Ag Weather Forum

Pattern Change Ahead

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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A pattern change to trough west-ridge northeast offers milder and drier Midwest conditions, along with a higher chance for precipitation in the Far West during the 10-day time frame. (TropicalTidbits.com graphic)

November has been a rough month weatherwise. Most crop areas have had some combination of rain, snow and cold, or all three. Numerous travel and safety hazards grabbed the headlines and video screens. Meanwhile, the western U.S., specifically California, has seen tremendous losses from wildfires fueled by hot, dry and windy conditions.

The upper-atmosphere pattern drove these contrasts in conditions. Up to and through the middle of November, the prevailing upper air pattern was ridge (high pressure) west, and trough (low pressure) east. Clockwise circulation with the western ridge, and counterclockwise circulation with the eastern trough, combined to pull very cold air from northern Canada south the entire north-south width of the contiguous U.S. That colder air, in turn, helped drive the harsh winter-like storm systems that lashed the central and eastern U.S. over the past week to 10 days.

Fortunately, the upper-air pattern is showing signs of a pronounced change. My colleague, DTN Senior Ag Meteorologist Mike Palmerino, addressed this scenario in comments Friday afternoon.

"The ... jet (stream) will feature a ridge in the Gulf of Alaska; a trough in the eastern Pacific Ocean extending into the west coast of the U.S.; a ridge over the interior western U.S.; a trough over the interior eastern U.S.; and some ridging along and off the east coast of the U.S." Palmerino wrote.

The spinoff from this change, however, is the major takeaway. "This will be a rather dry pattern for much of the central U.S. during the outlook period as Gulf moisture is unable to move northward due to the ridge to the west and the trough to the east," Palmerino said. "The main storm track will be along the Gulf Coast and the Atlantic Coast. Temperatures will be milder in the Plains under the ridge, and variable in the Midwest between the ridge to the west and the trough to the east."

With this pattern, Midwest temperatures have a variable trend, with -- a key feature -- precipitation below normal. The entire Plains region also has a variable temperature pattern with below-normal precipitation. And likewise in the Delta, variable temperatures with below normal precipitation are featured.

In contrast, the western U.S., especially California, has above-normal precipitation in the forecast. This does offer potential for wetter conditions to ease the tremendous wildfire situation. However, if precipitation is heavy -- and it can be -- the threat of mudslides will also be high.

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

Follow him on Twitter @BAndersonDTN

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