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 TUESDAY/

Issued at 231 AM MST Mon Jan 19 2026

High pressure will remain in place today and Tuesday (and through most of the week). Expect continued fog and stratus each morning, especially for the Eastern Magic Valley, Shoshone area, Snake plain, and adjacent valleys. The more widespread lower fog will continue to be in the Eastern Magic Valley, but expect fog to continue to spread northward into the Snake River plain as well. A dense fog advisory remains in effect this morning for the Eastern Magic Valley, Shoshone area, and the lower Snake River plain. A dense fog advisory will likely be needed for these zones on Tuesday morning as well.

Temperatures will remain in the 20s and 30s where inversion and lingering fog/stratus hold temperatures down, otherwise we will see some lower 40s around.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 1244 PM MST Sun Jan 18 2026

We are still looking at a pattern change, BUT it appears to more of another shift in where the low/high pattern sets up. The ridge breaks down, but now very briefly and ends up reestablishing itself farther out in the Pacific. There is a closed low still expected to drop into the southwest U.S. As this happens, we still active weather with the overall low pressure pattern over the northern U.S. shifting west. There is some moisture embedded within the pattern, so precipitation eventually returns, likely later Thursday or Friday now. It still looks like the mountains will see most of what falls, but with the flow now remaining more northerly...that means moisture will be much less than when it looked like we might get more a direct shot from the Pacific. Any moisture we see is likely not going to put any dent into our lack of precipitation issues of late, especially at lower elevations. Temperatures do warm up just a bit later in the week, but that is likely due just losing the ridge and some mixing takes place.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1035 AM MST Mon Jan 19 2026

Satellite imagery shows LIFR stratus/fog entrenched throughout the Snake Plain and adjacent valleys. Based on a nearby mountain web cam, the stratus is fairly thick at PIH, so erosion may be tougher today. Still believe that rapid erosion has strong potential at least for PIH and IDA within the next few hours, but BYI may be tougher as the terminal never broke out of the stratus yesterday afternoon. Regardless of expected breakout to VFR this afternoon, believe that the LIFR stratus will return for the overnight. SUN should remain VFR, despite some concern that the early afternoon diurnal wind shift to the south could advect some of the stratus north to the terminal. There is just enough erosion at the north end of the stratus field to make that probability quite low. Similarly, DIJ also expected to remain VFR throughout the terminal forecast window.

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 Tuesday for IDZ054-059.