National Drought Summary -- February 11, 2020

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilized include the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14 Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast web page used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

Heavy precipitation affected large parts of the Nation last week, with heavy snow in the central Rockies bringing some relief to the dry areas there. The broadest area of heavy precipitation stretched from the Middle Atlantic States southwestward into the Lower Mississippi Valley and the Southeast. At least 2 inches fell from the Ohio River to near the Gulf and southern Atlantic Coasts, with 7 to 10 inches measured across the much of the interior Southeast. On the other side of the 48 states, heavy precipitation covered parts of the Northwest. Near the coast in Washington and northern Oregon, most locations recorded at least 4 inches of precipitation, with isolated amounts to 10 inches in higher elevations. Just to the east, along the Cascade Range from central Oregon northward, a broad swath received at least 5 inches of precipitation, and most of a strip through central Washington reported 10 to locally 15 inches. Well inland, in the central and northern Rockies, precipitation was largely elevation-dependent,. The more elevated regions observed 2 to 5 inches, with lesser amounts in adjacent areas of lower elevation. Heavier amounts more broadly covered central Idaho and adjacent areas in Washington and Oregon, with totals of 4 to locally 8 inches common. It was another week of above-normal temperatures in the East and part of the interior Northwest, while subnormal readings were recorded in the central Rockies where the heavy snowfall dominated the week. Temperatures were 10 to 15 degrees F warmer than normal in the east-central States and part of the interior Southeast, and most sites east of the Mississippi River were at least 4 degrees F above normal. Many locations across the Country averaged 2 to as much as 5 degrees F above normal since mid-November 2019, especially east of the Mississippi River and the interior Rockies and Far West.


Alaska, Hawaii, and Puerto Rico

Moderate to heavy rain erased the southern tier of the dry region analyzed last week, but most sites received considerably less, keeping D0 intact farther north.. 60-day rainfall is at most 75 percent of normal in the abnormally dry area

The drought areas in Maui and the Big Island reported substantial rainfall this past week, but impacts have not tangibly improved at this time, so the depiction remains unchanged from last week

Generally light precipitation fell on the dry areas in Alaska, keeping the D0 area unchanged.


High Plains

Most of the region saw little to no precipitation this past week, leaving the Drought Monitor unchanged in south-central Kansas, and prompting some limited expansion of the D0 to D2 conditions in western Kansas and eastern Colorado. Farther west, most lowland areas received only light precipitation, but heavy snows blanketed the higher elevations from central Colorado into western Wyoming. Snowpack is now near to above normal for this time of year in western Wyoming, and considerably above normal from central Wyoming southward through most of the higher elevations in central Colorado. This prompted removal of the D0 area that had covered southwestern Wyoming. More limited improvement was noted in the D0 and D1 areas in central and western Colorado, where dryness is more entrenched.


Midwest

Heavy precipitation (over 2 inches) was restricted to the Ohio Valley, with most of the region recording a few tenths of an inch, if any. Still, longer-term surplus moisture covers most of the region, and no areas of abnormal dryness or drought have been identified.


Northeast

Between 1.5 and 3.0 inches of rain fell on D0 area on the Delmarva Peninsula, wiping out the abnormal dryness that had been there, and leaving the Northeast free from any Drought Monitor designation. The last 60 days brought somewhat below normal precipitation to several areas across northern Pennsylvania, New York, and New England, but given the time of year and lack of observed impacts, D0 does not seem warranted at this time.


South

Abundant rainfall eliminated D0 in relatively small parts of southeastern Louisiana and southernmost Mississippi, but most areas of dryness along the central Gulf Coast missed the bulk of the precipitation, keeping most of the D0 area unchanged. Farther west, moderate to heavy precipitation (1 to locally 4 inches) eliminated almost all dryness across western Louisiana and southwestern Arkansas, and induced improvement across the D0 to D2 conditions in eastern Texas as well. In addition, moderate rains in north-central Texas as well as the Red River Valley removed D0 from those regions, but left moderate drought largely intact across southwestern Oklahoma. But farther south, most areas of dryness and drought across central and southern Texas received little if any precipitation, prompting areas of drought intensification and expansion. Severe drought now covers large portions of central and southwestern Texas, and the D3 along parts of the Rio Grande Valley expanded into neighboring counties. Over the last 90 days, precipitation deficits reached 5 to 7 inches across interior eastern Texas, and less than 25 percent of normal has fallen around the areas of extreme drought in southwestern Texas.


Southeast

The heaviest precipitation fell away from the Gulf and Atlantic Coasts, but relatively moderate amounts were sufficient to remove the D0 area along the Carolinas Coast, though some mild moisture deficits remain in a few spots. Farther south, moderate to heavy rains eliminated D0 in both southern Georgia and southwestern Alabama, as well as the western sides of the D0 and D1 areas along the Florida Panhandle, where streamflows increased. East of the Apalachicola River, dryness and drought remained in eastern sections of the Florida Panhandle. The area of moderate drought recorded 5 to 8 inches below normal rainfall in the last 3 months. In addition, abnormal dryness was expanded into much of the northern Florida Peninsula where the last 30 days brought only 0.5 to 1.0 inch of rain (among the driest 5 percent of historic occurrences there).


