A powerful Arctic cold front will collide with rich Gulf of Mexico moisture to bring a plethora of wintry mess to the Gulf Coast before continuing on to the Georgia and Carolina coasts. Behind the frontal passage this evening, temperatures will quickly plunge into the 20s and 30s along the Gulf Coast between Houston and the Big Bend of Florida. A disturbance in the jet stream will rotate through the area on Tuesday, providing ample lift to generate a wintry mess of snow, sleet, and freezing rain.
Northern Gulf Coast
One of the trickiest aspect of a winter storm forecast this far south is to figure out just exactly how the warm sea surface temperatures will affect the coastal temperatures and precipitation types. Water temperatures along the northern Gulf Coast are in the 50s, which is plenty warm enough to impact the precipitation type at the coast. Models are currently showing that the snow/freezing rain line will be well north of the Gulf Coast on Tuesday evening, situated roughly along a line from Lake Charles, LA to Hattiesburg, MS to Columbus, GA. With the timing of the precipitation, I would expect coastal areas to see primarily sleet and freezing rain, since the precipitation should end at the coast before the mid levels of the atmosphere get cold enough to change the precipitation over to snow.
The coastal locales that are most likely to see snow are the areas between New Orleans, LA and Pensacola, FL. Atmospheric profiles may get cold enough for a change over to snow to occur shortly before the precipitation ends, so any accumulations will be minimal, if they occur at all. Coastal snow could fall as far east as Panama City, FL. The window for snow at the coast appears to be between 9 PM CST Tuesday and 3 AM CST Wednesday.
Further inland, areas along and north of Interstate 10 are much more likely to see accumulating snow. Atmospheric profiles there will be cold enough for it to snow, and with a driving north wind, those areas will not be affected by thermal radiation coming off the warm waters of the Gulf. Models are currently show a 1 to 3 inch swath of snow accumulations falling between Slidell, LA and Pensacola, FL. That swath is surrounded by an area of up to 1 inch accumulations between Baton Rouge, LA and Fort Walton Beach, FL, extending up into southeast Alabama and southwest Georgia. Snow could fall as far north as a line from Houston, TX to Jackson, MS to Birmingham, AL. Temperatures will quickly warm later in the week, so any snow and ice accumulations will not last very long.
Georgia and The Carolinas
The North and South Carolina coasts appear to be on tap to absorb the brunt of this storm. Atmospheric profiles along and north of a line from Savannah, GA to Panama City, FL should be cold enough for precipitation to fall as snow. The winter storm will have plenty of moisture available after tapping into the Gulf of Mexico moisture, but it will also have an ample supply of moisture available off the southeast coast, especially with the Gulf Stream so close by.
Soundings along the Carolina coasts are textbook winter weather soundings. There will likely be a warm layer around 4,000 feet over the South Carolina coast when the precipitation first starts falling, so it may start as sleet and freezing rain before changing over to snow. Over North Carolina, however, all layers will be below freezing from the outset, so it may start as a wintry mix before changing over to snow. Any sleet and freezing rain that falls will reduce snow totals, which could greatly affect snowfall totals in the Carolinas.
Models are currently showing that the coastal snow will fall between Savannah, GA and the southern tip of the Delmarva. Unlike the northern Gulf Coast, the duration of the precipitation will be much longer on the Carolina coast. Precipitation should really start cranking up around 7 or 8 AM EST on Tuesday and should last for about 24 hours. Models are showing impressive snowfall totals for the coastal areas, but I think they may be a little agressive. Some areas between Wilmington, NC and the Pamlico River could see up to a foot of snow, but I would expect to see most totals in the 4 to 8 inch range. Snowfall totals between 2 and 8 inches are possible between Charleston, SC and the North Carolina/Virginia border.
Further, inland, areas east of Interstate 95 between Richmond, VA and the South Carolina/Georgia border could see 2 to 6 inches, and 1 to 2 inch totals are possible across much of the remaining areas of North Carolina, South Carolina, and northeast Georgia. Just remember that there are a lot of variables in play for these complex forecasts, so the duration of any freezing rain and sleet that falls will have a significant impact on snowfall totals. This is one of those storms that could be a big snowstorm or a big ice storm, so stay tuned to your local news or weather bureau for the latest information.