Blinding, wind-swept downpours will plague the Southeast this weekend as a storm develops in the Gulf of Mexico and slowly treks toward the Atlantic Ocean. The onset of the storm in Florida and parts of the Deep South this weekend will coincide with the departure of millions of Americans traveling to holiday destinations. The intensifying storm is expected to bring gusty winds up to 50 mph and rainfall totals as high as 8” in the hardest-hit areas.
The storm will organize much like Nor’Easters common along the Northeast Coast this time of year. A robust jet stream is supplying a deep pool of relatively cold air toward the warm Gulf of Mexico. The Gulf’s surface temperatures, while warm, are too cool for the development of a tropical cyclone. Bands of heavy precipitation will develop ahead of a cold front and compose a shield of precipitation north of a warm front as a conveyor belt of warm air ascends above cooler air in the Deep South to the north of the low. Unlike most Nor’Easters however, this storm will be slow-moving and have access to deep tropical moisture. The result will be days of heavy, wind-swept, torrential rain. Flooding and travel delays are inevitable.
The rain will commence Friday night as scattered showers gradually organize and intensify through Saturday in southern Louisiana, Mississippi, Alabama, and the Florida panhandle. Winds will be on the rise as cloud ceilings begin to fall Saturday afternoon. The dreary weather will make for poor driving conditions and could result in flight delays from cities like Pensacola, Mobile, and New Orleans. Fortunately, travel delays are expected to be minor Saturday. Our Roads Conditions Index only reaches maximum Values between 2 and 3 out of 10 on the Florida Panhandle and southern Alabama as demonstrated by this snippet from our new Impact Portal, suggesting low risks to driving safety with some delays possible. It won’t be until Sunday when the weather truly deteriorates.
Travelers bound for Florida’s beaches and amusements will not find the warm and sunny weather that they may have anticipated. While Saturday will be salvageable on Florida’s peninsula, Sunday’s blinding downpours and gusty winds will likely sour any outdoor activities. Conditions will begin deteriorating across the Peninsula starting late Saturday evening as the low-pressure system develops a complete circulation and expands its field of downpours.
The heavy rain will impact many of Florida’s biggest metropolitan areas including Tampa Bay, Orlando, Jacksonville, and Tallahassee. Downpours will be less frequent in South Florida, but Miami-Beach goers will still find their sun-bathing interrupted by high surf, gusty winds, and intermittent heavy showers. Flight delays will be inevitable throughout the day Sunday across most of the state due to low cloud ceilings, low visibility, and high winds. Peak impacts in Florida will persist through Sunday evening.
The overall worst travel conditions Sunday afternoon and evening however, will be in Georgia, Alabama, and South Carolina. Here, the deluge will spread north Sunday afternoon and evening as it begins to decline on the Florida peninsula. Our Roads Conditions Index reaches a maximum value near 6 at 6pm in local areas near Birmingham, indicating a moderate danger to driving due to low visibility from blinding downpours and areas of flooding.
The coastal Southeast from Brunswick, GA to Morehead City, NC will take the brunt of the winds and rain Sunday night through early Monday afternoon as the low incrementally treks into the Atlantic Ocean. Winds here will be on the rise as the storm accelerates its intensification off-shore Monday. Its slow eastward departure will keep lingering showers around coastal areas as far north as Wilmington, NC until Monday evening.
Coastal impacts will linger long after the rain stops falling and spread as far north as Virginia Beach as the low churns the tides and delivers strong winds. Further south, rain may end on Florida’s east coast Monday morning, but winds will gust as high as 50 mph along the immediate coast as far south as St. Augustine Monday afternoon. Though the rain may have cleared by Tuesday, strong winds will persist. Unfortunately for beach-goers, so too will the rip tides along most of the Southeast coastline.
Rain chances will end everywhere in the Southeast by Tuesday morning. Over a month’s worth of rain will have fallen by then. Widespread rainfall totals of 2-3” are expected as far north as the I-20 corridor, including cities like Birmingham and Atlanta. Rainfall totals will incrementally rise further south and east, with rainfall totals of 3-5” common in far southern South Carolina, southern Georgia, southern Alabama, and northern and central Florida. Closer to the I-10 and I-95 corridors, rainfall is expected to be even more dramatic, where locally up to 8” of rain could fall.
Excessive rainfall amounts of 8” alone would be enough to result in a substantial flood risk. But the flood risk is particularly elevated because parts of the Southeast have already recently been inundated with heavy rain. Parts of central Georgia and central South Carolina have observed over 6” of rain in just the last seven days. While the 8” bullseye is not expected to impact these areas, an additional 3-4” of rain in quick succession as expected is nonetheless likely to agitate ongoing river flooding and quickly result in new flooding. Our Flood Index reaches a maximum value of 7 near Charleston, SC Monday as can be viewed in the progression of our Flood Index in the gif below for the Southeast US between 8pm EST Saturday and 6am EST Tuesday.