Drought Monitor: Widespread Rains In The Southeast, Warmer Than Normal On The Plains
11/19/2009 08:56AM
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The Northeast: Dry conditions across interior portions of the region contrasted with periods of heavy rain in southern and eastern locales. Rain bypassed western Pennsylvania’s D0 (Abnormal Dryness), where 7-day average streamflows and soil moisture levels remained below the 30th percentile. In addition, areas downwind of the Great Lakes have been drier than normal over the past 90 days, and will need to be monitored for a continuation of drier-than-normal weather.
The Mid-Atlantic and Southeast: The remnants of Hurricane Ida coupled with a slow-moving upper-air low triggered widespread heavy rain (3 inches or more) from southern portions of Maryland and Delaware into central Georgia. Rainfall totals exceeded 6 inches in southern and eastern Virginia as well as northern and eastern sections of North Carolina. Despite causing widespread coastal flooding, the storm provided much-needed drought relief to the Carolinas. Consequently, Severe (D2) and Moderate (D1) Drought were removed, while the coverage of the Abnormally Dry (D0) region was reduced and impacts changed to Hydrological (long-term). Underlying concerns regarding groundwater tables and long-term precipitation deficits (180- and 365-days) remain, especially from northeast South Carolina into central North Carolina. Rain stayed north of Florida, where increasing short-term rainfall deficits are beginning to impact vegetation. D0 was expanded northward in far southern Florida, while a small area of Moderate Drought (D1) was introduced along the east-central Coast.
The Delta: Dry weather was welcomed in the Delta, where the story has not been drought, but flooding and fieldwork delays. 90-day rainfall surpluses are greater than 12 inches over much of the region, and exceed 2 feet over the past 365 days in northern portions of the Delta. Short-term (30-day) deficits of 2 inches or more were noted near the mouth of the Mississippi River, and this area will be monitored over the upcoming weeks for developing dryness.
The Plains: Mostly dry, warmer-than-normal weather prevailed on the Great Plains during the past week, although a small area of rain and snow (0.50 inch or more liquid equivalent) was observed in Kansas and Colorado. No changes were made to drought designations in Texas, but western portions of the state are being monitored for possible expansion of D0 and D1. Short-term dryness (30 and 90-day) is most pronounced from the western Rio Grande northeastward into north-central Texas.
Upper Midwest: Rain and snow showers eased northeastern portions of Minnesota further out of drought, with D1 (Moderate Drought) eliminated from the state. More than an inch of rain along the western shores of Lake Superior helped reduce the coverage of D0 in eastern Minnesota. In contrast, Moderate to Severe Drought areas of northwestern Wisconsin received little if any precipitation. Temperatures for the week averaged more than 10 degrees F above normal from the eastern Dakotas into northern Wisconsin.
The West: Cold, wet weather in western portions of Washington and Oregon provided additional relief from Abnormal Dryness. Meanwhile, additional reassessment of the situation in Montana from experts in the field resulted in some modifications to the current drought depiction: D0 was removed from western portions of the state, while a small area of D0 was added along the U.S.-Canadian border. Farther south, negative Standardized Precipitation Indices on multiple timescales in southeastern Nevada led to an expansion to D1. The remainder of the West was unchanged from last week.
Hawaii, Alaska and Puerto Rico: While locally heavy rain was reported during the past week in Hawaii, much of the rain missed the primary drought areas. However, some improvement was noted from locally beneficial showers in southern portions of the Big Island as well as the eastern third of Molokai. Windy, cold, unsettled conditions were observed in Alaska, although the heaviest precipitation fell south of the current D0 area. In Puerto Rico, moderate to heavy rain (1-4 inches, locally more) recharged streamflows and alleviated Abnormal Dryness that had developed over the eastern half of the island.
Looking Ahead: A slow-moving upper-air low will generate rain across the Ohio River Valley, while showers accompany a trailing cold front in the Mid-Atlantic and Northeast. Farther south, a developing storm in the Gulf of Mexico will track northeastward, producing moderate to heavy rain from southern Texas into the Southeast. Mostly warm, dry weather is anticipated across the Great Plains and Upper Midwest, although a few showers may develop in the central and northern Corn Belt early next week. Out west, dry, warm conditions across the Southwest and southern Rockies will contrast with stormy weather in northern California and the Northwest.
The CPC 6-10 day forecast (November 24–28) calls for below-normal temperatures across the Southeast, with above-normal temperatures expected in New England and from the Pacific Coast into the northern Plains. Above-normal precipitation is anticipated across the eastern third of the nation, while drier-than-normal conditions are likely west of the Mississippi; the greatest likelihood of below-normal precipitation will be over central and northern portions of the Rockies and High Plains.
Author: Eric Luebehusen, United States Department of Agriculture
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
A ... Agricultural
H ... Hydrological
