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.

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.

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 mountainweather.com 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.

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 mountainweather.com and has been forecasting the weather in Jackson Hole for over 30 years.

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

Jackson Wyoming just experienced one of the coldest and snowiest Aprils in the last 100 years. It all began with a precipitous drop in temperatures, following a high temperature of 62 degrees on April 8th, 2022, four days later, the high on April 12th was only 26 degrees. That broke the record for the minimum high temperature for that date, which was 33 degrees, set 48 years ago, in 1974.

How Cold Was April

The average high temperature in April 2022 in the Town of Jackson was 44 degrees, that is eight degrees colder than the long-term average. The average low temperature was 22 degrees, or two degrees cooler than average.

The mean temperature for April 2022, the average of the monthly high and low temperatures, was 33 degrees. That is five degrees colder than the long-term average mean temperature in April, which is 38 degrees.

Combing through Jackson’s climate records, going back to 1922, there were only six other Aprils that recorded a colder mean temperature, the coldest of those was 29 degrees, back in 1928. Based on monthly mean temperatures, April 2022 would rank as the 7th coldest April in the last 100 years.

How Snowy Was April

From the official climate data for Jackson, of all the Aprils with complete records, there have only been three other Aprils that were snowier than this one, and those happened over 50 years ago.

April 2022 had 16 inches of snowfall recorded at the Jackson Climate Station. That was just shy of the total snowfall in April 1970 of 17 inches and the 18 inches that fell in April 1963. This April was 8 inches short of the all-time April snowfall record in town of 24 inches, from April of 1967.

The average snowfall in town in April is 4 inches. Last year, April 2021, only had 1.5 inches of snowfall.

It’s also worth noting that this April’s 16 inches of snowfall bested January 2022’s total of 15 inches and was also more than the total snowfall received in February and March of 2022 combined, which was 13 inches.

How Wet Was April

Total precipitation in town this April was 1.95 inches, which is 171-percent of the long-term average April precipitation of 1.14 inches. April 2022 would rank as the 13th wettest April in the last 100 years. That is not exactly headline worthy, but this April was a big improvement over last April’s precipitation, which was a measly 0.37 inches in April 2021.

April 1963 is the wettest April in the weather record books for Jackson, with 2.66 inches of precipitation. Second place was just a few years ago in 2019 when Jackson had 2.48 inches of precipitation in April.

Jackson’s total precipitation in town from October 1st, 2021, through April 30th, 2022, now stands at 9.08 inches, which is just a skosh above the long-term average precipitation during that seven month time period.

Mountain Snow and Water

If you are a powder skier, April was what we were hoping for all of January, February and March. Yes, the mountains got dumped on this April, which helped bring the Snow Water Equivalent (SWE) in the Snake River Basin up to 92-percent of normal on April 30th, 2022. At this same time last year, the SWE in the Snake River Basin was only at 65-percent of average.

The water year in the mountains begins on October 1st and SWE is the best indicator of how much water is stored in the snowpack. Typically, the numbers peak at the end of April, when the mountain snowpack begins to melt in earnest.

SWE and precipitation numbers outlined here are based on the averages on April 30th for the latest 30-year period, from 1991-2020.

Overall, the total precipitation, snow and rain combined, in the Snake River Basin from October 1st, 2021, through April 30th, 2022, was 87-percent of normal. Last year the precipitation total for the same time period was at 80-percent of normal.

The Philips Bench SnoTel site on Teton Pass, at the 8200-foot elevation, averages 28.4 inches of precipitation from October 1st through April 30th. This year the total was 26.4 inches or two inches less than average.  Last year on April 30th, 2021, the season’s precipitation total was almost only 24.5 inches or 4 inches below average.

The bottom-line here is, we’re still a little below normal with our snowpack and water in the mountains going into May, but we are certainly ahead of where we were last year at this same time, thanks to April’s bountiful snow.

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