#Drought news (December 16, 2021): The Rockies and Westward Region saw its warmest November (+5.8 deg F anomaly) on record as well as its warmest March-November period on record

Click on a thumbnail graphic to view a gallery of drought data from the U.
S. Drought Monitor.

Click here to go to the U.S. Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

This U.S. Drought Monitor (USDM) week was marked by a much more active storm pattern across the West Coast and Northern Rockies with areas of heavy rain along the coast and valley locations. Further inland, the higher elevations of the Cascade Range, Klamath Mountains, Sierra Nevada Range, northern Great Basin, and the Northern Rockies have all received significant snowfall accumulations this week. The storm event, fueled by an atmospheric river, provided a much-needed boost to snow water equivalent (SWE) levels in the Far West. On December 14, the NRCS SNOTEL network was reporting normal-to-above-normal SWE in Oregon’s Willamette (100% of median) and Southern Oregon Coastal (116%) basins as well as in the Lower Sacramento (113%), San Joaquin (106%), Tulare-Buena Vista Lakes (119%), Truckee (137%), Carson (120%), Walker (122%) and Mono-Owens Lakes (122%) basins of the Sierra Nevada Range. In the Lower Mississippi, Tennessee, and Ohio Valley, an outbreak of violent thunderstorms including dozens of tornadoes, erupted along a path spanning from northeastern Arkansas to northeastern Kentucky. The tornados moved very rapidly through the region on Friday night with devastating effect, especially in the southeastern Kentucky town of Mayfield. In Kentucky, latest reports announced at least 74 people lost their lives, and the death toll is expected to increase. In the Mid-Atlantic, unseasonably warm temperatures were observed over the weekend with daily high-temperature records broken in Pennsylvania, West Virginia, Virginia, Maryland, Delaware, New Jersey, and North Carolina where high temperatures ranged in the mid-60’s to mid-70’s. On the map, short-term precipitation shortfalls and anomalously warm temperatures led to the degradation of drought-related conditions in portions of the Mid-Atlantic, Southeast, South, and in the Midwest, while some improvements were made in the High Plains and isolated areas out West. According to NOAA’s National Center’s for Environmental Information (NCEI), November 2021 was the 7th warmest on record for the contiguous U.S. as well as the 7th warmest January-November period on record. In terms of precipitation, November marked the 8th driest for the contiguous U.S., while year-to-date precipitation ranked in the middle third (61st wettest). At a regional level, the Rockies and Westward Region saw its warmest November (+5.8 deg F anomaly) on record as well as its warmest March-November period on record…

High Plains

On this week’s map, eastern Wyoming, eastern Montana, central North Dakota, southern South Dakota, and northwestern Nebraska saw improvements based on short-term precipitation (30 to 90-day period). This included beneficial snowfall in southern portions of South Dakota where observed totals ranged from 6 to 18 inches with the highest totals in southwestern South Dakota. In these areas, soils have yet to freeze throughout the soil column and melting snows are infiltrating and helping to improve soil moisture levels. According to NOAA NOHRSC, snow coverage in the Upper Midwest Region (includes portions of Wisconsin, Minnesota, the Dakotas, eastern Montana, and northwestern Wyoming) is currently at 52.5% with an average depth of 1.5 inches and a maximum depth of 28.8 inches. Despite some improvements on the map, it is noteworthy that average temperatures across the High Plains region have been well above normal since September. This includes numerous high-temperature records that were recently broken across the region during the first week of December when high temperatures soared into the 70’s…

Colorado Drought Monitor one week change map ending December 14, 2021.

West

Out West, a weak-to-moderate atmospheric river made landfall in the Pacific Northwest on Saturday and moved southeastward bringing coastal and valley rains as well as heavy mountain snowfall accumulations across California and the Pacific Northwest. For the week, rainfall accumulations along the coastal areas from Washington to California ranged from 3 to 13+ inches with the highest accumulations observed in the coastal ranges of northwestern Oregon and along the Central Coast of California. In terms of snowfall during the multi-day storm event, total accumulations exceeded 6 feet in areas of the Central Sierra while areas in the southern Cascades received up to 3 feet. Further inland, areas of the Northern Rockies in Idaho and northwestern Wyoming, observed snowfall totals ranging from 12 to 20 inches. Despite the beneficial nature of this week’s storm event, significant precipitation deficits (ranging from 4 to 20+ inches) still exist across California and the state’s largest reservoirs are still at critically low levels, with Lake Shasta currently at 46% of the historical average (25% of capacity) and Lake Oroville at 62% of average (31% of capacity). In other areas of the West, basin-level SWE is well below normal, especially in New Mexico where median SWE ranged from 12% to 77% of normal as of Dec 14. On the map, some improvements were made in areas of Extreme Drought (D3) and Exceptional Drought (D4) in Montana, Oregon, and Utah as well as improvements in areas of Severe Drought (D2) and Moderate Drought (D1) in Idaho and Wyoming. According to NOAA NCEI, November 2021 was the 2nd warmest on record for the West and Southwest climate regions. Moreover, California and Wyoming both recorded their warmest average minimum temperatures on record for November while Nevada, Utah, and Colorado observed their 2nd warmest on record. In terms of precipitation, the Southwest Climate Region was notably dry having its 5th driest November on record…

South

In the South, conditions on the map continued to degrade across areas of Texas and Oklahoma where unseasonably warm and dry conditions prevailed this week. The dry conditions showed up on a variety of drought indicators including satellite-based soil moisture and evaporative demand tools. Additionally, numerous rivers and streams in the western half of the state showed flows dipping below the 20th percentile during the past 7-day period. Rainfall deficits (ranging from 3 to 6+ inches) during the past 60-day period were greatest in southeastern Oklahoma, eastern Texas, Louisiana, and southwestern Arkansas. For the week, average temperatures were above normal (2 to 10+ deg F) across Texas, Oklahoma, Louisiana, Arkansas, and Mississippi…

Looking Ahead

The NWS WPC 7-Day Quantitative Precipitation Forecast (QPF) calls for moderate-to-heavy liquid (liquid = rain + SWE) precipitation accumulations ranging from 2 to 5 inches in an area extending from Northern California to Washington state. Similar accumulations are forecasted In the Sierra Nevada Range, Cascade Range, and Olympic Mountains. In the Intermountain West, 1-to-2-inch (liquid) accumulations are expected across the Central and Northern Rockies. Elsewhere, 1-to-5-inch (liquid) accumulations are expected in far southeastern portions of the Southern Plains as well as in the Lower Mississippi, Tennessee, and Ohio River valleys. Along the Eastern Seaboard, light accumulations of generally <1 inch are expected in New England while most of the Mid-Atlantic and Southeast will continue to be generally dry. The CPC 6-10-day Outlooks calls for a moderate-to-high probability of above-normal temperatures across the southern half of the conterminous United States excluding California and Nevada. Below-normal temperatures are expected across the remainder of the West including the Pacific Northwest and the Northern Rockies. In terms of precipitation, the wetter-than-normal pattern is expected to persist across the western U.S., while there is a low-to-moderate probability of below-normal precipitation across the Central and Northern Plains as well as across most of the South. In the eastern third, near-normal precipitation is expected.

US Drought Monitor one week change map ending December 14, 2021.

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