textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- A dry cold front will bring breezy winds today, with temperatures cooling around 5 degrees by Wednesday.

- Showers and thunderstorms will increase starting Wednesday expanding across the entire area by Friday.

- There is potential for stronger thunderstorms Friday through Sunday bringing heavy rain and small hail.

SHORT TERM /Through Thursday Night/

Issued 300 PM MDT TUE APR 7 2026 A weak and dry cold front will exit the area to the east tonight. This will leave the area under a brief period of light winds and mostly clear skies, allowing temperatures to drop into the 30s for many mountain valleys and low 40s in the Treasure Valley.

On Wednesday, the flow aloft shifts to the southwest as a closed low off the northern California coast begins to influence our weather. This system will start to advect warmer air and mid level moisture into southeast Oregon by Wednesday afternoon. While the lower levels of the atmosphere remain somewhat dry, there will be enough instability to support a 10 to 20 percent chance of thunderstorms and a 20 to 40 percent chance of showers across Harney and Malheur Counties. Temperatures will be about 5 degrees cooler than today across most areas due to the post frontal airmass.

The coverage of precipitation increases on Thursday as the closed low moves closer to the coast, strengthening the southerly flow. This flow will allow temperatures to rebound quickly, with highs returning to the low to mid 70s in the lower valleys. Increased moisture, combined with daytime heating and cooling temperatures aloft, will create a more favorable environment for thunderstorm development. Expect shower and thunderstorm chances to spread across most of southeast Oregon and into far southern Idaho, particularly near the Nevada border. Thunderstorms will be capable of producing gusty outflow winds and small hail. Showers will likely continue into Thursday night as the main trough axis edges closer to the region.

LONG TERM /Friday through Tuesday/

Issued 300 PM MDT TUE APR 7 2026 The upper-level low off the California coast will move onshore Friday into Saturday. Quickly following this, another upper-level low from the Gulf of Alaska will move into the Pacific Northwest Saturday into Sunday. Both systems will provide sufficient moisture, instability, and lift for showers and thunderstorms.

Increased moisture advection from this upper-level pattern will lead to precipitable water values hovering around the 90th percentile (0.6 to 0.7 in.) Friday, slightly lowering to the 80th percentile Saturday. Friday will support a 30-70% chance of showers (highest near the Nevada border) with a 15-25% chance of thunderstorms. On Saturday and Sunday, the upper-level trough from the Gulf of Alaska will become the predominant system that looks to move directly overhead. Upper-level lapse rates rise to near 8 degrees C/km, combined with surface to 6 km shear values 20-30 kts. The additional lift provided by this system will act on the abundant moisture in place to further increase shower chances to 60-90% and thunderstorm chances 15-25% Saturday and Sunday. Impacts from these thunderstorms will be ironed out in future discussions as parameters become consensus across models.

Precipitation chances will begin to trend lower on Monday and especially Tuesday as the trough moves east of the area. Precipitation totals late this week through the weekend should be light to moderate on average (0.3-0.5 inches in lower elevations, 1- 1.25 inches in higher elevations), although heavier amounts will be possible from thunderstorms. Temperatures will cool to near-normal values Sunday through Tuesday as the trough moves overhead. Snow levels will be above 8kft MSL through Saturday, then fall to around 5-7kft Sunday and 4.5-6kft by Monday and Tuesday. Winds will be breezy under this pattern, especially Monday as the trough exits the area.

AVIATION /00Z Wednesday through Thursday/

Issued 547 PM MDT TUE APR 7 2026 VFR. Scattered cumulus across higher terrain will dissipate by 03Z this evening. Otherwise periods of mid-high level ceilings overnight into Thursday. Surface winds: NW-W 10-20 kt with gusts to 20-35 kt, dropping to 5 to 15 kt after 03Z. Winds aloft at 10 kft MSL: W-NW 15-30 kt.

KBOI...VFR. Gusty NW surface winds through evening, becoming light overnight into Thursday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.