Forecast Highlights:

• Dry and sunny conditions can be expected each day from Friday through Wednesday.
• Fresh snow cover down to 10,000-11,000 feet in the Tetons but most of this should melt off quickly, except for high elevation shaded terrain on the peaks. 
• High temperatures will reach the low/mid 60s in the valley on Friday, and low 70s from Saturday to Wednesday with overnight lows falling below freezing.
• Winds will be gusty at times on Friday and to a lesser extent on Saturday, then will be light from Sunday to Wednesday.

Quick Storm Recap:

A mid-week storm system resulted in widespread showers and thunderstorms on Wednesday afternoon and Wednesday night with active cloud-to-ground lightning. There were even some severe thunderstorms across South Central and Eastern Idaho, including a tornado warning issued in the hills near Pocatello due to radar-indicated rotation, though it appears that a tornado did not touch down. 

Locally, we saw our main rounds of heavy rain during the late afternoon hours on Wednesday and again during the overnight hours, followed by lighter and more intermittent showers on Thursday. Rainfall totals in the JH Valley on Wed-Thu ranged from 0.6 to 0.8 inches, with undoubtedly higher totals in the mountains though weather stations up high are not recording precipitation at this time of year.

Snow levels started out high but eventually lowered to around 10,000 feet during Thursday's shower activity. Snow did cover the summit of Jackson Hole Mountain Resort for a time on Thursday, but quickly melted away as the summit webcam is showing no snow on the ground as of this writing.

On Friday morning, it appears the snow line is likely around 11,000 feet in the southern end of the Tetons around JHMR, while webcams from Teton Valley (when there was some brief clearing on Friday PM) indicate the snow line may be closer to 10,000 feet on the northern and western side of the Tetons.

Most of this snow should melt away quickly on Friday and Saturday. However, shaded aspects on the higher peaks of the Tetons will be the exception, where lingering snow and ice will likely stick around for much longer.

Forecast for Friday (9/23) to Wednesday (9/28):

We're heading into a perfect fall weather pattern with dry conditions, clear skies, and pleasant temperatures. Fall colors have been a little slow to get going this year, but seem to have been picking up over the past few days. I expect the colors will be putting on a good show during the next 2 weeks with peak color likely around the end of September and beginning of October.

A ridge of high pressure building over the West will be the culprit of our quiet weather pattern over the next several days. During the winter and during the summer, high pressure is usually not our friend, but in the fall (when we've already had recent moisture), high pressure typically means nice weather and comfortable temperatures, so enjoy it.

On Friday, highs will reach the low to mid 60s in the valley with lingering breezy winds, though not as strong compared to recent days.

From Saturday to Wednesday, highs will top out in the low 70s in the valley each day with overnight lows dipping below freezing, as is typical on clear nights at this time of year. Saturday could still be a little breezy, especially up high, but then winds will be much lighter from Sunday to Wednesday. 

Outlook for Thursday (9/29) through the first week of October:

A weak disturbance is projected to move into the Northern Rockies around Thursday (9/29) and Friday (9/30). This could result in an increase in clouds, slightly cooler daytime temperatures, and a chance of showers.

However, significant precipitation is unlikely and if we do see any showers, snow levels are likely to remain high as only minor cooling is expected.

Looking further out, a ridge of high pressure will attempt to hold over the Intermountain West but gradually weaken with occasional disturbances approaching from the Pacific heading into the first week of October. This means we could see a mildly unsettled pattern with occasional shower chances.

But the pattern does not yet look favorable for major storm systems or significant cooldowns, and temperatures are still expected to be on the warmer side of average into early October.

Thanks so much for reading and have a great weekend! Next update on Monday (9/26).

ALAN SMITH