textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Above normal temperatures continuing through Friday, then cooler and wetter Saturday and into next week.

- Showers and thunderstorms Friday afternoon through Sunday, with gusty outflows, small hail, and heavy rain from the stronger storms. Heaviest rainfall Friday night and again Sunday.

- Dry and mild Tuesday.

- Showers and thunderstorms and cooler again Wednesday.

SHORT TERM /Through Saturday Night/

Issued 301 PM MDT THU APR 9 2026 Southerly flow aloft will keep temperatures warm through Friday, with scattered showers and isolated thunderstorms developing in southeast OR and along the ID/NV border late this afternoon and evening as a Pacific upper low slowly approaches northern California. That low will be overtaken late Friday by a stronger low from the Gulf of Alaska. The original low will weaken and accelerate inland and northeastward Friday night resulting in widespread showers and evening thunderstorms in our CWA. Instability will be greatest in Owyhee and Twin Falls Counties Friday evening where strong thunderstorms with hail and gusty winds are possible, but all areas will have enough instability for thunderstorms. Numerous showers will continue Saturday and Saturday evening, but fewer thunderstorms due to greater stability resulting from cooler surface temperatures. Later Saturday night the stronger upper low will reach the northern California coast and circulate another surge of moisture into our CWA from the south. That surge looks even wetter than the one Friday night, and will continue all day Sunday with widespread showers and 15 to 25 percent chance of thunderstorms. Total rainfall Friday night currently estimated at .25 to .50 inch, locally 1.00 inch in the Owyhees and on Steens Mountain. Rainfall Saturday night through Sunday should total .50 to 1.00 inch throughout southeast Oregon, and .25 to .75 inch in western Idaho, and near .25 inch in south-central Idaho.

High temps in the 60s and 70s (warmest in the Snake Basin) on Friday will lower about 10 degrees on Saturday and another 5 degrees Sunday. Nights will stay mild due to clouds and precipitation.

LONG TERM /Sunday through Thursday/

Issued 301 PM MDT THU APR 9 2026 The upper-level low creating the active weather pattern will move into the Great Basin/Intermountain West region on Sunday. Widespread showers will be ongoing Sunday, with slight-chances for thunderstorms Sunday afternoon. These thunderstorms carry the hazards of gusty winds, small hail, and brief heavy rain. While thunderstorms are not expected to be as intense Sunday compared to Saturday, upper-level lapse rates will still be near 8 degrees C/km, with surface to 6 km shear values of 15-25 kts. The parameters for thunderstorms are certainly muted from previous values Friday and Saturday, however a favorable sequence of events could lead to an over-achievement of expectations. Monday also carries widespread high precipitation chances across the region, however thunderstorm chances will be isolated due to the cooler surface temperatures during peak heating and less instability aloft. Through these continuous days of widespread precipitation chances, QPF across the area is something to monitor for hydrologic effects. Tracks of stronger thunderstorms will strongly determine where localized greater accumulations occur. Snow levels look to drop to 5000-6000 feet late Sunday, and 4000-5000 on Monday night, with snow accumulations largely limited to higher peaks. Gusty winds to 40 mph will occur over areas south of the Treasure Valley on Sunday as the low moves inland. Winds will remain breezy on Monday as well. Below normal temperatures will occur on Sunday and Monday, with valley highs only reaching the mid to upper 50s.

The low will exit the Great Basin/Intermountain West by early Tuesday, bringing a brief return to mostly dry conditions from a short-lived upper-level ridge. Shower chances quickly return Wednesday as another trough deepens into the region from British Columbia. This will bring much colder air and precipitation late Wednesday into Thursday. Model disagreement remains high on this system, with high uncertainty in timing and location of precipitation.

AVIATION /00Z Friday through Saturday/

Issued 634 PM MDT THU APR 9 2026 VFR. Scattered showers/thunderstorms will continue over SE OR and the OR/NV border areas this evening and overnight. Widespread showers and scattered thunderstorms expected over most areas Friday afternoon/early evening. Thunderstorms capable of gusty outflow winds and small hail. Surface winds: light and variable under 7 kt overnight, then SW-NW 5-10 kt in the afternoon. Winds aloft at 10 kft MSL: W-SW 10-25 kt.

KBOI...VFR with SCT high clouds from south. Showers with a 30% chance of thunderstorms expected Friday afternoon/early evening. Thunderstorms capable of gusty outflows and small hail. Surface winds NW 6-10 kt this evening, becoming SE under 7 kt after sunset.

Weekend Outlook...Showers and thunderstorms will persist across the area Saturday. Storms may be strong and produce heavy rain, small hail, and gusty winds. Thunderstorm chances will be more limited on Sunday, but widespread rain and mtn snow are expected. MVFR/IFR conditions possible in precipitation with mountain obscuration. Snow levels 6500-8000 feet Saturday, lowering to 5000-6500 on Sunday. Surface winds: SW-SE 5-10 kt Saturday and W-SW 10-15 kt Sunday with afternoon gusts to 30 kt both days.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.