All posts by Jim Woodmencey

Record Rainfall in Jackson from the Monsoon

Jackson, WY received a record amount of rainfall from Friday morning August 5th to Saturday morning August 6th when 0.80 inches of rain fell in that 24 hour period.

The previous one-day rainfall record on that date (measured on August 6th) was 0.54 inches from August 6th, 1993. The summer of 1993, by the way, was the coldest and wettest summer in Jackson’s weather history.

Rain continued through the day and into the evening on Saturday, adding another 0.74 inches of rain, measured on Sunday morning of August 7th. That one-day total did not beat the old record for that date, which was a whopping 1.16 inches that fell in a 24-hour period back in 2007.

According to the data from the Jackson Climate Station, the total rainfall for the two days was 1.54 inches, all of which fell in about a 36-hour period from this big surge of monsoon moisture.

Courtesy of the Monsoon

On the satellite image below that monsoon moisture stretched across most of Nevada, northern Utah, western Wyoming and Southwest Montana.

That Monsoon flow was aided by a relatively small upper-level Trof of Low-pressure that passed by to the north, across northern Montana this weekend.

Already a Wetter Than Normal August

Total Rainfall in the Town of Jackson so far in August 2022 is 1.94 inches. That is just for the first week. The average monthly rainfall in August is 1.20 inches.
July of 2022 only had 0.06 inches of rain. Average rainfall in Jackson in July is 0.94 inches
So, August has already made up for July’s precipitation deficit.
Jackson would only need another 0.14 inches of precipitation in August to bring the July & August rainfall total up to normal.


Posted Sunday August 7th, 2022 by Meteorologist Jim Woodmencey

If it’s so green, how are we in a drought?

We’ve heard a lot in recent months about how bad drought conditions are across much of the western United States.  As of June 30th, 2022 most of Teton County, Wyoming is still listed in the severe drought category. Considering how green everything looks outside on the First of July, and how much rain we had in April. May and June, that might be hard to believe.

Digging in to how drought conditions are determined, gives some insight into how the  U.S. Drought Monitor Map is made each week.

Above Normal Precip

When we talk about drought conditions the first thing that comes to mind is how much moisture, or lack thereof, we have had. Data from the Town of Jackson Climate Station shows that over the 8 month period, between October 1st, 2021 and May 31st, 2022, town had received 11.27 inches of precipitation. By the way, October 1st is when our water year begins.

The long-term average precipitation in Jackson for that same 8-month period is 10.80 inches. In other words, Jackson’s precipitation is above normal right now, by almost half an inch.

Rainbow after heavy rain in the Gros Ventre drainage on June 19, 2022.

Unfortunately, there was missing data at the Jackson Climate Station in mid-June, so June’s precipitation total is not available. But we all know that there was plenty of rain and I suspect that the total was at least near the monthly average of 1.63 inches.

Granted, we had a relatively dry winter, with below average precipitation from January through March. Although we also had a very wet fall, with above average precipitation in October, November and December. This spring it got wet again, with above average precipitation in both April and May.

Despite above average precipitation for five of the last eight months, there are other factors to consider when determining drought conditions.

Drought Indicators

Besides precipitation, things like soil moisture, streamflow, snowpack and the Palmer Drought Index, all factor into categorizing the severity of drought in a particular region. The Palmer Drought Index compares current precipitation amounts to normal precipitation numbers and also considers things like evapotranspiration, infiltration of water into the soil, and runoff.

Locally, the Teton Conservation District monitors the snow water equivalent in the headwaters of the Snake River, which actually peaked later than average this year, due to a snowy April. At the beginning of June,  there was still 4 to 5 feet of snow depth yet to melt at the 9,500-foot elevation in the Tetons.

The Conservation District also keeps tabs on the groundwater depth in the valley, which has been running below normal since January of 2022. At the end of May 2022 groundwater depths remained deeper than the average depth for this time of year.

The last thing that is considered in the calculation of drought conditions is reservoir levels. Locally, both Jackson Lake and Palisades Lake were quite low through most of June. On June 30th, Jackson Lake was at 48 percent full, Palisades was up to 76 percent. Palisades was below 40 percent just two weeks prior.

Since water managers look at stored water when considering how much water will be available for irrigation or agricultural uses, reservoir levels weigh in as a big part of the drought equation.

In the case of the Upper Snake River drainage, the low water levels in the reservoirs began last summer, when both Jackson and Palisades were drawn down to accommodate downstream dam reconstruction. Thus, making our drought conditions some what fabricated or man-made, if you will, by the Bureau of Reclamation.

Clickable diagram of USBR reservoir storage in the Upper Snake River Basin

Drought Monitor Map

The Drought Monitor map is compiled nationally by a number of different entities, including: The National Drought Mitigation Center (NDMC) at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Department of Agriculture (USDA).

