Drought Monitor Weekly: Fronts Bring Locally Heavy Rains

Summary

A stationary front was a focus for frequent showers and thunderstorms with locally heavy rainfall from eastern South Carolina south to the Big Bend of Florida from June 11 to 14. The heavier rainfall resulted in short-term rainfall surpluses and drought elimination to parts of the Coastal Plain of Georgia and South Carolina.

Another cold front progressed slowly south and east across the Great Plains, Corn Belt, and Mississippi Valley from June 14 to 16 before becoming stationary. Locally heavy rain (more than 2 inches) and hundreds of severe weather reports were common across the central and southern Great Plains, middle to upper Mississippi Valley, and Ohio Valley during mid-June. Excessively wet conditions continue to slow the emergence of corn and soybeans across the Corn Belt.

Meanwhile, drought intensified across northern North Dakota due to a lack of rainfall since April. A strong ridge of high pressure resulted in dry weather and record high temperatures (June 11 and 12) across the Pacific Northwest where drought is also intensifying.

Suppressed rainfall continues to affect parts of Puerto Rico.

Southeast

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Very heavy rainfall (5 to 11 inches) during the preceding week prompted a 2-category improvement from moderate drought (D1) to an absence of abnormal dryness from Charleston, SC southwest to Savannah, GA. Since June 1, rainfall amounts have totaled 16.72 inches near Bluffton, SC. This 2-category improvement coincides with where 30 to 90-day precipitation surpluses are now observed and there is no longer support for abnormal short-term dryness.

Despite these improvements, it should be noted that hot temperatures earlier in the month damaged corn in the reproductive stage. Moderate drought (D1) persists across southeast North Carolina along with the Pee Dee region of northeast South Carolina where field corn was rolled up and pasture conditions were poor.

Recent, heavier rainfall also led to improvements across parts of southern Georgia and northern Florida. A small area of severe drought (D2) remains centered over Ware County in southeast Georgia. The 28-day streamflow along the Satilla River near Waycross, Georgia is at the 9th percentile.

Drought severity was degraded to severe (D2) in parts of southeast Alabama due to large precipitation deficits from 30 to 180 days along with low streamflows. The 28-day streamflow along the Choctawhatchee River in Dale County of southeast Alabama is below the 8th percentile. The D2 area is generally consistent with where 180-day precipitation deficits range from 8 to 12 inches.

As of June 18, moderate drought (D1) remains centered over Leon County in northern Florida with a year-to-date precipitation deficit of 10.26 inches.

South

7-day rainfall anomalies (June 11 to 17) varied across the southern Great Plains, lower Mississippi Valley, and Tennessee Valley which is typical for this time of year. The heaviest rainfall (2 to 4 inches, locally more) was observed across scattered areas of Oklahoma, eastern Texas, and the Texas Gulf Coast.

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Less than an inch of rainfall was generally observed across most of Arkansas and adjacent areas of northwest Mississippi and western Tennessee. The Vegetation Drought Response Index (VegDRI) continues to reflect moist conditions throughout much of this region.

Soil moisture remains above the 99th percentile across most of Oklahoma and northern Texas. According to the Oklahoma Mesonet, the northeast quarter of Oklahoma has received 12 to 18 inches of rainfall during the past 30 days.

Abnormal dryness was expanded slightly across parts of the Tennessee Valley in areas where 60-day precipitation averages 50 to 75 percent of normal. However, much of this region remains drought-free since 28-day streamflows and soil moisture do not support a drought designation at this time.

A slight expansion of abnormal dryness (D0) and moderate drought (D1) was necessary across Deep South Texas due to increasing short-term rainfall deficits and periods of above normal temperatures during the past month.

Midwest

A majority of the Midwest remains excessively wet with precipitation averaging 150 to 200 percent of normal dating back 180 days. Due to the wet winter and spring, soil moisture remains above the 99th percentile across much of the Corn Belt. According to the USDA Weekly Weather and Crop Bulletin (valid on June 16), 79 percent of the nation’s corn had emerged which is 18 percentage points behind last year and the average.

Only 55 percent of the soybeans had emerged which is 34 percentage points behind last year and 29 points behind the average. Moderate flooding continues along the middle Mississippi and Illinois Rivers.

Farther to the north, a slight expansion of abnormal dryness (D0) was depicted for parts of northern Minnesota due to increasing short-term precipitation deficits.

