California and National Drought Summary for January 17, 2023, 10-Day Weather Outlook and California Drought Statistics – 43% of California in severe drought, down 28% week-over-week
January 19, 2023 – Atmospheric flow brought heavy rain and snow at high altitudes over part of the West, resulting in drought improvement in California, the Pacific Northwest, the northern Rockies and the Great Basin. A band of heavy rains combined with severe weather impacted the Southeast and resulted in areas of improved drought in Georgia. Meanwhile, prolonged drought has led to an extension of the drought in the Carolinas. The drought in the High Plains remains largely unchanged; Much of the excess moisture is retained in the snowpack and its impact on soil moisture and groundwater recharge remains to be seen. The drought spread across parts of the South, where short-term moisture deficits continue to build on top of longer-term droughts.
Much of the Northeast remains drought-free, with the exception of the ongoing long-term moderate (D1) drought in eastern Long Island. Despite recent improvements, rainfall anomalies are nearly 6 inches below normal for the past 60 days. The US Geological Survey also shows persistently low runoff and groundwater levels. Abnormal drought (D0) spread across southern New Jersey and the eastern panhandle of West Virginia, where short-term rainfall levels continue to increase, water flows remain low, and soils are dry.
The Southeast experienced a mix of drought improvement and expansion. A plume of heavy rainfall stretched from Alabama to Virginia. The excess rainfall improved unusually dry (D0) areas in Alabama; severe and moderate (D1-D2) drought and unusual drought in Georgia; D0 and D1 conditions in South Carolina; and abnormal drought in Virginia. Short-term precipitation deficits, runoff, and soil moisture showed improvement in these areas. However, South Carolina and North Carolina saw expansions of D0 and D1 in areas that missed the heaviest rain. Rainfall deficits range from 4 to 6 inches over the past 90 days. Runoff, groundwater and soil moisture are also low.
Much of Oklahoma and Texas missed this week’s precipitation events, causing the drought to widen. In Oklahoma, temperatures have averaged 10 to 13 degrees above normal for the last 2 weeks, while rainfall has been less than 50% of normal for the last 4 months. Extreme (D3) drought spread in response to well below normal (10th percentile or below) measurements of stream flow, groundwater and soil moisture. Texas also experienced a series of deteriorations from the north-central region to south Texas, where short-term moisture deficits have continued to build on top of longer-term drought, reducing stream flow, soil moisture, and groundwater levels from below (10th-24th percentile) to well below normal (10th percentile or lower). In the eastern part of the region, last week’s rains wiped out persistent areas of unusual drought.
The Midwest experienced a mix of drought improvement and expansion last week. Heavy rainfall (150 to over 300% of normal) in Ohio and Indiana led to improvements in moderate (D1) drought and unusual dryness (D0), where watercourses and soil moisture show signs of recovery. However, Missouri experienced an extension of the severe (D2) drought due to increasing rainfall deficits (6 to 12 inches in the last 6 months) and decreasing runoff. Sustained below-normal precipitation caused D0 to widen in Illinois and far southeastern Wisconsin as stream flows began to gradually decrease.
Much of the High Plains remained on hold last week. Areas that experienced ample snowfall during the water year are slow to improve due to the region’s prolonged drought. Until the spring melt shows verified evidence of soil moisture and groundwater recharge, it will be difficult to say how much of an impact snow has had on drought conditions. Severe drought (D2) improved in eastern North Dakota, which has seen 16 to 20 inches of snow this season. No areas deteriorated significantly except for unusually dry (D0) areas in South Dakota and Colorado.
The long-standing drought continues throughout California, the Great Basin and parts of the Pacific Northwest. However, a spate of atmospheric flow events — moisture flows in the atmosphere that transport water vapor from the tropics — have reduced drought intensity in recent weeks. In California, 1 category improvements were made along the north shore, around the delta and along the south shore region. While rainfall in much of the state has been over 300% of normal for the past 2 weeks (2 to 12.5 inches, depending on location), deficits have been manufactured over the years. While this latest bout of rain has helped bring smaller reservoirs back to historical averages, many of the larger reservoirs still remain below historical averages for this time of year. Historically, a long-lasting drought is interrupted by a period of unusually wet weather. However, it is still too early to say if the wet weather will be enough to end the drought. Many other parts of the West also saw improvements in droughts and unusually dry areas. In Oregon, Category 1 improvements were made to extreme (D3) and severe (D2) drought in Southeast and near Klamath County based on above-average snowwater equivalent and improvements in long-term indicators such as 6 to 24 months of rainfall and shallow groundwater. Severe (D2) and moderate (D1) drought improved in Idaho, where trailing-12-month rainfall deficits and stream flows showed improvement. In Utah, areas of D3 and D2 improved based on rainfall in excess of 300% of normal (3 to 10 inches, depending on location) in the last 30 days and the resulting impact on watercourses, soil moisture and groundwater. Heavy rainfall helped eliminate areas of unusually dry conditions in parts of Washington, Oregon, western Wyoming, western Colorado, Arizona and New Mexico. The only places in the west that experienced an extension of the drought were Oregon and Colorado. In Oregon, D1 was introduced in the southern Willamette Valley and central Oregon Cascades, and expanded D1 and D2 in the north-central part of the state. These expansions were in response to below-average rainfall in the current year, in addition to longer-term deficits and groundwater impacts.
