The Northeast and mid-Atlantic: A significant storm system brought widespread rains (2-4 inches) to coastal areas of the Northeast and mid-Atlantic region early this week, and generally up to a foot of unusually late-season snow across the higher terrain of west-central Pennsylvania, western Maryland, extreme eastern West Virginia, and portions of western New York. Even higher snowfall accumulations were reported over very localized areas. Towards the Atlantic coast, light to moderate rain fell for a 24-36 hour period, with most of it going right into the dry soils, and not as runoff into streams and rivers. As a result, stream flow gauges showed little rise overall, despite the impressive precipitation amounts. The precipitation departures from normal (DNP) during the past 60- and 90-days over this region are between 2-6 inches and 4-8 inches, respectively. Parts of the drought depiction in the Northeast and mid-Atlantic were scaled back to highlight improvement, especially along the coastal areas. In some cases, if the offsetting 60- and 90-day DNPs were not too large, a 1-category improvement was made.
The Southeast: During the past week, light to moderate rain (less than 2 inches) fell across a large portion of the Southeast, with heavy precipitation (2 inches or greater) observed near the spine of the southern Appalachians, a few locations over the coastal plain, and also over a significant portion of Florida. Though rainfall coverage was good across North Carolina, the stream flows apparently have not responded in tandem, suggesting no modifications to the state’s drought rendition. In South Carolina, showers and thunderstorms provided much needed rainfall to crops and pastures. Soil moisture conditions improved slightly to 9 percent very short, 39 percent short, 51 percent adequate, and 1 percent surplus. The average temperature for the state during this period was 3 degrees above normal with 6 days suitable for field work. The drought depiction was not altered. Minor trimming of the abnormal dryness (D0) region in northeast Georgia was performed, due to weekly rainfall amounts of 3 or more inches. The elimination of D0 conditions was applied to the counties of Habersham, White, Lumpkin, Union, Towns, and Rabun – all in far northeast Georgia.
Recent rainfall has also warranted a 1-category upgrade to much of southern Florida. One of the upgrades included removal of the extreme drought (D3) area in Glades County (west side of Lake Okeechobee). In northern Alabama, water demand from vegetation, higher sun angle, and low stream flows (lowest tenth of historical distribution) supported some southward expansion of D0 conditions.
The Ohio and Tennessee Valleys: During the past week, light to moderate rain (less than 2 inches) fell across the region. However, these amounts are not nearly enough to offset short-term deficits and increase the low stream flows. Accordingly, abnormal dryness (D0) was expanded across western and central sections of Kentucky and central Tennessee. Moderate drought conditions (D1) were also expanded in western Kentucky to include the Paducah area.
The Midwest/Northern Plains: A band of heavy precipitation (2 inches or greater) was observed from north-central Iowa into southern Wisconsin. Widespread moderate precipitation (0.5 to 2 inches) was observed across most of the remainder of Iowa, Wisconsin, and southern Minnesota. One-category improvements were made in southeast Minnesota, and the northeastern quarter of Iowa. In southern Minnesota, the topsoil moisture situation has improved, while the remaining drought concerns focus on subsoil moisture and surface hydrology. The precipitation deficits currently in place are primarily attributed to deficits accrued from August through October of last year. Therefore, southern Minnesota’s drought impact designation has been changed from short-term (S) to long-term (L).
In eastern South Dakota, D0 conditions were removed from the counties of Sanborn, Miner, and Hanson, which is consistent with the recent precipitation. Elsewhere, in central South Dakota, lingering D0 conditions were removed, while in the drier western portion of the state, the D1 region was expanded and connected to the D1 area in western North Dakota. In west-central Illinois, little rainfall resulted in the merging of the D0 area with neighboring southeastern Iowa, and D0 was expanded across several counties in the southeastern corner of Iowa. These expansions of abnormal dryness (D0) are supported by 60- day and 90-day DNP. D0 conditions were also extended eastward from Illinois across northwestern Indiana, based on similar conditions to those in Illinois and southeastern Iowa. Stream flows across northwestern Indiana are mostly within the lowest ten percent of the historical distribution.
