JACKSON, Wyo.– Last week was another active period for daily thunderstorms in Teton County, and it will go down as one of the wettest Augusts on record. We have now shifted to a much drier pattern as a strong ridge of high pressure builds over the western United States. This will result in near-record heat as we approach Labor Day weekend.
August 23-29 Recap
Last week we saw the 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 wash away monsoon moisture, bringing dry and windy conditions on Saturday and Sunday. A cold, dry front also moved in on Sunday bringing briefly cooler temperatures.
The strongest winds of the weekend occurred Saturday afternoon and evening ahead of the cold front, when a 41mph gust was recorded at Jackson Hole airport and an 85mph gust was recorded at Lower Saddle Weather Station (elevation 11,610 feet) between the Grand and Middle Teton peaks.
The city of Jackson received a total of 0.74 inches of rain last week and, going back to the previous week, saw measurable precipitation seven days out of eight. Jackson has now received 3.65 inches of rain during the month of August, nearly triple the August precipitation average.
High temperatures in Jackson over the past week ranged from 75°F on August 28 to 84°F on August 24 and low temperatures ranged from 37°F on August 29 to 53°F on August 25. The 37°F low on the 29th was the first sub-40°F low on record all month, although average lows at the end of August are in the upper 30s.
Forecast from Tuesday (30/08) to Monday (05/09)
We have moved out of the wet pattern that was present for most of August, and are now entering an extended period of dry weather with above average temperatures. A strong ridge of high pressure over the western United States will lead to a widespread late summer heat wave over the next week, and even here in Jackson we will be feeling the effects of that heat.
After these few comfortable days, high temperatures will gradually increase 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 Labor Day weekend, highs are expected to reach around 90 in Jackson each day from Saturday through Monday, which puts us in record territory for this end of the year. Daily highs from the end of this week through the holiday weekend are between 88 and 92°F.
Despite the unusual heat for this end of the year, the drier air mass will result in cooler morning temperatures in the valley with lows in the 30 to 40 degrees each day. We’re at the time of year when longer nights often result in 50 degree temperature swings between high and low temperatures during dry, steady patterns like this.
Overall winds are expected to be relatively light this week with the only exception being Thursday when the winds will be gusty due to a weak disturbance passing north of the area.
We may also see some occasional “blur” in the sky as light smoke from fires in Idaho and the Northwest occasionally drifts across the region, but significant impacts are not expected at this time.
The hot and dry pattern with near record highs is expected to continue into the middle of next week. During the second half of next week, we should finally see a cooling trend with a chance of showers as a few low pressure troughs are expected to move into the northwestern United States and into the northern of the Rockies.
Alan Smith, Meteorologist
Climatology of the city of Jackson from August 30 to September 5:
Medium top: 77
Medium Low: 36
High record: 92 (various dates)
Record low: 18 (September 4, 1964)
Precipitation since October 1: 16.50″ (104% of average)