459 FXUS65 KPIH 061246 AFDPIHArea Forecast Discussion National Weather Service Pocatello ID 646 AM MDT Sat Sep 6 2025
.KEY MESSAGES...
- Thunderstorm threat expands to everywhere by this early evening. Thunderstorm threat increases further on Sunday.
- Cloud cover and precipitation will bring a gradual cooling in both highs and lows today through Friday.
- Gusty wind outside of thunderstorms both this afternoon and Sunday afternoon.
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.SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 200 AM MDT Sat Sep 6 2025
Upper level trough to the west will slowly push eastward, bringing increased southwest to south wind today, then more westerly on Sunday. This southerly airflow will bring in moist unstable air that will act as a trigger for thunderstorms both today and Sunday, both for the afternoons and evenings. The stronger flow aloft on Sunday will mean the potential for stronger wind gusts Sunday after a prolonged period of light wind. A break in the moisture flow from the west on Mon will provide a break in precipitation and thunderstorms.
The increase in cloud cover and eventual shift to westerly flow will allow temperatures to have a gradual cooling trend to both highs and lows into the medium range forecast.
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.LONG TERM /TUESDAY THROUGH FRIDAY/... Issued at 200 AM MDT Sat Sep 6 2025
An upper level trough is expected to slowly move across the western states during this period. There are a variety of solutions in the clusters, with no cluster having more than a 30 percent chance of occurrence, so any timing has low confidence and the threat of showers continues each day and evening, with a reduced but continuing threat of thunderstorms.
The cooling trend for highs and lows continues through this period.
The risk of showers peaks on Thu, then a gradual drying seems to develop in the NBM guidance.
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.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 641 AM MDT Sat Sep 6 2025
Thunderstorm probabilities this afternoon reach PROB30 category, mostly 25 to 35 percent chance of occurrence over a period anywhere from 2 to 6 hours. The risk shifts from west to east across eastern Idaho so KDIJ will not see that kind of risk until 06/21Z, western airdromes should start seeing that kind of risk until 06/19Z. Wind should not be impactful unless it is thunderstorm outflow, and even that should be limited to around 25KT. CIGs should stay above FL100. VSBY could be limited to marginal VFR due to FU, erroneously reported as HZ for weather stations with no augmentation.
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.FIRE WEATHER... Issued at 200 AM MDT Sat Sep 6 2025
Remnants of the southwest monsoon will make its way into eastern and central Idaho for the next couple of days. This will increase humidity and instability, pushing up the mixing heights and increasing the chance of thunderstorm activity. There is a break for Mon and Mon night, then showers return, with a reduced chance of thunderstorms. This means a gradual cooling to both highs and lows with humidity staying rather high both for recovery and afternoon minimum.
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.PIH WATCHES/WARNINGS/ADVISORIES... None.
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SHORT TERM...Messick LONG TERM...Messick AVIATION...Messick FIRE WEATHER...Messick
NWS PIH Office Area Forecast Discussion