U.S. Drought Monitor Report for the Week Ending April 9 (Text)
By Apr 11, 2013-
Weather Summary: An active weather pattern, with several fronts and storm systems traversing the lower 48 States, brought welcome precipitation to much of the Nation, and particularly the Plains. Decent precipitation (2 to 6 inches) returned to the Northwest, with 1-2 inches as far south as central California and the Sierra Nevada. Two separate storm systems, one in the Midwest and one in the South, dropped light to moderate precipitation on both areas earlier in the week. As the period ended, a potent storm system located over the central Rockies had already produced beneficial precipitation in parts of the north-central Plains and western Corn Belt, with more rain and severe weather possible for the eastern half of the U.S. during the next few days. Unfortunately, little or no precipitation fell on the Southwest, northern Plains, and Northeast, although the latter area was expecting precipitation this week. After a cold start to the period in the East and a mild one in the West, temperatures began to moderate as the week ended. In Alaska, dry and cold conditions enveloped the state except the southeastern Panhandle, while Hawaii was mostly dry with some light windward showers. Puerto Rico experienced scattered light showers during the week. The Northeast: With another week of little or no precipitation (less than 0.5 inches), deficits accumulated during the past 90- (2 to 4 inches) to 180-days (4 to 8 inches) continued to grow. However, with temperatures averaging 2 to 4 degrees F below normal, the growing season not yet started, snow still covering parts of western New England, and most streams running near normal, only a slight expansion of D0 was added where the deficits were the greatest. This included western New York, along the Vermont and New Hampshire border, and in central Pennsylvania. The latter state will be closely monitored as USGS stream flows have dropped below the tenth percentile. Deficits also existed in Maine, but with much of this state still snow covered, soil moisture will be assessed once the snow melts and the ground thaws. The Southeast: Much of this region received light to moderate precipitation (0.5 to 1.5 inches), with a few areas (southern sections of Louisiana, Mississippi, Alabama, and Florida) recording over 2 inches of rain. With the wet pattern continuing across Georgia since late January, additional removal of D1 and D0 were made in central and eastern sections as 3-, 6-, and 12- month surpluses were common in these areas. The April 9 NASS/USDA statewide topsoil (subsoil) moisture for Georgia was rated 2 percent (7 percent) very short to short, 67 percent (71 percent) adequate, and 31 percent (22 percent) surplus. In addition, stream flows, soil moisture models, CMI and PDI, and SPI indices were all near normal to moist. Where medium- to long-term deficiencies persisted, D0 and D1 remained, mainly in east-central and coastal Georgia. Farther north, where 3-month totals have been lower than Georgia, conditions were unchanged. In Florida, extreme southern sections measured 2 to 3 inches of rain, improving conditions by one category. In central and northern Florida, 0.5 to 1.5 inches of rain were not enough to make a significant dent in the 60- (3 to 6 inches) to 90-day (5 to 10 inches) departures, hence no improvement was made. USGS stream flows remained below the tenth percentile in north- central Florida. Farther west, heavy rains (more than 2 inches) along the Gulf Coast erased abnormal dryness in parts of southeastern Louisiana and southern Mississippi; however, lighter rains (0.5 inches) in southern Alabama increased short- term deficits, and D0 was expanded slightly eastward. The Midwest: Light to moderate precipitation (0.5 to 1.5 inches), with pockets of heavier amounts (more than 2 inches), fell across the western Corn Belt, providing some relief in areas where there was no snow cover and the soil had thawed. To back this, NWS frost tubes showed that the last of the frozen soils in northern and central Iowa had thawed, and that some farm tiles were running in eastern Iowa and northern Illinois, indicating more subsoil moisture than previously thought. Many USGS stream flows were in the upper 75th percentile. Accordingly, improvements included the removal of D0 in eastern Iowa, northern Illinois, and southern Wisconsin, D1 to D0 in east-central