textproduct: Pocatello

KEY MESSAGES

- Fog and low clouds will continue to affect some areas through Tuesday, especially during the overnight and morning periods, amid a continued quiet weather pattern for the region.

- A pattern shift is expected by Friday with a trough moving through, which should clear out the daily fog and stratus. However, models have pushed off any precipitation until next weekend.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 203 AM MST Tue Jan 20 2026

Strong high pressure remains over our area. Expect continued overall light winds and clear skies outside of fog and stratus. Fog and stratus are occurring currently for the Shoshone region, Eastern Magic valley, and the Snake River plain. Models show a very weak trough moving over southern Montana this afternoon and clipping our very northeastern areas by Island Park. Models show mid to upper level clouds over our northeastern areas with very little, if any, precipitation. The biggest impact will be northerly winds dropping down over the Montana Divide late today through Wednesday. Models show very light northerly winds dropping down the Snake River plain Wednesday. Models have taken fog and stratus out of the forecast on Wednesday. However, there is a lot of uncertainty of how much fog and stratus will clear out. There would be a lot of moisture to push down the Snake Plain and the wind forecast is generally under 5 to 10 mph. It's not likely all the moisture gets pushed out of our area, maybe just the Upper and, possibly, the Lower Snake River plain. Its not until late Friday into Saturday before high pressure erodes significantly due to a stronger trough moving through the area.

Day-time temperatures will be in the upper 30s and low 40s outside of fog and stratus this afternoon and in the mid 20s to low 30s under fog and stratus. Wednesday models show temperatures dropping around 10 degrees with highs in the mid 20s and lower 30s by Wednesday.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 206 PM MST Mon Jan 19 2026

From Wednesday into the weekend, eastern Idaho is generally expected to stay dry and relatively seasonal temperature-wise under a continued ridge of high pressure. This should lead to mostly sunny to partly cloudy skies each day although some localized inversions low stratus /fog could continue to remain problematic especially in the lower valleys. As a whole though, no significant storm systems appear to be on the horizon into the weekend although maybe some low end PoPs could be realized across the higher terrain later this week, it likely won't amount to much. Expect things to remain generally quiet.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 516 AM MST Tue Jan 20 2026

High pressure will continue over the area today. Expect stratus and fog through most of the day, especially for BYI and PIH. There will a weak trough move over the Island Park area today. Expect this to bring clouds and slightly elevated winds that will likely remove the fog and low stratus for DIJ and, to a lesser degree, IDA. Expect isolated snow showers for DIJ this afternoon. Fog and stratus could hang for IDA and PIH. It will all depend on how fast the drier, northerly flow moves over these TAF sites. SUN will likely get stronger northerly winds this morning moving out the stratus and fog. However, as soon as the winds turn back to southerly, expect fog and stratus back into SUN. SUN has a good chance of clearing back out tonight with a return of northerly winds.

AIR QUALITY

Issued at 1244 PM MST Sun Jan 18 2026

We have extended the AIR STAGNATION ADVISORY out through Tuesday for now. We really haven't seen any movement of poor air across the Pocatello area as well as across the Cache Valley, even with the flow more northerly and no longer directly under the ridge. This pattern should hold through Tuesday. We do see the pattern change, or more of a shift farther west again, by midweek. The issue that we will see increase in wind and precipitation, but moisture potential is lower than before and the pattern shift may not be strong or different enough to completely scour things out especially down near the Utah border. Stay tuned.

PIH WATCHES/WARNINGS/ADVISORIES

Air Stagnation Advisory until noon MST today for IDZ054-059.