An active start to the week across Northwest Wyoming has been replaced by dry and breezy conditions. From late last week through the first part of this week, daily thunderstorms were common as a trough of low pressure approached from the Pacific Northwest.
Behind the trough, much drier air has arrived along with cooler but very comfortable temperatures. The wind has been the real story over the past couple of days though, thanks to an unusually strong summer jet stream over the Northwest U.S. Take a look at the current position of the jet (image source: College of DuPage).
We are on the southern fringe of the strongest jet stream level winds (at an elevation of about 30,000ft), but we are certainly seeing the effects here. The breeze felt very refreshing during my mountain bike ride at Grand Targhee earlier today, but at the high elevations the gusts have been very strong this afternoon. Check out the wind speed and gust chart at the top of the Jackson Hole Tram, where gusts of up to 57mph have occurred in the past hour (image source: Mesowest).
For the upcoming weekend, dry conditions will persist with a gradual decrease in wind speeds. Friday will be another windy day across the area, so heads up if you’ve got high elevation plans. Saturday and Sunday will then see a trend toward decreasing winds.
This will be a great weekend to get outdoors as thunderstorm chances will be near zero for most areas on Saturday and Sunday. If anywhere was going to see a stray thunderstorm with some sprinkles it would be along the Continental Divide in the Wind River’s, but even there the threat is low.
Next week, we will see very warm temperatures to start the week followed by increasing thunderstorm chances over the second half of the week. The warm-up will start Sunday, and by Monday and Tuesday some valley areas will be pushing 90. The next image from the European Model Ensemble shows a strong ridge of high pressure building over the Western U.S., which will be the culprit for the heat (image source: pivotalweather.com).
By Wednesday and Thursday next week, the south/southwest flow around the center of high pressure (being further driven by the trough of low pressure off the WA/OR coast) will help to draw in some monsoonal moisture northward into Western Wyoming.
As a result, we should see thunderstorm chances increase across the area from Wednesday through the end of the week. The Wind River’s will be in line to see the most aggressive thunderstorm activity during this time, but medium range projections show the Tetons and Yellowstone getting in on the action as well.
There is still a lot of time between now and late next week, and individual moisture surges remain uncertain in terms of timing and strength. But for now, go ahead and plan on thunderstorm chances returning to the region over the second half of next week and prepare accordingly if you have outdoor plans.
Temperatures will gradually trend downward over the second half of next week as well.
Below are 7-day temperature outlooks for Jackson, Pinedale, and Yellowstone Lake (all three image charts courtesy of weathermodels.com). At this time of year, a general rule of thumb is to subtract 5 degrees per 1,000ft of elevation gain for HIGH temperatures only. Overnight low temperatures are much more variable and sometimes warmer the higher you go due to inversions, valley drainage patterns, etc.