Area Forecast Discussion

KEY MESSAGES

- Light to moderate rain with very high elevation snow today and tonight.

- Near normal high temperatures today and Saturday (40s and 50s) before temperatures drop 8 to 12 degrees below normal (30s and 40s) late Saturday through Monday.

- A slight tapering off of precipitation Saturday, then moderate to heavy rain and light to moderate snow (mainly in the Central mountains) Saturday evening through early Monday morning.

DISCUSSION

Issued at 1152 AM MDT Fri Oct 30 2026

There is currently moist, southwesterly flow aloft over southern Idaho with light showers currently, mainly over our western areas. Currently, there is an upper level low centered just off the coasts of Washington and Oregon as part of an overall trough that extends much farther south to off the coast of California, where there is ample sub-tropical moisture available. This low/trough is bringing our current moisture and will drive the weather/precipitation today and the upcoming weekend, especially as this low/trough moves over our area late Saturday into Sunday.

Today look for slightly warmer temperatures, compared to Thursday, with highs in the 40s for the Central Mountains and 50s to near 60s for valleys elsewhere. With a trough with moisture moving into the area today look for wind gusts to begin to increase, closer to 20-30 mph for many. This will also bring some scattered to widespread showers today to the Central Mountains and isolated showers for the rest of our area. This first round of precipitation will still bring about 0.10 to 0.50 inches of precipitation for the Central mountains and .01 to .10 for the rest of the area. Expect snow today mainly in the Central mountains, mainly above 7500 feet, with about 1 inch of snow expected on Galena Summit today and 2 to 5 inches for elevations above 8000 feet.

Expect patchy to areas of fog Saturday morning and become more patchy Sunday and Monday mornings. Precipitation for lower elevations Saturday still looks to be around 0.10 to 0.10. This precipitation will likely have some impacts on Halloween activities. However, the bulk of the precipitation is still arriving later Saturday evening through Sunday and lingering into Monday morning.

By late Saturday into Sunday the low off the Washington coast begins to move and makes it way inland aided by an deepening trough, which will really picks up more Pacific moisture and transports it over southeastern Idaho. This more organized round of precipitation will begin in the Central Mountains/Wood River Valley/eastern Magic Valley as early as 6 PM Saturday and then spread eastward throughout the night. The NBM model is still showing about an 90 to 100 percent chance of the entire CWA receiving at least 0.25 inch of precipitation with this system. Precipitation amounts have not changed much from the last couple days of model runs. It still seems likely that many will see 0.25 to 0.50 inches in the eastern Magic Valley and Challis area, 0.50 to 0.75 inches in the Snake River Plain and lower elevations of the Eastern Highlands and Central Mountains. For higher elevations (above 8000 feet) precipitation will be pushing 0.80 to 1.50 inches, especially for Sun Valley Region, Big Lost Highlands/Copper Basin, Lost River Range, and the Montana Divide as well as the Southern areas along the Utah border including the Wasatch mountains. Temperatures will still be "warm" on Saturday with highs in the 40s and 50s, but by Sunday our highs will drop into the mid and upper 30s and 40s. Snow impacts are likely at Galena Summit Saturday night into Sunday morning with the forecast still showing 4-10" (90th and 10th NBM percentiles with 7 inches being the 50th percentile) of snow there. A winter weather advisory is in effect for the Sun Valley Region and the Big Lost Highlands above 7000 feet for Saturday evening through Sunday. Elsewhere, the bulk of our snow is expected to remain above most of the rest of our mountain passes, but that could change easily with temperature changes of just a few degrees. Even though snow levels will start high, convection can lower snow levels, which could drop snow levels to pass levels especially for areas like Emigration and Raynolds pass.

A few showers linger on Monday morning, but we will be drying out from west to east by that point and high pressure builds in over the area through mid week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1136 AM MDT Fri Oct 30 2026

VFR conditions persist into the evening across all East Idaho terminals, but SHRA producing a roughly 30% chance of lowering CIGS or VIS to MVFR at times. SHRA becomes more widespread through the afternoon into the evening, lowering CIGS and VIS to persistent MVFR around/after 06Z for all sites. Winds remain under 10kts sustained, but SHRA could locally induce a brief gust to 10-15kts.

FIRE WEATHER

Issued at 216 AM MDT Fri Oct 30 2026

Rain and high elevation snow can be expected starting today and continuing, off and on, through Sun night/Mon morning. Very high humidity with only occasionally breezy to windy conditions expected as the low crosses through the western states during this period, tracking south of Idaho for its center. Temperatures peak today, with some low elevations reaching to around 60 degrees, but cooling for Sat and even more cooling Sun. Some snow is possible at elevations down to around 7000ft or so.

PIH WATCHES / WARNINGS / ADVISORIES

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