textproduct: Boise

KEY MESSAGES

- Afternoon and evening showers/thunderstorms today and Friday, mainly across southwest/central Idaho and far east Oregon.

- Some thunderstorms may become strong to severe today, capable of gusty outflow winds up to 60 mph, heavy rain, and hail.

- A marginal risk for excessive rainfall is forecast for Friday afternoon across central and south-central Idaho.

- Hot temperatures continue into early next week, with valley highs around 100 degrees; Hottest today.

SHORT TERM /Through Saturday Night/

A push of monsoonal moisture this afternoon will make way for showers and thunderstorms this afternoon this evening. The bulk of this plume, and therefore thunder activity, will primarily be across southwest and southcentral Idaho... although isolated thunderstorms can't be ruled out for eastern Oregon. Inverted-V soundings and steep lapse rates underneath this mid-level moisture will primarily support a wind threat. Storms will be capable of wind gusts to 40-50 mph, up to 60 mph out of the strongest storms the develop. While wind will be the main hazard, brief heavy rain and small hail are also possible. Steep terrain and recent burn scars will be the most susceptible to heavy rain impacts, should a precipitation core pass over them.

Showers and thunderstorms will taper off after sunrise tonight, before returning Friday afternoon/evening. Monsoonal moisture will continue to increase across Idaho, with precipitable water values increasing to near the 95th percentile of climatology (model soundings indicate values of near an inch). This moisture will continue to elevate heavy rain concerns, as scattered showers and thunderstorms redevelop. Some guidance resolves precipitation cores exceeding an inch in an hour. As is typically the case, steep terrain and recently burned areas are of most concern for flash flooding impacts. A Flash Flood Watch has been issued for the Wapiti burn scar for Friday afternoon/evening.

By Saturday, precipitation chances will begin tapering off as a trough lifting towards British Columbia pushes the axis of moisture east. Saturday afternoon, most of the activity will be east of our area; isolated showers and thunderstorms will be confined to higher terrain in the West Central Mountains and southern Idaho. Heat will stick around throughout the short-term period, with today being the hottest day as temperatures increase up to 103 degrees in the Snake Plain this afternoon. Temperatures will cool ever so slightly Friday and Saturday, with lower elevation highs ranging from the mid-90s to around 100 degrees.

LONG TERM /Sunday through Thursday/

The Four Corners / Central U.S. upper-level ridge is expected to remain through the extended, with continued bouts of monsoonal moisture coming into the area. Clusters and ensembles agree on upper- level troughing off the Pacific NW coast with varying amplitude of the ridging, thus placing the region in southerly/southwesterly flow aloft. This will continue to funnel in higher moisture content air, bringing precipitable water values back over 1.00" by Monday (widespread PWAT values over 95% climatology). From Monday on, this will fuel daily flooding threats from thunderstorms as they will be heavy rain producers. Outflow winds will also remain a concern as rain-induced cold pools will drive surface density gradients due to surrounding heat. Hot and mostly dry conditions are anticipated Sunday, with shower/thunderstorm chances limited to south-central Idaho. Precipitation chances will increase Monday through Thursday with continual pulses of monsoonal moisture.

AVIATION /18Z Thursday through Friday/

Issued 1151 AM MDT THU JUL 16 2026

Mainly VFR. Isolated to scattered showers and thunderstorms returning over southwest/central ID and far east OR this afternoon. Stronger storms capable of outflow winds to 35-50 kt, heavy rain with vis reductions, and small hail. Mtn obscuration in storms. High density altitude due to heat in the afternoon. Surface winds outside of storms: SW-SE 5-15 kt in the afternoon, with gusts to 20-25 kt in SE Oregon. Winds aloft at 10kft MSL: southerly 5 to 15 kt.

KBOI...Mainly VFR. Isolated showers/thunderstorms in the area this afternoon, with best chance at terminal between Thu/22Z and Fri/02Z. Stronger storms capable of outflow winds to 30-45 kt, brief heavy rain with vis reductions, and small hail. High density altitude due to heat in afternoon. Surface winds outside of storms: SE-S 5-12 kt, with gusts up to 20 kt in the afternoon.

Weekend Outlook...Mainly VFR. Showers/thunderstorms developing Fri afternoon over portions of southwest/central Idaho, capable of strong outflow winds, heavy rain with vis reductions, and small hail. Mtns obscured in precip. Slight chance of showers/thunderstorms over same areas Saturday afternoon, then limited to south-central ID Sunday afternoon. High density altitude due to heat. Surface winds outside of storms: SW-NW 5-15 kt, afternoon gusts 15-25 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Red Flag Warning until 9 PM MDT this evening for IDZ420-423- 424-426. Heat Advisory until 9 PM MDT this evening for IDZ012-014-033. Flash Flood Watch from Friday afternoon through Friday evening for IDZ013. OR...Heat Advisory until 9 PM MDT /8 PM PDT/ this evening for ORZ064.