A series of storm systems traversed across the lower 48 States this week, dropping precipitation on most section of the contiguous U.S. The exceptions to this included most of California, northern Montana, the central High Plains, and southern sections of Texas and Florida. In contrast, light to moderate precipitation fell on the Northwest, parts of the Southwest, most of the Plains, Midwest, Northeast, and Southeast. Widespread heavy precipitation (more than 2 inches) inundated coastal Washington and the Cascades, the southern Great Plains, lower Missouri, lower and middle Mississippi, and Tennessee Valleys, parts of the mid-Atlantic, and the Deep South (Mississippi, Alabama, and Georgia). With dozens of stations measuring their wettest year on record in the East and Southeast (e.g. Wilmington, NC, 102.26 inches, old record 83.65 inches in 1877), it was not surprising that very little drought existed east of the Rockies. With subnormal weekly temperatures in the western half of the Nation and above-normal readings in the eastern half, the precipitation fell as snow in the southern Rockies, central and northern Plains, and upper Midwest. Snow also fell on most of the interior West, boosting WYTD basin average Snow Water Content (SWC) and precipitation closer to or above normal as of Jan. 1, according to the NRCS SNOTEL data.
Light to moderate precipitation (0.5-2.5 inches) fell across New England and the mid-Atlantic, adding onto an already record or near-record wet year in the region. For example, Washington, DC, Baltimore, MD, Elmira, NY, Atlantic City, NJ, State College, PA, Charlestown, WV, Wheeling, WV, and Pittsburgh, PA marked 2018 as their wettest year on record. The few remaining D0 areas located in extreme northern sections of New York, Vermont, and Maine received 0.5-1.5 inches of precipitation, boosting their short-term SPIs to normal or above, and allowing for some removal of D0 where 90-day deficits were greatly reduced. USGS 1-, 7-, 14-, and 28-day average stream flows have rebounded and are at above (76-90th percentile) to much-above (>90th percentile) normal values. Although some longer-term deficiencies (>6 months) remained, the low temperatures and dormant plant growth are ideal for soil moisture recharge where the soils are not frozen.
An active weather pattern brought various amounts of rain across most of the Southeast, with the greatest totals (4-8 inches, locally to 10) located in western sections (Alabama and western Georgia), while 0.5-3 inches was measured at most locations in Virginia, the Carolinas, eastern Georgia, and northern Florida. The rains missed central and southern Florida, and short-term (90-day) deficits of 3-6 inches have accumulated across southeastern sections of the state, with a few coastal Atlantic areas seeing 6-9 inch shortages. Some USGS 7-day average stream flows have dropped below the 10th percentile (much-below normal), but since it is the dry season, periods of subnormal rainfall are not that unusual for this time of year, so the addition of D2 was held off for now. Nevertheless, some slight expansion of D0 and D1 was made into southern Florida and the Keys.
Heavy rains (3-8 inches, locally to 12 inches) soaked much of eastern Texas, eastern Oklahoma, western and southern Arkansas, and most of Louisiana, Mississippi, and Tennessee, with light to moderate totals (1-3 inches) falling on the central and northern Texas and the remainder of Oklahoma and Arkansas. Only western and southern Texas missed out on the plentiful precipitation. Accordingly, a general 1-category improvement was made to the D0 and D1 areas of Oklahoma, most of northern Texas, northwestern Arkansas, southern Kansas, and southwestern Missouri. In northern Texas, however, the small D1 area and the surrounding D0 was left since it was longer-term (>6-months), and the 0.25-1.5 inches of rain this week were not enough to alleviate the deficits. In extreme southern Texas, no rain increased 90-day deficits of 1-4 inches, thus the existing D0 area was expanded slightly northward, a new D0 area added to near Corpus Christi, and two new D1 areas were drawn where the biggest deficiencies were found in southern Texas.
In addition to the removal of D0 across southwestern Missouri (see South), light to moderate precipitation, some in the form of moderate to heavy snow in northwestern area, enveloped most of the Midwest, keeping much of the region rather moist and drought-free. Parts of Michigan, Indiana, and northern Ohio have recorded short-term (60-days) subnormal precipitation (60-80% of normal), but the recent rains quelled the development of D0. In northwestern Minnesota, although the ground is frozen with 6-12 inches of snow blanketing the D0 area, 0.5 inches of precipitation fell on its southern section, reducing the long-term deficit enough for a slight improvement. USGS 7-day average stream flows are at near-record highs in western portions of the Midwest, and closer to normal or slightly above-normal in eastern sections.