The Southeast and Mid-Atlantic: Once again, significant precipitation fell on the Southeast and mid-Atlantic, although the greatest totals (2 to 5 inches) were shifted farther south compared to the previous week. A wave of low pressure formed along a stalled cold front in the Gulf of Mexico and tracked northeastward, dropping over 2 inches of rain along the Gulf and southern Atlantic Coasts, with mixed precipitation and lower totals (0.5 to 1.5 inches) farther north in the southern Appalachians, mid-Atlantic, and New England. The precipitation continued a pattern of near- to above-normal precipitation for the drought-stricken Southeast since early December, although the core of the extreme to exceptional drought (D3-D4) received between 0.5 to 1 inches. This was far less than last week, which kept conditions status-quo there, but did include rare accumulating Southern snows.
In contrast, the heavy rains along the GulfCoast were enough to alleviate abnormal dryness in extreme southern sections of Louisiana, Mississippi, and Alabama, and improve portions of southern and eastern Georgia, eastern South Carolina, and extreme southeastern North Carolina by 1-category. Nearly all monitored USGS stream flows at 1-, 7-, 14-, and 28-days (ending Jan. 22) have risen back into the normal range (30th to 70th percentiles), and short-term surpluses (30- and 60-days) have accumulated in these aforementioned areas, especially aiding the topsoil moisture. However, it should be noted that some states have maintained their severe drought status even after the recent precipitation as reservoirs, ground water, and many rivers remained at very low levels. This included South Carolina, where Lakes Marion and Moultrie were at very low elevations, and approximately 26% and 56% of the population is under mandatory and voluntary water conservation, respectively. In northern Georgia, Lake Lanier, the major water supply for Atlanta, was at 1051.38 feet at Buford Dam, only a tad above its record low of 1050.79 feet on Dec. 26, although other reservoirs were doing better (e.g., West Point and George were above the top of conservation level). Farther north, another round of light to moderate precipitation (0.2 to 0.8 inches) trimmed the northern edge of the D0 from eastern Kentucky into the Delmarva Peninsula where surpluses now exist out to 90-days.
The Great Lakes Region and Midwest: For the third consecutive week, a storm system dropped moderate precipitation (0.4 to 0.7 inches liquid equivalent, or 5 to 10 inches of snow) on the upper Great Lakes region, upping the snow depths to between one and two feet and creating a 30-day surplus of 1 to 3 inches. Accordingly, the recent precipitation was enough to decrease the D1 in northeastern Wisconsin, although D0(H) persisted as precipitation remained below normal from 90-days out to 12-months plus. In east-central Missouri and southwestern Illinois, little or no precipitation fell on the small area of D0(H) as 1-, 7-, 14-, and 28-day USGS stream flows stayed in the lower 25th percentile, although no other impacts were noted.
The Plains: Much of the Plains experienced little or no precipitation and very cold weather, with temperatures averaging 4 to 10°F below normal and lows plunging to -25°F in eastern Montana and North Dakota, 0°F as far south as the Oklahoma Panhandle, and into the teens into south-central Texas. After last week’s expansion, conditions were left status-quo, except in the upper MissouriValley. With less than 25% of the normal precipitation during the past 90-days, some degradation was made in eastern Montana, based upon suggestions from the latest Montana drought subcommittee. In contrast, heavy rains soaked extreme southeastern Texas (along the western GulfCoast as mentioned in the Southeast and mid-Atlantic section) where 1.5 to 5 inches improved conditions by 1-category along the Texas coast.
The Rockies, Intermountain West, and Far West: After a very wet December, especially in the Pacific Northwest, Southwest, and central Rockies, and a very stormy but beneficial early January that doubled snow water equivalent and season-to-date precipitation in the Sierra Nevada and brought values close to normal, the weather has gradually quieted down, particularly this week. A much colder weather pattern (departures -4 to -15°F in the Far West, -6 to -20°F in the Rockies) only brought light precipitation (0.1 to 0.5 inches) to the Pacific Northwest, Sierra Nevada, and northern and central Rockies (although 0.5 to 1.5 inches in the north-central Rockies), and little or no precipitation to the Southwest and Intermountain West. After further assessment, however, from the latest NRCS/USDA products and recent state drought updates and surveys, additional improvements were made in the northern Rockies. In western Montana, the recent state drought report depicted a 1-category improvement due to above-normal precipitation (105-115% of normal) and seasonable snow water equivalent (SWE), while Idaho has also benefited from frequent Pacific storminess this season. In central Idaho, water year (Oct. 1) precipitation has run from 110% to 130% and SWE from 100% to 115%. In response, the D1 was removed from central Idaho, and the D1-D2 was shifted farther south in Idaho. The rest of the West was left untouched as one to three categories of improvement have already been made in the West since the late Fall.
Alaska: Above-normal temperatures accompanied light snow (0.1 to 0.3 inches liquid equivalent) across most of interior and northeastern Alaska, slightly building up the area’s snow depth, but not enough to remove the region’s abnormal dryness.
Looking Ahead: For January 24-28, cold weather will envelop the lower 48 states early in the period, but by the weekend, milder air will return to the eastern half of the nation. A few weak systems will generate light showers in the southern Great Plains and the western GulfCoast, and lake-effect snows will blanket orographically favored parts of the Great Lakes. In the West, an upper-air low off the CaliforniaCoast will bring more January precipitation to California, Sierra Nevada, and Great Basin, with heavier totals expected by the weekend as the system gradually tracks inland. The Rockies should receive light precipitation on Sunday, and as the system moves into the nation’s mid-section on Monday, showers will occur from the upper Delta to the upper Great Lakes region, with snow in the upper Midwest.
