California and National Drought Summary for May 12, 2015
Summary
During the current U.S. Drought Monitor week, a series of storm systems moved out of the southwest and ejected onto the plains. With the Gulf of Mexico wide open, there has been ample atmospheric moisture feeding into these storms. Severe weather and record-setting rains were widespread on the front end, while areas on the backside of these storms recorded several feet of wet snow. The greatest precipitation amounts were recorded in Oklahoma, Arkansas, and north Texas, with widespread areas of 8-10 inches of rain. Portions of southeast Nebraska also recorded up to 10 inches of rain, with a swath of 6-8 inches from north central Kansas into southeast Nebraska. Many areas in the western half of the U.S. received 200-400 percent of normal precipitation for the week. Tropical storm Ana impacted portions of the southeast where 3-6 inches of rain fell along the coastal Carolinas. Temperatures for the week were above normal over the eastern United States with departures of 5-10 degrees above normal while the western half was cooler than normal with departures of 5-10 degrees below normal.Great Plains
Most of the region had below-normal temperatures for the week, with the greatest departures (10 degrees or more) over portions of eastern Wyoming, western Nebraska and western South Dakota. Areas of eastern Kansas, eastern Oklahoma, and most of Texas were above normal for temperatures, with departures of 4-6 degrees common. The big story for the region was the torrential rains and severe weather. The widespread 2-4 inch readings across South Dakota resulted in 1-category improvement to the D2 and D1 conditions in the state. Much of the precipitation which did occur was snow. Snow amounts ranged from 12 inches in the plains of South Dakota to 16 inches in the Black Hills while portions of western Nebraska had up to 24 inches of snow. The improvements extended into North Dakota where D1 was improved in the southeast part of the state, while D0 was expanded over the northern and northwest portions of the state. There was a slight trimming of D1 and D0 conditions over Nebraska where the rains were enough to show improvements. The recent rains allowed for a large-scale 1-category improvement across southern Kansas and parts of southwest and west central Kansas. A small area of D2 was introduced into northwest Kansas where the recent rains have not been as substantial and conditions are worsening. In Oklahoma and Texas, large-scale 1-2 category improvements were made after copious rains of 6-10 inches or more were recorded. Most areas in Texas and Oklahoma were good out to 24 months, but some residual dryness was still evident at 36 months. D4 has been completely eliminated from Texas and Oklahoma for the first time since July 2012. With the short-term indicators all showing drought-free conditions, a substantial shift of the long-term delineation line to the north was made this week as only long-term issues are impacting the southern plains.Hawaii, Alaska and Puerto Rico
No changes were made in Alaska and Hawaii this week. For Puerto Rico, conditions continued to worsen as precipitation and streamflow values all are declining and D0 and D1 conditions were expanded as a result.Midwest/Great Lakes
Warmer than normal temperatures dominated the entire region outside of Minnesota. Temperatures were 9-12 degrees above normal over the eastern Corn Belt and 3-6 degrees above normal over the rest of the region. Minnesota was cool with temperatures 3-6 degrees below normal. Precipitation was below normal over the eastern portions of the region while portions of Missouri, Illinois, Michigan, western Wisconsin, and Minnesota were up to 4 inches above normal precipitation for the week. Changes made this week included an expansion of D0 across northern Ohio, northern Indiana and northern Michigan. In response to recent rains, some improvement was shown to the D0 and D1 regions of northwest Iowa as well as a full category improvement over all of western Minnesota.Southeast
A warm and fairly dry week was observed over most the region. Temperatures were above normal throughout the area, ranging from 3 degrees above normal in the south to 6-9 degrees above normal to the north. Most of the region ended up the week below normal for precipitation except those areas along the coastal Carolinas that received 2-6 inches of rain associated with tropical storm Ana. D0 was expanded across southern Georgia and into extreme northeast Florida as well as southern and northeast Alabama. A new area of D0 was introduced into central Tennessee and northwest Alabama.The Northeast
Warm conditions dominated the region this week, helping to finally bring spring conditions to the area. Temperatures were generally at least 4 degrees above normal, with portions of New York, Pennsylvania and western New England being 12-16 degrees above normal. Overall, dry conditions dominated the region, with only some of the northern extent of the region recording up to 1.50 inches of precipitation. Changes made this week included D0 being expanded across all of New England and southeastern Pennsylvania. D0 was also expanded across northern Maryland and northern New Jersey. While spring has been off to a slow start, the dryness is starting to develop into impacts that are short-term in nature while water supply is in good shape.West
Cooler than normal temperatures along with scattered precipitation through the region this week allowed for some changes. The D0 in Montana was connected to the areas of D0 in the Dakotas. After another good week of rains and cooler temperatures, D0-D2 conditions improved in southeast Colorado. In west central Colorado, D2 was improved as well. Western Wyoming saw a large expansion of D0 while eastern Wyoming had improvements to D0.Looking Ahead
Over the next 5-7 days, temperatures over the eastern United States are anticipated to be above normal with departures of up to 6 degrees. Most of the rest of the United States will have temperatures at or below normal, with the greatest departures (up to 9 degrees below normal) over the west coast. An active pattern looks to continue over much of the plains states and into the southeast. Precipitation forecast amounts of more than 6 inches are being projected over east Texas and up to 3 inches through the Dakotas. The latest 7-day projections have precipitation chances over almost the entire country.The 6-10 day outlooks show the likelihood of above-normal temperatures over the southeast, Pacific Northwest, and Alaska while there are above-normal chances of temperatures being below normal through the plains, Midwest and southwest. There are below-normal chances of precipitation over the upper Midwest and Great Lakes regions. A good portion of the United States has above-normal chances of seeing precipitation above normal, with the best chances over the southeast and Great Basin.
Author(s):
Brian Fuchs, National Drought Mitigation 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 DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