High Plains

Late May through mid-June is typically a wetter time of year across the northern Great Plains. However, during the past 60 days, parts of northwest North Dakota have received less than 50 percent of their normal rainfall. Given the lack of rainfall since the snow melt in early April, multiple adverse impacts to agriculture and livestock are being reported across the northern tier of counties in North Dakota.

These reports include: lack of forage production on pastures, culling of cattle herds, and delayed crop growth. Based on the increasing short-term deficits, soil moisture conditions, and reported impacts, severe drought (D2) is warranted for parts of northern North Dakota. A lack of late spring rainfall also continues to result in an expansion of abnormal dryness (D0) and moderate drought (D1) across the northern half of North Dakota.

In contrast to the worsening conditions across North Dakota, abnormal dryness was removed from the Big Horn Mountains of Wyoming based on a continuation of a favorably wet pattern through May and June.

West

The month of May tied for the 9th warmest for Washington dating back to 1895 and statewide March thru May tied for the 13th driest period on record Based on 90-day precipitation deficits of more than 8 inches along with 28-day streamflows and soil moisture below the 10th percentile, severe drought (D2) was expanded across western Washington. Levels along Rimrock Lake are extremely low with adverse impacts to boating docks.

Record high temperatures during early June also played a role in the intensification of drought across western parts of Washington and Oregon. On June 12, a daily-record high of 95 degrees F was set in Seattle. In Oregon, daily-record highs on June 12 included: 98F at Portland, 99F at Medford, and 101F at Roseburg. The expansion this week of D0 and D1 across Oregon and Washington is generally reflective of the current 28-day streamflows.

Long-term D0 remains in parts of southern California due to the multi-year drought. Elsewhere across California and the Great Basin, many reservoirs are full and 28-day streamflows remain high after the onset of the snowmelt season.

Northeast

Scattered showers and thundershowers fell throughout much of the Northeast during early to mid-June with the heaviest 7-day totals (more than 2 inches) across the northern mid-Atlantic and western to central Pennsylvania. 30-day precipitation has averaged at or above normal for most of this region although a small pocket of below average precipitation is located in the lower Hudson River Valley and southern New England.

28-day streamflows remain normal to much above normal throughout the Northeast with this region completely free of abnormal dryness since mid-April.

Alaska, Hawaii, and Puerto Rico

The southern Alaska Panhandle had its driest June 2018 through May 2019 period on record, which supports the ongoing extreme drought (D3). Based on low 28-day streamflows along the Yukon River in eastern mainland Alaska and below average precipitation from March through May 2019, abnormal dryness (D0) was introduced to eastern mainland Alaska.

90-day precipitation has averaged less than 50 percent of normal across southwest and south-central Puerto Rico. Also, as of June 18 the year-to-date precipitation deficit at San Juan, Puerto Rico is 8.57 inches. Based on these increasing precipitation deficits, moderate drought (D1) was expanded to include more of southern Puerto Rico and the San Juan area.

No changes were made this week to the drought status in the Hawaiian Islands.

Looking Ahead

During the next 5 days (June 20-24, 2019), a couple of cold fronts are forecast to progress east across the northern half of the central and eastern U.S. On June 20, locally heavy rain (more than 1 inch) is expected to accompany a cold front as it crosses the Northeast and northern mid-Atlantic.

A second frontal system is likely to trigger severe thunderstorms with heavy rainfall across the central U.S. The NWS WPC 5-day quantitative precipitation forecast (QPF) calls for widespread amounts of 1 to 3 inches, locally more, from eastern portions of the central and southern Great Plains east to the Midwest and Ohio Valley.

Dry weather is likely to persist across southern Texas and the Pacific Northwest. The most anomalous warmth is expected across the Gulf Coast States. Overall suppressed rainfall is expected to continue for Puerto Rico through late June.

The CPC 6-10 day outlook (June 25-29, 2019) favors above-normal temperatures across much of the central and eastern U.S. with below-normal temperatures lingering over the western U.S. Enhanced odds for above-normal precipitation are forecast for much of the eastern U.S., Ohio and Tennessee Valleys, middle to lower Mississippi Valley, and southern Great Plains.

A slight tilt in the odds for below-normal precipitation is forecast for southern areas of Florida and Texas, the High Plains, and central to southern Rockies. A relatively warm and dry pattern is most likely to persist across Alaska.


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