This Week’s Drought Summary
A low pressure system developed across the southern Great Plains by February 17 and rapidly tracked northeastward to the Ohio Valley and Northeast a day later. To the northwest of the surface low track, snowfall amounts exceeded 6 inches across northeast Kansas, northern Missouri, and north-central Illinois. In the warm sector of this storm system, severe thunderstorms with locally heavy rainfall (more than 1 inch) affected the Tennessee Valley and parts of the Lower Mississippi Valley. Another low pressure system developed by February 21 with a similar northeastward track to the Ohio Valley. 7-day precipitation amounts, from February 15 to 21, exceeded two inches across much of the Ohio and Tennessee Valleys, Ozarks region, southeast Oklahoma, and parts of northern Texas. Farther to the south and west, little to no rainfall occurred closer to the Gulf Coast along with the Rio Grande Valley and central to southern high Plains. This precipitation pattern during mid-February and the primary storm track across the Ohio Valley are typical during La Nina. Although there was accumulating snow across the northern to central Rockies and northern Cascades this past week, the drier-than-normal pattern persisted throughout most of the West. 7-day temperatures, for the week ending on February 22, averaged above normal across the East, lower Mississippi Valley, and western Gulf Coast. Meanwhile, intrusions of Arctic air began to shift south from Canada into the northern Great Plains and upper Mississippi Valley where weekly temperatures averaged as much as 10 degrees F below normal. Periods of rainfall continued to occur along the windward sides of the Hawaiian Islands.
A sharp gradient in precipitation was observed from north to south across this region which is typical for La Nina during mid-February. 7-day precipitation amounts, from Feb 15 to 21, exceeded 2 inches across most of the northern half of Mississippi, northern two-thirds of Arkansas, southeastern Oklahoma, and northwestern Texas. A 1-category improvement was made to these areas that received the heavier rainfall. Conversely, farther to the south, a 1-category degradation was made to parts of the lower Mississippi Valley, western Gulf Coast, and central to southern Texas where little to no rainfall occurred this past week. Extreme drought (D3) was added to parts of southwestern Louisiana based on 30 to 90-day SPIs and soil moisture indicators. As temperatures warm heading into March and water demand increases with vegetative growth, additional degradation may be warranted for the lower Mississippi Valley. Although no changes were made this week to the southern high Plains, soil moisture continues to rank in the lowest 5th percentile consistent with much of this region being designated with D3 levels of drought. The lack of adequate soil moisture remains a major concern for the winter wheat crop across the southern Great Plains, while many counties of Oklahoma and Texas remain under a burn ban.