Area Forecast Discussion

KEY MESSAGES

- Winter Weather Advisory starts 6 PM MDT today and goes through 5 PM MST Sunday. Snow above 7000ft elevation.

- Moderate to heavy rain redevelops starting late tonight, continues into Sunday night.

- Cooling trend to high temperatures starting today, with warming returning to western areas Monday, other areas Tuesday.

DISCUSSION

Issued at 200 AM MDT Sat Oct 31 2026

Today through Mon night...First round of showers is currently moving through the eastern half of the forecast area at this time. Light precipitation will continue on and off today and this evening. The trend compared to yesterday is that it will be lighter amounts for the evening hours tonight, with moderate amounts of rainfall/snowfall in the central Idaho mountains. At this time, expecting 3 to 5 inches of snow on Galena Summit, with heaviest amounts of snowfall on the mountain ranges on the east side of the Wood River Valley. Winter Weather Advisory still appears to be valid and will continue. Rain amounts appear to be up slightly, with storm totals at Pocatello near an inch for the Fri night through Mon morning period. Peak rainfall accumulation occurs in the Snake River plain Sun afternoon and Sun evening.

By Mon morning only the highlands bordering WY will still be receiving precipitation. Mon night will be a transition to dry conditions, save for the likely high humidity that will bring a threat of fog, including dense fog, to the Tue morning commute.

Temperatures will cool compared to Fri, and cool some more from today to Sun. This is mainly due to airmass displacement. Clouds will have cleared enough in the central Idaho mountains for a warming trend to develop starting Mon, but the Snake River plain and eastern highlands will have to wait election day.

Southern Idaho's relative postion in relation to the low's center means not a lot of wind with this storm. However, there area some windy conditions after the low shifts eastward in the southwest quadrant of the forecast area.

Tue through Fri...An upper level ridge keeps conditions calm and sunny on Election Day, but the breakdown of this upper level ridge is in question. There are four different clusters of solutions in this medium range period. It is about a 60-40 split that the ridge will remain on Wed, then flatter, zonal flow or weak troughing developing Thu. Zonal flow makes timing of shortwave energy more difficult, so there is quite a bit of uncertainty in the forecast starting Thu.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 533 AM MDT Sat Oct 31 2026

Potential problems with stratus and BR making airdrome operations this morning difficult. IFR conditions possible at KDIJ, KBYI, and KIDA. Marginal VFR will be off-and-on throughout the 24 hour period. There is a break during the afternoon and evening, before a second round of SHRA BR with at least marginal VFR impacts on both VSBY and CIG. Wind is incredibly light and at most might increase this afternoon to just under 15KT, except for some gusty wind in the afternoon at KPIH from the south due to downslope. Finally, KIDA does have a weak chance of TSRA during the afternoon. TSRA outflow shouldn't be much, perhaps G30KT.

FIRE WEATHER

Issued at 200 AM MDT Sat Oct 31 2026

A low moving through the great basin, to Idaho's south, will bring rain and high elevation snow, with most of the wind on the southern side of the low. Expect low temperatures through Mon, high humidity through at least Tue, and some possible wind in the southern Sawtooth NF on Sun.

PIH WATCHES / WARNINGS / ADVISORIES

Winter Weather Advisory from 6 PM this evening to 5 PM MDT Sunday for IDZ073-074.