558 FXUS65 KPIH 300508 AFDPIHArea Forecast Discussion National Weather Service Pocatello ID 1108 PM MDT Mon Sep 29 2025
.KEY MESSAGES...
- Showers and storms increasing with the peak tonight.
- More precipitation coming through the rest of the week.
- Much cooler temperatures on the way.
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.SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 1251 PM MDT Mon Sep 29 2025
Showers and thunderstorms will peak tonight/early Tuesday, with bulk of moisture falling across the central mountains. The range in that area is still generally 0.50-1.0" this evening and overnight. There is a bigger threat of thunder before midnight, which lends some credence toward the higher end amounts. There is a MARGINAL RISK for enhanced rainfall in place. In terms of impacts for debris flows especially on the Wapiti, the risk will likely be mitigated by a transition toward more widespread rain and embedded heavier rain/thunderstorms vs just purely convective and very high hourly rainfall rates. There is a window where hourly rates could exceed 0.10", but the overall risk is on the low end of things. There is a 10-30% chance of gusts over 35 mph with stronger showers and storms as well. Other more isolated showers and storms are expected elsewhere through the overnight hours. As that main band shifts north and east, it will weaken...but multiple bands/rounds of showers and storms are forecast through tomorrow night. Precipitation amounts will be lighter overall tomorrow, but we could still some decent bursts of rainfall at times. There is a similar probability for gusty winds tomorrow vs today. It will be noticeably cooler tomorrow, with highs only in the 50s and 60s...and 40s if you are headed to high country.
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.LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 1251 PM MDT Mon Sep 29 2025
We really don`t too much of a break in the chance of showers and potential storms through the rest of the week. While we will be "in between" lows Wednesday, there is still some chance mainly over the mountains. The pattern for the rest of the week and into next weekend will be showing a split flow pattern over the western U.S. This means as each storm moves inland, we will the pattern splitting with one or more closed lows developing somewhere over the West. While this type of pattern has a bit more difficulty with predicting where these closed lows end up, it will remain showery at this point...along with even colder temperatures likely. Our current Blend of Models forecast has highs only in the 50s down low and 30s/40s up in the mountains. This means we will see some potential for snow falling for our higher peaks and ranges. Welcome to October!!
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.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1108 PM MDT Mon Sep 29 2025
Few changes made with the 06z TAF package...main ones were to delay onset of the main period of rain/showers by another hour tonight at most terminals, end the period at 11z for KSUN, and massage cigs a bit lower Tuesday afternoon based on forecast soundings. Have also added TEMPOs at KBYI and KPIH to capture a 2-3 hour burst of stronger W/SW winds with the approaching cold front tonight. Overall cigs still appear to hold VFR tonight into Tuesday with the main batch of moisture, then we watch for isolated redevelopment of thunderstorms Tuesday afternoon and evening...especially if significant breaks in the clouds develop during the early afternoon.
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.FIRE WEATHER... Issued at 1251 PM MDT Mon Sep 29 2025
General trend is for chances of showers and thunderstorms daily through next weekend. The initial showers this afternoon through Tuesday will likely provide amounts above a half inch to higher elevations of zones 422, 475 and 476 with a lower chance of approaching 1 inch total. Lower elevations and throughout the other zones amounts in the 0.10 to 0.25 range is most likely. Temperatures will be closer to normal through Thursday with a significant cool down expected Friday through Monday with highs in the 40s mountains and 50s valleys expected. Elevated humidity expected through the remainder of the week with minimum staying above 30 percent.
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.PIH WATCHES/WARNINGS/ADVISORIES... None.
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SHORT TERM...Keyes LONG TERM...Keyes AVIATION...01 FIRE WEATHER...GK
NWS PIH Office Area Forecast Discussion