textproduct: Boise

KEY MESSAGES

- Showers and thunderstorms continue Thursday and Friday, mainly across southwest Idaho, capable of gusty outflow winds and heavy rain.

- Hot temperatures late week into the upcoming weekend with valley highs around 100 degrees, hottest on Thursday.

SHORT TERM /Through Friday Night/

The pattern will remain active through the short term as south to southwest flow aloft continues to draw up monsoonal moisture into the area. Isolated showers and thunderstorms across the higher terrain this afternoon will taper off this evening. Isolated showers and thunderstorms will then lift northeast through southeast Oregon Thursday morning as a weak shortwave lifts north. Coverage will expand Thursday afternoon across southwest Idaho with daytime heating, initiating off the higher terrain with enough instability for storms to survive into the Treasure and Magic Valleys. Drier air moving into southeast Oregon will limit thunderstorm potential there, except for isolated thunderstorms along the Idaho border. Thunderstorms will be capable of outflow gusts 40-60 mph, cloud- to-ground lightning, and brief heavy rainfall. Temperatures will increase 5-10 degrees from today under southerly flow and a ridge building to our east, resulting in highs exceeding 100 degrees in the Treasure Valley and Upper Weiser River, where a Heat Advisory is in effect. It will be locally breezy across southeast Oregon with gusts 20-30 mph.

Monsoonal moisture will continue to increase across southwest Idaho on Friday under southerly flow aloft. This will produce another round of afternoon and evening showers and thunderstorms, primarily across south-central Idaho north into the mountains. The increasing moisture may allow storms to produce heavy rain, resulting in a flash flood threat mainly over burn scars. Gusty outflow winds are also possible from storms. Temperatures should decrease a degree or two as a weak impulse moves through.

LONG TERM /Saturday through Wednesday/

The region will remain on the western edge of a hot upper level ridge through the period. After a break from the deeper monsoon moisture over the weekend, the chance of showers and thunderstorms will expand over the area early next week. Higher terrain in southwest Idaho zones will be the focus development while southeast Oregon is positioned on the fringe of the deeper moisture. The water content of the air mass will again reach the +95th percentile as precipitable water values are forecast to surpass 1.20 inches. This would certainly favor heavy rainmakers. Temperatures will remain above normal with lower elevations seeing highs near 100 while dew points in the 50s to low 60s will increase the humidity early next week.

AVIATION /18Z Wednesday through Thursday/

Issued 1207 PM MDT WED JUL 15 2026 VFR with scattered cumulus development over higher terrain through sunset. Widely scattered showers and thunderstorms over SE Oregon and SW Idaho mtns will produce gusty outflow winds to 40 kt. Surface winds: variable up to 10 kt with localized gusts to 15 kt. Winds aloft at 10kft MSL: Southerly 5 to 15 kt.

KBOI...VFR with northwest winds through sunset.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Red Flag Warning from noon to 9 PM MDT Thursday for IDZ420-423- 424-426. Heat Advisory from noon to 9 PM MDT Thursday for IDZ012-014- 033. OR...Heat Advisory from noon MDT /11 AM PDT/ to 9 PM MDT /8 PM PDT/ Thursday for ORZ064.