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Thu May 17, 2018, 08:15 AM

Drought Monitor 5/17; D4 Now In Contiguous Area From S-Central KS To N-Central AZ



Spotty heavy downpours brought localized drought relief to portions of Oklahoma and Texas, while dry, warmer-than-normal weather prevailed across the rest of the region. Locally heavy showers (2-4 inches) dotted drought areas from central Texas northward into western Oklahoma. Where rain was heaviest, reductions in drought intensity and coverage were made; however, considerable longer-term deficits remained, with the remaining Exceptional Drought (D4) areas reporting less than 25 percent of normal precipitation (locally less than 10 percent) over the past six months. Along the Gulf Coast, Abnormal Dryness (D0) was expanded eastward to reflect increasingly dry conditions over the past 30 to 60 days, while D1 and D2 were added in coastal locales where 90-day rainfall was less than half of normal. Farther inland, Moderate to Severe Drought (D1 and D2) were expanded in western Texas to reflect increasingly dry conditions at both the shorter term (60-day rainfall averaging 10 to 25 percent of normal) and longer time frame (6-month precipitation averaging less than 50 percent of normal, locally less than 25 percent).

Warm, wet weather in southern portions of the region compared with dry albeit cooler conditions farther north. A wide area of moderate to heavy rain (an inch or more) was observed from Missouri and Iowa eastward into the lower Great Lakes Region. Rainfall locally topped 2 inches, resulting in modest reductions in Abnormal Dryness (D0) and Moderate Drought (D1) across Missouri, Iowa, as well as northwestern Minnesota. However, the heaviest rain largely missed the lingering core drought areas, so overall the central Corn Beltís drought depiction remain largely unchanged. Farther north, increasingly dry conditions over the past 60 to 90 days (25-60 percent of normal) led to an expansion of D0 and D1 in northern portions of Minnesota and Wisconsin as well as the upper peninsula of Michigan, particularly in areas which reported less than 0.5 inch of rain during the 7-day period.

High Plains

The overall trend toward improving conditions in the south contrasting with increasingly dry weather in the north continued. From northeastern Colorado into central and southern Kansas, areas of moderate to heavy rain (1-3 inches) netted reductions in drought intensity and coverage. The most significant improvements were made in south-central Kansas, where a large area of 2 to 4 inches of rain (locally more) fell on areas of Severe (D2) to Extreme (D3) Drought. Moderate to heavy rain (1-3 inches) was similarly beneficial in northeastern Colorado, trimming the aerial extent of Abnormal Dryness (D0) and Moderate Drought (D1). Farther north, outside of locally beneficial downpours (1-3 inches) in northwestern South Dakota, acute short-term dryness over the past 30 days resulted in expanding D0 across southwestern South Dakota, southeastern North Dakota, and northeastern Montana, while a more prevalent dry signal over the past 90 days (50 percent of normal or less) led to expanding D1 and D2 in northeastern North Dakota.


utside of beneficial rain and high-elevation snow in the north, pronounced short- and long-term dryness led to drought intensification and expansion across the Southwest. In southern Idaho, Abnormal Dryness (D0) was removed from most locales north of the Snake River, as recent rain and snow have pushed Water Year (to date) precipitation at or above the 35th percentile. However, sub-par seasonal precipitation coupled with increasingly dry conditions over the past 30 days led to the expansion of D0 in northeastern Montana and Moderate Drought (D1) in southwestern Idaho. Abnormal Dryness was expanded westward across central and northern portions of Californiaís Coastal Range due to a sub-par water year coupled with increasingly dry conditions over the past 30 days (deficits of 2 inches or more, locally less than 10 percent of normal). Farther south, Severe, Extreme, and Exceptional Drought (D2-D4) were increased from southern California into much of New Mexico. Changes were most pronounced in eastern portions of the region, where Water Year precipitation was in the 2nd percentile or lower, particularly across the northern third of New Mexico. Satellite-derived vegetation health data indicated conditions have deteriorated rapidly across the region, with the worst vegetation indices with respect to normal noted from Arizona southeastward into southern New Mexico. Drought Monitor authors are in close contact with local and regional experts from the Southwest, and further detailed analysis will likely result in additional intensification and expansion of drought as the situation is assessed over the upcoming weeks.



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