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The U.S. Drought Monitor is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.
For local details and impacts, please contact your State Climatologist or Regional Climate Center
National Drought Summary for Nov 18, 2014
Bitter cold along with some snow settled over the central U.S., affording little — if any — drought relief. Farther east, soaking rainfall eased drought conditions in the Southeast, while highly variable rainfall in the Mid-Atlantic and Northeast mostly prevented expansion of abnormal dryness. Out west, most of the region’s core drought areas remained dry, though locally heavy rain and mountain snow were observed in parts of the Northwest. A shallow to moderate snow cover encompassed more than 50 percent of the contiguous U.S. at the end of the period, establishing a new benchmark for the date.
There were no changes made to the drought depiction in Alaska and Puerto Rico this week, and only a minor change on Hawaii. In Alaska, unseasonably warm weather (10°F or more above normal) was in sharp contrast to the bitter cold in the contiguous U.S., with precipitation (locally more than an inch) confined to southern-most portions of the state. In Hawaii, showers tallied 1.3 inches over the Moderate Drought (D1) of Molokai, but were not heavy enough to warrant drought reduction. In contrast, additional assessment from the field noted some improvement – albeit minor – in Abnormal Dryness (D0) on the Big Island. In Puerto Rico, the heaviest rain (greater than 2 inches) fell west of the island’s remaining D0, where streamflows still remain below the 20th percentile.
Despite a mostly dry week, the drought depiction over the central Plains remained unchanged due to bitter cold. A historically cold air mass settled over the region, with temperatures averaging 20°F or more below normal. Long-term drought remained entrenched over the central High Plains, where precipitation dating back 36 months has tallied 60 to 75 percent of normal.
Locally heavy rainfall led to reductions in drought coverage and intensity in the south, while mostly dry but cool weather resulted in little, if any, change elsewhere. From central Mississippi into central and northern Georgia, a strong cold front generated 2 to 4 inches of rain (locally more), easing or eradicating Abnormal Dryness (D0) to Severe Drought (D2). Despite the rain, streamflows in the remaining D0 and D1 areas remained below the 30th percentile, and were locally below the 10th percentile in southern Georgia, where D1 and D2 persist. Farther north and east, rain generally bypassed the eastern half of the Carolinas, with some increases in D0 and Moderate Drought (D1) noted where streamflows were historically low. The D1 area south of Augusta, Georgia has reported 30 to 50 percent of normal rainfall over the past 90 days, and streamflows have dropped below the 20th percentile. Likewise, D0 expanded across central and southwestern Arkansas, where rainfall of 50 to 75 percent of normal over the past 60 days has caused soil moisture and streamflows to decline.
Cool, showery weather was mostly sufficient to prevent widespread expansion of Abnormal Dryness (D0) in the region, with rainfall amounts averaging a half inch to locally more than one inch from central Virginia into New England. However, D0 was expanded to include central Pennsylvania and southern New York, where amounts were less than 0.5 inch and 90-day precipitation was 50 to 75 percent of normal. Despite the cool weather, streamflows across much of central Pennsylvania and southern New York have dropped below the 20th percentile, indicative of the gradually increasing dryness impacts. The rainfall across the remainder of the Mid-Atlantic and Northeast prevented a more widespread increase in Abnormal Dryness and Moderate Drought (D1), as the region copes with pronounced precipitation shortages dating back over the past 3 months.
Bitter cold along with some shallow to moderate snow cover resulted in no change to the drought depiction during the monitoring period. Temperatures averaged 10 to 20°F below normal in eastern portions of the region, and locally more than 25°F below normal in western portions of the Midwest. Parts of the Upper Midwest, particularly from the eastern Dakotas into Minnesota, are still contending with significant short-term dryness, with precipitation over the past 90 days totaling a meager 40 to 70 percent of normal, resulting in unfavorably low soil moisture for winter crops.