The map is updated every Thursday, identifying areas of drought and rating the intensity of drought on a scale of D0 to D4. On the lowest end of the scale, D0 indicates abnormally dry conditions. D1 is Moderate drought, D2 is Severe, D3 is Extreme, and D4 is Exceptional drought. Earlier in June, Teton County was in the D2-D3 category. Wyoming as a state rarely ever experiences D4 conditions, or exceptional drought.

Each state has their own criteria for what those intensity numbers mean, based on the impact the drought conditions will have on that region of the country. For Teton County, low snowpack in the mountains affects runoff and groundwater, with impacts to streamflow, stream water temperatures critical to fisheries, and vegetation for grazing.

By definition, when you are in the D2 category, pasture conditions are poor, trees and vegetation are stressed, and well levels decline. In D3 category, snowpack is low, and surface water is inadequate for ranching or farming.

I suspect if the Bureau of Reclamation continues to draw down water from Jackson Lake and Palisades this summer, that will put us back into the D3 or severe drought category, no matter how much rain we get n July and August.

Jim is the chief meteorologist at and has been forecasting the weather in Jackson Hole and the Teton Range for over 30 years.


Note: This post was updated from an article that originally appeared in the Jackson Hole News and Guide on June 15th.

Will it be a hot, dry summer, or not?

The latest long-range outlook for the summer season from NOAA is out, and it shows that the Jackson Hole area should have warmer and drier conditions for June, July and August.

At first glance, that might seem like ominous news, as far as drought conditions and fire danger are concerned. Although, when you dig a little deeper into the meaning of that forecast and how it was derived, it may not sound quite so bad.

Let’s take a closer look at how to interpret these long-range outlook maps from NOAA, then you can decide for yourself how good or bad this summer might be in Jackson Hole.

Warm and Dry, Maybe

This summer’s temperature outlook has most of the United States in the warmer than normal category. Jackson Hole falls under a 50 to 60 percent probability of temperatures being above normal, overall, for June, July and August 2022. Which means it is slightly more likely than not that we’ll end up warmer than a normal summer.

Precipitation-wise, the outlook is for below normal rainfall for June through August 2022, across the far northern Rockies and into the Plains States. In Jackson, the probability of it being drier than normal is somewhere around 40 percent, that is to say, the outlook is leaning towards a drier summer.

That is the official outlook from NOAA. What follows are the official instructions from NOAA on how these outlook maps are made.

How to Read the Outlook

“The contours on the map show the total probability (%) of three categories, above, indicated by the letter “A”, below, indicated by the letter “B”, and the middle category, indicated by the letter “N”. At any point on the map, the sum of the probabilities of these three categories is 100%.

For any particular location, and season, these three categories are defined from the 30 observations from 1981-2010. The coldest or driest 1/3 (10 years) define the B category, the warmest or wettest 1/3 (10 years) define the A category, and the remaining 10 years in between define the middle (N) category.

When the forecasters decide that one of the extreme categories, say above (A), is the most likely one, they assign probabilities which exceed 33.33% to that category, and label the map with an “A” in the center of the region of enhanced probabilities. To make it possible to display three categories on one map, we assume that, when either A, or B is the most likely category, the probability of the middle category remains at 33.33% for most situations. This means, for example, that when the probability of A (B) is 40%, the probability of N is 33.33%, and the probability of B (A) is 100% minus 40%+33.33%=26.67%.

When probability values of the favored category reaches 70%, or higher, the probability of the opposite category is fixed at 3.3%, and the probability of the middle category is adjusted to values (less than 33.33%) which cause the sum of the three probabilities to equal 100%.

When the middle category (N) is higher than 33.33%, the probabilities of the A and B categories decline by (equal) amounts required for the sum of the A, N, B probabilities to equal 100%.

In regions where the forecasters have no forecast tools which favor the chance of either A, or B, the chance of these two categories is defined to be 33.33% each, and the region is labeled “EC”, which stands for equal chances.

Shading is used to indicate different levels of probability above 33.33%.”

Say What?

You really need to read that explanation several times to understand the methodology used to arrive at these probabilities. I picture a team of meteorologists and statistics nerds sitting around, 5 days a week, 40 hours a week, tweaking numbers. After all that, they rarely ever commit to probabilities that exceed much more than 50 percent. Basically, a coin flip.

It might help to know that last summer’s outlook was also for warmer and drier than normal weather. The summer of 2021 ended up one-degree warmer than the long-term average, however, Jackson was wetter than normal by 0.81 inches.

My forecast for this summer is for warm and dry weather on the days I have outdoor plans and just enough rain to keep the dust down and hold the fire danger at bay. I’m giving that “wish-cast” a 50-50 chance of happening.

Jim is the chief meteorologist at and has been forecasting the weather in Jackson Hole for over 30 years.


Note: This article originally appeared in the Jackson Hole News & Guide