Following a drier-than-normal winter, a pattern change at the beginning of March resulted in widespread heavy precipitation (1 to 3 inches, locally more) and a 1-category improvement to parts of the Ohio and Middle to Lower Mississippi Valley. This drought improvement extended east to the Central Appalachians and the Northeast. However, a long-term drought continues for much of the Northeast. Despite the much-needed rainfall for portions of the Southeast and Southern Great Plains, severe (D2) to extreme (D3) drought persists for many areas. A low snowpack and early onset of snowmelt are a major drought concern for the West. As of March 10, drought of varying intensity was designated for parts of Hawaii. Alaska and Puerto Rico remain drought-free.
Widespread precipitation of 1 to 2 inches led to a 1-category improvement to parts of southeastern New York, northern New Jersey, Pennsylvania, and West Virginia. Despite the recent beneficial precipitation since late February, a long-term drought of varying intensity persists for much of the Northeast. This long-term drought depiction is supported by the meteorological and hydrological drought metrics. For example, 28-day average streamflows remain low (below the 10th percentile) from the Northern Mid-Atlantic into New England. Note that the drought impact was changed to long-term only for much of the Northeast where short-term drought has mostly ended.
Small improvements in the Southeast region were made near Mobile (around 5" rainfall from March 3-9) and across northern Alabama. Extreme (D3) drought was expanded in northeastern Georgia as 90 to 120-day precipitation deficits continue to increase and low streamflows persist in the upper headwaters of the Chattahoochee River. Increasing short-term precipitation deficits resulted in a 1-category degradation across southwestern Virginia. Consistent with a La Nina winter, drought has worsened the past few months across Florida with more than two-thirds of the Sunshine State designated with extreme (D3) drought. According to the National Interagency Fire Center, a wildfire at Florida’s Big Cypress National Preserve has grown to over 35,000 acres burned.
Despite the locally heavy rainfall across the Lower Mississippi Valley along with eastern Oklahoma and Texas, only modest improvements were warranted as a favorable response among the various indicators was not enough to justify more widespread 1-week changes. However, targeted 1-category improvements were made to parts of northwestern Arkansas, eastern Oklahoma, eastern Texas, and the Lower Mississippi Valley where weekly precipitation amounts exceeded 2 inches. In areas that missed out on the beneficial rainfall, drought intensified for parts of west-central Oklahoma and the Oklahoma Panhandle. A majority of the South Region has received less than half their normal precipitation with a temperature departure of more than 6 degrees F above normal during the past 90 days. These 3-month precipitation and temperature observations are consistent with a La Nina wintertime pattern.
Major drought improvement occurred across the Midwest Region as a couple of low pressure systems and associated fronts tracked through the central U.S. during early March. A 1-category improvement was generally made to areas that received 1.5 inches or more of precipitation from March 3 to 9. This included central to southern Indiana, Illinois, and Ohio along with east-central and southern Missouri. Given the time of year, this recent precipitation was very beneficial in recharging soil moisture. There was a sharp cutoff to the heavier precipitation (near the I-70 corridor) with severe (D2) to extreme (D3) drought continuing farther to the north across Illinois, Indiana, and Ohio.
Widespread drought of varying intensity continues across much of the Central Great Plains and Central Rockies. Drought expanded this past week to include all of southwestern Colorado and intensified for northwestern parts of the state. The low snowpack throughout the Central Rockies, especially Colorado, remains a major concern heading into the spring. As of March 10, snow water equivalent for the river basins of Colorado is running below 70 percent of the 1991-2020 average. There were a couple exceptions to the worsening conditions. A wet snow (1” or more, liquid equivalent) supported the removal of extreme (D3) drought across parts of the Denver metro area. Heavy rainfall (more than 1.5 inches) prompted small 1-category improvements to eastern Kansas and southeastern Nebraska.
The low snowpack throughout much of the West is a major concern heading into the spring. As of March 10, snow water equivalent (SWE) is less than 40 percent of normal from the Cascades of the Pacific Northwest southward through the Great Basin and Four Corners region. 14-day temperatures, valid from February 25 to March 10, have averaged 5 to degrees F above normal. This warmer-than-normal end to February and start to March has led to an early onset of snowmelt for parts of the West. Although California remains drought-free, SWE is 53 percent of normal statewide according to the California Department of Water Resources. Overall, only minor changes were made this past week to the West Region. Based on increasing 60-day precipitation deficits and to reflect the low snowpack, abnormal dryness (D0) was added to parts of northern California. Drought expanded into southeastern Utah while intensifying to severe (D2) and extreme (D3) drought across northeastern and western portions of the state. Moderate (D1) drought was expanded across north-central to northeastern Washington along with central Oregon due to 30 to 90-day precipitation deficits and low snowpack.
