Abundant sunshine can be expected on Mon & Tue with a chance of t-storms both days, though coverage will be fairly isolated and will favor the mountains with lesser chances for the valleys. Temps will also be warmer with highs in the 70s in the valleys. Another uptick in t-storms & showers can be expected starting Wed & continuing into the weekend with a slight cooling trend also expected.
Short Term Forecast
This past weekend was drier than expected. We did see rain, but rain totals were lower than forecasted and there were plenty of breaks.
We did have unfavorable easterly winds aloft for much of the weekend, and while convective precipitation can largely overcome this, cloud cover and cooler temps on Friday and Saturday limited the amount of convection possible, and I think this played a role in letting the unfavorable easterly flow be the driving factor.
Friday did start out wet with widespread rain and some drying in the afternoon. Saturday was cloudy for much of the day with only occasional light rainfall with clearing late in the day.
On Sunday, we switched to more of a southeast flow (typically not a bad direction for summer precip) with more abundant sunshine. Showers and thunderstorms did fire up in the afternoon, but nearly all of the action stayed south and west of the Tetons and across the ranges east of Jackson Hole, keeping the Tetons and Yellowstone primarily dry.
Forecast for Monday:
Monday is shaping up to be a beautiful day with warmer temperatures and comparatively lower rain/thunderstorm chances than we've been accustomed to lately.
We are starting out with scattered mid-level clouds on Monday morning, but check out this beautiful sunrise we had over the Tetons.
A weakening area of low pressure is located over Central Idaho on Monday morning and this will move due northward and will not have any impacts on our weather. In fact, a drier and more stable layer in the atmosphere around 18,000-20,000 feet (known as a cap) could end up inhibiting thunderstorm development for much if not all of the day.
We are going to have low level moisture working its way back into our area as the day progresses with plenty of instability in the low to mid levels of the atmosphere as well. So by midday, we will see cumulus clouds developing, which will cover the tops of the higher peaks at times (cloud bases 10-11k feet or so).
The question is if and when these convective updrafts will be able to break through the cap, which could result in some isolated thunderstorms developing. If we do see thunderstorms, it will likely be later in the day, in the 3pm-8pm timeframe. Storms will move from SSW to NNE at moderate speeds, with higher probabilities over the higher terrain compared to the valleys.
The Storm Prediction Center's thunderstorm probabilities are fairly low for our area on Monday afternoon, with higher probabilities in Yellowstone and also east of Jackson Hole.
Forecast for Tuesday:
Temperatures will warm up a few more degrees on Tuesday with isolated afternoon thunderstorms expected. Instability looks higher on Tuesday compared to Monday and we are not expected to have a mid-level cap. Therefore, we could see thunderstorms fire up by midday to early afternoon across the Tetons and surrounding ranges as well as the Yellowstone plateau.
However, winds aloft as well as wind shear (change in winds with altitude) are expected to be weak, which will likely result in thunderstorms remaining anchored to the higher terrain with lower odds of storms reaching the valleys.
Forecast for Wednesday to Friday:
This period is looking more active as a large area of low pressure over Southern California work its way inland and then meanders on a south-to-north track over time. Moisture will increase over this period, resulting in higher chances of showers and thunderstorms along with the potential for heavier rainfall at times.
Temperatures should also trend a bit cooler with more cloud cover expected.
Outlook for this Weekend (June 10th-11th) and Beyond:
One large area of low pressure will give way to another one moving into Southern California and eventually meandering its way into the Intermountain West. As a result, we will stay in an active pattern with daily shower/thunderstorm chances continuing this weekend and into the early part of next week.
Thanks so much for reading! Next update on Tuesday (June 6).