JACKSON, Wyo. — Jackson Hole has received much-needed moisture over the past several days with 2-3 inches of rain recorded across Teton County since Friday. In fact, the Jackson Hole Valley received more precipitation on Friday alone than it did in March, April, and the first 20 days of May combined!
In addition to rainfall, snow has fallen across the higher elevations, while thunderstorms have also occurred including a particularly powerful lightning strike that East Jackson residents described as “feeling like an earthquake” on Saturday night.
Recent Rainfall Totals
A powerful trough of low pressure set up to the west of Teton County on Friday, resulting in a moist southerly flow that culminated in a soaking rain event on Friday. The southerly flow negated the rain shadow effect of the Tetons, and as a result, the Jackson Hole valley received similarly heavy rain totals in addition to the Tetons.
The Town of Jackson recorded an impressive 1.25 inches of rainfall on Friday, which set a daily record for the date of May 21. Jackson does not often receive an inch of precipitation or more in one day, so it’s noteworthy when it does happen.
The last time Jackson recorded an inch or more of precipitation in one day was on March 14, 2020 which occurred in the form of snow. The last time an inch of rain was recorded in one day was on June 17, 2018, though we also came close on September 28, 2019 when 0.95 inches was recorded.
It should be noted that official weather station reporting at the Jackson station is for reporting periods ending at 9.am., so theoretically, there could have been other instances when an inch or more of rain/precipitation was recorded during a 24-hour window.
After Friday’s deluge, rain picked back up again late Saturday afternoon and into Saturday night with another 0.80 inches recorded in Jackson. Rainfall totals were lighter on Sunday and Monday, but rain was persistent and conditions remained wet.
In total, Jackson received 2.43 inches of rain from Friday morning through Tuesday morning. Average rainfall/precipitation for the month of May as a whole in Jackson is 1.83 inches, so thanks to just this four-day stretch, May 2021 will go in the books as a wetter than average month.
Here are the rain (and liquid equivalent precipitation) totals reported across Teton County from Friday morning through Tuesday morning:
- 2.83″ – JHMR Rendezvous Bowl
- 2.70″ – JHMR Raymer Plot
- 2.60″ – Phillips Bench
- 2.58″ – JHMR Mid Mountain
- 2.46″ – Moose
- 2.43″ – Jackson
- 2.28″ – Teton Village
- 2.24″ – Jackson Hole Airport
- 2.20″ – Togwotee Pass
- 2.06″ – Moran
The science behind the powerful lightning strike felt in Jackson on Saturday Night
I had some readers reach out to me regarding an intense lightning strike in Jackson on Saturday night. Lightning is common in Jackson Hole from May through September and we’ve had a number of embedded thunderstorms during this rainy pattern recently. However, the strike that occurred on the outskirts of Jackson on Saturday night was not your typical strike.
At 10:23 p.m. on Saturday evening, a rogue lightning strike occurred in Cache Creek and produced a jarring rumble of thunder that shook homes in East Jackson.
Residents in East Jackson reported the strike being the most intense they’ve ever experienced, feeling more like an earthquake or an explosion. Several reported pictures falling off of walls and spices falling off of spice shelves. I live in East Jackson and experienced it, too, and it was certainly more intense than a “normal” close lightning strike.
So what happened exactly? When it comes to lightning strikes, there are two different types: negative-charged strikes and positive-charged strikes.
Negative-charged strikes account for 95% of all lightning strikes and originate in the lower to middle part of a thunderstorm cloud. Negative strikes contain about 300 million volts and 30,000 amps of power and are strong enough to kill a human.
Positive-charged strikes only account for 5% of all lightning strikes, but they originate near the top of a thunderstorm cloud and are up to 10 times more powerful than a negative strike, containing about 1 billion volts and 300,000 amps of energy.
While all cloud-to-ground lightning is deadly, positive lightning strikes account for the majority of lightning fatalities despite accounting for only a small percentage of strikes.
The strike felt in Jackson on Saturday night was almost certainly a positive strike, and likely even a strong one at that.
Negative charges near the bottom of a thunderstorm cloud often protect the underlying ground surface from positive charges near the top of a thunderstorm cloud.
However, during instances when winds in the upper atmosphere are stronger compared to the lower atmosphere – which often happens during spring-time systems such as what we saw on Saturday night – then the top part of a thunderstorm cloud can spread farther out ahead of the negatively-charged lower portion.
When this happens, the ground loses its “protection” from the negative charges, and a positively-charged leader from the top of a thunderstorm cloud can produce a more powerful lightning strike.
That is likely what happened in this case. Saturday night’s strike was a loner, meaning that no other lightning occurred in the area around that time, and loner strikes are often positives.
Positive lightning strikes also occur when the top of a thunderstorm cloud (known as a cumulonimbus cloud) spreads out horizontally in a mushroom-shaped anvil away from the base of the cloud.
This can result in lightning strikes occurring 20+ miles away from a thunderstorm – a phenomenon often referred to as a “bolt-from-the-blue”. These are the most dangerous instances of lightning since they are both unexpected and more powerful than typical negative strikes that occur “expectedly” under a thunderstorm.
Lightning strike data from Saturday night indicated that this strike occurred in the lower portion of Cache Creek, just above the Putt-Putt Trail. It’s extremely fortunate that this lightning strike occurred late at night, rather than during the day when people could have been out recreating in Cache Creek.
It just goes too show that while open flat areas and exposed mountain-tops and ridges are the most dangerous places to be during a thunderstorm, lightning can occur anywhere, even in valleys.
A more thorough discussion of positive-charged lightning strikes can be found HERE.
New snowfall above 9,000 feet from the recent pattern
In addition to rain and lightning, new snow fell across the higher elevations of the Tetons and surrounding ranges from Friday through Monday.
Most areas above 9,000 feet recorded about a cumulative total of about a foot from Friday morning through Tuesday morning, but of course melting and compaction occurred in between each round given that we are now in late May.
One exception was the Rendezvous Bowl Plot at Jackson Hole Mountain Resort, who received a cumulative four-day total of 18 inches of snow!
More rain ahead for Tuesday and Wednesday
After a brief lull in the action on early Tuesday, another storm will arrive from the west with scattered showers and thunderstorms on Tuesday afternoon giving way to more widespread rain on Tuesday night and Wednesday. High elevation areas will pick up a few more inches of snow as well.
Additional rain amounts of roughly a half-inch in the valley and an inch in the mountains can be expected, adding to the already impressive rainfall totals from the past week.
If you’re sick of the rain, there is good news. Dry and sunny weather will return on Thursday and for the most part will continue into the holiday weekend, though it’s possible we could see some (lighter) shower activity return over the weekend, mainly during the afternoons/evenings.
Alan Smith, Meteorologist