No changes were made to the map in Puerto Rico this week.
Fluctuating rainfall in the US Virgin Islands resulted in no changes in plot, with short-term drought (D0-S) persisting on St Thomas and St Croix. Rainfall was heavier on St. John, which remained dry, with 2 to 3 inches reported at the two volunteer observatories (CoCoRaHS). The observer at Windswept Beach, St. John, received measurable rain totaling 3.89 inches on each of the first 16 days of January — above the January long-term average of just under 3 inches.
Meanwhile, rainfall from Dec. 1 to Jan. 16 was less than 50 percent of normal at airport observatories on St. Thomas and St. Croix. During those 47 days, precipitation was only 2.06 inches at King Airport on St. Thomas and 1.94 inches at Rohlsen Airport on St. Croix. CoCoRaHS observations showed isolated heavier showers during the 7-day drought monitoring period, with weekly amounts ranging from 0.20 to 0.75 inches on St. Thomas and 0.23 to 2.20 inches on St. Croix. US Geological Survey borehole observations showed a slight increase in water depth at St. Thomas and St. Croix, consistent with short-term drought.
No changes were made to the map in Alaska this week.
The drought persisted in Hawaii. On Kauai, Oahu, Maui, and the Big Island, drought conditions worsened as the rainfall deficit increased, resulting in decreased stream flow and stressed vegetation, as well as island-specific impacts. On Maui, for example, the county’s water treatment plant near Kaanapali was closed due to lack of flow. On the Big Island, supplies from the catchment area are running low and pastures are not growing, forcing ranchers to fetch water.
In the United States-affiliated Pacific Islands (USAPI), the only change was to address the unusual aridity of Ulithi in the Federated States of Micronesia (FSM) due to weekly rainfall totaling more than 6 inches. As a result, Kapingamarangi, FSM was the only USAPI site with a drought designation that continued to be affected by severe drought (D2-SL). Elsewhere in the FSM, data from Pingelap was again missing, while some other sites have trended drier in recent days but are not yet abnormal drought candidates.
In contrast, heavy rain continued to fall in the Republic of Palau while this month saw extremely wet conditions in the Mariana Islands and American Samoa. In the Mariana Islands, Guam International Airport netted 13.66 inches (452 percent of normal) for the first 17 days of January, putting it within range of the two highest January totals ever recorded: 18.09 inches in 1976 and 16, 89 inches in 2014. The Republic of the Marshall Islands (RMI) experienced a decrease in rainfall during the drought monitoring period, but remained wet after the early January downpours. For example, Mili, RMI, received weekly rainfall of 2.26 inches, after the previous week’s 9.39-inch deluge. Data for Utirik, RMI, remained lost.
The National Weather Service Weather Prediction Center forecast for the remainder of the week (effective January 18 through January 20) calls for a winter storm that will bring freezing rain and snowfall to the High Plains and upper Midwest. Showers and thunderstorms with localized heavy precipitation are expected in the southeast. Chances of a wintry mix of snow, sleet and freezing rain along the East Coast increase as the storm system moves northeast on Thursday. Much of the southern US can expect unseasonably warm temperatures. Meanwhile, another storm system is expected to move southeast through the Pacific Northwest to the northern Rocky Mountains, Great Basin, California and the desert southwest, bringing rain and snow at lower elevations and heavier snow in the mountains. Over the next week (effective January 21 through January 25), the forecast calls for a storm system to be traced from the central plains to the northeast, bringing strong winds and wintry weather to the northern regions and rain to the south. At 8 – 14 days, the Climate Prediction Center Outlook (valid January 25 – January 31) calls for below normal temperatures for most of the country except for the Northeast, Southeast and Alaska. The Northeast can expect near-normal temperatures, while the Southeast and Alaska are the most likely to be warmer than normal. Most of the US can expect almost to slightly above average rainfall. Only the Pacific Northwest and northern Minnesota have increased chances of below-average rainfall.
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