textproduct: Pocatello

KEY MESSAGES

- Showers and thunderstorms continue for the next few days with gusty winds and heavy downpours possible

- Critical to near-critical fire weather conditions due to thunderstorms through this evening and wind/humidity Wednesday

- Rain chances increase this weekend and early next week as monsoon moistures increases due to potential tropical connections

DISCUSSION

Issued at 1154 AM MDT Tue Sep 1 2026

As low pressure settles along the coast for the next several days, we will see multiple "ripples" swing around through during that stretch. We have one of those ripples crossing this state through tonight. The highest chances through late afternoon/early evening will be across the central mountains south through the Magic Valley and South Hills/Albion Mountains. Besides the potential for some locally heavier rainfall, there is a 50-90% chance of for gusts over 35 mph with the strongest storms. High end gusts up to 45 mph are possible over most of eastern Idaho, with a corridor of gusts approaching 60 mph potentially across the Magic Valley, Lower Snake Plain, and South Hills/Albion Mountains. Through this evening and overnight, the better chance of showers and storms will exists north of a Shoshone to Driggs line. Gusty winds and a good downpour are possible with storms, even past midnight. The focus quickly shifts to the central mountains tomorrow. We have a slightly stronger "ripple" racing northeast. As drier air works in across most of eastern Idaho, enough moisture and proximity to the low itself will keep a decent chance of rain and thunderstorms across the central mountains. It is possible a storm or two develops across the eastern highlands, but that is still under 20%. Gusts over 35 mph with storms in the central mountains remains possible, although timing suggests the strongest winds develop across western Montana. The main impact will increasing wind across the rest of eastern Idaho. Sustained winds of 15-30 mph with higher gusts are expected, with a fairly narrow corridor of sustained 30-35 mph with gusts closer to 45 mph from Craters to Monida Pass. We decided to NOT issue a WIND ADVISORY for tomorrow due to the localized coverage of highest winds, but that may need to change based on trends over the next 6-12 hours. We will briefly reach LAKE WIND ADVISORY for American Falls Reservoir, but again we will opt of that for now based on the limited timeframe. For Thursday, the pattern really doesn't change much from tomorrow. Any potential for showers and storms is confined to the central mountains. Some higher resolution models want to spread that into portions of the Magic Valley and also eastern highlands, but will let the current Blend of Models forecast ride. It will be breezy again, slightly "weaker" than Wednesday. The pattern will bring in cooler conditions, especially for the central mountains. Higher valleys will only be in the 60s after today, with lower valleys running in the 70s to near 80.

This pattern really doesn't budge until we get to Sunday and beyond. In fact, we may see enough drier air that only low chances of showers and storms occur across the central mountains Friday and especially Saturday. We do see a small rebound in temperatures both days, with some low 80s returning for some valley locations. The forecast gets a bit tricky for early next week. There is a window where we do see a surge of monsoon moisture, including tapping into what's associated with current Tropical Storm Marie. The ECMWF and associated models, as well as the GEFS and AIGFS, have a shorter window where we see that surge of moisture vs. the main GFS model. All of the models, however, keep low pressure over the western U.S. despite any type of interaction with Marie. This should drop highs back into the 60s and 70s during that period.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 447 PM MDT Tue Sep 1 2026

Scattered storms developing which may impact TAF sites this evening with gusty winds. Expect most activity to dissipate this evening. Although models show another round of showers and thunderstorms moving into the SUN towards 12z.

FIRE WEATHER

Issued at 119 PM MDT Tue Sep 1 2026

Instead of issuing yet another Red Flag Warning for FWFZ 422, have extended the current one, as thunderstorm activity in that zone will increase again somewhere around 0600 MDT and continue until 1500 or so in the afternoon. The area of thunderstorms will push from south to north over the region, and the activity will move into the Salmon-Challis NF by that time.

The Red Flag was necessary as a trough with associated surface front moves in from the southwest, pushing the front through from south to north over central Idaho. The result will be much windier conditions over all of the fire weather district, and isolated showers and thunderstorms in western portions continuing all Wed, Thu, and Fri. Meanwhile, the eastern portions have mostly isolated thunderstorm activity for tonight, Wednesday, and Thursday. Little rainfall, so the effects will be mainly one day of strong cooling, then a gradual warming and drying. Wind will continue to be a factor, staying moderate to strong. Currently, humidity readings are expected to stay in the upper teens and higher, but will have to be monitored and could change depending on how much precipitation develops from the original low.

PIH WATCHES/WARNINGS/ADVISORIES

Red Flag Warning until 3 PM MDT Wednesday for IDZ422.