US Drought Monitor and Summary, Sept. 11, 2018
South (Texas and Oklahoma): Moist inflow from the western Gulf and a stalled cold front across the south-central Plains triggered widespread, numerous showers and thunderstorms across much of Texas into central Oklahoma, along with bands of heavy showers across most of Louisiana. About the only area in the South that missed out on decent rains were eastern Oklahoma and the northern Texas and western Oklahoma Panhandles. With widespread weekly totals of 4-8 inches and locally more, much of southern, central, western, and southeastern Texas saw 1-2 category improvements as most station SPIs were normal or wet at 2-, 3-, and 6-months, and even 12-month SPIs were improved. Average 1-, 7-, and 14-day USGS stream flows responded into the 76th (above normal) or 90th (much above) percentiles where the improvements occurred. In Oklahoma, 1.5-6 inches of rain allowed for a 1-cat improvement in parts of southwestern, south-central, and northeastern Oklahoma.
Looking Ahead: For the ensuing 5 days (Sept. 13-17), the focus will be on Hurricane Florence’s landfall and where it tracks thereafter. As of Wednesday afternoon, the most likely scenario is landfall near the NC-SC border, with the hurricane slowing down and dropping catastrophic amounts of rain (over 20 inches near landfall), with possible devastating floods in parts of the Southeast and mid-Atlantic. The 5-day QPF targets the Carolinas and Virginia with 4-10 inches, with heavy rains moving northward into the Northeast during Days 6-7. Elsewhere, a tropical disturbance is expected to move into the western Gulf from the Caribbean, dumping more heavy rain (2-6 inches) on the southern half of Texas. Pacific systems traversing along the US-Canada border may drop light to moderate amounts from Washington to Minnesota. Little or no precipitation is expected elsewhere. Temperatures should average below-normal in the Far West, northern Rockies, and Texas, and above-normal from the Southwest northeastward into New England.
For the CPC 6-10 day extended range outlook (Sep. 18-22), the odds favor above-normal precipitation in the northern half of the Plains, in the eastern quarter of the country (from Florence), and northwestern Alaska. Chances are good for subnormal precipitation in most of the West, south-central Plains, lower and middle Mississippi Valleys, and southern Alaska. Above-normal temperatures are likely in the southern and eastern sections of the U.S. and most of Alaska, with subnormal readings limited to the Northwest and northern Rockies and Plains.