Map released Jan. 2, 2019 | Data valid Dec. 31, 2019
This Week’s Drought Summary: An area of upper-level low pressure entered southern California by Dec. 26 and then progressed east across the Four Corners region. This upper-level low resulted in heavy rain and high-elevation snow from southern California east to southwest Colorado and New Mexico. A surface low developed across the south-central Great Plains on Dec. 28 with a subsequent track northeast to the upper Mississippi Valley and Great Lakes. Heavy snow fell to the northwest of this low pressure system, while moderate to heavy rainfall accompanied the cold front as it shifted east from the Great Plains to the East Coast. Following the heavy precipitation across the Pacific Northwest during mid to late December, precipitation average below normal during the final week of December. Enhanced onshore flow resulted in periods of heavy precipitation along the Alaska Panhandle, but longer-term precipitation deficits persist. A low pressure system and trailing front brought locally heavy rain and damaging winds to parts of the Hawaiian Islands this past week.
South: As an upper-level trough ejected from the desert Southwest, a surface low developed over the southern Great Plains. Beneficial rainfall (more than 1 inch) resulted in improving conditions across the eastern Oklahoma Panhandle and northwest Oklahoma. Moderate (D1) to severe (D2) drought continues across southwest Oklahoma and adjacent areas of the Texas Panhandle and northwest Texas which received lighter rainfall amounts (0.75 inches of less). Changes to the drought depiction across the remainder of Texas included a slight reduction in D0/D1 in central and southwest parts of the state, based on recent rainfall and lack of short-term dryness. Although it was a dry week across deep southern Texas, a reassessment of indicators supported a slight reduction of severe (D2) drought. A small area of severe (D2) drought was added to Burleson County, based on 120-day indicators. On December 29, a cold front crossed the lower Mississippi Valley where 0.5 to 2 inches of rainfall occurred. The heaviest rain fell to the north and east of the ongoing D0 to D2 areas.
Looking Ahead: During the next 5 days (Jan. 2 to 6), another surface low is forecast to develop across the southern Great Plain on January 2. This surface low and trailing cold are likely to bring heavy rainfall (1 to 3 inches) to the lower Mississippi Valley and Tennessee Valley with more modest amounts (1 inch or less) along the East Coast. A low pressure system with onshore flow is expected to bring rain and high-elevation snow to the Pacific Northwest, beginning of Jan. 4. Although rainfall of around an inch is forecast along the Texas Gulf Coast during the next week, dry weather is likely across the remainder of Texas. Mild temperatures are forecast to prevail across the continental U.S. during the first week of January 2020, while bitterly cold temperatures persist throughout Alaska.
The CPC 6-10 day extended range outlook (Jan. 6 to 10, 2020) indicates a slight tilt in the odds for above normal precipitation across much of the central and northeastern U.S. Below normal precipitation is favored for the Southeast along with California and the Southwest. The highest confidence in the temperature outlook exists across Alaska where below normal temperatures are likely to persist into the second week of January. Below normal temperatures are favored for the Great Basin and Rockies, while a warming trend is anticipated across the south-central and eastern U.S.