West

Moderate to heavy precipitation in the Northwest and parts of the northern Intermountain West boosted snowpack enough improve drought designations in parts of the region. In Idaho, D0 was retracted to cover only the central part of the state, with some D1 remaining across the interior where snowpack remained unfavorably low (10th to 20th percentile historically for this time of year). A bit of abnormal dryness was also pulled out south-central New Mexico and northwestern Utah, but an unremarkable week kept dry conditions essentially unchanged across the rest of the Four Corners States outside Colorado. Across Nevada and California, however, dryness and drought intensification prevailed. On the 60-day time scale, markedly low precipitation totals (among the driest 5 percent of historical occurrences) covered most of a swath across central sections of California and Nevada, and 30-day amounts were less remarkable but still significantly below normal across most of the 2 states, outside the far northern and southern tiers. Since mid-December, less than half or normal precipitation has fallen from central and southern Nevada westward across most of California, with less than 25 percent of normal observed in the southern Sierra Nevada and adjacent central valleys. Central and southern sections of coastal California accumulated 3 to 8 inches less precipitation than normal during this period while deficits of 5 to 12 inches piled up in the Sierra Nevada. Precipitation summed over the past 6 months is notably below normal over most of both states. In particular, central and southern parts of the Sierra Nevada accumulated a deficit of 9 to locally near 20 inches of precipitation (about half of normal), and snowpack is less than 60 percent of normal for the date in the central and southern Sierra Nevada. The confluence of all these factors led to the introduction of moderate drought in the central and southern Sierra Nevada, and the adjacent central valleys. The state had been drought free since the first few days of December. Farther east, D0 was broadly expanded to cover part of northeastern California and a broad swath across much of interior Nevada. The last 6 months brought less than half of normal precipitation to this region, but with lower normals than farther west, accumulated deficits were less dramatic (generally 3 to locally 6 inches).


Looking Ahead:

During the next 5 days (February 13 to 17), the pattern is expected to be similar to last week, but with less extreme precipitation amounts. Still, over an inch is expected in a swath from southeast Louisiana to the upper Ohio River Valley, with a stripe of 1.5 to 2.5 inches expected from east-central Mississippi through northwest Alabama, central Tennessee, and southeast Kentucky. This, however, will be enough to exacerbate and already-soggy situation there. To the west, precipitation should again be orographically dependent. The higher elevations from central Colorado northwestward through the northern Intermountain West are expecting 1 to locally near 3 inches of precipitation, with the higher amounts most prevalent in the lower Idaho Panhandle. Farther west, moderate to heavy precipitation is expected along both the Pacific Coast and Cascade Mountains from central Oregon northward. Between 1.5 and 4.0 inches will douse many areas along the coast, and a strip through the middle of the Cascades can expect 2 to 5 inches. Meanwhile, nearly all areas of dryness and drought from the southern half of the Plains to the Pacific Coast will see less than 0.2 inch, with most sites recording little or none. Areas from the northern Plains and western Great Lakes southward into the middle Mississippi Valley should average colder than normal during this period, and subnormal daytime highs are expected along most of the northern tier of states. Across most of the western, southern, and eastern parts of the country, daytime highs should average near normal but nighttime lows are expected to remain above normal.

In the extended range forecast for the ensuing 5 days (February 17 to 21), odds favor surplus precipitation across the southern half of the Plains and from the Mississippi Valley eastward to the Atlantic Coast. Florida is an exception, with slightly enhanced chances for subnormal precipitation noted on northern and central parts of the Panhandle. Wetter than normal weather is also favored in much of the Pacific Northwest and Idaho, but enhanced chances for subnormal precipitation exist in the dry areas from Wyoming and the western Four Corners region to the Pacific Coast. The largest tilt of the odds toward dryness will be centered across California. Meanwhile, the mild winter is expected to continue from the lower Mississippi River, lower Ohio Valley, and eastern Great Lakes to the Atlantic Seaboard, except northern New England. Meanwhile, colder than normal conditions seem more likely through the southern half of the Plains, and most of the Rockies and Intermountain West. Wetter than normal weather is favored across the south-central and southeastern parts of Alaska, with odds tilting toward colder than normal weather in south-central parts of the state.


Author: Richard Tinker, NOAA, NWS, NCEP, CPC

Dryness Categories
D0...Abnormally Dry...used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1...Moderate Drought
D2...Severe Drought
D3...Extreme Drought
D4...Exceptional Drought

Drought or Dryness Types
S...Short-term
L...Long-term