081 FXUS65 KPIH 082206 AFDPIHArea Forecast Discussion National Weather Service Pocatello ID 406 PM MDT Mon Sep 8 2025
.KEY MESSAGES...
- Dry through this evening, then slight chance of showers beginning late tonight.
- Cooler and unsettled Tuesday through Friday with daily chances for isolated showers and thunderstorms.
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.UPDATE... Issued at 405 PM MDT Mon Sep 8 2025
Updated forecast to include a slight chance of thunderstorms across the southern highlands as radar shows a few isolated returns. Not expecting much rainfall from these storms, mainly dry variety. The storms should fizzle pretty quickly this evening.
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.SHORT TERM /THROUGH TONIGHT/... Issued at 143 PM MDT Mon Sep 8 2025
Afternoon satellite imagery shows some slow CU field development across the region along with some smoke moving into the Magic Valley and Snake Plain from CA/NV wildfires. Doesn`t look the smoke will be too much of a concern going forward aside from some haze and air quality issues. As far as the forecast is concerned, expecting clouds to increase as we progress through the evening and especially into the overnight. Upper level flow becomes more S to SW with a trough moving into the Pacific NW and this will allow some additional moisture to stream into our area. Looks like we`ll stay dry through midnight but hi-res CAMs show some rare nocturnal shower/storm chances for the area after about 3AM or so with chances increasing after daybreak on Tuesday and continuing into the mid- afternoon. Any precip that does occur early tomorrow AM will likely be mostly showers although can`t rule out a stray tstm chance. The better thunderstorm chances will be from late morning into the mid- afternoon hours tomorrow. Highest PoPs are focused across the central mountains and eastern highlands tomorrow but still have 20- 40 percent coverage in the lower valleys. Clouds should keep temps a touch cooler than this afternoon by a few degrees but the downward trend will continue as the aforementioned trough moves closer to the region for the middle and later parts of the week. More on that below.
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.LONG TERM /TUESDAY THROUGH MONDAY/... Issued at 143 PM MDT Mon Sep 8 2025
Unsettled pattern continues through the week, though models have started to consolidate precipitation mainly over the higher elevations with less coverage through the Snake Plain. This may be due to pulling drier air between weak shortwaves rotating around the upper low. Development and progression of convection throughout the week will also have significant input to how much QPF falls over any particular location. As such, long term estimates of the precipitation should be taken with a dose of skepticism this far out. Temperatures remain cool, with highs generally in the 70s for many lower elevation locations. Once the upper trough shifts east for the weekend, there is still a potential for wrap around showers to occur especially Saturday. Temperatures remain cool with ensemble means dropping daytime highs to the mid to upper 60s for portions of the Snake Plain, and lows generally in the 40s.
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.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 405 PM MDT Mon Sep 8 2025
A couple isolated thunderstorms developed south of TAF sites. Expect those to remain south of the sites before dissipating this evening. Models show a shortwave trough arriving late tonight into Tuesday morning. This will produce isolated to scattered showers and thunderstorms for the TAF sites. Plan on including a mix of VCSH and PROB30 storms at TAF sites during this time.
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.FIRE WEATHER... Issued at 143 PM MDT Mon Sep 8 2025
Dry day continues through this evening in between systems. Next round of moisture shifts into the region after midnight with showers developing across the southwest half of the district, shifting northeast through the day Tuesday. Although chances are low overnight and early Tuesday, there is potential for a thunderstorm or two, and chances increase into the afternoon and evening. This is the beginning of a broad period of unsettled conditions for the week. Daytime humidities are expected to remain above critical thresholds throughout the week. Precipitation amounts remain variable, with the Snake Plain expected to remain the driest overall compared to higher elevations. Thunderstorm activity could provide periods of locally heavy rainfall. The deep Pacific trough shifts east by the weekend, but moisture could linger for continued isolated to widely scattered showers and thunderstorms both Saturday and Sunday.
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.PIH WATCHES/WARNINGS/ADVISORIES... None.
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UPDATE...13 SHORT TERM...McKaughan LONG TERM...DMH AVIATION...13 FIRE WEATHER...DMH
NWS PIH Office Area Forecast Discussion