Source: droughtmonitor.unl.edu | Map released 3-19-20 | Data valid 3-17-20
This week’s drought summary: The U.S. Drought Monitor week ending March 17 saw another round of winter storms, bringing above normal precipitation to parts of the northern High Plains, Southwest, southern plains, and Tennessee Valley. Many areas recorded totals that exceeded 200% of normal over the seven-day period, leading to improvements to areas of abnormal dryness and drought in areas where the excess moisture erased deficits and improved soil moisture and streamflow. Once again, precipitation over the Northwest and Gulf Coast states was below normal with most areas having received less than 50% of their normal amount over the last 30 days. The lack of precipitation, combined with warmer than normal temperatures, led to expansions in pockets of abnormal dryness and drought.
South: Last week, a band of heavy rainfall fell across the northern half of the region, extending from West Texas to western Tennessee with amounts ranging from one to more than four inches (equivalent to more than 300% of normal in some locations). In Southwest Oklahoma and Northeast Texas, the excess moisture erased short-term precipitation deficits and recharged streamflow leading to reductions in D0 (abnormal dryness) and D1 (moderate drought). Additionally, the “S” was removed from the “SL” drought designation to indicate that drought and dry conditions are now only present at timescales longer than six months. With more than an inch of rain falling after the close of the Drought Monitor week (Tuesday, 8 a.m. EDT) and more expected on the way, additional reductions may take place on next week’s map. Other areas seeing improvements include West Texas with reductions to D0 and D1. Unfortunately, the rain missed the parts of South Texas that need it most and conditions continued to deteriorate, resulting in expansions to ongoing areas of abnormal dryness and drought and the introduction of D4 (exceptional drought). Supporting data include rainfall deficits of two to eight inches (25 to 50% of normal) over the last six months combined with mean temperatures consistently ranking in the top 10 warmest over the same time interval. The combination of dry weather and high temperatures has dried out soils and stressed vegetation with USDA reporting only 28% of topsoil as adequate for crops in the Southeast and 3% in the Southwest. Other areas seeing deterioration this week include Southwest Louisiana and Southeast Mississippi with expansions in D0.
Looking ahead: The National Weather Service Weather Prediction Center forecast for the remainder of the week shows a winter storm developing east of the Rockies and tracking northeast across portions of the North and Central Plains into the Upper Midwest. This storm is expected to bring heavy snow to the Southern and Central Rockies with a swath of light to moderate snow extending from Nebraska northeast into Minnesota and Wisconsin. A cold front associated with the storm system is forecast to trigger showers and thunderstorms from the Southern Plains into the Mississippi, Ohio, and Tennessee valleys. Temperature are expected to be below normal by 10 to 20 degrees across California into the Central Great Basin and Southwest. Meanwhile, the Gulf Coast states and Ohio and Tennessee valleys can expect temperatures three to six degrees above normal. The Central Plains should see large temperature swings as the system passes through.
Moving into next week, the Climate Prediction Center six to 10 day outlook (valid March 22-26) favors below normal temperatures for much of the western half of the CONUS, especially near the West Coast, near normal temperatures east of the Mississippi, near normal temperatures in the Midwest and Northeast, and above normal temperatures for states along the Gulf and Southeast Coasts. The precipitation outlook favors an active storm track and above normal amounts for nearly the entire CONUS. Probabilities are highest for California, parts of the Great Basin, and the Tennessee and Ohio valleys.