Ashton, ID Weather

Key messages

- Slightly warmer highs today and Friday.

- Showers return to the Central Mountains as early as Friday.

- More organized and widespread precipitation returns for the weekend as temperatures begin to drop.

Discussion

Issued at 1209 PM MDT Thu Oct 29 2026

There is currently dry, southwesterly flow aloft over southern Idaho. Also, currently there is an upper level low centered just off the coast of Washington as part of an overall trough that extends much farther south to off the coast of California, where there is ample moisture available. This low/trough will drive the weather/precipitation over the upcoming weekend.

We are in-between systems today. Expect dry conditions today with temperatures warming a few degrees, compared to yesterday, with southwesterly flow aloft. Highs today reach the mid to upper 50s for most of us in the lower elevations with more cities reaching the upper 50s. Winds will be fairly light today with gusts around 15 to 20 mph.

Friday morning look for patchy fog, especially in lower elevations near water sources. Expect better fog chances Saturday and, especially, Sunday and Monday mornings. Friday look for slightly warmer temperatures, compared to Thursday, with highs in the 50s to near 60s. On Friday, the low currently off the Washington coast and the associated trough will gather Pacific moisture and eject a weak shortwave through Idaho. Wind gusts begin to increase on Friday, closer to 20-30 mph for many. This will also bring some isolated to scattered showers back to the Central Mountains as early as Friday morning with coverage increasing a bit on Friday afternoon through early Saturday. This first "quick" round of precipitation will bring about 0.10 to 0.20 inches of precipitation the the area which will also mean to expect a few inches of snow up on top of the mountains, too. Most of this will be above pass level, but there is about a half inch to an inch of snow in the current forecast for Galena Summit from Friday morning to Saturday morning.

Saturday late afternoon into the early evening models still show a chance for 0.01 to 0.08 inch of rain across lower elevations that 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 pick up more Pacific moisture and transport 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 80 to 100 percent chance of the entire CWA receiving at least 0.25 inch of precipitation from 5 AM Saturday to 5 AM Monday. Precipitation amounts have not changed much from yesterdays model run. It still seems likely that many will see 0.25 to 0.50 inches in the eastern Magic Valley, 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 to 85000 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 50s, but by Sunday our highs will drop into the mid and upper 40s. Snow impacts seem likely at Galena Summit Saturday night into Sunday morning with the forecast still showing 4-6" of snow there. A winter weather advisory for the Sun Valley Region and the Big Lost Highlands above 7500 to 8000 feet for Saturday evening through Sunday will likely be needed. 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

Issued at 510 PM MDT Thu Oct 29 2026

VFR conditions with generally light winds through the period. Expect increasing clouds this evening. High-resolution models indicate VCSH at KBYI and KSUN between 07z and 09z Friday, with VCSH at KPIH by around 15z as precipitation chances spread eastward. The best chance of precipitation at KSUN will be between 18z and 00z in showers. Both KIDA and KDIJ still look to remain dry through the end of the TAF period/after 00z Saturday.

Fire weather

Issued at 233 AM MDT Thu Oct 29 2026

We stay mild and dry today as we are in between systems. Highs will range from mid to upper 50s in most of the lower elevations with wind gusts around 15-20 mph and min RHs around 30 to 50 percent. A shortwave passing through on Friday will bring precipitation chances back to the Central Mountains first and then expand eastward overnight into Saturday. However, it's Saturday evening through Sunday night that the bulk of the next precipitation will impact the entire area. This will bring plenty of low elevation rainfall and mountain snowfall. It seems likely that many will see 0.25 to 0.50 inches in the eastern Magic Valley, 0.50 to 0.75 inches in the Snake River Plain and lower elevations of the Eastern Highlands and Central Mountains, while the higher elevations will be pushing 0.80 to 1.50 inches. Temperatures will also drop during the weekend with highs mainly in the 40s for Sunday and Monday.

Watches, warnings and advisories

None.