The changing face of U.S. drought: shrinking but still sprawling

Drought across the Lower 48 in the last year has undergone wild swings.  From just regional pockets of drought last spring to one of the worst droughts on record last summer, drought has now begun an aggressive retreat.

Consider that in April 2012 just 37 percent of the contiguous U.S. was experiencing at least moderate drought conditions, a number that shot up over 63 percent by mid-summer.  Now it’s back down to 47 percent.

As the drought situation stands now, it’s a tale of two halves of the country. East of Mississippi river, most locations are in good shape water-wise. But west of the Mississippi, the hydrological circumstances deteriorate. A large area of extreme to exceptional drought conditions stretches from south Texas into the High Plains.


(U.S. Drought Monitor)

Animation of drought assessment every three months beginning in April 2012 (U.S. Drought Monitor)

Since the fall, the most radical changes have occurred in the Middle and Upper Mississippi River Valley where the hydrological state of affairs has flipped. A large part of this area, which received almost no rain last summer, is under flood warnings due to recent heavy rains and snowmelt. Climate Central conveys the remarkable reversal from the summer with the illustration below.


(Climate Central)

“Over eight months, runoff in the Upper Mississippi River Basin has jumped from way below average to extremely high – including near record levels in some locations. In August 2012, drought had left runoff in the bottom 10 percent,” Climate Central writes. “It was dry, even for the summer. Now, water levels are in the top 95 percent. Obviously April numbers are not final yet, but many locations have already broken their record rainfall for the month.”

What happens next?

If last summer’s flash drought and this spring’s step back teach us anything, it’s that long-term drought forecasting is difficult and not always reliable.

Link: Lack of Warning on Drought Reflects Forecasting Flaws (Climate Central)

In the near term, don’t expect much improvement in the drought situation in the most affected areas says the U.S. Drought Monitor:

Warmer- and drier-than-normal conditions will spread from the western U.S. eastward into the central and northern Plains.  In contrast, a slow-moving, upper-air low will bring wet, cool weather to the Southeast, although rain activity will subside in Florida.  Showers are also expected in central and southwestern Texas; however, the core Exception Drought (D4) areas of the central and southern High Plains will mostly miss the heaviest rainfall.  The [Climate Prediction Center] 6-10 day forecast for April 30 – May 4 calls for warmer- and drier-than-normal weather across much of the west, with dryness extending eastward into the central Plains.  In contrast, above-normal precipitation and near- to below-normal temperatures are expected across southern portions of the Rockies and High Plains and from the eastern Gulf Coast into the Great Lakes region.

In the longer term, the National Weather Service’s Climate Prediction forecasts some improvement  in the drought in the Upper Midwest and Plains. But drought persistence is the expectation in much of the West and Southwest, with perhaps new areas of drought developing in California


(National Weather Service)

Related post: Historic U.S. drought will continue into spring and summer, experts say

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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David Streit · April 25, 2013