National Drought Summary -- December 05, 2017

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/.

This U.S. Drought Monitor week saw continued intensification and expansion of areas of drought across portions of the Southwest, Plains, lower Midwest, South, Southeast, and the Mid-Atlantic. For the conterminous U.S., this past autumn (September-November) was the 10th warmest on record according to NOAA’s National Centers for Environmental Information (NCEI). In terms of precipitation this fall, October and November were very dry in various regions with the South experiencing its 11th driest on record and the Southwest its 6th driest. Conversely, areas of the Midwest experienced above normal precipitation with Michigan having its 2nd wettest and Ohio its 5th wettest on record. Looking at changes in drought conditions nationwide during the past three months, the focal point of drought development has been centered over portions of the Desert Southwest, Deep South, and southern Plains while conditions have steadily improved across the Pacific Northwest.


Alaska, Hawaii and Puerto Rico

No changes were made on this week’s map in Alaska or Puerto Rico. In the Hawaiian Islands, one-category improvements were made in areas of Severe Drought (D2), Moderate Drought (D1), and Abnormally Dry (D0) on the Big Island as recent rains helped improve pasture conditions. In Alaska, the state was generally dry with the exception of Southeast Alaska, Prince William Sound, and eastern portions of the Kenai Peninsula. According to the NRCS SNOTEL network, snowpack conditions are below normal in the Chugach Range near Anchorage as well as in the Kenai Mountains while further north near Fairbanks stations are reporting slightly above normal snowpack conditions. Average temperatures were generally above normal across much of the state with the exception of east-central portions of the Interior where negative anomalies ranged from 3-to-9 degrees below normal during the past week.


High Plains

On this week’s map, conditions deteriorated in eastern portions of the Dakotas as well as in eastern Nebraska and Kansas. In the Dakotas, areas of Abnormally Dry (D0) and Moderate Drought (D1) expanded as a result of unseasonably warm temperatures and below normal precipitation during the past 30-to-60 days. Moreover, the lack of snow cover and warm temperatures have raised concern in relation to the condition of the winter wheat crop. According to NOAA’s NCEI, North Dakota experienced its 4th driest October-November period on record. In Nebraska and Kansas, below normal precipitation and above normal temperatures during the past 30 days led to the introduction of new areas of Abnormally Dry (D0). During the past week, the region was generally dry and temperatures were well above average (5-to-15 degrees).


Midwest

On this week’s map, changes were made in northwestern Iowa, the eastern half of Missouri, and southwestern Illinois. In Missouri, areas of Severe Drought (D2) expanded in east-central where streamflows dipped below the 10th percentile and soil moisture levels declined. According to the November 27th USDA Crop Progress and Condition report, topsoil moisture was rated 64% short to very short in the south-central district and 59% short to very short in the east-central district. In southern Missouri, farmers are expressing concern as stock water supplies are getting low. Overall, the region was generally dry with the exception of some rain and snowfall activity in Upper Peninsula Michigan. Average temperatures for the week were well above normal (7-to-17 degrees) across the region with the greatest positive anomalies observed in Iowa, Minnesota, and Missouri.


Northeast

According to NOAA’s NCEI, the Northeast experienced its 4th warmest autumn on record. On this week’s map, changes occurred in central Maryland, eastern Pennsylvania, northwestern Connecticut, southeastern New York, southeastern West Virginia, and southwestern Vermont where precipitation has been below normal for the past 30 days leading to degradation in soil moisture conditions and streamflow levels in these areas. According to the USGS, numerous creeks and rivers have dipped below the 20th percentile range - leading to expansion of areas of Abnormally Dry (D0). From a longer-term perspective looking at the 24-month precipitation deficits in the region, 8-to-20+ inch deficits exist in southeastern New York, Connecticut, and portions of Massachusetts. In Maryland, an area of Moderate Drought (D1) was introduced in response to short-term precipitation deficits, low streamsflows, and below normal groundwater levels. During the past week, the region was generally dry with the exception of some smaller accumulations of less than 1 inch (liquid) in Upstate New York, Vermont, and eastern Maine. Average temperatures were near normal in coastal areas of the region while further inland temperatures for the week ranged from 2-to-8 degrees above normal.


