JACKSON, Wyo. – A late-season cold snap resulted in a hard freeze with daily record low temperatures in Jackson (24ºF) and Driggs (25ºF) on Wednesday morning. The chilly temperatures will be short-lived, as we will see highs soar into the 80s this weekend and early next week.
Brief But Intense June Cold Snap
June has been a roller coaster weather month so far. The month as a whole has been warmer and drier than average, but we have also seen high snowmelt runoff, thunderstorm wind damage, and most recently, record cold.
Last week, we saw highs in the 80s followed by a gradual cool-down over the weekend as the first weaker cold front arrived.
On Monday, a deep trough of low pressure moved from the Pacific Northwest into the Northern Rockies and a strong cold front reached our area.
We were on the southern fringe of the moisture with this system and ended up with only light precipitation. However, a sharp drop in temperatures occurred on Monday afternoon and snow ended up falling in the valley, though it didn’t accumulate except for wet dusting on roofs and other elevated surfaces.
Non-accumulating snow is not unheard of in the lower Jackson Hole Valley this late in the season, but it is atypical. Although records are spotty for non-accumulating snow events, data from local observers indicates the last time we saw snowflakes in Jackson this late in the season was in June 2014.
Even though snow fell in the valleys, the overall duration of snowfall was brief and the higher terrain only received light snowfall. Limited snow measurement data at this time of year indicates that areas above 8,000 feet picked up anywhere from a dusting to 2 inches, and this new snow has likely disappeared already.
Record Low Temperatures
The cold temperatures were more notable than moisture and snowfall from this system. Once skies cleared on Tuesday and Tuesday night, temperatures plummeted to record levels on both sides of the Tetons.
The JKNW4 weather station in Jackson recorded a low of 24ºF on Wednesday morning, breaking the old record of 26ºF set on this date in 2001 (data obtained from the JKNW4 weather station since 2010, and the COOP Jackson station prior to 2010).
This was also the coldest morning in the month of June in the town of Jackson since June 13, 2008, when the temperature also dipped to 24ºF.
The Driggs Airport recorded a low of 25ºF on Wednesday morning, breaking the old record of 26ºF set on this date in 1973.
The record cold is even more notable in the sense that June temperatures prior to this cold snap were well above average, and we are likely to see a return to well-above-average temperatures after the cold snap.
For perspective, average highs in June over the previous 15 years (JKNW4 weather station) are in the low 70s and average lows are around 40. We have been fluctuating from well above to well below these levels recently.
Upcoming Weather Pattern
A ridge of high pressure will rebuild over the Western U.S. and we will see a quick return to summer warmth. On Wednesday, highs will reach the mid to upper 60s under mostly sunny skies and it’s shaping up to be a beautiful day.
On Thursday and Friday, highs will warm up into the upper 70s which is close to average for this time of year (average highs are in the 74-77ºF range over the next week). However, we will also see an increase in cloud cover on both days as a little bit of moisture streams northward from a tropical disturbance in the Gulf of Mexico.
Despite the slight uptick in moisture, rain chances will be minimal late this week. We could see some isolated light showers or thunderstorms on Friday, but any rainfall looks to be light and spotty. Cloud-to-ground lightning and locally gusty winds will be possible with any storms, however.
On Saturday and Sunday, moisture will decrease and sunny skies will return with highs warming up into the low to mid 80s. The June cold snap we just experienced will be a distant memory by this point.
The warm pattern looks to continue through at least the first half of next week, with little to no chance of rainfall.
Taking a look at the 7-day precipitation projection, we can see Friday’s light rain chances in our area with much heavier rainfall over the Southwest.
The heavier rain over New Mexico, Colorado, and the Southwest is a result of moisture from Tropical Storm Alberto, as well as the beginnings of the North American Monsoon which is a seasonal moisture circulation across the Southwest that occasionally impacts our area later in the summer.
Looking further out, the pattern looks to remain quite dry through the end of June. The weather station in North Jackson near the visitor center has only received 0.46 inches of rain this month, putting us on track to have our second driest June in the past 10 years (June 2021 was the driest with only 0.33 inches).
Temperatures are generally expected to stay above average through the end of the month, but we may see some occasional minor cooldowns due to low pressure troughs projected to pass just north of our area from time to time.
Alan Smith, Meteorologist
