through SE Oregon Sunday morning and will bring an area of light to moderate precipitation to southern Harney and Malheur counties in Oregon and far southern Owyhee County in Idaho. Precipitation type will be mostly snow as snow levels drop to 4500 feet. This will result in accumulations of up to 2 inches above 5000 feet with 2-4 inches above 6000 feet (mainly Steens Mtn). Not sure this will impact roads given warm surface temperatures, but Hwy 95 from Blue Mtn Pass to the OR/NV border could see brief slushy accumulation. Instability showers/thunderstorms will fire off over higher terrain on Sunday on the backside of the upper low. Northerly winds of 20 to 30 mph with gusts of 30 to 45 mph will setup across SE Oregon and SW Idaho. In this instance the more northerly component will focus the strongest winds across SE Oregon and from Murphy to Bruneau in the Snake Plain.

A broad trough remains over the western US on Monday, putting our area under northwest flow aloft. Daytime heating will bring cumulus buildups over the mountains, which could put down a sprinkle on higher peaks. With the core of the cold air to the east temperatures Monday will run 6-10 degrees warmer than Sunday. Winds remain breezy across SE Oregon and the lower Snake Plain in Idaho with gusts of 25 to 40 mph in the afternoon.

For frost and freeze concerns, the wind tonight should be enough to keep frost/freeze at bay across most of the lower Snake Plain. The coldest spots will be Gooding/Jerome/Hazelton area with lows of 35-40 expected. Sunday night will see temperatures a couple of degrees cooler, and forecast remains consistent with forecast lows of 33-37 from Mountain Home to Twin/Jerome. Have added patchy frost wording to areas from Glenns Ferry to Hazelton where the winds are lightest.

LONG TERM /Tuesday through Saturday/

Issued 236 PM MDT SAT MAY 16 2026 Showers will linger across the higher terrain of southwest Idaho Tuesday/Wednesday as the upper level trough makes it's way east. Northwest flow aloft will prevail behind this trough the work-week, with increasing heights supporting a warming trend throughout the period. Come Friday, a shortwave embedded in the northwesterly flow will graze our area; this will give way to a slight chance of showers, primarily over the West Central Mountains. This shortwave will also slow the warming trend come Friday. Following that shortwave, ridging will likely build in through the coming weekend with a deepening Gulf of Alaska low. Temperatures are forecast to be 5-10 degrees above normal after Wednesday. Winds will be on the breezier side throughout the period, with afternoon gusts to 20-25 mph across the typical windy areas.

AVIATION /00Z Sunday through Monday/

Issued 620 PM MDT SAT MAY 16 2026

Generally VFR. Brief MVFR-IFR conditions in scattered showers near KBKE-KMYL this evening. Precip expanding into SE Oregon, far SW Idaho (south of Snake Plain), and central ID overnight through Sunday afternoon, creating IFR-LIFR in mtn snow. Mtns becoming obscured. Snow levels: lowering to 3000-4500ft MSL overnight. Surface winds: W-NW 10-20 kt with gusts to 20-30 kt through sunset, then W-N 5-15 kt overnight. Becoming NW-N 15-30 kt with gusts 25-40 kt late Sun morning/afternoon. Winds aloft at 10kft MSL: W-N 15-30 kt.

KBOI...VFR. Surface winds: NW 10-18 kt with gusts around 25 kt through sunset, then NW 5-15 kt overnight. Winds/gusts increasing again late Sunday morning, peaking at 20-30 kt with gusts up to 30-40 kt Sunday afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.