South

On this week’s map, conditions continued to deteriorate in the region despite some precipitation (generally less than 1 inch) being observed in portions of Arkansas, northern Louisiana, northern Mississippi, eastern Oklahoma, and the northern Gulf Coast of Texas. According to NOAA’s NCEI, the South experienced its 3rd driest and 8th warmest November on record. In Arkansas, areas of Severe Drought (D2) and Extreme Drought (D3) expanded in response to declining soil moisture levels and very low streamflows statewide. In Texas, areas of drought expanded across the eastern portion of the state as the warm and dry pattern continued. According to NOAA’s NCEI, Texas experienced its 12th driest and 6th warmest October-November period on record. In Oklahoma, hot and windy conditions continued to degrade pasture and rangeland conditions. Average temperatures across the region were 6-to-14 degrees above normal for the week with the greatest anomalies observed in northeastern Texas, eastern Oklahoma, and northwestern Arkansas.


Southeast

On this week’s map, areas of Abnormally Dry (D0) and Moderate Drought (D1) expanded in central portions of Virginia and southern Georgia. In Virginia, short-term dryness caused streamflows to dip and soil moisture levels to decline. In Georgia, the combination of short-term precipitation deficits during the past 30-to-60 days, above normal temperatures, and declining soil moisture levels led to expansion of areas of drought in southern portions of the state. Overall, the region was dry with the exception of parts of Alabama that received rainfall accumulations ranging from 0.5-to-1.5 inches. For the past week, average temperatures were above normal across the entire region with the greatest positive anomalies (8-to-10 degrees) observed in the Panhandle of Florida and southern Georgia.


West

During the past week, the region was dry with the exception of the Pacific Northwest where coastal areas of Oregon and Washington as well as the North Cascades received liquid accumulations ranging from 2-to-3.5 inches. Some lesser precipitation accumulations were observed in the northern Rockies where Water Year-to-Date precipitation accumulations are normal to slightly above normal. In southern California, four rapidly spreading large wildfires (exacerbated by strong Santa Ana winds) broke out this week near Los Angeles and further north in Ventura County. Elsewhere in the region, the Southwest continued to be unseasonably warm and dry leading to expansion of areas of Moderate Drought (D1) across northern Arizona. According to the National Weather Service in Flagstaff, several locations saw their Top-5 warmest autumns on record including: Flagstaff (4th warmest), Prescott (warmest), Payson (2nd warmest), and Winslow (2nd warmest). As a region, the Southwest experienced its 6th driest and 2nd warmest October-November period on record. Further north in Montana, conditions have been improving in the western portion of the state leading to slight reductions in areas of Abnormally Dry (D0) and Moderate Drought (D1). During the past week, average temperatures were near normal in the Far West and above normal (5-to-15 degrees) across the remainder of the West.


Looking Ahead:

The NWS WPC 7-Day Quantitative Precipitation Forecast (QPF) calls for dry conditions across the western U.S., Plains, and lower Midwest while liquid precipitation accumulations of <1.5 inches are expected in the upper Midwest, New England, eastern portions of the Mid-Atlantic, Southeast, and Gulf Coast. Some slightly higher accumulation (2-to-3 inches) are expected across the coastal plains of the Carolinas. The CPC 6-10-day outlook calls for a high probability of above-normal temperatures across the western half of the conterminous U.S. as well as in Alaska while below normal temperatures are expected in the eastern third of the U.S. In terms of precipitation, below normal precipitation is expected across most of the West, southern Plains, South, Southeast, lower Midwest, and Mid-Atlantic while there is a high probability of above normal precipitation for the upper Midwest and western portions of New England.


Author: David Simeral, Western Regional Climate Center

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