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Heavy Rainfall Along the Central Gulf Coast; Critical Fire Weather Conditions in Southern California

Heavy to excessive rainfall, and the potential for scattered flash flooding is forecast through midweek along portions of the Gulf Coast and into the Southeast. A Slight Risk (level 2 of 4) of Excessive Rainfall is in effect Monday and Tuesday. Damaging Santa Ana winds and very low humidity will result in Critical Fire Weather conditions Monday and Tuesday across Southern California. Read More >

Overview

Two strong winter storms moved through the Dakotas during late March and early April 2023, bringing with them heavy snow, icing in eastern SD and western MN, along with gusty winds.  They were both tied to a "Colorado Low", which is a low pressure system that develops east of the Rockies in Colorado and then moves through the Plains and into the Upper Mississippi Valley. While the process that created the storms was similar, there were differences in how each storm evolved.

The March 31st storm had the heavy snow falling over central and northeast SD (amounts over a foot in a corridor between Pierre and Ipswich) while there were winds gusting to 40 to 55 mph. This produced blizzard conditions over much of central and northeast SD during the day and evening on March 31st. In addition, ice accumulations of over a quarter of an inch were reported in Grant, Codington, and Deuel counties. 

The April 4-5th event on the other hand had the heavy snow falling on April 4th over central and northeast SD, with northeast winds of 15-30mph. The combination of the snow and the winds led to visibilities being frequently reduced below a mile and at times down to a quarter mile in central and northeast SD. Meanwhile, the initial snow over east central SD transitioned to freezing rain for a period of time during the late afternoon and evening hours before switching back to snow. As the snow came to an end on April 5th, the winds shifted around to the west-northeast and with gusts of 30-45 mph, led to blowing and drifting of the new snow.  

These two storms capped off an already snowy winter season. Such late-season abnormal cold and snow also set the stage for significant spring flooding for parts of northeastern South Dakota and west central Minnesota. 

View of Highway 47 in Faulk County after the March 31 event (Image from Faulk County EM)
View of Highway 47 in Faulk County after the March 31 event (Image from Faulk County EM)
Surface weather map for the March 31, 2023 Event Surface weather map for the April 4-5, 2023 Event Surface weather map for the April 4-5, 2023 Event Surface weather map for the April 4-5, 2023 Event
Surface weather map for the March 31, 2023 Event Surface weather map for the April 4-5, 2023 Event Seasonal snowfall totals as of April 9th, 2023 Snow depths across places such as Aberdeen and Sisseton were unprecedented for April. 
Surface weather map for the March 31, 2023 Event Surface weather map for the March 31, 2023 Event    
Satellite imagery on April 9th shows plenty of snow yet in place, as a quick melt continued.  The 2022-2023 winter season finished Severe to Extreme according to the Accumulated Winter Season Severity Index.    
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