#Drought news: Long-term drought continues to plague western and southern #Colorado

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

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

This Week’s Drought Summary

A major pattern change occurred during mid-December as a strong area of upper-level low pressure developed over the northeast Pacific. Following a rather dry November, enhanced onshore flow resulted in heavy rain and high-elevation snow across the Pacific Northwest where 7-day total amounts (liquid equivalent) ranged from 2 to 6 inches, liquid equivalent, or more. Surface low pressure formed over the Gulf of Mexico on December 21 with an eastward track. Widespread heavy rainfall (2 to 6 inches) accompanied this low pressure system from the western Florida Panhandle north to nearly all of Alabama, Georgia, and South Carolina. An expansive area of surface high pressure led to mostly dry weather (December 17 to 23) across the Great Plains, Corn Belt, and Northeast. Mostly dry weather also prevailed across mainland Alaska with periods of precipitation occurring along the Alaska Panhandle. A low pressure system recently developed to the west of the Hawaiian Islands but the heaviest rainfall associated with this low pressure system remained west of Hawaii…

High Plains

Dry weather prevailed during mid-December from the central Rockies east to the northern and central Great Plains. This is a relatively dry time of year for much of these areas and 90- to 180- day precipitation averages much above normal across the eastern two-thirds of Montana and the Dakotas. However, long-term drought continues to plague western and southern Colorado. Short-term drought of varying intensity persists across southwest and south-central Kansas…

West

Widespread rain and high-elevation snow continued across the Pacific Northwest through December 21 before the storm track shifted south to California. 7-day precipitation amounts (as of 12Z December 23) ranged from 2 to 8 inches, liquid equivalent, or more along and west of the Cascades in western Washington and northwest Oregon. Based on this recent heavy precipitation, an increase in 28-day stream flows above the 25th percentile, and recovery in the 90-day SPIs, abnormal dryness (D0) was reduced slightly in coverage across northwest Washington and coastal Oregon. However, despite the recent heavy precipitation, no changes were made to the remainder of the ongoing abnormal dryness (D0) area given such a dry start to the wet season. Water year to date (since October 1) precipitation deficits of more than 12 inches, 28-day stream flows in the lowest 10th percentile, and basin average snow water content less than 50 percent support the short-term moderate drought (D1) across parts of Oregon and Washington. Heavy precipitation (more than 2 inches, liquid equivalent) during the past week resulted in a slight reduction in moderate drought (D1) in northern Idaho.

Lighter precipitation (generally less than 2 inches) extended south into northern California this past week, while mostly dry weather prevailed across the remainder of the West. Although basin average snow water content values are above normal across Arizona, New Mexico, and Utah, drought persists in these areas where 180-day precipitation deficits are relatively large and 6-month SPI values support ongoing long-term moderate (D1) to severe (D2) drought…

South

Mostly dry weather prevailed across much of the southern Great Plains during the past week. Therefore, a slight increase in abnormal dryness (D0) and moderate drought (D1) was warranted for southwest Oklahoma and northwest Texas. Also, a small increase in severe drought (D2) was necessary in parts of central Texas, based on 90day SPI values. Soil moisture currently ranks below the lowest 10th or 5th percentile from the Hill Country of Texas southwest to the Rio Grande River which supports areas of severe (D2) to extreme (D3) drought. In contrast to these worsening conditions, a brief period of heavy rainfall (2 to 4 inches) resulted in 1-category improvements in the Brownsville and Corpus Christi areas of Texas…

Looking Ahead

During the next 5 days (December 26-30), an upper-level low is likely to bring rain and high-elevation snow to southern California and the Southwest. This upper-level low is then likely to spawn a surface low across the southern Great Plains with a subsequent track northeast to the Great Lakes. Beneficial rainfall (0.5 to 1.5 inches) is expected with this low pressure system in southeast Colorado, Kansas, and Oklahoma. Light to moderate precipitation (an inch or less) will overspread the eastern U.S. on December 29 and 30. Following the brief period of heavy precipitation across the Pacific Northwest during mid-December, a drier pattern is likely to end December. Above-normal temperatures are forecast during late December across the central and eastern U.S., while below-normal temperatures prevail across the Great Basin and Southwest. A low pressure system is forecast to move away from the Hawaiian Islands on December 26. Strong onshore flow is likely to result in heavy precipitation (5 to 10 inches, or more) along the Alaska Panhandle. Arctic air with much below-normal temperatures are forecast to affect much of mainland Alaska.

The CPC 6-10 day extended range outlook (December 30, 2019 to January 3, 2020) indicates large probabilities (greater than 80 percent) for below normal temperatures throughout mainland Alaska as anomalous northeast surface flow persists. Wetter-than-normal conditions are forecast to continue into the beginning of January 2020 along the Alaska Panhandle. The strong Pacific flow is likely to prevent the arctic air over Alaska to shift south anytime soon. Therefore, above-normal temperatures are favored for a majority of the continental U.S. Increased chances of below normal precipitation are forecast for California and the Great Basin. Forecast confidence in the precipitation outlook decreases across the central and eastern U.S. with either near or above normal precipitation most likely.

Here’s the one week change map ending December 24, 2019.

US Drought Monitor one week change map ending December 24, 2019.

Leave a Reply