National Drought Summary -- November 26, 2019

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilized include the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14 Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast web page used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

Mild weather returned across much of the country for several days, following a mid-November cold blast in the central and eastern United States. Meanwhile, significant precipitation fell during the drought-monitoring period in several areas, including the Southwest and interior Southeast. The Southwestern precipitation, which reversed a drying trend that began with a sub-par monsoon season, provided much-needed moisture and limited drought relief. In contrast, little precipitation fell in the Northwest, which continued to experience an increase in dryness-related impacts (e.g. poor snowpack, low streamflow, and dry soils). Farther east, rain further chipped away at lingering dryness across the South and East. Patchy drought persisted, however, across portions of the central and southern Plains, leading to adverse effects on some rangeland, pastures, and winter grains. As the drought-monitoring period ended on November 26, a pair of major storm systems—one emerging from the central Rockies and the other approaching the Pacific Coast—brought the promise of widespread precipitation that will be evaluated for next week’s U.S. Drought Monitor.


Alaska, Hawaii, and Puerto Rico

Short-term wetness continued across much of southeastern Alaska, leading to a change in the designation of the drought type from “SL” to “L.” This reflects the fact that any lingering dryness (D0) and moderate drought (D1) is apparent only at longer time scales. In Yakutat, for example, November 1-25 precipitation totaled 17.12 inches (142% of normal), while the year-to-date sum stood at 89.97 inches (66% of normal). Meanwhile in Hawaii, windward showers led to some erosion of the recently introduced areas of abnormal dryness (D0), particularly on Oahu, Maui, and the Big Island. Elsewhere on the Big Island, however, there are indications of vegetation stress as far west as the South Kohala coast; as a result, moderate drought (D1) was extended westward across the northern part of the island. Finally, abnormally dry conditions (D0) were slightly expanded in eastern Puerto, where low streamflow is being reported and the 2019 wet season will soon be winding down.


High Plains

Drought is confined to parts of Colorado and Kansas. However, further worsening of the drought situation occurred from southwestern through central Kansas, where moderate to severe drought (D1 to D2) was expanded. More than one-sixth (17%) of the winter wheat in Kansas was reported in very poor to poor condition on November 24, according to USDA. On the same date, USDA reported that topsoil moisture was more than 40% very short to short in Kansas (48%) and Colorado (42%).


Midwest

The Midwest remained free of drought for a third consecutive week. The only part of the Midwest experiencing abnormal dryness (D0) is southeastern Kentucky, where some lingering groundwater shortages have been reported. In contrast, Midwestern wetness has contributed to the second-slowest U.S. corn harvest in the last 25 years. On November 24, only 84% of the nation’s corn had been harvested, compared to the 5-year average of 96%. The only recent year with a slower U.S. corn harvest was 2009, when 71% of the crop had been cut by November 24.


Northeast

Light to moderately heavy precipitation further reduced the coverage of abnormal dryness (D0) in Delaware, Maryland, New Jersey, and Pennsylvania. Some snow fell farther north, with 5.5 inches reported in Caribou, Maine, on November 19.


South

There were only minor changes made to the drought depiction in Oklahoma and Texas, where mostly dry weather accompanied a gradual warming trend. Oklahoma’s panhandle (and neighboring areas) continued to experience some of the region’s harshest conditions, with moderate to severe drought (D1 to D2) further expanding. On November 24, the U.S. Department of Agriculture (USDA) reported that topsoil moisture was 43% very short to short in Texas, along with 41% in Oklahoma. On the same date, Texas led the nation with 28% of its winter wheat rated in very poor to poor condition, compared to the national average of 14%. Farther east, there were few changes, although rain chipped away at pockets of abnormal dryness (D0) and moderate drought (D1) in a few areas. Though not in an area experiencing dryness, Knoxville, Tennessee, reported a daily-record rainfall total of 2.64 inches on November 23.


