The Southeast and Mid-Atlantic: A general decrease in the coverage and amounts of precipitation was observed this week compared to the last several weeks, although 1 to 3 inches of rain fell on southern sections of Louisiana, Mississippi, and Alabama, and in central Florida. In the latter area, the rains were quite welcome, easing wildfire conditions and falling on the KissimmeeRiver basin that drains into Lake Okeechobee, still at a near-record low level. The water, however, was mostly captured and held by the many lakes around the Disney World area (the Upper Chain of Lakes), and very little flowed into the Kissimmee River. With surpluses accumulated in the central GulfCoast region and central Florida during the past 30- and 60-days, a slight reduction of D0 was made.
Meanwhile, precipitation totals were generally between 0.1 to 0.5 inch in the remainder of the Southeast, and between 0 and 0.2 inch in the mid-Atlantic and Carolinas. Normally, the winter months are ideal for soil moisture recharge, with greatly reduced levels of vegetative, agricultural, and human demands; lower temperatures; and minimal evaporation. During the past 90-days, however, less than half of normal precipitation had fallen from central Mississippi northeastward into northern Virginia. Not surprisingly, 1-, 7-, 14-, and 28-day USGS stream flows ending Jan. 29 remained or dropped into near-record (<10th percentile) or record low levels in approximately the same area, from central Mississippi northeastward into central Maryland. Based upon stream flows, short- and long-term indices, continued short- and long-term shortages, and several soil models, the following areas had expansion of: D3 and D4 in northwestern Alabama; D4 into northeastern North Carolina; D3 into extreme southern Virginia; D2 into east-central Mississippi and in central Virginia; and a general northward shift of the D0 from southern Arkansas into south-central Kentucky. Since early August, the core extreme to exceptional (D3-D4) drought has persisted in northern Alabama, central Tennessee, and northern Georgia while shifting northeastward into North Carolina, while significant relief has occurred along the southern and northwestern edges.
The Great Lakes Region and Midwest: After three consecutive weeks of light to moderate precipitation and some slight drought improvement last week, drier weather (0.2 inch or less) was reported in the upper Great Lakes region, keeping conditions status-quo. Farther east, slightly greater totals (0.2 to 0.6 inch) occurred in lower Michigan, but not enough to warrant any improvement. In western Illinois and east-central Missouri, little or no precipitation maintained the small area of D0(H). USGS stream flows continued to slowly drop, as the 1-, 7-, and 14-days values (ending January 28) declined from the 25th percentile last week to below the 10th percentile, although no other impacts were reported.
The Plains: For the second straight week, much of the Plains, except far southern sections, saw little or no precipitation, although temperatures gradually warmed up from last week’s Arctic blast and averaged close to normal. Farther south, subtropical moisture combined with a weak system, bringing light to moderate precipitation (0.2 to 1 inch, locally to 2 inches) across southern and eastern Texas. The greatest totals, however, fell on non-drought eastern Texas, while lower amounts (less than 0.3 inch) occurred to the west, doing little if anything to reduce short-term deficits. An exception to this was in the Big Bend of Texas where continued light but above-normal precipitation has accumulated surpluses at 7-, 14-, 30-, and 90-days, and also at longer time frames (6- and 12-months), and D0(A) was removed.
In contrast, after a very wet Spring and Summer throughout the Plains last year, much drier weather has returned to most of the region since the Fall, and has continued into this Winter. Although subsoil moisture appears to be adequate, the lack of precipitation and recent windy conditions have combined to generate short to very short topsoil moisture conditions across the Texas and Oklahoma High Plains. This has caused 62%, 58%, and 37% of the Texas winter wheat, oats, and pastures/ranges to be rated as poor or very poor as of Jan. 27, respectively. In addition, numerous wildfires recently broke out across northern Texas, including a 20,000 acre grass fire near Muleshoe, and a statewide burn ban was ordered for Oklahoma. With plenty of tree debris from last December’s ice storm, widespread ample vegetation from last summer’s wet weather, and the dry and windy weather, “Oklahoma is like a giant tinderbox”, according to Assistant State Climatologist Gary McManus, “and this scenario is similar to what we saw with the genesis of the drought that began in earnest during the Winter of 2005-06”. Accordingly, D0(A) was expanded into central Oklahoma and west Texas.