There were no changes the drought designation as increasingly cold weather along with a shallow to moderate snow cover developed over much of the area. Precipitation — in the form of rain and snow — was heaviest in southern and eastern portions of the region, where amounts during the period totaled more than an inch (liquid equivalent). However, dryness concerns persist in central and eastern Ohio, where 90-day precipitation has averaged 50 to 75 percent of normal
Bitter cold — albeit dry — weather resulted in no change to the drought depiction except along the Texas Gulf Coast. Temperatures averaged 15 to 25°F below normal for the week, with some shallow snow noted over northern portions of the region at the end of the monitoring period. Despite the frigid, mostly dry conditions, some Abnormal Dryness (D0) was reduced along the southeastern coast of Texas where rainfall totaled locally more than 2 inches. Short-term drought remained most intense (Exceptional Drought – D4) along the Texas-Oklahoma border west of Wichita Falls, where 90-day precipitation has totaled less than 50 percent of normal. In contrast, many of the long-term drought areas (“L” designation) from Texas into Colorado have received above-normal precipitation over the past 90 days, but are still wrestling with the impacts of longer-term deficits (60-80 percent of normal over the past three years).
Variable conditions in the north contrasted with ongoing drought elsewhere. In addition, Santa Ana winds developed in California, exacerbating drought and enhancing the risk for wildfires. The current Water Year has been largely a disappointment in central and southern portions of the region, but has gotten off to a good start in the Northwest.
In northern portions of the region, a steady plume of Pacific moisture helped produce 1 to more than 4 inches (liquid equivalent) of precipitation in the Cascade Range, providing localized relief from Abnormal Dryness (D0) to Severe Drought (D2) in southwestern Oregon. Despite the beneficial moisture, the drought areas of southwestern Oregon are still contending with the impacts of last season’s poor end to the Water Year; 12-month precipitation averaged 60 to 85 percent of normal in the state’s remaining drought areas despite this week’s higher totals. In contrast to the localized Northwestern improvements, D0 was increased northward in Idaho and far northwestern Montana, where 60-day precipitation has tallied locally less than 60 percent of normal
Farther south, the 2014-15 Water Year has afforded little — if any — drought relief to California. Despite some light to moderate precipitation (0.2 to 1 inch, liquid equivalent) during the period across central and northern California, the totals still fell short of normal and did nothing to offset the impacts of the ongoing three-year drought. The current Water Year (which began October 1) has gotten off to an abysmal start; rainfall to-date (since October 1) has totaled 10 to 35 percent of normal in the Exceptional Drought (D4) areas around San Francisco, and locally less than 20 percent of normal in the D4 around Los Angeles. Likewise, the dry, mostly mild start to the winter has left snowpacks in the Sierra Nevada well short of normal. The dryness has been exacerbated by Santa Ana winds, which gusted over 40 m.p.h. in southern California.
In the Great Basin and Four Corners, there were no changes to this week’s drought depiction despite the very poor start to the current Water Year, particularly in western portions of the region. The season’s poor initial prospects are reflected by season-to-date (since October 1) precipitation, which has totaled locally less than 10 percent of normal in the Great Basin and western portions of the central and southern Rockies, with most areas reporting less than 30 percent of normal. Changes to the drought depiction across much of the west are typically slow to occur during the early part of winter, as the development of the Water Year will be crucial to the region’s drought relief (or development) prospects.
Milder weather will gradually develop over much of the nation, with precipitation chances greatest east of the Plains and in the Northwest. Following bitter cold early in the period, intensifying southerly flow will allow above-normal temperatures to develop across much of the nation. The moist, warm flow from the Gulf will set the stage for locally heavy rain from the southeastern plains and Mississippi Valley to the Appalachians. Meanwhile, an additional influx of Pacific moisture will produce locally heavy rain and mountain snow in the Northwest, with some moisture expected to spread into the northwestern quarter of California. However, the southern Rockies will remain mostly dry. The NWS 6-10 day outlook for November 25 – 29 calls for below-normal temperatures across much of the U.S., with warmer-than-normal weather confined to New England and west of the Rockies. Meanwhile, below-normal precipitation from California to the central and southern Plains and Delta will contrast with wetter-than-normal conditions along the East Coast and across the nation’s northern tier.
Eric Luebehusen, U.S. Department of Agriculture
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