Weather Summary: Showers and thunderstorms from a cool front brought areas of rain to parts of the northern and central Plains, Midwest, and Northeast during this U.S. Drought Monitor (USDM) week. The rain provided little relief to the central Plains to Ohio Valley, where deficits over the last 6 months ranged from 4 to 10 inches and locally over 12 inches. Early in the week, the remnants of an old cool front triggered showers and thunderstorms from the southern Plains to the Southeast. Pacific fronts brushed parts of the Northwest, but the week was dry for most of the West. Temperatures averaged below normal beneath upper-level troughs in the Northwest and along the Eastern Seaboard and Gulf Coast states, while above-normal temperatures dominated from the Southwest to Great Plains and Great Lakes. It was a drier-than-normal week for much of Alaska, Hawaii, and Puerto Rico.
The East: Locally heavy rains (2+ inches) were enough to eliminate the D1 (moderate drought) in southern New Jersey and contract the New Jersey-Maryland-Delaware D0 (abnormally dry area) and western New York D0. The remaining D0 in eastern Pennsylvania (around Philadelphia) was reshaped to better reflect precipitation deficits.
In the Southeast, improvement was made to the depiction from northeast Florida to southwest South Carolina due to beneficial rains this week which followed the Gulf Coast deluge from last week. Rainfall surpluses for the last 90+ days resulted in generally a 1-category improvement of the D0-D2 (severe drought) across this area. D2 was contracted in east-central Florida, and D3 (extreme drought) was trimmed in eastern Alabama. But D0 was expanded in southwest Florida and west central Alabama, and D3-D4 (exceptional drought) expanded in the vicinity of Augusta, Georgia where deficits continued to grow. Augusta still suffered from its driest rolling 365-day period (June 20, 2011 to June 19, 2012) ever on record (with 25.57 inches of precipitation, or 19.16 inches below normal) and driest 2-year period (June 20, 2010 to June 19, 2012) on record (57.41 inches of precipitation, or 32.05 inches below normal).
The Midwest: Very dry and abnormally warm weather during spring tapped moisture reserves across the Midwest. The percentage area of Midwest states having short or very short (dry or very dry) topsoil and poor to very poor condition pastures and rangeland jumped significantly (10 to 20 points) compared to the previous week. According to June 17 reports from the U.S. Department of Agriculture (USDA), more than two-thirds of the topsoil was short or very short in Illinois (70%), Arkansas (71%), Ohio (77%) Missouri (82%), and Indiana (85%), while a third or more of the pasture and rangeland was in poor or very poor condition in Illinois (33%), Indiana (41%), Missouri (47%), and Arkansas (56%). Streams were low, ponds were shrinking, and crops were stressed across much of the area. The USDM drought depiction showed deteriorating conditions across the region. D0 expanded eastward to eastern Tennessee, western Virginia, West Virginia, Pennsylvania, and the westernmost county in Maryland, and northward further into Lower Michigan. D1 spread across most of Missouri, Illinois, and Indiana, expanded in Ohio, Kentucky, and Tennessee, and crept further into Iowa. D2 engulfed most of Arkansas and advanced in southern Missouri, Illinois, and Indiana, and in western Kentucky and Tennessee. Islands of D2 appeared in northern Missouri and Indiana as well as central Illinois. And an area of D3 was introduced along the confluence of the Ohio and Mississippi rivers. This week was generally drier than normal, but in the midst of this drought depiction deterioration, heavy showers and thunderstorms dropped notable amounts of rainfall in local areas. While not enough to make up for months of deficits, rainfall amounts of 2 inches or more locally held the drought expansion at bay in parts of Iowa, Missouri, Illinois, Indiana, Ohio, and Kentucky. A large area of SL impact type was introduced to reflect the combination of short-term (agricultural) and longer-term (hydrological) impacts.