Farther north, minimal Fall and Winter precipitation has also created short- to medium-term deficiencies in parts of the Dakotas. Less than 25% of normal precipitation has fallen since the end of December from central North Dakota and northeastern South Dakota eastward across northern Minnesota, keeping snow packs below normal. Although the ground is frozen and snow covered and impacts are negligible, D0 was increased in northeastern South Dakota and eastern North Dakota as a head’s up to subnormal winter precipitation and potential Spring moisture shortages. Similarly, D3 was introduced in far north-central North Dakota as this area has measured very little precipitation during the past 6 months, recording less than 25% of normal precipitation.
The Rockies, Intermountain West, and Far West: A strong, slow-moving, meandering upper-air low off the California coast funneled subtropical moisture into much of the Southwest while unseasonably cold air remained entrenched over the West. This resulted in very heavy rains along the central and southern California coast (11 to 12 inches near Santa Barbara and Ojai), heavy low-elevation snows in southern California, Sierra Nevada, and southern Intermountain Plateau, and widespread, moderate to heavy precipitation throughout California, western and southern Nevada, Arizona, and southern Utah. In California’s Sierra Nevada, the NRCS average basin water year-to-date precipitation rose in one week from 79-82% to 90-98%, and the snow water content went from 86-98% to 100-114%. Accordingly, much of California saw a 1-category improvement, with a 2-category improvement near Santa Barbara where a foot of rain fell. The few areas that remained status-quo (D2) were the southern San JoaquinValley near Bakersfield and extreme southeastern California. Rainfall was much lower in both areas, with a rain shadow affecting the southern San JoaquinValley (totals ranged from 0.2 to 1 inch). With totals less than 0.5 inch in the desert Southwest, long-term deficits (6-months and longer) still remained. In Arizona, this was the fourth major system to hit the state this water year, and with top soils already moist, the heavy rains (2 to 6 inches) produced widespread flash flooding. Even arid desert locations in the southwest and west-central received 0.5 to 1 inch (normal annual totals are 3 to 7 inches), and ample standing water was reported. This also warranted a general 1-category improvement across the state. For the three central Arizona basins, the Jan. 29 NRCS average snow water content was 134-170%, and Oct. 1-Jan. 29 precipitation was 128-170%. According to WFO Phoenix, water was being spilled from the Verde River reservoirs, and with snowmelt runoff this Spring, these reservoirs will be effectively at capacity through at least the end of May. Runoff from this storm and future snowmelt will fill the Salt River reservoirs, including RooseveltLake, with both the Verde and Salt reservoirs major water suppliers to Phoenix. In addition to the Southwestern storm, another late-week system brought light to moderate precipitation to the Northwest and northern Rockies, maintaining conditions there.
In addition, the recent spate of precipitation required a re-examination of short-term wetness versus long-term drought, especially in data-sparse areas. For long-term hydrologic drought, 12- and 24-months precipitation and SPI values were compared with 6-months and less periods. The results from this included expanded long-term severe drought (D2) in northeastern California and south-central Oregon, and some improvement in southwestern Nevada and southwestern Utah. Moderate drought (D1) was left along parts of the California coast, namely south of Los Angeles (OrangeCounty) and in southern San Luis Obispo and northern Santa Barbara, which have missed out on the heavier rains that surrounding locations have observed. A more complete analysis of the West can be made in early February when additional information becomes available in the February 1 Western Snow Pack Conditions and Water Supply Forecasts.
Alaska: Light to moderate precipitation occurred in western and southern sections of the state, while subnormal temperatures and little or no precipitation fell on the northeastern quarter of Alaska, maintaining D0 there. From the limited NRCS/USDA SNOTEL sites in northeastern Alaska, the Water Y-T-D precipitation (since October 1) was generally 35-70% of normal as of January 29, while the few Snow Water Equivalent sites were also below normal.
Looking Ahead:For January 31-February 4, the upper-air pattern will consist of troughing in the West and ridging in the East. This will produce cold and unsettled weather in the Pacific Northwest and Rockies, and mild and wet conditions in the eastern third of the nation. A series of Pacific storms will bring coastal rains and mountain snows to the Pacific Northwest and northern Rockies early in the period, then over the weekend, move farther south and drop light precipitation on the Southwest. In the East, a system will track from the southern Great Plains on Thursday and into New England by late Friday, producing heavy snow from the south-central Great Plains northeastward into western New England, icing in the central and northern Appalachians, and rain in the Southeast and AtlanticCoast states. By Monday, another storm will generate showers in the Delta, middle Mississippi, Tennessee, and western OhioValleys, and snow in the western Corn Belt.