Iowa, and some slight improvement of D2 to D1 in central Iowa. In Missouri, the eastern edge of the D0 and D1 areas were slightly edged westward in response to 1 to 1.5 inches of rain and declining deficits. In contrast, soils north of this region still had some ice in lower soil layers, and snow remained on the ground in most of North Dakota and the northern halves of Minnesota and Wisconsin. The southern third of Minnesota was thawed to a depth of 12 inches, and will be reassessed next week to determine soil moisture infiltration amounts. Therefore, no changes were made to the upper Midwest this week. For Nebraska improvements, please refer to The Plains narrative. Lower Mississippi Valley/Delta region: Two bands of heavy rain (more than 2 inches) fell across the Delta, but in-between the rain, little or no precipitation fell. In central Arkansas, 1.5 to 2.5 inches of rain (and more extending into Oklahoma) was enough to reduce D0 and D1 by a category as 60- and 90-day small deficits shrunk or were eliminated. Another band of heavy rain fell along the Gulf Coast, easing drought in southeastern Texas and extreme southeastern Louisiana. In-between the bands, only 0.5 to 1 inch fell on northwestern Louisiana and southwestern Arkansas, maintaining D0 and D1. The Plains: Beneficial, soaking rains finally fell on badly- needed D2, D3, and D4 drought areas of hard-hit Texas, Oklahoma, and Nebraska, with more falling after the 12 GMT Tuesday cutoff. In Texas, 1 to 3 inches of rain was measured in north-central, central, and southeastern Texas, providing a one category improvement many areas. Unfortunately, little or no rain was observed in western and extreme southern Texas, and some degradation was made. In Oklahoma, a large band of heavy rain (2 to 5 inches) fell from central to southeastern parts of the state, resulting in a one-category improvement. Most other areas of the state received enough precipitation (0.5 to 1.5 inches) to maintain conditions. Kansas was unfortunately left out of the heavy rains, with most stations reporting under 0.5 inches. In extreme northeastern Kansas, however, a small band of heavier rain (1.5 to 2.5 inches) was enough to diminish deficits and ease drought from D2 to D1. Farther north, long overdue widespread and heavy rains finally fell on much of north-central Plains, especially from the southwestern Nebraska northeastward into southeastern South Dakota. Most locations reported 1.5 to 3 inches of rain, and a significant number of them likely received their greatest 24- hour totals in the past 12 months. According to the Nebraska State Climatologist Al Dutcher, all soil moisture sites in this area have hit 25 percent for the 4 foot layer, and 20 percent for the top 5 five foot. By next week it will become apparent how deep the moisture made it into the profile. Based upon past experiences, it is likely that field capacity will be reached in the top 2 feet of the profile at most locations. But due to the prolonged and severe drought, there is no deep moisture, but moisture is available to support planting and early emergence. Even with the April 9 rains, 12-month deficits still stood at: 10.59 inches at North Platte; 9.31 inches at Valentine; 16.59 inches at Broken Bow; and 6.55 inches at Imperial. And it will take substantial additional moisture to improve drought conditions further. Some reanalysis may occur next week as the full extent of the precipitation associated with this event can be examined. This event was a good start to the northern and central Plains rainy season which normally occurs from April into August. Similarly, some improvements were made farther north in western South Dakota and eastern Montana as 0.5 to 1.5 inches of precipitation reduced deficiencies. This area will also be reassessed next week as additional precipitation fell after the 12 GMT Tuesday cutoff. And lastly in North Dakota, snow covered ground and frozen soils meant status-quo for this state. The Rockies and Intermountain West: Light to moderate precipitation (0.5 to 2 inches) fell on the northern and central Rockies and Intermountain West, with little to no precipitation measured in southern sections. Temperatures averaged above normal throughout the region. In general, enough precipitation fell to keep conditions status-quo, with a few exceptions. In northeastern Utah, the Uinta Mountains received between 1 to 2 inches liquid equivalent, which was