A warm day on Friday will give way to significant changes over the weekend as a low pressure system arrives. Widespread showers and thunderstorms with heavy rain at times on Saturday afternoon and Saturday night will give way to colder temperatures and lowering snow levels on Sunday and Monday. We’ll start to dry out on Tuesday with a gradual warming trend over the second half of next week.
This will be our last quiet day and south/southwest flow ahead of the approaching system will usher in warmer air with highs rising into the 80s under partly cloudy skies. There will be just enough moisture and instability ahead of the system to result in a chance of isolated thunderstorms late this afternoon and evening.
We may see somewhat of a weather window on Saturday morning, though isolated to widely scattered light showers will be possible prior to noon. Showers and thunderstorms will then become more widespread on Saturday afternoon and into the evening with heavy rain possible at times.
There is some potential for strong thunderstorms on Saturday afternoon as well with hail and frequent cloud-to-ground lightning. Temperatures will be cooler on Saturday given the cloud cover and rain, but the big push of cold air will hold off until Sunday. The first and weaker cold front arriving Saturday night will result in snow levels falling to 9,000 or so by Sunday morning.
Off-and-on showers will continue throughout the day with much cooler temperatures as highs only reach the low 50s in the valley. A second stronger cold front will arrive by late Sunday afternoon, and snow levels will continue to lower heading into Sunday night.
Snow levels will fall to the valley floor by Monday morning, and we could even see some light accumulations in the GTNP valley (north of town) and especially farther north up into Yellowstone. Off-and-on showers will continue into Monday afternoon with snow levels rising above the valley floor but remaining fairly low. Precipitation will eventually taper off on Monday evening. Temperatures will be unseasonably cold on Monday with high temperatures a good 25 degrees below average.
Total precipitation amounts from Saturday through Monday will range from 1-2 inches in the Tetons and 0.5-1.5 inches in the Jackson Hole Valley. Snow amounts across the higher elevations (above 9,000 ft.) will range from 3-6 inches.
We will start to dry out on Tuesday, but temperatures will remain chilly for this time of year with highs in the 50s. A more noticeable warm-up will occur over the second half of next week.
Alan Smith, Meteorologist