textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Showers and thunderstorms increase area-wide today, then chances remain over higher terrain Wednesday through next weekend.

- Locally heavy rainfall could affect burn scars across southeast Oregon.

- Hot temperatures continue this week and coming weekend.

SHORT TERM /Through Thursday Night/

Issued 245 AM MDT TUE JUL 14 2026 The monsoonal moisture continues due to southerly flow aloft, as strong high pressure resides to the east and a Pacific trough to the west. At this time, a healthy round of moisture is arriving from Nevada into southeast Oregon early this morning. The influx of numerous showers will initially extend across eastern Oregon and into west-central Idaho, before moving through the rest of southwest Idaho by late morning. Models indicate a broad swath of breezy outflow winds will be associated with this moisture, with gusts to 25-40 mph possible. Precipitable water values across the region are currently over 1.00", and are expected to increase further throughout the morning and afternoon. Therefore, showers will become heavier with time as low levels continue to moisten, and a Marginal Risk (at least 5%) of flash flooding due to excessive rainfall is forecast across E Oregon and the Owyhee Mountains today. The first round of showers will exit toward the northeast by late morning/early afternoon, allowing surface heating and instability to strengthen near the OR-NV and ID-NV borders. Meanwhile, an upper level shortwave will propagate northeast through the area this afternoon and generate additional lift. These conditions will help support a new round of showers and thunderstorms by late afternoon and evening. The highest thunderstorm chances will be near the NV-OR border, the Owyhee mountains, and south-central Idaho, but cannot be ruled out for areas farther north. Outflow wind gusts to 30-40 mph are possible with storm activity. Temperatures will be cooler today compared to previous days in response to cloudy skies and showers.

Beginning Wednesday, the aforementioned Pacific trough will start encroaching on the Pacific Northwest and nudge the bulk of the monsoon moisture toward the east. As a result, drier and sunnier conditions are anticipated, allowing high temperatures to return above normal. Lingering moisture and afternoon instability will keep a threat of isolated showers/thunderstorms around, with best chances (10%) across E Oregon and central Idaho. Due to the low-level heating, outflow wind gusts will become a threat in the afternoon if thunderstorms develop. Similar conditions are anticipated Thursday, with temperatures heating up a few degrees more. Temperatures may exceed 100 degrees for lower elevations, particularly across the Snake Plain and Weiser Basin. The path of monsoon moisture will attempt to shift westward on Thursday, increasing shower and thunderstorm chances across portions of southwest/central Idaho once again.

LONG TERM /Friday through Tuesday/

Issued 245 AM MDT TUE JUL 14 2026 Conditions will remain similar on Friday, as hot, southerly flow dominates over E Oregon and SW Idaho. Shower/thunderstorm chances will favor portions of southwest Idaho Friday through the weekend, with daytime temperatures persisting above normal. Beyond the weekend, models attempt to shift the Pacific trough northeastward into BC/Alberta Canada, which may disrupt our access to the monsoonal moisture plume. Depending on the rebound efforts of the upper ridge toward the east, shower/thunderstorm chances and max temperatures have become much more uncertain for early next week. Overall, expect Heat Risk to hover in the Moderate and Major categories each day, affecting most individuals sensitive to heat.

AVIATION /18Z Tuesday through Wednesday/

Issued 1141 AM MDT TUE JUL 14 2026 VFR and overcast in a band of steady rain moving through Idaho. Behind the band as it heads east, skies become broken before a 20% chance of thunderstorms this afternoon and evening. Thunderstorms could produce gusty outflow winds and heavy rainfall. Storms are most likely in SE Oregon and along the Idaho-Nevada border. Surface winds: W-NW 10-20 kt with gusts to 20-30 kt from KBOI to KJER. Storms could produce wind gusts to 25-35 kt. Winds aloft at 10kft MSL: SW 5-20 kt.

KBOI...VFR with light rain. Clearing out early in the afternoon, then 5% chance of showers/thunderstorms moving in vicinity this evening. Surface winds: NW 5-15 kt with gusts to 20 kt possible through the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.