textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Heat Advisory in effect for the Snake Plain through this evening.

- Showers and thunderstorms increase area-wide tonight and Tuesday, then chances remaining over higher terrain Wednesday through next weekend.

- Tuesday and Wednesday storms will be capable of heavy downpours, potentially affecting steep terrain and burn scars.

- Hot temperatures continue this week and coming weekend.

SHORT TERM /Through Wednesday Night/

Issued 304 AM MDT MON JUL 13 2026 Mid and upper level monsoon moisture is streaming in from the south- southwest today. As the atmosphere continues to moisten, virga will transition to isolated rain showers this morning and afternoon across E Oregon and the higher terrain of west-central Idaho. Temperatures will once again be hot today, supporting weak instability this afternoon and a 10% chance of thunderstorms developing near the OR-NV border. Both showers and thunderstorms will be capable of localized outflows up to 35 mph during peak daytime mixing hours. Low levels will moisten further late tonight and Tuesday, expanding rain shower coverage across much of the area by Tuesday. Precipitation chances will be highest (30-40%) across far E Oregon and the higher terrain of SW Idaho, with lower chances (5-15%) across the Snake Plain. Instability will become greater Tuesday due to the higher moisture content, as PWATs peak at 1.10" to 1.20" (99th percentile). As a result, hi-res models signify isolated thunderstorm development for the forecast area. Showers and thunderstorms will be capable of gusty outflow winds to 25-45 mph Tuesday afternoon/evening, along with localized heavy downpours. Depending on the rainfall path and duration, downpours could lead to a minor flood risk in steep terrain and across newer burn scars. Temperatures will be a few degrees cooler on Tuesday due to the thickening of cloud cover and increase in shower activity. Beginning Wednesday, a Pacific trough to the west will alter the path of the monsoon moisture, slightly lowering PWAT values across the region from west to east. This will reduce the chance of showers and thunderstorms for much of the forecast area, but a 20% chance over the higher terrain of SW Idaho will remain a concern. High temperatures will rebound by a few degrees as cloud cover/showers thin out.

LONG TERM /Thursday through Monday/

Issued 304 AM MDT MON JUL 13 2026 Hot, southerly flow will persist over E Oregon and SW Idaho Thursday through early next week, with shower/thunderstorm chances currently favoring the higher terrain each afternoon and evening. Models have a poor handle on the extent of precipitation over the area, but the continuation of hot south-southwesterly flow aloft will promote temperatures in the mid to upper 90s across lower elevations for the remainder of the forecast period. Heat Risk will hover in the Moderate category, affecting most individuals sensitive to heat.

AVIATION /12Z Monday through Tuesday/

Issued 525 AM MDT MON JUL 13 2026

VFR. Isolated rain showers today, and 15% chance of PM thunderstorms in east Oregon. Activity producing gusty erratic winds up to 30 kt this PM. Shower coverage increasing late tonight-Tue. Areas of smoke, especially near KBKE. High density altitude due to heat. Surface winds: variable up to 10 kt this morning. Then, SW to NW 5-15 kt this afternoon, with localized gusts to 20-25 kt. Winds aloft at 10kft MSL: SW 10-25 kt.

KBOI...VFR. A 5% chance of light rain today, then a 15% chance of rain showers beginning early Tuesday. Surface winds: SE 4-10 kt, shifting to NW 5-12 kt late this morning. Afternoon gusts around 20 kt. High density altitude due to heat.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory from 2 PM this afternoon to 9 PM MDT this evening for IDZ012-014. Heat Advisory until 9 PM MDT this evening for IDZ016-030. OR...Heat Advisory from 2 PM MDT /1 PM PDT/ this afternoon to 9 PM MDT /8 PM PDT/ this evening for ORZ064.