Summer weather outlook | TheFencePost.com

Summer weather outlook

Amy Hadachek
for The Fence Post

Farmers and ranchers determinedly check weather forecasts, almost as much as meteorologists and climatologists. Now, as the people who grow our food are pondering what to expect this summer to feed livestock and grow crops, here's insight from several meteorologists, climatologists and agricultural extension district officials.

The Climate Prediction Center released its latest official outlook for June, July and August. As of May 17, the CPC's summer 2018 forecast, on a large scale, appears fairly uneventful for agriculture in the central Plains, although there are possible signs of hope for precipitation in parts of the Rockies, and other dry areas.

"There wasn't a strong signal for temperature or precipitation for much of the area," said Tyler Williams, ag climate and weather Extension educator at the University of Nebraska-Lincoln. Williams referred to the neutral (or average) precipitation outlook for the entire Plains region; from Texas northward throughout Oklahoma, Kansas, Nebraska and the Dakotas (meaning equal chances of having either: normal, or above normal, or below normal precipitation.)

HOPEFUL RAINS

Meanwhile, forecast guidance from the CPC indicates that above-normal precipitation is favored in Colorado generally west of the Continental Divide. Specifically, precipitation chances are indicated to possibly be higher than average in an area including: western Colorado, southern Wyoming, northwest New Mexico, northeast Arizona, and parts of Utah, specifically central, southern and eastern Utah.

Then, precipitation chances are also higher in the eastern cornbelt from Iowa, eastward.

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"The good thing about all that, is the only area of above-normal probabilities for below normal precipitation is clear out in the Pacific Northwest. For June, there are increased odds for above-normal temperatures for most of the U.S. This places a higher demand on water resources, thus, precipitation and the timing of precipitation becomes more crucial," said Williams, noting, "Most of the central Plains area is not sitting on a lot of moisture in the (soil) profile, so there is a risk of being able to withstand any hot and dry periods. Nebraska is in decent shape, but conditions drop off quickly along the Nebraska/Kansas border."

DROUGHT AREAS

Some drought improvement is indicated for portions of Oklahoma, Kansas, northern Texas, and New Mexico, which are in the deepest drought. "That's based on seasonal cycles as thunderstorms generally increase in June and July across those areas. So those are predicted to reduce the magnitude of the drought (improvement) where it is most intense but not ameliorate (remove) the deep, entrenched drought. Specifically for areas with wildfire burn scars, significant soil erosion and mudslides are possible," said Matthew Rosencrans, head of forecast operations for the Climate Prediction Center in College Park, Md.

WESTERN COLORADO

In western Colorado, a range management specialist notes the timing of precipitation is also critical, and cool-season grasses, which make up much of the forage on the western slope of Colorado, grow best with spring moisture (either soil moisture from snowmelt or spring rains).

"Since we've had such a dry spring and winter, even if we get moisture in the coming months, forage at lower elevations (below 8,000 feet) will remain low, impacting grazing," said Retta Bruegger, regional specialist, range management, Western Region at Colorado State University Extension in Grand Junction, adding, "Thus, I predict even if we get a lot more rain soon, forage production may not recover, especially at lower elevations dominated by cool-season grasses."

Bruegger said drought is expected to persist in southwestern and southern Colorado. "The drought outlook is not promising for southern/western/southwestern Colorado (based on the May 17 U.S. Seasonal Drought Outlook.)

"Though forecasts lose accuracy the farther out in time they go, they are just one 'tool in the tool box.' The most recent report, released May 17 and valid through Aug. 31, shows drought persisting in much of western and southwestern Colorado, although some sites along the Colorado River and in the Grand Valley are looking like drought conditions will improve, but not end," Bruegger said.

GRASS CAST

There's a new tool to help northern Great Plains ranchers and range-land managers calculate expected forage production. In a press release issued May 22, Dannele E. Peck, director of Northern Plains Climate Hub for the U.S. Department of Agriculture's Agricultural Research Service in Fort Collins, Colo., announced the launch of the Grass-Cast which forecasts forage production in parts of the following states: Nebraska, the Dakotas, Colorado, Wyoming and Montana. This grassland productivity forecast, which is updated every two weeks, uses over 30 years of historical data about weather and vegetation growth combined with seasonal precipitation forecasts to predict if rangelands in specific counties are likely to produce: above-normal, or near-normal or below-normal amounts of vegetation for grazing.

By looking at one of three possible scenarios shown on their graphics (maps). the Grass Cast, for example, will show, that if May, June and July precipitation is near normal in southeastern Colorado, then the counties will be expected to have 5 to 15 percent fewer pounds per vegetation acre than their 34-year average. Peck suggests using the introductory video, and also sharing the Grass Cast if it can be helpful to any other ranchers or other rangeland managers at http://grasscast.agsci.colostate.edu/.

"In a nutshell," Peck said, "Grass-Cast provides three maps, which represent three different possible scenarios that a rancher can use to make their grazing management decisions." The three maps are based on whether precipitation in that area has been either: above-normal, near-normal, or below-normal.

"So, the maps should be interpreted as follows… (For example:) If precipitation between now and July 31 is above-normal, grassland production in your county (in pounds per acre) will be approximately ____ percent more or less than your county's 34-year average. But if precipitation between now and July 31 is near-normal, grassland production in your county (in pounds per acre) will be approximately ____ percent more or less than its 34-year average. And, lastly, if precipitation between now and July 31 is below-normal, grassland production in your county (in pounds per acre) will be approximately ____ percent more or less than your county's 34-year average."

