Drought Monitor Weekly: Extreme Heat, Dryness; Upper Midwest Cool

Texas A&M AgriLife Extension Service photo by Kathleen Phillips

Summary

The United States is in the thralls of summer, and with that can come heat, flash droughts, and occasional, if not frequent, thunderstorm activity. Several areas of the U.S. experienced extreme heat this past week, particularly notable across much of the South and in the East. Parts of western Texas and eastern New Mexico were 6-10 degrees F above their typical averages, with little rainfall to speak of in much of the region.

On the other hand much of the northern tier of the U.S. into the Upper Midwest was cool for this time of year, although precipitation amounts there were a mixed bag. In the Southwest, the North American monsoon continues to fail, worsening conditions in areas that had received more than ample precipitation over the winter and spring.

To the north, south central Alaska continues to see record or near-record heat and dryness, and conditions are deteriorating quickly there, with severe impacts.

Southeast

Northern Virginia received adequate rainfall over the past week and a large part of the abnormally dry (D0) conditions that appeared the previous week have disappeared again. Despite near-record heat at Dulles International Airport, green up has been substantial. Southwestern Virginia, on the other hand, did not receive widespread precipitation, but rather bursts from thunderstorm activity. Above-normal temperatures have contributed to parched topsoil in places and D0 expanded to the south and to the north near Roanoke.

Coastal North Carolina received heavy rain that totaled 5 or more inches in many areas, including Wilmington and New Bern, substantially lowering three-month deficits. As a result, streamflow conditions have improved and recently planted crops such as soybeans are doing well. As such, much of the immediate coast improved one drought category, to D0 or back to normal conditions.

In South Carolina, Charleston and Myrtle Beach reported over 4 inches of rain for the week. On the other hand, some counties in the Low Country near the Georgia border reported less than 0.25 inch over the same period, accompanied by extreme heat, with areas reaching temperatures of 100 degrees F or higher. With reports of crop stress, reduced pasture forage and yield, and increased irrigation, severe drought (D2) was introduced and moderate drought was expanded. Abnormally dry conditions were expanded in surrounding counties in the west.

D0 also expanded in west central Georgia, but conditions improved farther to the south in the state, with moderate drought (D1) substantially declining.

In Alabama, Huntsville reached 100 degrees F on August 19th for the first time since July 2016 and precipitation was lacking in many areas, with the exceptions of southern Alabama and the far northwest. D0 and D1 were expanded in the eastern half of the state. Severe drought was expanded in the central part, but removed by the Florida border.

South

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Aside from isolated and scattered rains, most of the area was very hot and dry, with daytime temperatures climbing to near or above 100 degrees F over portions of the region. Nighttime temperatures did not help alleviate the heat stress in places. Along the northern Gulf Coast, Galveston, Texas — which had never observed a minimum temperature above 85°F since its records began in 1874 — has recorded three to date this month: on August 8th, 12th, and again on the 18th.

Overall, there was some drought relief in a few spots in the South, but mostly there was drought expansion across the area where changes were made this week.

There is a flash drought in north central and northeast Texas, with some stations that are 10 inches above normal for the year, but 8 inches below normal for just the past two months. In eastern Texas, abnormally dry conditions (D0) were expanded across much of the area. Reported rainfall in areas was only 20 percent of normal.

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The D0 in far east Texas expanded eastward into extreme southwestern Arkansas where there have been reports of a sharp drop off in the green up along the interstate across southern Miller County, with some exposed areas browning quickly, and in northwestern Louisiana where reported precipitation at some stations has been just 50-70% of normal over the past two months.

In Oklahoma, much of the southwest has seen less than 25% of its normal precipitation over the past two months, and less than 50% over the past three. Severe and moderate drought were expanded here and a couple of pockets of extreme drought (D3) were introduced to the west in the Texas Panhandle.

In southeastern Tennessee near Chattanooga, abnormally dry conditions and moderate drought (D1) were each extended farther to the northeast. Over the past month there have been several periods of high temperatures leading to stress on vegetation and livestock.

Midwest

Heat and a lack of substantial rain in many areas contributed to expansion of abnormally dry (D0) conditions across parts of the Midwest, including northern Michigan into the Upper Peninsula, west central Ohio, eastern Indiana, and Kentucky. An area of moderate drought (D1) was also introduced in central Kentucky, with reports that late planted corn, soybeans, and pastures are affected and that some farm ponds are beginning to get low, especially in Hardin, LaRue, and Breckinridge Counties.

Ohio reports indicate that crop stress and brown lawns are now evident. In Iowa, the rainfall had a relatively strong gradient, as conditions improved across parts of southern Iowa, although D1 did expand a bit in the southeastern corner.

