The following content was provided by meteorologist Gail Martell of MartellCropProjections.com:
Welcome Rain in Pacific Northwest, Cold and Snow in U.S. Heartland
A strong jet stream is bringing drought-breaking rain to the Pacific Northwest and a chance for snow in hard red wheat, while cold hangs on in the Midwest. Welcome rain and snow is predicted this week in Washington, Oregon and northern California, easing severe drought. Previously, a stable warm ridge of high pressure had prevailed blocking showers. The sudden change in the weather pattern is due to a southern shift in the jet stream now dipping south across the Pacific Northwest.
Precipitation is desperately needed in the West to alleviate severe drought. Coastal Washington state has received only 55% of normal rainfall this winter, and coastal Oregon just 30-35% of normal precipitation California precipitation was the lowest on record in 2013, leading to strict water rationing in the Central Valley. Reservoirs are drying up. Forage for cattle grazing is virtually nonexistent. State grape growers report the driest conditions in several decades.
The south-tracking jet stream storm track would affect the US heartland promoting snow in top wheat states Kansas, Oklahoma and West Texas. Polar air would sink into the western two-thirds of the United States where the jet stream carves out a deep trough of low pressure.
Stormy cold weather would continue in the Midwest, a familiar pattern in a harsh winter. Chicago Illinois reported zero F (-18 C) this morning. Four inches of snow is predicted tomorrow in the windy city followed by a fresh cold wave. Thursday morning the temperature would plummet to -11 F (-24 C). Salt supplies are running short across the Upper Midwest, required to melt snow and ice on streets and highways. Snow coverage has expanded to 57% of the United States.
Moisture Needed in Hard Red Wheat
A stormy wet forecast is welcome in hard red winter wheat, where winter weather conditions have been much drier than normal. Kansas, Oklahoma and West Texas have "severe" to "extreme" drought on the US Drought Monitor January 28. Drought has become "extreme" on the High Plains the western third of the wheat zone. This area has a semiarid climate but current drought is much worse than normal. Wheat grown on the High Plains is important swing factor in hard red winter wheat production, bolstering output in wet growing seasons but shrinking the harvest in years of drought.
Drought has lingering in the Midwest corn belt. Iowa, Illinois, Minnesota and west Wisconsin still have pockets of "moderate" to "severe" drought in the wake of dry autumn.
La Nina Signal
The reduced precipitation this winter on the West Coast and Southern Great Plains may be linked to a La Nina effect. La Nina winters typically are dry both in California and the southern Great Plains, where the southern jet stream has been weak or nonexistent. The subtropical jet stream typically is the source of good showers in winter due to embedded disturbances it carries across the southern third of the United States.
The Climate Prediction Center is sticking with "ENSO-neutral" conditions this winter though a distinct dry "signal" from La Nina has developed on the West Coast and southern Great Plains.