Only a small area of abnormal dryness remains designated for southern Puerto Rico with most areas receiving above-normal precipitation during the past 30 to 120 days.
Precipitation was low for the U.S. Virgin Islands over the past week but was above normal in February, typically a dry time of year. St. Thomas and St. John both received 0.26 inches, according to citizen weather observers. St. Croix got 0.19 to 0.28 inches.
The Standardized Precipitation Index showed slightly dry conditions at the one-month time scale for St. John’s East End, with wetter conditions at longer time scales. Conditions were fairly normal for all time scales for St. Croix’s East Hill.
The Vegetation Health Index indicates some mild stress for St. Croix. Water levels in wells on all three islands are dropping as this is a dry time of year. All islands continue to be drought-free.
Abnormal dryness continues for portions of Alaska and generally reflects below-normal snowfall. No changes were made this past week.
No changes were made this past week and as of March 10th, there are varying levels of drought intensity across the Big Island, Maui, and Molokai.
The Republic of Palau received 2.28 and 3.68 inches of precipitation at Palau IAP and Koror, respectively. Water supplies should be sufficient as these locations need 2 inches of rainfall per week to meet minimum water needs.
The Mariana Islands received more than 2 inches for the week. Guam reported 3.46 inches, Rota got 3.51 inches, and Saipan International Airport collected 2.05 inches. One inch is the weekly amount these islands need to meet minimum water needs.
The Federated States of Micronesia mostly received more than 2 inches for the week. Lukunor was put back in normal condition from D0 after receiving 2.28 inches of precipitation. Woleai and Yap were also returned to normal conditions after receiving 6.13 and 2.11 inches of rain, respectively. All other locations in the FSM received more than 2 inches, apart from Kapingamarangi and Nukuoro, which got less than an inch, but both locations had adequate precipitation in prior weeks.
Precipitation over the Marshall Islands was mixed. Utirik and Wotje remain in D2 and reported just 0.12 and 0.1 inches, respectively. Kwajalein collected 2.32 inches and was moved from D0 back to normal condition. Ailinglaplap, Jaluit, and Mili received more than 2 inches of rain, while Majuro got 1.48 inches.
American Samoa received enough rainfall to leave D0 and return to normal conditions. Pago Pago received 2.68 inches of rain, while Siufaga Ridge and Toa Ridge got 2.5 inches and 2.19 inches, respectively. These islands require 2 inches of rain per week to meet minimum water needs.
Looking Ahead
In the wake of a cold front, sharply colder temperatures are forecast to overspread the eastern U.S. on March 12. A second and even stronger cold front is expected to progress east from the Great Plains to the East Coast by March 16. Following this strong March cold front, subfreezing temperatures are forecast to extend as far south as Oklahoma and the Texas Panhandle. According to the Weather Prediction Center, 5-day precipitation amounts from March 12-16 are forecast to exceed 1 inch, liquid equivalent, across the Great Lakes and New England. Much needed rainfall is also anticipated for drought-stricken Florida. Elsewhere, drier weather is forecast for the Ohio Valley, Middle to Lower Mississippi Valley, and Great Plains. During mid-March, dry weather will be accompanied by an increasing chance of record heat across California, the Great Basin, and Southwest. A powerful Kona low will bring heavy to excessive rainfall to Hawaii through at least March 14.
The NWS 6-10 day outlook (valid March 17-21) leans toward below-normal temperatures for the East, while above-normal temperatures are likely from the West Coast to the Great Plains. Above-normal temperature probabilities exceed 90 percent across most of California, the Great Basin, and Southwest. In contrast to the warmer–than-normal temperatures over the West, Alaska is likely to be colder-than-normal. A majority of the lower 48 states are favored to have below-normal precipitation from March 17-21 with the largest below-normal precipitation probabilities (greater than 50 percent) forecast across the Central to Southern Great Plains, Southwest, and much of California. The wet pattern is forecast to persist for Hawaii with enhanced above-normal precipitation probabilities.