High Plains

Eastern Nebraska was fairly dry over the past week where the D0 is present. With little rainfall over the past month and a half, the D0 area was extended slightly north into Thurston and eastern Wayne counties.

To the north, some beneficial rains fell across North Dakota over the last week; however, considering local crop impact reports, only the D0 area in the west central region was improved to normal. Unfortunately, the rains were not adequate enough for improvement across the northern tier of the state.

West

Far into the monsoon season, the rains continue to fail in the Southwest. Only the abundant precipitation that fell last winter is keeping substantial impacts at bay so far this summer. Even so, declining topsoil moisture and poor rangeland conditions through Mohave County, Arizona, are now being reported.

Abnormally dry conditions (D0) were expanded nearby in central and north central Arizona through all of Yavapai County and most of Coconino County. It was also expanded southwestward into Riverside and Imperial Counties in California.

Moderate drought (D1) was extended farther south in western New Mexico, and a small area was introduced to the south central part of the state at the Texas border. Abnormally dry conditions and moderate drought also crept into the far southeastern corner this week.

Northeast

There was an expansion of abnormally dry conditions (D0) in southwestern West Virginia. This area has received very little rain over the past couple of weeks, combined with above-average temperatures since the start of summer. In New England, there was some much needed precipitation over the abnormally dry areas there. This prevented the need for deterioration, but was insufficient to erase the longer-term deficits.

There were reports of brown fields and rolled soybeans in New York’s Monroe and Orleans over the past week, but rainfall there over the weekend seemed to be sufficient for the time being. This is an area to watch.

Alaska, Hawaii, and Puerto Rico

While heavy rain fell in the interior over the Yukon Flats, alleviating a region of abnormal dryness there, conditions in south central Alaska deteriorated as record and near-record heat and dryness continued. The Anchorage Airport has received only 0.84 inches of rain since June 1st and is on track to record its driest June-August on record. For August to date, little to no precipitation has fallen in what is typically the peak of the wet season.

Extreme drought (D3) was introduced to this area, extending north toward Talkeetna and south to the top of the Kanai Peninsula. Severe drought (D2) was extended south across most of the remainder of the Peninsula. The lack of precipitation along with the persistent warmth has led to unprecedented dry conditions and very high to extreme fire danger.

Smoke from multiple wildfires is prevalent across portions of the Kenai Peninsula, Anchorage Bowl, and Mat-Su Valleys, reducing visibility to less than one mile near active fires. Widespread areas of deciduous trees and bushes are turning brown and dropping leaves now, which is unprecedented, exacerbating the fire danger. Kodiak is now in voluntary water restrictions, receiving only 33% of its normal precipitation since June 1st. Moderate drought (D1) has been introduced across the island.

On the Alaskan Peninsula, new fires have been reported, and the community of Chignik is reporting severe water issues and a water emergency. Abnormal dryness (D0) and some D1 was introduced across the region and will continue to be monitored closely.

Hawaii has generally been dry recently, with the exception of the western and interior sections of the Big Island. An anomalous shift in the direction of the trade winds has also affected trade wind rainfall over the Hamakua and windward Kohala portions of the Big Island. These areas have been unusually dry for this time of the year.

Ranchers near Paauilo and Ookala in the Hamakua District have been hauling water for their livestock. Severe drought (D2) was introduced to this area. Conditions worsened across the island of Lanai and D2 was introduced in the southwest.

Looking Ahead

Over the week beginning Tuesday, August 20, according to NOAA’s Climate Prediction Center, dry conditions are expected to continue across much of the western half of the continental U.S. Some heavy rain may fall over parts of the Midwest and Southeast, with as much as five inches in areas of southern Iowa, northern Mississippi, eastern Nebraska, and parts of the Carolinas. Southern Louisiana may see up to seven inches.

Looking further ahead to August 25-29, below-normal temperatures are favored across parts of eastern Montana, the Dakotas, Nebraska, Kansas, Minnesota, Iowa, and Missouri, while above-normal temperatures are forecast for parts of the Southern Plains and the Southwest. There are enhanced probabilities of above-normal temperatures for most southern coastal locations of Alaska due to above-normal sea surface temperatures.

Near to below-normal precipitation is possible for the west, although parts of Southern California may see above-average rainfall. Rainfall may be above normal across the central and eastern U.S., except for parts of the Northeast.

Above-normal precipitation is favored across northern and eastern Alaska, but may be below-normal across southwestern mainland Alaska and the Aleutians, where drought conditions prevail. Please note the forecast confidence for this period is average, according to CPC.


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