793 FXUS65 KPIH 290704 AFDPIHArea Forecast Discussion National Weather Service Pocatello ID 104 AM MDT Mon Sep 29 2025
.KEY MESSAGES...
- Increasing risk of showers and thunderstorms across the entire forecast area today, peaking on Tuesday.
- Much cooler temperatures for Tuesday.
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.SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 103 AM MDT Mon Sep 29 2025
A slow moving cold front will approach the region today. We will showers and thunderstorms mainly across the Magic Valley into the central mountains today. As we move through the night, the band of showers will follow the front and linger into Tuesday morning. It looks like we may clear enough and become unstable in the afternoon for isolated to scattered showers and thunderstorms Tuesday afternoon. The only real area that we have for potential flooding would be around Stanley with the Wapiti burn scar. Rainfall amounts of 0.50 to 1.00 inches seems likely Tuesday night. Although most of this rain may be falling over several hours and part of this rain may soak into the soil. Elsewhere rainfall amounts are around 0.25 inch for this event. Although there is roughly a 25% chance that much of east Idaho may only see 0.10 inches or less. On the other hand, there is a 10% chance central and east Idaho may see 0.50 inches of rain. High temps on Monday are above normal with temperatures in the mid to upper 70s across the Snake Plain and Magic Valley. But on Tuesday, highs fall to the mid and upper 60s for those same areas.
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.LONG TERM /WEDNESDAY THROUGH SUNDAY/... Issued at 156 PM MDT Sun Sep 28 2025
Southwest flow aloft continues with upper low churning off Seattle/Vancouver coast. Ensembles begin to shift the low inland Wednesday, opening it up and ejecting a weak shortwave across the region. Showers and a few thunderstorms remain possible Wednesday, but the main trough passage appears to be Thursday to Friday. There are significant differences in how the ensemble clusters portray passage of the trough. NBM blend brings the greatest precipitation chances Friday, but spread the chances out from Thursday night into Saturday. Breezy conditions accompany another cooldown, this time lasting into the weekend with deterministic NBM reaching only into the 50s for lower elevations both Saturday and Sunday. It is worth nothing that there is roughly a 15 degree spread between low-end and high-end temperatures, so not a lot of confidence yet. That said, the late week frontal system does look more robust and amplified than the previous features ejecting across the region.
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.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1043 PM MDT Sun Sep 28 2025
Models have trended a bit drier on potential VCSH overnight, and we have pulled mention from KBYI and KPIH. Confidence remains low on afternoon shower and thunderstorm potential Monday as well, although KSUN and KBYI seem to have the best chance as our next system approaches from the west, so have added PROB30s there. Overall, expect a VFR day Monday before clouds thicken and lower and rain with embedded thunder moves in from the west Monday night.
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.FIRE WEATHER... Issued at 103 AM MDT Mon Sep 29 2025
A slow moving cold front will bring wetting rains to the region. South Idaho and Central Idaho will see most of its rain Monday afternoon and Monday Night while East Idaho will see it Monday Night and Tuesday. Rainfall totals of 0.50 to 1.00 inches of rain will fall across much of 422, 475 and 476. Valley locations around Salmon and south may see closer to 0.25 inches. Most other locations should see 0.10 to 0.25 inches.
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.PIH WATCHES/WARNINGS/ADVISORIES... None.
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SHORT TERM...13 LONG TERM...DMH AVIATION...01 FIRE WEATHER...13
NWS PIH Office Area Forecast Discussion