textproduct: Pocatello

KEY MESSAGES

- Fog and low clouds will be around through Tuesday

- Pattern change still coming by midweek

- Someone, somewhere will see rain or snow later this week

SHORT TERM /THROUGH TUESDAY/

Issued at 1235 PM MST Sat Jan 17 2026

The fog and stratus forecast is proving problematic, AGAIN. In fact, this issue will be around through Tuesday at this point. The higher resolution models already show what is out there at the moment diminishing. It is TRYING to, but not making too much progress in reality...and is slower to erode than yesterday at this time. We do think things will eventually thin out/erode by early evening...although confidence in widespread clearing is waning at the moment. The trends are for some pockets of fog and stratus overnight up and down the Snake Plain into the Magic Valley. We've tried to shape the forecast similarly. The winds at the surface are light but are wanting to drive some of this back toward Boise, and some up across the INL and upper end of the Plain. For tomorrow, the wind becomes more from the west and southwest into Monday morning. It appears that what stratus/fog is in the vicinity of the Magic Valley in the afternoon makes quick progress across the rest of Magic Valley and Snake Plain. It does appear we may also see a return of fog and stratus to places like the Stanley Basin, the valleys across the eastern and southeast highlands, Oakley, and the entire Raft River Valley. We may also see some of this encroach the southern end of the Wood River Valley. For Tuesday, we are going to see more of the same although the potential extent is in question right now. We did, however, include patchy dense freezing fog in basically the same areas as tonight and tomorrow night...with the idea we will have to massage the forecast a bit. Otherwise, the rest of the area NOT impacted by this will be clear and enjoying temperatures at or just above average. Where clouds/fog influence things, looks for temperatures to be held down a bit.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Issued at 1235 PM MST Sat Jan 17 2026

Everything points to this pattern still breaking down for midweek and beyond. Temperatures will be fluctuating a bit daily, but it does appear we will seeing the inversion issue weaken or completely disappear for a bit. Again, with the flow splitting across the western states, we will have to see where the main push of moisture comes from and where it will be directed. The models still are struggling with how much falls where in the central and eastern Idaho, especially lower elevations. Trends do suggest that any appreciable moisture likely ends up across portions of the central mountains and eastern highlands. For places that haven't seen much snow this winter may still not see it, or much of it. The pattern is just not very favorable for it to get cold enough to consistently snow at lowest elevations.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 431 PM MST Sat Jan 17 2026

In an inversion with BR/FG and stratus, the uncertainty is as high as it comes. Based on last night's observations, probability of at least marginal VFR in the blended forecast, and time-height cross sections in the NAM, have come up with the forecast for each TAF. KSUN is the easiest with only wind shifts, KDIJ is expected to get some good boundary layer moisture late tonight, which could lead to some stratus issues at that time through the entire TAF, but right now only calling for SCT010. KIDA, KPIH, and KBYI are the toughest, however the blended guidance is showing much longer times below IFR for KBYI and KPIH, mainly for CIG but in KBYI's case including VSBY. Wind is the lightest it has been in the last seven days, so extended periods of fog into the mid-afternoon, as it did on Sat, are likely again.

AIR QUALITY

Issued at 1235 PM MST Sat Jan 17 2026

An AIR STAGNATION ADVISORY remains in place for the Pocatello area, our side of the Cache Valley, and south of Malad toward Samaria. We will continue to see limited mixing for the next several days. Even with the ridge shifted back to the west, nothing has been strong enough to completely mix out any inversions and help clear things out. We may have to wait until midweek to see if that happens entirely. We may end up extending the advisory until then, but will make that determination tonight or tomorrow morning.

PIH WATCHES/WARNINGS/ADVISORIES

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