In northwest Missouri, recent dryness has been especially pronounced around the Kansas City area, extending into neighboring parts of eastern Kansas. Pending what rainfall occurs this week, D0 may need to be introduced next week. The same is true for portions of the Missouri Boot-heel (portions of Mississippi, New Madrid and Pemiscot Counties) where less than 1-inch of rain has fallen so far this month. If this dryness persists, it will likely impact regional cropland irrigation. Temperatures during the past 7-days have averaged between 2 degrees below normal to 2 degrees above normal across the Corn Belt region.
Central and Southern Plains: No alterations were made to the drought depiction in Oklahoma this week, while the small sliver of lingering D0 in extreme northwestern Louisiana was eliminated. Notable improvements were made in Texas, especially the Coastal Bend and far southern Texas. In addition, some of the D0 in east Texas has retreated, while some trimming of extreme drought (D3) and exceptional drought (D4) areas was also performed in the Panhandle. The dominant impacts across most of the state are considered to be long-term (L). The small patch of SL (both short- and long-term impacts) denotes where rice farmers have had their water allocation curtailed. Insufficient recharge so far this year (and inadequate rainfall in central Texas in 2011) has led to drastic reduction in rice yield, with no migratory waterfowl thriving in the rice patties as before. This is a case where remote long-term drought leads to local short-term drought impacts.
The West: Severe drought (D2) expansion appears warranted across central portions of Utah. The D2 areas in both eastern Nevada and western Colorado were therefore merged across central Utah. SNOTEL Snow Water Equivalent (SWE) values in this area generally range from 10 to 35 percent of normal. In east-central New Mexico, D3 conditions were extended northward across Guadalupe County. The drought depiction in south-central New Mexico was degraded by one category (from D1 to D2 conditions) to better reflect the unusually warm and dry conditions which have prevailed across the region. A slight improvement was made in far western New Mexico (D2 to D1).
Additional degradation (from last week) was made across northeastern Arizona and extreme northwestern New Mexico, with a slight eastward extension of D2 across this area. The situation across northeastern Arizona justifies a D3 designation, and is supported by longer-term deficits. Deteriorating drought conditions across southeastern parts of the state support the change from D1 to D2. In southwestern Colorado and nearby southeastern Utah, moderate drought conditions (D1) were expanded based upon 60-day SPI’s (ranging from -1 to -1.5) and 6-month SPI’s (near -1). The rains that fell over California several weeks ago have helped to alleviate drought conditions across the Sacramento Valley, justifying removal of the D2 area.
Hawaii, Alaska and Puerto Rico: Windward locations of the Hawaiian Islands generally received 1-3 inches of precipitation during the past 7-days, while leeward locations reported little if any rainfall. Stream flows across the state are currently near to above normal. No changes to the drought depiction for Hawaii were deemed necessary this week. There were no drought conditions noted in Alaska or Puerto Rico.
Looking Ahead: Over the next five days (April 26-30), a cold front will move across the Pacific Northwest and northern Rockies, while a slowly meandering front is predicted to stretch from the southern Great Plains eastward to the southern Atlantic coast. Heavy precipitation (2 inches or greater) is forecast across portions of South Dakota, Nebraska, and the middle Ohio River Valley, which will help to alleviate drought conditions in those areas. Moderate amounts of precipitation (0.5 to 2 inches) are anticipated over parts of California, eastern Montana and much of North Dakota, the middle Mississippi Valley, the mid-Atlantic region, northern New York, northern New England, and southeastern parts of Florida. Light precipitation (less than 0.5 inch) is predicted across most of the Southeast, Texas, the central and southern Rockies and Colorado Plateau, and the Great Lakes region, while most remaining areas are likely to receive little if any precipitation.
The CPC 6-10 day forecast (May 1-5) shows favorable odds for above median precipitation over the Midwest, the Pacific Northwest, extreme southern Florida, southeastern Alaska, and the Alaska Panhandle. Odds for below median precipitation are elevated over the Atlantic Coast states, the Southeast, the Southwest as far north as Idaho and Wyoming, and west-central Alaska. Warmer than normal temperatures are favored over most of the lower 48 states, with the highest probabilities (60 percent) centered over the Corn Belt region. Cooler than normal temperatures are favored over the Pacific Northwest and most of Alaska.
Author: Anthony Artusa, Climate Prediction Center/NCEP/NWS/NOAA
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, typically <6 months (e.g. agricultural, grasslands)
L ... Long-Term, typically >6 months (e.g. hydrology, ecology)