This Week's Drought Summary (3/12)

March 12, 2020

A low pressure system propagated eastward across much of the southern tier states early in the period (March 4-6) and merged with a short-wave trough dropping southeastward from the Midwest before moving off the Mid-Atlantic coast on March 7. This system dropped more than 2 inches of rainfall over large areas from extreme southeastern New Mexico eastward to South Carolina. Some areas of central Alabama and Georgia saw more than 5 inches of rainfall, which fell over saturated soil. However, much of the heavier rainfall remained north of the I-10 corridor from southern Texas to northern Florida, while areas south of I-10 received only modest amounts, which were not nearly enough to reduce deficits. The Pacific Northwest and California also saw some precipitation over the past week, but amounts were not enough to reduce any deficits. Some recent dryness over southern Iowa and northern Missouri was mitigated a bit with near- to above-normal precipitation falling last week as well. Deficits increased in the Mid-Atlantic and New England over the past 30 days, but were kept at bay, as these areas saw 0.1 to 1 inch and 0.1 to 0.5 inches of rainfall, respectively. The active storm track continued last week for Alaska, with the southeastern Panhandle receiving 2 to 6 inches of precipitation over many areas. This precipitation, along with near- to below-normal temperatures, has finally produced above-normal snowpack in the Alaska Panhandle for the first time in 7 to 8 years, warranting D0 removal. Hawaii remained dry on the leeward slopes last week due to persistent trade winds, leading to some D0 expansion and development on the Big Island and Oahu, respectively. Puerto Rico saw D0 removal, as northern portions of the island saw much above-normal precipitation, eliminating short-term deficits.


New England and parts of Maine have seen drier-than-normal conditions since the start of 2020, with several areas seeing 2 to 4 inch deficits, and localized pockets of 4 to 6 inch shortages. However, February brought above-normal precipitation to much of the Northeast, reducing deficits in some of the dry areas. The past 7 days brought near-normal precipitation to much of the region, although New England and coastal Maine received slightly less than surrounding areas (0.1 to 0.25 inches, compared to 0.25 to 1 inch in surrounding areas). In addition, 7-day average USGS stream flows saw reductions, compared to 14-day average flows, which was enhanced by below-normal snowpack. Although D0 is not warranted at this time, New England and coastal areas of Maine will need to be closely monitored in the coming weeks if the dryness continues.


A large swath of more than 2 inches of rain fell across central Alabama and most of Georgia and South Carolina as a mid-level low pressure system propagated eastward across the southern tier states early in the period. Parts of central Alabama and Georgia saw more than 5 inches of rainfall. Unfortunately, the sharp north-south precipitation gradient along the I-10 corridor was reinforced, as much of the precipitation fell to the north over saturated areas. Locations south of the I-10 corridor, near and along the Gulf Coast, only received a trace to 0.25 inches, which is well below what is needed to overcome deficits (60- and 90-day deficits of around 5 inches and 6-month deficits over 10 inches in some locations). The Florida Peninsula saw little to no precipitation over the past week. D0 was added in southern Florida due to seeing 1 to 2 inch deficits over the past 30 days and slightly below-normal rainfall at 60 and 90 days, along with below-normal stream flows downstream from the area. Much of Virginia has also seen some dryness over the past 30 days, as 1 to 2 inch rainfall deficits have developed, and 7-day average USGS stream flows were below normal (10th to 24th percentile with some gauges reporting flows in the 10th percentile), particularly in the Tidewater area. Parts of the Tidewater saw some temporary relief, as 0.5 to 1 inch of rainfall fell March 6-7, in association with the low pressure system that moved northeastward off the Mid-Atlantic coast. In addition, soil moisture conditions were near to slightly below normal for the region. The status quo remained for Virginia this week, but this area bears watching in the coming weeks if the dryness continues.


D0 was expanded northward from the Gulf Coast of Louisiana, Mississippi, and Alabama. Many of these areas have 6-month deficits of over 8 inches; 6-month deficits over 12 inches in southeastern LA (i.e. 50 to 75 percent of normal). Rainfall over the past 30 days has been particularly low, with precipitation falling to 25 to 50 percent of normal, with some locations in the new D1 area seeing 10 to 25 percent of normal. Some expansion of D1 was made northeast of Corpus Christi, Texas, and D2 toward the coast, as USGS stream flows were well below normal at many locations and soil moisture has diminished further in recent weeks. Meanwhile, many areas in western and northern Texas (north of the I-10 corridor) saw anywhere from 0.5 to 3 inches (in isolated locations). The heavier rainfall extended southward into the upper Rio Grande Valley where many areas saw 0.25 to 1 inch of rainfall, warranted some re