This Week's Drought Summary (5/7)

May 7, 2020

A strong cold front progressed southeast across the Great Plains, Mississippi Valley, and Southeast on April 28 and 29. This cold front was a focus for a severe weather outbreak from Oklahoma and eastern Texas east to the middle and lower Mississippi Valley. As this front shifted south, heavy rain (more than 2 inches) fell from the western Gulf Coast east to the Florida Big Bend and Florida Gulf Coast. A summer-like ridge of high pressure aloft led to an early and persistent heat wave across southern California and the Desert Southwest during late April into early May. Much above normal temperatures also affected the southern Rockies and southern Great Plains. To the north of this upper-level ridge, multiple low pressure systems along a nearly stationary front resulted in occasional thunderstorms with locally heavy rain (1 inch or more) to the central Great Plains, middle Mississippi Valley, and Ohio Valley. Onshore flow led to a wet start to May across the coastal Pacific Northwest, but little to no precipitation was observed across the Great Basin. Surface low pressure, centered across the Gulf of Alaska, resulted in light to moderate precipitation amounts to the Kenai Peninsula, southeast mainland Alaska, and the Alaska Panhandle. Rainfall was generally suppressed across the tropical central and eastern Pacific, including Hawaii, during late April into the beginning of May. This dry pattern over the tropics extended east to Puerto Rico.


Heavy rainfall (1 to 3 inches) soaked areas from the mid-Atlantic north to southern New England on April 30 and May 1. This heavy rainfall triggered flash flooding and small stream flooding. According to AHPS, 30-day precipitation amounts totaled 5 to 8 inches from Maryland northeast to eastern Maine. 90-day precipitation has averaged 125 to 200 percent of normal across the mid-Atlantic and the central to northern Appalachians. This region remains drought-free due to these wet conditions at the 30 to 90-day time scale.


Locally heavy rain (2 inches or more) resulted in a decrease in moderate drought (D1) across the Big Bend of Florida. D1 was maintained in areas that received less than one inch of rain, roughly from Apalachicola to Tallahassee FL. 28-day streamflows remain low along the Sopchoppy and St. Marks Rivers in eastern Wakulla County. Widespread rainfall (0.5 to 3 inches) was observed across the central Florida Peninsula during the past week. Moderate short-term drought was reduced in areas that received more than 1 inch of rainfall. However, many 28-day streamflows remain below the 20th percentile across central and southern Florida. Meanwhile, severe drought continues to plague southwest and south Florida where the Keetch Byram Drought Index is high (above 550) in Collier, Broward, Miami-Dade, and Monroe Counties.


Heavy rain (widespread amounts of more than 2 inches) at the end of April prompted a 1-category improvement to parts of the western and northern Gulf Coast, including southern Louisiana and southeast Texas. This recent heavy rain resulted in precipitation surpluses during the past 30 days and normal (25th to 75th percentile) 28-day streamflows. However, dating back 6-months, large precipitation deficits (more than 8 inches) remain across southeast Louisiana and the along the Mississippi Gulf Coast. In contrast to the improving conditions across southeast Texas, drought coverage/intensity remained nearly steady or worsened slightly across south Texas. Abnormal dryness (D0) was expanded across the Texas Panhandle and northwest Oklahoma due to increasing 30 to 60-day precipitation deficits, above normal temperatures (highs well into the 90s and low 100s), and periods of strong winds during late April into the beginning of May. These indicators along with impact reports (poor pastures, low ponds, and poor winter wheat quality) support the introduction of a small D1 area in northwest Oklahoma.


The Corn Belt remains drought-free due to long-term precipitation surpluses, favorable soil moisture, and a cool start to spring (30-day temperatures averaging 2 to 4 degrees F below normal). A small area of abnormal dryness (D0) was decreased this week due to recent rainfall. The largest 30-day precipitation deficits (around 3 inches) exist across northern Iowa.

High Plains

Increasing short-term precipitation deficits, exacerbated by above-normal temperatures recently and high evapotranspiration rates, support an expansion of abnormal dryness (D0), moderate drought (D1), and severe drought (D2) across Kansas. 60-day precipitation deficits range from 2 to 4 inches extending from southwest Kansas northeast to north-central Kansas. Russell, KS received only 0.40 inches of precipitation during April which was the 2nd driest on record (dating back to 1950) for the month. Russell’s normal April precipitation is 2.62 inches. Abnormal dryness was reduced in coverage across parts of South Dakota that received more than 1 inch of rainfall at the beginning of May. Recent heavy rainfall (more than 1 inch) also brought a 1-category improvement to the high Plains of northeast Co