The weather pattern will remain relatively mellow over the next two days, although there will be a chance of thunderstorms on Thursday and Friday afternoons. Big changes will occur this weekend as a powerful trough of low pressure arrives. Showers and thunderstorms will become widespread on Saturday with heavy rain possible at times. Summer snow is then looking increasingly likely in the days to follow as a cold front arrives with snow levels falling to the valley floor by Monday morning.
Jet stream energy moving across Northern Wyoming is leading to mostly cloudy skies and isolated showers on Thursday morning. This pattern will continue into the afternoon with a stray thunderstorm possible as well, but any rain will be brief and light with conditions drying out by the evening.
Highs will reach the 70s again in the valley with gusty west/southwest winds continuing.
Southwest flow will usher in warmer air ahead of the weekend storm system with highs rising into the 80s. Skies will be partly cloudy with increasing chances for thunderstorms by late afternoon and evening as some moisture/energy arrives in advance of the mentioned storm system.
The latest trends have delayed the timing of showers this weekend, so we may get a window on Saturday morning with only isolated shower chances, before more widespread rain arrives on Saturday afternoon and continues into Saturday night. Rain could be heavy at times as this looks like the wettest stretch of weather in this pattern.
Temperatures will be cooler on Saturday under increased cloud cover, but the serious cold push will hold off until the next day.
Off-and-on showers will continue throughout the day Sunday and into Sunday night. The first cold front will arrive overnight Saturday and by Sunday morning snow levels will range from 9,000-10,000 ft.
A second stronger cold front will arrive sometime during the day on Sunday, leading to gradually lowering snow levels on Sunday afternoon and evening, eventually falling to the valley floor by late Sunday night. Highs will only be in the 50s in the valley on Sunday.
Unseasonably cold temperatures can be expected on Monday with light off and on showers continuing throughout the day. Snow levels will be down to the valley floor on Monday morning, including the town of Jackson, and highs Monday afternoon will only be in the low 40s!
Precipitation will eventually taper off late on Monday. Total precipitation amounts from Saturday through Monday will range from 1-2 inches (possibly higher) across the Tetons and higher elevations, and 0.5-1.5 inches across the Jackson Hole Valley. The higher elevations can expect to pick up 4-8 inches of snow on Sunday and Monday.
Alan Smith, Meteorologist