Nationwide
On Jan. 4 and 5, a low-pressure system developed across the Central Great Plains and tracked eastward to the Mid-Atlantic.
Along its track, widespread precipitation (1 to 2 inches, liquid equivalent) was observed throughout eastern Kansas, Missouri, the Ohio and Tennessee Valleys, Central Appalachians, and Mid-Atlantic. Total snowfall amounts were near or more than a foot in portions of these areas. This winter storm also resulted in freezing rain for the Ohio Valley and parts of Virginia and West Virginia. Drought improvements were generally made to portions of the central and eastern U.S. where precipitation amounts exceeded 1 or 1.5 inches, liquid equivalent. Drought coverage and intensity declined for the Upper Ohio Valley and New England.
After the winter storm exited the East Coast, an arctic air outbreak overspread the eastern two-thirds of the lower 48 states. A favorable start to the wet season, coupled with an above-normal snowpack, supported a decrease in drought coverage across the Pacific Northwest. Conversely, drought worsened in southern California and the Southwest.
The West
A dry start to the winter and using the 90-day Standardized Precipitation Index (SPI) and soil moisture, moderate drought (D1) was expanded across southern California.
The National Drought Mitigation Center (NDMC) short-term blend, 90-day SPI, and many 28-day average streamflows below the 10th percentile supported the addition of severe drought (D2) to portions of southern California. The Santa Ana winds during early January are likely to exacerbate the worsening drought conditions. Consistent with the NDMC short-term blend along with 30 to 120-day SPI, D2 was expanded for portions of southeastern Arizona and southwestern New Mexico.
Based on water year to date (WYTD: October 1, 2024, to January 6, 2025) precipitation averaging above normal and snow water equivalent (SWE) above the 80th percentile, a 1-category improvement was made to southwestern Idaho, eastern to central Oregon, eastern Washington and a small part of northwestern Montana. NDMC drought blends and SPIs support this 1-category improvement at various time scales. As of January 7, SWE was above normal (period of record: 1991-2020) across the southern Cascades along with eastern Oregon and southwestern Idaho. SWE was highly variable for the Sierra Nevada Mountains and below-normal across the Four Corners Region.
The High Plains
Based on 30—to 60-day SPI and a lack of early-season snowpack, southwestern Colorado was degraded in one category.
Farther to the north across northwestern Colorado, improving snowpack resulted in a minor reduction in abnormal dryness (D0). Southwestern Nebraska has received little to no precipitation during the past 7 weeks, prompting an expansion of D0. In addition, above-normal temperatures during the late fall and into the early winter exacerbated increasing short-term dryness. Heavy precipitation (more than 1 inch, liquid equivalent) for this time of year resulted in a 1-category improvement to northeastern Kansas. No changes were made to the Dakotas; early January is one of the driest times of the year.
The South
Parts of the Edwards Plateau in Texas were degraded in one category based on 30—to 120-day SPI, 28-day streamflow, and soil moisture.
SPIs at various time scales and soil moisture supported a 1-category degradation as well for parts of the Rio Grande Valley. Heavy rainfall during late December supported additional improvements across southeastern Texas. Recent rainfall (1 to 2 inches) prompted a 1-category improvement to parts of Mississippi and Tennessee. Despite the recent rainfall, 28-day average streamflow and 90-day SPI support a continuation of D1-D3 intensity for the Tennessee Valley. Although precipitation was lighter this past week, the lack of support among the indicators for D0 and D1 led to improvements in much of Arkansas. — UNL Drought Monitor