enough to improve from D2 to D1. In southwestern Montana, 90-day subnormal precipitation warranted the expansion of D1 and D2, with WYTD basin average precipitation declining to 87 percent of normal and SWC at 85 percent of normal. Elsewhere, conditions remained the same, with the exception of modifying the Impact lines to better reflect the short-term dryness in the Far West and more medium-term impacts (both short and long term) elsewhere. The Far West and Southwest: Moderate to heavy rains (2 to 6 inches) fell west of the Cascades, from northern California northward to the Canadian border. In the Sierra Nevada, 1 to 2.5 inches of precipitation occurred, but the Water Year-to-Date (WYTD) average basin precipitation was still between 74 to 86 percent of normal, and the April 9 basin average snow water content (SWC) between 37 to 49 percent of normal. Values were better farther north in southern Oregon, with the southern Cascades WYTD precipitation close to normal, and SWC between 63 to 74 percent of normal. With the heavy rains, D0 was removed from much of southwestern Oregon and extreme northwestern California, although some short-term deficits still remain due to a dry January-March. However, since October 1, WYTD precipitation is close to normal thanks to a very wet November and December. Recent and WYTD precipitation was also enough to make improvements in northwestern Nevada/ northeastern California/southern Oregon (D2 to D1), and D0 removal in northeastern Oregon. Farther south, little or no precipitation and warm weather aided deteriorating conditions in parts of the Southwest. In Arizona and New Mexico, growing deficits in southwestern, southeastern, and northeastern Arizona, and central New Mexico expanded D1-D3 drought. Since early October, precipitation has been less than half of normal in eastern Arizona and much of New Mexico, and the same hold true at 12-months. As a result, drought worsened in Yavapai and Maricopa Counties in southwestern Arizona, and most of southeastern Arizona was degraded to D2. D3 was expanded into northeastern Arizona (Apache County), and increased in size in western and southern New Mexico. Amazingly, central Arizona was close to normal as the WYTD basin precipitation was between 85 to 97 percent of normal. Unfortunately, reservoir storage as of April 1 was below average in Arizona, New Mexico, and Nevada. Hawaii, Alaska, and Puerto Rico: In Hawaii, although most locations received little or no rain during the week (except for 0.5 to 1 inches on windward sites on Oahu, Maui, and the Big Island), solid March rainfall (150 to 200 percent of normal) on northeastern Kauai eliminated the D0 there. On Maui and the Big Island, the windward slopes have been unseasonably dry recently, thus D0 was added to the rest of those islands. On Molokai, the current D2 area for low reservoir levels at Kualapuu Reservoir was eased from 30 percent to 20 percent cutback, but since this is still a significant reduction, D2 remained. Although the level is 4 to 5 feet higher than a year ago, it’s currently at 21 feet, and the maximum capacity is 51 feet. In Alaska, cold and dry weather, except in the southeastern Panhandle (2 to 3 inches), maintained conditions there. In Puerto Rico, widespread light showers (0.5 to 2 inches) were enough to maintain conditions but not improve them. Looking Ahead: The next 5 days (April 11-15) are expected to be wet across much of the eastern half of the U.S., with the greatest totals (more than 2 inches) forecast for the South and lower Great Lakes region. Light to moderate precipitation should fall along the Pacific Northwest Coast and in the northern Rockies. Much of the Southwest and High Plains will be dry. Temperatures should average below normal across the northern third of the U.S., especially in the northern Plains and upper Midwest, while above-normal readings are expected in the Southwest and Southeast. For the ensuing 5 days (April 16-20), the odds favor above- normal precipitation in the eastern half of the Nation and the north-central Plains. Drier-than-normal weather is forecast for the West, Southwest, southern Florida, and Alaska. Temperatures are expected to be similar to the Day 1-5 forecast, with odds favoring below-normal readings in the North-Central States, and above-normal temperatures in California and the eastern Gulf and southern Atlantic States.
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