Thunderstorm coverage will increase across NW Wyoming on Thursday in response to an area of low pressure just to our south. Storm motions will be weak & erratic but will generally move from SE to NW with frequent lightning & locally heavy rain possible. Friday will feature more moisture & cloud cover with numerous showers & reduced lightning activity. Sat-Sun will also be active w/showers/tstorms.
Short Term Forecast
Forecast for Thursday:
We are starting out with a mix of sun and thin mid-level clouds on Thursday morning. We should have a good weather window through the morning hours, at least across Jackson Hole and Teton Valley.
Otherwise, an uptick in rain and thunderstorm chances will begin today and continue through the weekend. An area of low pressure is slowly working its way into Western Colorado with moisture and energy increasing northward into Wyoming.
Storm development over the Tetons will most likely hold off until 1pm or later, but storms could develop by 11am-noon along and east of the Continental Divide, including Yellowstone.
Weak and erratic winds in the mid-levels of the atmosphere will result in slow-moving and erratic storm motions, but with a general movement over time in a southeast to northwest direction thanks to stronger winds in the upper levels of the atmosphere that will be blowing out of the southeast.
Locally, storm coverage will favor the Tetons and may have trouble moving off of the higher terrain initially, but once they do then Teton Valley could see quite a bit of thunderstorm activity as well. The JH Valley will certainly be in play for storms, though I suspect coverage/intensity will be less compared to surrounding environs.
Storm coverage will also be higher north and east of the Continental Divide, including Yellowstone and the Absaroka Range. The Gros Ventre Range should also see more widespread coverage.
Instability and wind shear (change in wind speed/direction with height) will be high enough today that we could see some stronger storms develop, which will be capable of producing frequent lightning and hail. Moisture levels will also be on the increase, which will result in some locally heavy rainfall rates under stronger/slower moving storms.
As moisture continues to increase overnight, we can also expect scattered showers to develop during the overnight hours.
Forecast for Friday:
We will be under the influence of two low pressure systems, one to our south and one to our west, with a further uptick in moisture expected.
Cloud cover will be more widespread throughout the day on Friday, resulting in cooler daytime temperatures and more numerous off-and-on showers. Instability will be more limited under the cooler/cloudier pattern, resulting in less lightning activity overall (though occasional lightning is possible).
Winds in the middle levels of the atmosphere will remain weak and erratic, and generally not favorable for orographic lift in the Tetons. But the convective nature of showers and overall high moisture levels will result in a fairly wet day with light showers possible in the morning and heavier showers in the afternoon and evening. Showers will also be possible through the overnight hours on Friday night.
Rainfall will favor areas along and east of the Continental Divide, but we will likely see some heavier downpours at times in Jackson Hole and the Tetons as well.
Here are projected 2-day rainfall totals across Wyoming on Thursday and Friday. This doesn't take into account the potential for localized heavier showers but gives a good idea of what to expect on a larger scale.
Forecast for Saturday to Sunday:
A wet pattern will remain in place with a high likelihood of showers and thunderstorms both days with locally heavy rain possible at times. Coverage will be greatest during the afternoon and early evening hours, but overnight and morning activity is also possible.
Lightning potential and frequency will largely be dependent on cloud cover and whether or not we get enough breaks in the clouds with sunshine to heat up and destabilize the atmosphere.
Outlook for Monday (June 5) and Beyond:
We should see a relative downturn in activity early in the week, around Monday and Tuesday, with more sunshine and warmer temperatures. However, afternoon thunderstorms will remain possible both days.
During the second half of next week, another area of low pressure will work its way into the Intermountain West, which could potentially result in another uptick in shower and thunderstorm activity.
Generally speaking, the first half of June is expected to be wetter and stormier than average with our cycle of daily shower/thunderstorm chances persisting as the large-scale weather pattern is not expected to shift anytime soon.
Thanks so much for reading! Next update on Friday (June 2).