National Drought Summary -- August 06, 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/.

Heavy rain fell on large parts of Alaska this past week, bringing significant short-term relief, including an end to large fire development and expansion, at least for the time being. In contrast, dryness and drought expanded across broad sections of the contiguous 48 states, with relief restricted to parts of the Southeast. Most notably, hot and dry weather brought significant D0 expansion in the southern half of the Great Plains and across the Midwest and lower Ohio Valley. In the Northeast Climate Region, a few abnormally dry areas were introduced; this is only the fourth week since mid-January that dryness existed in any part of the Region. Meanwhile, heavy rain in eastern Puerto Rico improved conditions over eastern parts of the Commonwealth.


Alaska, Hawaii, and Puerto Rico

Heavy precipitation and cooler temperatures brought widespread improvement to central and northern Alaska, squelching wildfire expansion and sharply reducing the threat of new fire development, at least for the time being. Areas from the easternmost Seward Peninsula eastward through the central Yukon Valley recorded 2 to 5 inches of precipitation, with the heaviest amounts found along the northern tier of the Koyukuk National Wildlife Refuge and at an isolated site in the central Yukon Valley. Generally 0.5 to 2.0 inches of rain doused most other parts of the state’s western tier, and from the Yukon River through the northern Alaska Range. Most D0 and D1 areas improved in these regions, with moderate drought remaining over the Yukon Flats, where precipitation was less generous. Farther south, light precipitation left dryness and drought unchanged in southern Alaska.

Heavy rains in eastern Puerto Rico removed D0 from most areas, and trimmed areas of moderate drought there. Rainfall was closer to normal over the rest of the Commonwealth, leaving D0 to D2 areas essentially unchanged across central and southwestern areas.

Heavy precipitation brought an end to D0 and D1 conditions across central sections of the Big Island, but conditions were unchanged or deteriorated elsewhere. D0 expanded through the central Hawaiian Island, and parched areas in the extreme northern parts of the Big Island degraded to D3.


High Plains

It was a dry week in and near existing areas of dryness and drought. Broad expansion of abnormal dryness occurred across central and southern Kansas, where conditions have deteriorated quickly as in Oklahoma and Texas. Much of central and south-central Kansas received 0.5 inch or less of rainfall over the last 30 days. In the rest of the region, D0 and D1 conditions generally persisted, with very limited expansion brought into parts of northern North Dakota, east-central Nebraska, and southeastern Colorado.


Midwest

Generally 0.5 to 2.0 inches of rain fell last week on central and southern Wisconsin, but most of the region recorded only a few tenths of an inch, if any. The last 30 days brought only 10 to 50 percent of normal rainfall to most areas from central Iowa through east-central Illinois and part of western Indiana, with the largest deficits affecting a swath from east-central Iowa southeastward through central Illinois. Abnormal dryness was expanded extensively to cover this region, plus sections of southwestern Ohio, northeastern Kentucky, and southern Indiana, where rainfall has been slightly more generous. Since early June, 40 to 75 percent of normal rain has been recorded in central and eastern Iowa and adjacent Illinois. Farther north and west, patches of D0 persisted in and near the Upper Peninsula of Michigan, northeastern Minnesota, and southeastern Michigan. No drought exists in the region at this time, though aforementioned sections of Iowa and Illinois are approaching D1.


Northeast

A broken pattern of moderate to locally heavy rain (up to 3 inches) affected the region this week, primarily from southern New York through Pennsylvania and eastern West Virginia. Over the past month, rainfall totals were 2.0 to 3.5 inches below normal in a few scattered areas in western West Virginia, southwestern New England, upstate New York, and lower Maine, prompting D0 introduction in those areas. In southwestern New England, upstate New York, and part of southwestern West Virginia, totals are 2 to locally 6 inches below normal since early June.


South

Another drier-than-normal week affected central and eastern sections of Texas and Oklahoma as well as the northern tier of Louisiana, where little or no rain was reported. Recent hot and dry weather there has spawned broad development of D0 and D1 conditions in the south-central Plains, with severe drought introduced in southwestern Oklahoma and adjacent Texas. Broad swaths of central and western Oklahoma, the Texas Panhandle, and southwestern Texas recorded only a few tenths of an inch of rain at best over the last 30 days, and about 25 to 60 percent of normal since early June.


Southeast

Precipitation varied markedly across the region, which is typical for summer. Generally, heavy rain fell around the periphery of the dry areas in Alabama, much of Georgia, and northern South Carolina, leading to some reduction in D0 to D2 coverage. D0 was removed entirely from southeasternmost Georgia and northeastern Florida. In contrast, areas that missed most of the rain experienced limited deterioration. Small-scale expansion of D0 and D1 was noted in south-central and eastern Georgia, and southern South Carolina. In most dry areas, the last 60 days brought 2 to locally over 6 fewer inches of rain than normal, and 50 to 75 percent of normal during the past month.


West

Severe drought persisted in portions of northwestern Washington where only 40 to 75 percent of normal precipitation fell during the past six months. Light to locally moderate rain fell this week from central Arizona through central New Mexico, and across portions of southern and eastern Montana. Other areas recorded very little or none. Increasing moisture deficits induced moderate drought expansion into northwestern New Mexico while D0 expanded in southeastern Washington and across northern Montana. Conditions were unchanged in other areas. The past 60 days brought only 25 to 50 percent of normal rainfall to the new moderate drought area in northwestern New Mexico.


Looking Ahead:

During the next 5 days (August 8 - 13, 2019) should bring heavy rains of 1 to locally 4 inches to portions of western New Mexico, a swath through the central Plains, and many locations across upstate New York and southern Maine. Most of the area from northern Idaho eastward through northern Montana are expecting 1 to 2 inches, as are most of the Dakotas and scattered patches across the Pacific Northwest. Other areas of dryness across the contiguous 48 states should get lesser amounts. Locally up to an inch is expected in the Southeast and southern New England, and little or none is anticipated in most of the new D0 area in the southern Plains from central Kansas through Oklahoma and Texas. Temperatures are forecast to be a few degrees above normal in the southern Plains and the Southeast while subnormal temperatures should extend from the northern half of the Plains to the Pacific Ocean.

The CPC 6-10 day outlook (August 14 -18, 2019) favors above-normal precipitation in east-central Alaska, the Pacific Northwest, the central and northern Plains, the lower Mississippi Valley, and the Southeast. Meanwhile, subnormal precipitation is expected in southern and southeast Alaska, the eastern Great Basin, the Four Corners States, most of Texas, and the Northeast. Temperatures should average below normal from the Intermountain West eastward through the Midwest and Northeast, and across east-central Alaska. Farther south, southern and southeastern Alaska have enhanced chances of warmer than normal weather, along with the Pacific Coast and a large swath from the Great Basin through the Four Corners States, central and southern High Plains, lower Mississippi Valley, and Southeast. The highest likelihood for hotter than normal weather are across most of Texas and the lower Southeast.


Author: Richard Tinker, NOAA, NWS, NCEP, CPC

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