Ag Weather Forum

Dryness Increase for Early May

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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At the end of April, the U.S. Drought Monitor noted abnormal dryness in growing areas of the Northern and Central Plains, with drought deepening in the southwest Plains. (NDMC graphic)

In sharp contrast to 2019, dry conditions are a bigger part of the crop environment going into late spring 2020. Here's the description from the Drought Monitor for the end of April.


An active pattern of storms brought cold, wet weather to the Northeast, rain and locally severe thunderstorms to parts of the South, lower Midwest, and Southeast. Drought areas along the western Gulf Coast missed the heaviest rains, while those in the eastern half fared better. A ridge of high pressure over the West kept conditions warm and dry.


A series of weather systems brought cold, wet weather to the Northeast, keeping the region free of abnormal dryness and drought. A dip in the jet stream allowed an influx of cold air into New England and the Mid-Atlantic, setting record daily low temperatures and bringing snowfall to the northern tier and high elevations in the region. The week ended with mean temperatures ranging from 3 to 10 degrees below normal and precipitation totals ranging from less than 0.3 inches (less than 50% of normal) across the northern part of the region to more than 2 inches (greater than 200% of normal) across the southern part.


The Southeast saw locally heavy rainfall and thunderstorms with parts of Georgia, Alabama, and Florida receiving upwards of 5 inches of rain. Average temperatures generally ranged 1 to 3 degrees below normal, with the exception of Florida, which saw temperatures of 2 to 5 degrees above normal. The rain helped improve the abnormally dry (D0) areas near the border of Alabama, Georgia, and Florida.

In the Florida Panhandle, the rain finally was enough to help reduce moisture deficits and improve streamflow, resulting in the removal of the area of severe drought (D2) that had been in place since mid-February. Other improvements in Florida include a broad one-category improvement across the northern and central part of the state as excess rain over the last two weeks erased deficits, replenished soil moisture and streamflow, and improved vegetation health. Southeast Florida saw small reductions in moderate and severe drought (D1 and D2) where more than 1.5 inches of rain fell and where precipitation, streamflow, and vegetation health indicators no longer supported the depiction.


The western half of the region saw warmer-than-normal average temperatures, with departures ranging from 1 degree above normal in eastern Iowa to 8 degrees above normal in western Iowa. In the eastern half, temperatures were 1 to 7 degrees below normal, with the greatest departures generally occurring in the Upper Great Lakes area. Precipitation occurred across much of the region with weekly totals generally between 0.5 and 1.75 inches. A band of 3 to 4 inches of rainfall stretched from southwest Missouri to central Illinois. The only change in the region to this week's map was a small reduction in abnormal dryness (D0) in Minnesota.


Temperatures across the High Plains were generally warmer than normal last week with departures of 2 to 6 inches above normal. Much of the region received less than 0.5 inches of precipitation. Exceptions included parts of eastern North Dakota, South Dakota, and Nebraska, with totals of more than 1 inch, and eastern Kansas, with amounts of more than 2 inches -- nearly 200% of normal. The warm, dry conditions led to an expansion of abnormal dryness (D0) in the Dakotas, southwest Nebraska, northwest Kansas, and eastern Colorado. Additionally, moderate and severe drought (D1 and D2) expanded over Colorado's eastern plains. This area has failed to receive the timely spring rains needed, resulting in reductions in soil moisture, streamflow, and vegetation health. Across the entire High Plains region, local drought experts are discussing the emerging dryness and closely monitoring the situation as planting begins and the need for moisture increases.


Locally heavy rain and thunderstorms fell across the eastern half of the southern region. The largest totals (4 inches or more) were recorded in Louisiana and Mississippi. Temperatures were near to below normal, with the largest departures (5 degrees below normal) recorded in Tennessee. For the most part, the rain either missed the drought areas near the coast or wasn't enough to warrant improvements in conditions, instead preventing degradations. The western half of the region generally saw little or no rain again this week. Weekly average temperatures ranged from 2 to 8 degrees above normal, with locations in south Texas setting daily record highs with temperatures reaching triple digits. The warm, dry weather continued to deplete moisture supplies, stress vegetation, and deteriorate drought conditions across parts of the Texas Gulf Coast, with expansions to moderate (D1), severe (D2) and extreme (D3) drought. Texas also saw improvements as localized rain improved soil moisture, vegetation health, and streamflow.


Most of the western U.S. received little to no rain, except for small pockets of the Pacific Northwest and the Southwest. Temperatures were generally above normal, with record-setting heat across parts of the Southwest and daily highs of 10 to 20 degrees above normal. The heat and dry weather led to deteriorating conditions across several states. In Oregon, severe drought (D2) expanded near Portland and in the north-central part of the state in response to drying soils, vegetation stress, and streamflow and groundwater declines. Precipitation for the water year ranks as the third driest in the Portland station's 89-year period of record.

In northern California, moderate drought (D1) expanded. While the state coordination committee noted that reservoir levels are acceptable, precipitation deficits are less 50% of normal for the water year, streamflow values are low, and rangeland grasses have been affected by the lack of moisture and heat. Likewise, parts of central Nevada also saw expansions to D1 and the introduction of D2 in response to increasing moisture deficits, declining streamflow and groundwater levels, and vegetation stress. The only improvements on this week's map included minor reductions in D1 in Oregon and D0 in Washington in response to locally heavy rainfall.

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