This Week's Drought Summary (12/20)
This week, another strong storm system crossed the southern continental United States, delivering moderate to heavy precipitation from parts of Texas and Oklahoma east and northeastward through the Ohio Valley and Southeast to the Atlantic Coast. Moderate to heavy precipitation also occurred from the central California coastline northward to the Canadian border, and in the interior northwest in northeast Oregon, eastern Washington, and the Idaho Panhandle. Elsewhere, little to no precipitation fell. With the exception of southern Texas, Louisiana, Mississippi, Alabama, Florida, northern New England, and a few pockets in the Intermountain West, most of the continental United States experienced warmer than normal weather this week. The warmest conditions with respect to normal occurred in the central and northern Plains and Upper Midwest. Relatively minor changes were made to the drought depiction this week. Abnormal dryness expanded over much of the southern Plains in response to increased short-term precipitation deficits and windy conditions. Areas of the South and Southeast that were in drought were adjusted in response to where the moderate to heavy rain fell and missed this week. Any changes to the map in the Northwest have been deferred to next week, when the effects of recent precipitation on meteorological and hydrological drought in the region can be more thoroughly evaluated. Moderate drought was added to the leeward sides of some of the Hawaiian Islands, where short-term dryness and windiness led to agricultural impacts. Abnormal dryness expanded in Puerto Rico, where soil moisture, streamflow, and short-term precipitation deficits worsened. Precipitation in the Alaska Panhandle this week was insufficient to improve any of the areas experiencing short- and long-term drought or abnormal dryness.
During the past week, the storm system that traversed the southern U.S. delivered precipitation ranging from a half inch to 3 inches to parts of the Northeast. The largest amounts fell in West Virginia, Pennsylvania, and New Jersey, while precipitation totals were much lower in interior parts of New York and New England. Temperatures in northern New England were mostly below normal by a few degrees, while temperatures in the rest of the Northeast were warmer than normal. Drought conditions remained unchanged this week, with short-term precipitation deficits continuing in northern Maine, where abnormal dryness remains. Abnormally dry conditions also continued in northern parts of New York and Vermont.
Near or slightly below normal temperatures were common in Florida and southern Georgia, while above-normal temperatures occurred from northern Alabama and Georgia northward through the spine of the Appalachians in the Carolinas and Virginia. As the aforementioned storm system moved across the southern U.S. this week, moderate to heavy rain fell in much of the Southeast region. The heaviest amounts, with isolated totals as high as 5 to 6 inches, occurred in the Florida Panhandle and northern Florida Peninsula. The southern edge of this heavy rain alleviated abnormally dry conditions in the north-central Florida Peninsula, while areas to the southeast of the heavy rain axis saw degradation to abnormal dryness due to increased short-term rainfall deficits. The rest of the region remained drought free this week.
Widespread moderate to heavy precipitation from this week’s storm system occurred from central Oklahoma eastward through Arkansas into Tennessee and northern Mississippi. Western north Texas, east Texas, and Louisiana also received moderate to heavy precipitation, while the dry slot of the storm system kept precipitation amounts minimal from central Texas to the Dallas-Fort Worth area. Generally warm conditions prevailed from the Texas Panhandle eastward through Tennessee this week, while more moderate temperatures and a few areas of below-normal readings were common in southern Texas, Louisiana, and Mississippi. With continuing dry conditions on short and long timescales, abnormal dryness expanded from the Amarillo area to cover more of the Texas Panhandle. Continued dryness in the 1- to 2-month timeframe in western Oklahoma and the Texas and Oklahoma panhandles, combined with very high winds associated with this week’s strong storm system increasing evaporative stress, led to the introduction and expansion of abnormal dryness over parts of western Oklahoma and the panhandles. The short-term dryness and depleted soil moisture here is beginning to apply stress to wheat, and fires are starting to become a concern in the region too. Adjustments to moderate drought and abnormal dryness were made in central and northeastern Oklahoma in response to where the heavy rain fell and where it missed this week. Areas that missed out on the heavier rains saw status quo or degradations as short- and long-term precipitation deficits increased, while deficits decreased and conditions improved in areas that received more rainfall. Short-term dryness also continued in the Lower Rio Grande Valley, where abnormal dryness expanded.
Moderate to heavy precipitation occurred this week, generally along and southeast of the I-44 corridor in Missouri and the I-70 corridor in Illinois, Indiana, and Ohio. Above-normal temperatures occurred in the entire region, with the warmest weather compared to normal taking place in northern Minnesota, where temperatures spiked to more than 10 degrees above normal. Relatively dry conditions over the last couple months continued in northern Wisconsin and parts of Michigan, though precipitation surpluses beyond the last two months in these areas prevented degradation. Aside from a slight expansion of moderate drought and abnormal dryness in southwest Missouri, no changes were made to the drought depiction for this week in the Midwest.
Warm and dry conditions dominated the region this week, with the warmest weather compared to normal occurring in the Dakotas. Dry conditions continued this week in southern Kansas, which led to the introduction of abnormal dryness where 1- to 2-month precipitation deficits increased and high winds increased evaporative demand. Outside of southern Kansas, no changes to the drought depiction were made this week.
Widespread heavy rain and snow fell along much of the Pacific Coast this week, from central California northward to the Canadian border. As much of this precipitation fell around the data cutoff for this week, any changes to the drought depiction are being deferred to next week’s map, when the effects of this precipitation on ongoing meteorological and hydrological drought can be more thoroughly evaluated. Elsewhere in the region, precipitation also fell in northeastern Oregon, eastern Washington, and much of the Idaho Panhandle. Above-normal temperatures were common this week in the West, particularly in eastern Washington and Oregon, while near or cooler than normal temperatures occurred in northern Utah, southeastern Wyoming, northeastern Nevada, and southeastern New Mexico. Low snowpack is evident in some of the mountainous regions of central Idaho, northwestern Montana, and the region around Yellowstone National Park, though overall conditions in these areas were not sufficient for degradation this week. Short-term and long-term precipitation deficits in the Sangre de Cristo mountains and adjacent foothills and high plains in northeastern New Mexico had improved enough for small improvements to the drought depiction here. Abnormal dryness was also slightly expanded near Laramie, Wyoming. Elsewhere, no changes to the drought depiction were made.
Alaska, Hawaii, and Puerto Rico
Precipitation continued this week in the Alaska Panhandle, though amounts were insufficient to allow for any improvement to the drought depiction here. In Puerto Rico, low soil moisture, low streamflow, and short-term precipitation deficits led to the expansion of abnormal dryness over a much larger section of the island. Strong winds and short-term dryness in the leeward sides of Hawaii, Maui, Molokai, and Kauai led to adverse impacts on vegetation and pastures. In these areas, abnormal dryness continued, and some pockets of moderate drought were introduced.
For the rest of this week, the National Weather Service Weather Prediction Center is forecasting widespread moderate to heavy precipitation, with the highest amounts generally confined to an area ranging from eastern Texas northeast to the Atlantic Coast. Moderate to heavy precipitation is also forecast in the Pacific Northwest. Primarily warmer than normal temperatures are also expected in the Lower 48 this week.