textproduct: Pocatello

KEY MESSAGES

- Precipitation & Mountain Snow Tapering Tonight: Light-to- moderate rain will diminish areawide around midnight, while accumulating snow above 7,000 feet near Sun Valley winds down by early evening, allowing the high-elevation Winter Weather Advisory to expire on schedule.

- Overnight Patchy Fog Risk (Upper Snake Plain): Abundant boundary-layer moisture combined with lighter winds will support patchy fog and low stratus development across the Snake Plain tonight, focused particularly in the Upper Snake. Breezy winds in the Magic Valley should keep widespread fog at bay.

- Chilly Monday with West-to-East Clearing: Fall-like temperatures will linger on Monday, holding afternoon highs in the 40s to lower 50s as clouds steadily break from west to east.

- Predominantly Quiet Workweek & Eventual Warm-Up: Aside from weak, passing upper-level impulses that may spark low-end precipitation chances over mountain terrain, the upcoming week looks mostly dry, with ensemble guidance trending toward above-normal temperatures by next weekend.

DISCUSSION

Issued at 117 PM MST Sun Nov 1 2026

A dreary Sunday continues across eastern Idaho, with afternoon satellite imagery showing a broad cloud shield streaming northward across the Great Basin. Regional radar shows light-to- moderate rainfall persisting across the area, though high- resolution convective-allowing models (CAMs) indicate precipitation will steadily wind down around midnight. For the higher terrain around Sun Valley, a Winter Weather Advisory remains in effect for elevations above 7,000 feet, but CAMs indicate snowfall will taper off by early this evening as dynamic lift weakens and moisture pushes further east.

The primary operational concern overnight will shift to low stratus and fog development given abundant low-level moisture over saturated soils. Surface winds are forecast to remain elevated across the Magic Valley, which should promote enough mixing to keep fog largely at bay there. However, lighter winds across the Snake Plainespecially the Upper Snakewill allow the boundary layer to decouple and promote patchy fog development. Patchy fog has been introduced into the forecast grids to address this impact through early Monday morning.

Cool, fall-like conditions will linger to start the workweek. As the departing disturbance pulls eastward, cloud cover will gradually clear from west to east throughout the daytime hours on Monday. Persistent cool advection and early morning cloud cover will suppress diurnal heating, keeping daytime highs capped in the 40s to lower 50s across the region. Not much variation from one day to the next through the upcoming workweek as far as temps are concerned. No major, high-impact storm systems are on the horizon once today's precipitation clears out. Operational models depict a series of weak, transitory upper-level impulses tracking across the northern tier, which may spark low-end PoPs occasionally across the higher terrain, but lower-elevation valleys look predominantly dry. Medium-range ensembles continue to trend toward building heights and above- normal temperatures late in the period and into the start of next week. Given typical model spread at days 6 and 7, this warming trend will be monitored in subsequent cycles as guidance converges.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1049 AM MST Sun Nov 1 2026

Broad rain shield remains firmly anchored across east Idaho per regional radar, satellite, and surface observations. While CIGS currently show localized variability, expect prevalent MVFR to dominate this afternoon through mid-evening across all terminals, with periodic dips to IFR in heavier RA/BR. Precipitation will begin tapering from northwest to southeast during the late evening and early overnight hours for KSUN, KBYI, KPIH, and KIDA. KDIJ remains the outlier, holding onto steady precipitation and persistent low CIGs/VIS until roughly 12Z14Z Monday morning.

Fog development becomes a primary forecast challenge overnight as mid- and high-level clouds scatter out from the west over rain-saturated surface. High-resolution ensemble guidance (REFS) highlights a 6575% probability of visibility dropping below 3SM between KPIH and KBYI after 09Z. Subsequent issuances may require a prevailing or VCFG mention for both terminals depending on clearing trends. However, surface winds behind the passing front remain a significant complicating factor: gusts of 2530 kt across the Snake River Plain (KBYI, KPIH, KIDA) this evening into tonight could mitigate fog formation and instead favor redevelopment or reinforcement of MVFR stratus deck.

FIRE WEATHER

Issued at 147 AM MDT Sun Nov 1 2026

Humidity remains high with a low moving through during the evening hours today. Moderate to locally heavy rain is likely. Wind is fairly weak save for the southern Sawtooth NF. A shift to northerly air flow late tonight keeps temperatures cool, especially once skies fully clear for Tue/Tue night. Wed through Fri continue unsettled, with weak impulses moving through a westerly flow that could trigger light showers and bring windy conditions. By Saturday, upper level ridging develops over Idaho as a more substantial low approaches the west coast.

PIH WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 5 PM MST this afternoon for IDZ073-074.