In future years, Peck hopes they can scale down Grass-Cast from the county level to smaller geographic areas, such as 10 or 20 square-miles. "We also have plans to begin producing it for Kansas and other states (Oklahoma and Texas) in the southern Plains in the spring of 2019," Peck said.

SNOW PACK

Regarding the vital snow pack in the Rockies, a climatologist analyzing the latest snow analysis and snow depth maps in the Water and Climate Update issued on May 24, said that above-normal temperatures this spring in central and northern Colorado have led to a rapid decline in snow-pack levels. He issued a rather disappointing forecast.

"Snow-pack levels are virtually non-existent for the southern one-third of the Rockies, including south central Colorado. Most locations below 9,000 feet east of the Continental Divide are below 10 percent of normal, while SNOTEL (an automated snowpack sensor network) locations with elevations above 9,000 feet are running from 25 percent to 75 percent of normal," said Al Dutcher, associate state climatologist in the Nebraska State Climate Office in Lincoln. "However," Dutcher said, "The vast majority of sites are less than 50 percent of normal." See the forecast at https://www.wcc.nrcs.usda.gov/ftpref/support/drought/dmrpt-20180524.pdf.

Dutcher said, with above normal temperatures anticipated for most of the next two weeks, he expects snow-pack levels to continue falling fairly rapidly, and that locations under 12,000 feet elevation could likely be "snow-free" before mid-June. "Therefore, mid-level atmospheric moisture from snowmelt will be virtually non-existent, which will likely compromise front range thunderstorm development and would allow critical dryness from the southern Rockies to expand northward as we approach the end of June," Dutcher said.

WYOMING

Currently Wyoming is looking fairly good with only some moderate drought persisting in Sweetwater and Carbon counties.

"The northeast and northwest corners of Wyoming, as well as south-central need to be watched but the rest of the state has received a fair amount of moisture the last two weeks. The area of D1 (Moderate Drought) in Carbon and Sweetwater have only received a half-inch or less in the last two weeks but, with the exception of a few isolated pockets in the northern quarter of Wyoming, that is about the only area that hasn't received a half-inch or more," said Tony Bergantino, deputy director of the Water Resources Data System in the Wyoming State Climate Office, and Wyoming CoCoRaHS state coordinator.

Reservoirs in Wyoming are reported to be "sitting fairly well" with almost all being two-thirds full or more and most streamflow stations are showing normal to above normal flows for this time of year. "There are a few exceptions such as the Bear River, parts of the Powder River, the Medicine Bow River and the Little Snake by Dixon. There is little guidance on precipitation for Wyoming out at the 30- and 90-day outlooks, though the temperature for those periods is favored to be above-normal," Bergantino said.

"Agriculturally, it's tough to make firm decisions based on a three-month outlook, given that important temperature and precipitation extremes can (and will) occur on a much shorter time scale, such as hours or days," said Brad Rippey, USDA meteorologist in the office of the Chief Economist/World Agricultural Outlook Board in Washington, D.C., noting there could possibly be wetter conditions in the eastern Corn Belt, and somewhat cooler and drier weather, on average, in the western Corn Belt. "However, I caution that the aforementioned extremes, which might include short-duration heat waves and flash flooding, can be masked by a summer outlook — and yet be critical to the outcome of local or regional-scale agricultural production."

SUMMER TEMPS

Temperature-wise, above-normal temperatures are favored across central Kansas into southern and western Kansas, then south into Oklahoma and Texas.

"We are getting into a hotter and potentially drier pattern already in late May — it's a pattern that is more typical of late June or July that features the jet stream north of the region across the Dakotas into Canada and that can keep the stronger storms and better chances for widespread rains further north. If this pattern doesn't change in the next few weeks that could mean a drier late spring into summer across Kansas and exacerbate drought conditions," said Chad Omitt, warning coordination meteorologist at the National Weather Service in Topeka, Kan.

Above-normal temperatures are also forecast for much of Colorado and Wyoming. There's an even higher chance for warmer than average temperatures in extreme southwest Colorado, much of New Mexico, Arizona, Utah and into eastern Nevada.

But, as Mary Knapp, assistant state climatologist at Kansas State University in Manhattan, said, "The three-month outlook is the average of the three-month period, and doesn't eliminate the possibility of colder-than-normal conditions during the period. The precipitation outlook is driven mainly by the sea-surface temperature and constructed analog (computer) models," Knapp said.

EL NINO

The large-scale climate pattern shows that La Nina is done. The outlooks for next fall/winter are hinting at an El Nino (the opposite of La Nina.) El Niño conditions frequently favor higher than normal precipitation in the Plains.

"Interestingly, the extended outlooks from August on, looks like a classic El Nino precipitation signal. For the central Plains, l think precipitation will be heaviest in June, the first month of the period, then a drier trend building into the region during July and August," said Dutcher, noting, "The most likely impacted areas from above-normal moisture will be the eastern half of Kansas and Nebraska, drier for the western halves of both states."

Meanwhile, Rosencrans expects the El Nino wetter pattern to show up in late fall/early winter.

"El Nino would not have dramatic impacts until much later in the year (Oct.-Nov.-Dec.) The odds for El Niño are 49 percent by winter. That's higher than normal odds, but not a slam dunk, and subject to revisions," Rosencrans said.

Meanwhile, some inspiration, the broad scale three-month outlook also doesn't account for individual events such as a thunderstorm or tropical system that can produce a heavy rainfall event. ❖