Looking at eastern Idaho’s heat, drought trends and if conditions will improve
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IDAHO FALLS – Drought conditions throughout the state, combined with lower-than-average rainfall and unseasonably hot temperatures, have made 2021 a year to remember.
These conditions are expected to continue.
Kevin Smith, a meteorologist with the National Weather Service in Pocatello, tells EastIdahoNews.com the climate prediction center’s long-range outlook for temperature and precipitation shows above normal temperatures continuing for all of eastern Idaho through at least October.
“We’ll still see normal periods, slightly cooler periods. We may occasionally have systems come through. You’ll see the usual weather variability. But big picture, the odds are favoring above-normal temperatures for our region,” Smith says.
One of the biggest contributors to this trend is a constant stream of abnormal ridging (an area of high pressure) over the spring and summer months.
“We’ve seen a big ridge of high pressure — which is associated with sunnier, drier weather — that is further north and maybe a little stronger than what we would normally see, over and over again this season,” says Smith.
Many times, these ridges can be attributed to El Nino or La Nina climate patterns in the Pacific Ocean. Smith says that’s not the case this year, which means there’s no explainable reason for the cause of the heatwave.
Data provided by Smith indicate the average high temperature for the month of July in Pocatello is 88.8 degrees. The average high for Idaho Falls in July is 86.7 degrees.
Smith says Pocatello experienced its 22nd consecutive day at or above 90 on Monday, making it the second-longest streak of temperatures at or above 90 on record. The longest streak of 90 or above happened in 2018, and it lasted 30 days.
“The forecast over the next seven days shows us hitting 90 or better each day,” Smith says. “It’s possible we (could beat the record).”
Though Pocatello is experiencing temperatures slightly above this month’s average high, Idaho Falls’ streak of 85 or above is similar to the normal average high.
“If you use 85 degrees as the threshold, Idaho Falls is at a 23-day streak at or above 85, as of (Monday), which puts it in 10th place,” says Smith.
Measurable precipitation in 2021
Compounding the heat is the lack of measurable rainfall throughout the region. The last time there was more than a trace of rain in Pocatello was June 24, and it was only .01 inches, Smith says. Before that, May 25 was the last time there was measurable rainfall, which amounted to .05 inches.
The last measurable rainfall for Idaho Falls was .01 inches, and it occurred on July 5. Prior to that, Idaho Falls received .16 inches on June 24.
“More broadly, we’ve had isolated thunderstorms over the past couple of weeks on several different days that have really targeted our mountain areas … but precipitation has been hit and miss. On a couple of occasions, we’ve had a heavier thunderstorm that’s produced localized heavy rain. The thunderstorms that we’ve seen have generally been quite dry,” Smith says.
Historically, the normal annual precipitation for Pocatello is 11.82 inches. For Idaho Falls, it’s 10.07 inches. From January through July, Pocatello typically averages 7.33 inches of precipitation, and Idaho Falls averages 6.19 inches. Since January 1, Smith says Pocatello has picked up 4.46 inches of precipitation, and Idaho Falls has gotten a total of 4.23 inches of precipitation.
“So far, we’re roughly 2 inches behind in Idaho Falls, and, of course, we have 10 more days to go,” says Smith. “We’re almost 3 inches behind in Pocatello compared to normal.”
The water outlook and its impact on the drought
The amount of precipitation along with snowpack levels have an impact on how much water is in the reservoirs, which determines the water supply for eastern Idaho.
Tony Olenichak, the watermaster for the Upper Snake River Water District, says the two largest reservoirs for the region — American Falls and Palisades — are significantly lower than what is typical in a normal year.
“Jackson and Palisades will be drawn down lower than we’ve seen in several years. I think that will be most noticeable to people who recreate there. American Falls is going to be just as low, but we typically draw down American Falls every year, regardless of the water supply,” Olenichak says.
The water district’s latest data show American Falls Reservoir is 17% full, and Palisades is 63% full. The main reason for this is high demand for irrigation water due to drought.
Farmers throughout the area rely heavily on the water in the American Falls Reservoir, but Olenichak says they’re reaching a point where they’ll have to start drawing on the Palisades water supply so the water level doesn’t drop below its inlet.
The last major drought in Idaho occurred between 2014 and 2016. Before that, there was a drought that lasted four years from 2001 to 2005 with drought conditions ranging from extreme to exceptional.
“That was when we failed to fill the reservoirs, and Palisades was completely dry. You could see the old highway (U.S. Highway 26) that goes up to Alpine, Wyoming, submerged underneath the reservoir. We could see that again this year,” says Olenichak.
So far, the drought this year hasn’t been nearly as bad as the one in 2001. Data from the U.S. Drought Monitor show most of eastern Idaho is in the moderate or severe drought category.
Olenichak anticipates the boat ramps at Palisades becoming useless by the end of August as more of the water supply is used. He says farmers will likely have enough water to get through the season, but next year could be disastrous if there isn’t a good snowpack this winter.
On the weather front, Smith offers a glimmer of hope for the immediate future.
“Over the next several weeks, we do have some potential for some monsoon moisture to intrude into southeast Idaho,” says Smith. “There is potential for some localized, heavy rainfall. There will be opportunities for some better monsoon moisture to come north into the state of Idaho and give us some wetter thunderstorm days.”
Meanwhile, one of the biggest concerns this summer is fire season, and Smith says that’s something that’s always on their mind.
“When we’re in a hot and dry year, everyone is concerned that the fire season will continue to be very active,” he says. “We’ll continue to see how things unfold.”
For an in-depth forecast and the latest conditions in your area, visit the EastIdahoNews.com weather page.