A pair of late-December storm systems moved ashore in the West, delivering heavy precipitation in the Pacific Coast States and significant snow from the Cascades and Sierra Nevada to the western slopes of the Rockies during the week of Dec. 25-31, according to the Jan. 3 USDA Weekly Weather and Crop Bulletin.
Weekly precipitation totals in the Sierra Nevada and adjacent foothills locally totaled 4 to 12 inches or more, with an average of more than 5 inches of liquid equivalency being added to the Sierra Nevada snowpack during the final week of December.
Farther east, mostly dry weather prevailed across the nation’s mid-section, although light snow and blowing snow continued to cause rural travel disruptions across parts of the northern Plains and upper Midwest. Meanwhile, variable rainfall occurred along and east of a line from eastern Texas to southeastern Michigan. Some of the heaviest rain, locally 2 to 4 inches or more, fell in the central Gulf Coast region and parts of the mid-South.
Throughout the central and eastern U.S., sudden warming in the wake of the previous week’s brutal cold snap boosted temperatures to near- or above-normal levels, except in the southern Atlantic region. The parade of daily-record highs began on Dec. 29 with a high of 73°F in Columbia, Missouri — exactly 80 degrees higher than the minimum reading of -7°F just 6 days earlier. Elsewhere on the 29th, daily-record highs surged to 70°F in locations such as Springfield, Illinois.
Sunny, increasingly warm weather dominated major farming areas of central Argentina. Furthermore, temperatures rose to stressful levels by week’s end, with daytime highs reaching the upper 30s (degrees C) regionwide on several days. While hastening drydown and harvesting of winter grains, the dryness and heat reduced soil moisture for germination of summer grains and oilseeds and stressed emerged crops. According to the government of Argentina, corn and soybeans were 77 and 82% planted, respectively, as of Dec. 29, still lagging last year’s pace for both crops.
A drying trend persisted over large sections of southern Brazil, where moisture remained limited for normal development of soybeans and first-crop corn. As in recent weeks, many locations from Mato Grosso do Sul southward recorded less than 25 mm with few days of measurable rainfall. Summer warmth (daytime highs often reaching the lower and middle 30s degrees C) compounded the impact of the dryness on diminishing soil moisture reserves. In Rio Grande do Sul, corn was 91% planted as of Dec. 29, with 70% of the sown crop having reached reproduction; in contrast, 95% of soybeans were planted but flowering was still in the early stages (5%). Meanwhile, mild, showery weather maintained overall favorable crop prospects farther north, including the main production areas in Mato Grosso, Brazil’s largest producer of soybeans.
