Jackson Hole Weather Aug 30

JACKSON, Wyo. — Last week was another active one in terms of daily thunderstorms across Teton County, and this will go down as one of the wettest Augusts on record. We have now transitioned into a much drier pattern as a strong ridge of high pressure is building over the Western U.S. This will result in near-record warmth heading into Labor Day weekend.

August 23-29 Recap

Last week, we saw a continuation of an active thunderstorm pattern with daily rounds of thunderstorms developing each afternoon through Friday thanks to the presence of monsoonal moisture.

Over the weekend, a trough of low pressure moved across the Northern Rockies and a strong jet stream dipped far enough south to scour out the monsoonal moisture, resulting in dry and windy conditions on Saturday and Sunday. A dry cold front also moved through on Sunday, resulting in briefly cooler temperatures.

The strongest winds over the weekend occurred on Saturday afternoon and evening ahead of the cold front, when a 41 mph wind gust was recorded at the Jackson Hole Airport and an 85 mph gust was recorded at the Lower Saddle weather station (elevation 11,610 feet) between the Grand and Middle Teton summits.

The Town of Jackson received a total of 0.74 inches of rain last week, and dating back to the previous week, recorded measurable rainfall on seven out of eight days. Jackson has now received 3.65 inches of rain during the month of August, which is nearly triple the August rainfall average.

High temperatures in Jackson over the past week ranged from 75ºF on August 28 to 84ºF on August 24 and low temperatures ranged from 37ºF on August 29 to 53ºF on August 25. The low of 37ºF on the 29th was the first sub-40ºF low temperature recorded this entire month, even though average lows in late August are in the upper 30s.

Forecast for Tuesday (8/30) to Monday (9/5)

We have transitioned out of the wet pattern that was present for most of August, and now we are entering an extended stretch of dry weather along with above-average temperatures. A strong ridge of high pressure building over the Western U.S. will result in a widespread late summer heatwave over the next week or so, and even up here in Jackson we will feel the effects of this heat.

After the past few comfortable days, high temperatures will gradually creep upward from Tuesday through Labor Day weekend. Highs on Tuesday and Wednesday will reach the mid 80s in the valley, before rising into the upper 80s on Thursday and Friday.

Over the Labor Day holiday weekend, highs are projected to top out around 90 in Jackson each day from Saturday through Monday, which puts us right around record high territory for this late in the year. Daily record highs from late this week through the holiday weekend are in the 88-92ºF range.

Despite the unseasonable heat for this late in the year, the drier airmass will result in cooler morning temperatures in the valley with lows in the upper 30s to low 40s each day. We’re at the time of year where longer nights often result in 50-degree temperature swings between high and low temperatures during dry and stable patterns such as this.

Overall, winds should be relatively light this week with the only exception being on Thursday when winds will be gusty due to a weak disturbance passing north of the area.

We could also see some occasional “haziness” in the skies as light smoke from fires in Idaho and the Northwest drift into the area from time to time, but significant impacts are not expected at this time.

Extended Outlook

The hot and dry pattern with near-record highs looks to continue through about the middle of next week. During the second half of next week, we should finally see a cooling trend along with a chance of showers as a couple of low pressure troughs are projected to move across the Northwest U.S. and into the Northern Rockies.

Alan Smith, Meteorologist