Southeast

Rain continued to generally reduce coverage of abnormal dryness (D0) and moderate drought (D1), especially from Alabama to Virginia. However, two pockets of severe drought (D2) persisted in northern Georgia. Farther south, little rain fell in Florida. There was a small expansion of D0 and D1 in northern Florida, while a large area of D0 persisted across southern Florida. In Tallahassee, Florida, precipitation totals for the year to date (35.59 inches, or 65% of normal, from January 1 – November 25) and the season (5.22 inches, or 48% of normal, from September 1 – November 25) remained substantially below average.


West

The Southwest’s most significant storm since spring 2019 delivered drought-easing precipitation in Arizona and portions of neighboring states, starting on November 19. A record-setting, 155-day streak without measurable precipitation finally ended in Saint George, Utah, as 1.29 inches fell in a 24-hour period on November 19-20. Elsewhere in Utah, Bryce Canyon Airport netted 1.85 inches in a 48-hour period from November 19-21. In northern Arizona, Flagstaff received 2.37 inches (6.6 inches of snow) on November 20-21. The 20th was a particularly wet day in several desert locations, including Kingman, Arizona (0.83 inch), and Las Vegas, Nevada (0.67 inch). From November 19-21, totals in southern California reached 2.67 inches in Campo and 2.14 inches in Ramona. Where the heaviest precipitation fell in southern California, abnormal dryness (D0) was removed. General reductions in the severity of moderate to severe drought (D1 to D2) were introduced across Arizona’s wettest areas, including the central one-third of the state. Farther east, however, drought continued to worsen in northeastern New Mexico, where severe drought (D2) was bridged across two previously existing areas. On November 24, New Mexico’s topsoil moisture was rated 57% very short to short, according to USDA, while subsoil moisture was 68% very short to short. Meanwhile, precipitation remained scarce across much of the Northwest. Although September was wet in the Northwest and October was rather cold, effects of short-term dryness are becoming more apparent in indicators such as streamflow, snowpack, and soil moisture. On November 24, topsoil moisture was rated 60% very short to short in Nevada, along with 44% in Oregon. Abnormal dry (D0) were expanded across northern sections of California and Nevada, as well as parts of Oregon and Washington. Through November 25, early-season snowpack was less than 25% of average in several river basins across California, Nevada, Oregon, and Washington. In addition, low streamflow values were apparent in the Pacific Northwest, especially across western Oregon.


Looking Ahead:

During the remainder of Thanksgiving week, a pair of major storm systems will result in a variety of weather hazards across the country. Both low-pressure systems will take similar paths across the central Plains, upper Midwest, and Northeast, although the latter storm will be a higher-impact event across the West. Five-day precipitation totals could broadly reach 1 to 3 inches or more from the Plains to the Appalachians, with higher liquid amounts (in the form of heavy snow) expected in some Western mountain locations—especially in California and the Southwest. East of the Rockies, both storms have the potential to produce major accumulations of wind-driven snow, particularly across portions of the northern and central Plains and upper Midwest, leading to holiday-week travel disruptions. In addition, strong to locally severe thunderstorms could sweep across the South, especially on November 29-30. By December 1, a coastal low-pressure system may begin to intensify along the Atlantic Seaboard, while a new Pacific storm will begin to affect the Far West.

The NWS 6- to 10-day outlook for December 2 – 6 calls for the likelihood of near- or below-normal temperatures nationwide, except for warmer-than-normal weather in coastal California and across portions of the southern High Plains and the Southwest. Meanwhile, near- or below-normal precipitation in the eastern half of the country should contrast with wetter-than-normal conditions from California to the Rockies and northern High Plains.


Author: Brad Rippey, U.S. Department of Agriculture

Dryness Categories
D0...Abnormally Dry...used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1...Moderate Drought
D2...Severe Drought
D3...Extreme Drought
D4...Exceptional Drought

Drought or Dryness Types
S...Short-term
L...Long-term