Area Forecast Discussion

KEY MESSAGES

- Widespread smoke has infiltrated most of eastern Idaho today with the effect dropping high temperatures substantially. Air Quality Advisories have also been issued through Wednesday for the smoke.

- Monsoon moisture remains with a daily chance of light showers and thunderstorms through at least midweek

- ABOVE AVERAGE temperatures expected to return by mid week with extremely hot conditions expected Friday and Saturday.

- Critical to near-critical fire weather conditions in place for the next few days.

DISCUSSION

Issued at 104 PM MDT Mon Jul 27 2026

Main impact today is significant smoke has moved into southeast Idaho and dropped daytime temperatures substantially from the previous few days. Expected to get at least a bit of clearing Tuesday but still lack confidence in widespread 90s in low elevations for high temperatures tomorrow. Air quality alerts have been issued for a large portion of southeast Idaho for the smoke present. Isolated showers and thunderstorms are expected this evening as well as Tuesday and Wednesday in southwest flow aloft. By Thursday upper level ridge begins to expand north and dry conditions are in the forecast grids Thursday through next Monday. With this extreme heat is expected to return with low elevation highs nearing 100 again both Friday and Saturday. Presence or non presence of smoke will be a factor in temperatures for several days.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 941 PM MDT Mon Jul 27 2026

Main issues involve smoke which seems to have thinned around BYI and PIH this evening. It hasn't yet at IDA but think some improvement is possible there. Anticipating slightly worsening conditions again tomorrow looking at the HRRR. Included VCSH at BYI and PIH tomorrow afternoon with storms possible across the southeastern highlands. Potentially may warrant a PROB30 for thunder as we get closer.

FIRE WEATHER

Issued at 142 PM MDT Mon Jul 27 2026

Monsoon moisture remains locked in through Wednesday across central and eastern Idaho. This will keep some mention of thunderstorms going through that point. We will continue to see more dry than wet thunderstorms overall. For today, increasing smoke from fires in Oregon and southwest Idaho have kept temperatures much cooler than forecast across much of the area. This has led to more stable conditions but areas that see just enough clearing, and thus heating, could see some isolated tstm activity. It should remain breezy especially over the central mountains, portions of the Arco Desert, and Magic Valley. A RED FLAG WARNING remains in effect for the Zone 475/476 in the central mountains, although this remains marginal. For Tuesday, the pattern remains similar, although cloud cover will be less overall tomorrow and smoke should improve for the eastern half of the area based on latest model output. The main push storms will be outside of the central mountains, although a small corridor is possible across 475 and 476. We may also be close again on critical fire weather threshold for wind and humidity in those zones. Another deeper surge of moisture arrives for a better chance of showers and storms overall into Wednesday.

By Thursday and into the weekend, the ridge shifts west and potentially even southwest. This should cut off most, if not all, of the monsoon moisture for a while. This will allow for very low humidity issues and hotter temperatures to return. At the moment, we do not have any thunderstorm chances in the forecast. With hotter temperatures, any amount of moisture that crosses the state may produce at least some virga if not a thunderstorm or two.

PIH WATCHES / WARNINGS / ADVISORIES

Air Quality Alert until 3 PM MDT Wednesday for IDZ051>058- 062>075.