Widespread heavy rains moved across the Upper Mississippi Valley, with 3 inches or more reported in southeast Minnesota and adjacent Wisconsin. D0 was pulled back here where the heaviest rains fell.
The Plains: Bands of heavy thunderstorms moved across southeast Nebraska to south central Kansas, northern and eastern Texas, and parts of North Dakota. In the central Plains, the 3+ inch rainfall dented the D0 in southeast Nebraska and the D2 in north central Kansas, and improved soil moisture conditions from really bad to not as bad. Half or more of the topsoil was rated short or very short in Texas (56%), Kansas (62%), and Nebraska (63%), and nearly half (48%) of the pasture and rangeland in Kansas was rated poor to very poor. But otherwise the rains simply held at bay any further deterioration. The rest of the central Plains was not as fortunate. D0-D2 expanded across the rest of Kansas to South Dakota, where dry (short to very short) topsoil jumped to half (50%) of the state. To the north, locally heavy rains eased drought conditions in part of southwest North Dakota, but the rains missed the other end of the county, so D0 and D1 expanded in Slope, Bowman, and Golden Valley counties.
In the southern Plains, the patchwork of thundershowers resulted in expansion of some D0-D2 and contraction of other D0-D3 in parts of Texas. D0-D2 expanded in Oklahoma, with D3 expanding in the Oklahoma panhandle and into southwest Kansas. The impact boundaries were also adjusted in the southern and central Plains to reflect the changing nature of hydrological and agricultural (long-term and short-term) impacts.
The West: Scattered showers dropped an inch or less of rain in the vicinity of Tucson, Arizona, and in the southern and central Rockies, and showers brought rainfall across Montana (mostly northern Montana) and the northern portions of the Pacific Northwest. But with essentially no rainfall for much of the West this week and large wildfires burning from California to Wyoming, changes mostly involved deterioration of the drought depiction. D0 expanded in Montana and adjacent Idaho, with D1 introduced in southeast Montana. D0-D3 expanded in Wyoming, and D1-D3 grew in Colorado and Utah. D2-D3 grew in northwest New Mexico. Growing numbers of dead livestock, drying wells, and communities without water prompted expansion of D1-D3 in Arizona. More than two-thirds of the topsoil was rated short to very short in Wyoming (71%), Colorado (79%), and New Mexico (95%), and half or more of the pasture and rangeland was rated poor or very poor in Nevada (55%), Colorado (58%), Wyoming (59%), California (60%), Arizona (67%), and New Mexico (85%). The impact boundaries were adjusted northward to reflect growing short-term and long-term impacts.
Hawaii, Alaska and Puerto Rico: Below-normal precipitation at time scales ranging from 7 days (this week) to the last 6 months, combined with low streamflows and the development of three large wildfires, prompted the addition of an area of D0 to northwestern Alaska. Showers dropped generally an inch or less of rain across the Hawaiian Islands this week, with most stations averaging below dry season normal, but no change was made to the drought depiction. The week was drier than normal across eastern and northern Puerto Rico. This pattern holds for the month to date, but streamflow was generally near to above normal, so Puerto Rico remained drought-free.
Looking Ahead: During the June 21-25, 2012 time period, the Pacific Northwest coast, the central Plains to western Great Lakes, the mid to northern Atlantic Seaboard, Deep South Texas, and much of Florida can expect the highest probability of precipitation. Temperatures are forecast to be above normal from the intermountain West to the Great Plains and Southeast. For June 26-July 4, below-normal precipitation is expected across most of the West, southern and central Plains, Midwest, and mid-Atlantic states, with wetter-than-normal conditions expected in the northern Plains, New England, Florida, and from monsoon showers in the Southwest. Above-normal temperatures are predicted for most of the country except the west coast early in the period and the Northeast. Wetter-than-normal conditions are expected for southern parts of Alaska, warmer-than-normal for the northeast, and cooler-than-normal for the southern and western coastal areas.
Author: Richard Heim, National Climatic Data Center, 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)