Forecast for Friday:

A Pacific disturbance is moving across the area on Friday morning with numerous snow and rain showers across the Tetons and Jackson Hole. Snow levels started out on the valley floor first thing on Friday morning, but as of this writing, we have seen a transition to a rain/snow/graupel mix in town.

These showers are convective in nature and a favorable jet stream position has resulted in periods of heavy showers. Check out the image from Teton Pass where a heavier shower is visible to the east over the Jackson Hole Valley.

Once again, the Tetons will likely pick up a couple of inches or so of new snow during the day on Friday. Shower activity will become more isolated on Friday afternoon with a period of dry conditions expected on Friday evening.

Forecast for Saturday:

Another Pacific disturbance will arrive from the west on Saturday morning with showers developing across the area once again. Warmer air will be arriving with this feature, and as a result, snow levels will rise from roughly 6,500 feet in the morning to 8,000 feet in the afternoon.

New precipitation amounts on Saturday will range from about a quarter-inch to a half-inch in the Tetons and about a tenth of an inch to a quarter of an inch in the Jackson Hole Valley. Snowfall of 1-3 inches can be expected above 8,000 feet. I also wouldn't rule out a thunderstorm on Saturday afternoon. 

Forecast for Sunday:

We will enjoy a well-earned dry, warm, and sunny day on Sunday as a ridge of high pressure builds into the Northern Rockies from the south. Highs will top out in the upper 60s in the Jackson Hole Valley, which will be our warmest day of the year so far. Get out and enjoy while you can!

Forecast for Monday:

Monday will be another nice and warm day, and we could even top 70 in the valley for the first time this year. However, a minor disturbance approaching from the west could potentially trigger some afternoon thunderstorms. 

We will have a decent amounts of CAPE to work with (700-1,000 Joules/kilogram) which is more than enough to support thunderstorms in the mountains.

CAPE stands for convective available potential energy, and is essentially a measure of "fuel" available for developing thunderstorms, provided there is moisture to work with and a trigger to set air parcels in motion vertically. In this case, the trigger will likely come in the form of the Pacific disturbance approaching as well as terrain-enhanced uplift as moist air encounters mountain ranges and is forced to rise.

At any rate, I would count on a nice day to get outside on Monday, but keep an eye on the sky during the afternoon for towering cumulus clouds.

We will see a gradual cooldown starting on Tuesday, but generally speaking, conditions will remain on the milder side on Tuesday and Wednesday. Additional weak disturbances will be possible, resulting in chances for afternoon showers/thunderstorms both days.

A significant change in the weather pattern is likely late next week as a deep trough of low pressure with cold approaches from the northwest. 

As a result, next Thursday (5/19) and Friday (5/20) are looking wetter and colder with falling snow levels and the potential for significant late-season mountain snow. There is also a chance we could see snow levels dip to the valley floor once the cold air becomes established. 

The cool/unsettled pattern will likely linger into the weekend of May 21st-22nd as well with gradual moderation in terms of temperatures then projected heading into the week of May 23rd.

Thanks so much for reading!

I will be traveling for the next couple of weeks so will be taking a break from JH forecasts. Look for my next post on or around May 26th. My goal then is to keep updating the JH Daily Snow 2-3 times/week through the summer months (except for when I'm traveling) to account for summer recreation in the Tetons, Yellowstone, etc.

ALAN SMITH