Ag Weather Forum

Questions on NOAA July Forecast

By Bryce Anderson , DTN Ag Meteorologist and DTN Analyst
Persistent upper-atmosphere troughing over central Canada could lead to both cooler temperatures in the northern U.S. and enhance Midwest rainfall. (NOAA graphic by Nick Scalise)

It is not exaggeration to say the commodity markets have been truly atwitter over the latest 30-day forecast from the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center. Forecast temperature maps came out with brick-red or adobe-brown coloring for everywhere but the Northwest, and the interpretation immediately went to "above normal temperatures almost everywhere" for the month of July.

Well, that trend may occur, but there's also reason to not just take this spin and run with it. I discussed this forecast with my colleague Mike Palmerino, and he offered these comments:

"I don't feel great about such a call because it doesn't reflect the pattern we've had in the past few months," Mike said. "It appears that the forecast is based heavily on the forecast model presentations. There is certainly a core of heat in the Southwest, and that's where the greatest probability is for above normal on temperatures. Also, the Deep South has a call for that trend. That's probably okay." But the heart of the Grain Belt is more in a slightly-above-normal chance."

A notable feature that has been part of the upper-level scene is the presence of a strong polar vortex in the eastern Canadian Prairies. This trough has brought cooler temperatures to both the Canadian Prairies and the U.S. Northern Plains in the days after blistering early-June heat. The flow around that Canada trough also combines with stifling hot high pressure in the upper atmosphere over the Far West and Southwest areas of the U.S. to produce a strong thermal boundary, and develop thunderstorm potential over the Midwest.

"This is more like an early to mid-spring pattern," Mike Palmerino said. "Here in late June-early July, this strong polar vortex is shutting off Pacific (Ocean) flow and it's leading to an active pattern with rain and a decent amount of severe weather. There is a lot going on in the Midwest."

One notable area that is a recipient of the active storm and rain pattern is in the Midwest between Interstate 70 and Interstate 80, from Iowa and Missouri east to Indiana. The first 12 days of June were very dry in this swath of the Corn Belt, to the point that the June 13 Drought Monitor assessed this sector of the Midwest in the beginning stage of drought at "Abnormally Dry."

This setup -- as would be expected -- does not bring precipitation chances into the Southern Plains. And, while Northern Plains temperatures may stay mild or even below normal with the influence from the central Canada trough, precipitation is still not promising. "Only limited rainfall is expected during the next week for the Northern Plains, but the temperatures staying near to above normal will limit stress," Palmerino said.

Bryce Anderson can be reached at Bryce.anderson@dtn.com

Follow him on Twitter @BAndersonDTN

(CZ)

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