Florida faces a once-in-a-century winter storm: Will snow or ice prevail?

North Florida is little more than 24 hours from the start of what could be the most devastating winter storm in Gulf Coast history.

And while uncertainty about the nature of precipitation in the Eastern Panhandle will likely reach extremes, colder trends aloft tend to tip the odds away from rain and toward a messy mix of ice, sleet and snow Tuesday night into early morning Wednesday morning tend to be.

Winter storm warnings, the first for Florida in seven years, are in effect from Pensacola to Gainesville and Jacksonville.

Looking at the meteorological setup, the seven keys I discussed on Thursday that are needed to square Florida’s snow circle are rotating simultaneously. In recent days, uncertainty regarding the presence of these components – Arctic air mass, triggering trough and storm track – has decreased.

That’s why both global and regional weather models have converged on a scenario that has few precedents in Florida’s weather history: one in which an impressive amount of precipitation falls, mostly in frozen form, from East Texas to Florida’s Big Bend.

The unknowns of a historic Florida storm: snow or ice? And how much?

For Florida, there are two major uncertainties to discuss. The first is the amount of precipitation.

Model ensembles have trended upward in recent days and are now in good agreement that there will be between 0.25 and 1 inch of precipitation in liquid equivalents across the Panhandle (that is, if you have melted snow or ice), heaviest toward Jacksonville and easier towards Pensacola. Tallahassee shows a strong gradient in expected totals, with around 0.5 inches being the most likely, but some models are closer to 1 inch.

The amount of precipitation that falls in North Florida, all or most of it as snow or ice, is borderline unprecedented. For example, in the December 1989 blizzard, 1 inch and 2.5 inches of snow fell from 0.1 and 0.35 inches of liquid equivalent in Tallahassee and Jacksonville, respectively. Regardless of where we are in the forecast range, we expect cold temperatures to be very high, meaning plenty of potential for winter unrest.

The biggest uncertainty, as always, is the type of precipitation, which is notoriously difficult to predict until a winter storm is underway.

The reason is that a strong storm like this turns the atmosphere into a complex layer of layers above and below freezing, where airborne snowflakes fall, melt, and then possibly refreeze. Freezing rain forms when a relatively thin layer on the surface is below freezing, while ice pellets form when the surface cold layer is thicker beneath a so-called “warm nose” about a mile up in the air.

Snow requires temperatures near or below freezing at all levels of the atmosphere.

This will be a historic storm no matter how you slice the pie, but the worst impacts will come when the bulk of the precipitation falls as freezing rain, icing surfaces like roads, power lines and trees that have been dragged here repeatedly in the last Decade of hurricanes, tornadoes and severe thunderstorms.

The good news is that ensemble guidance is showing a slightly colder trend in air temperatures through midday Monday as we get closer to the event. But even taking that trend into account, North Florida will become a battleground for different types of precipitation Tuesday night into Wednesday morning.

Let’s take a look at some rough humidity and precipitation forecasts by region, keeping in mind the following: 1) These forecasts are uncertain and could change before they begin and 2) the hyperlocal variability in the way the storm develops could be quite extreme here.

Western Panhandle, including Pensacola: Snow likely on the beach

For Pensacola and surrounding areas, the forecast is somewhat simpler as the consensus of data suggests that west of the Apalachicola River and away from the immediate coast, snow will be the predominant precipitation type, possibly starting with a small layer of ice.

Expected precipitation in liquid equivalents is lower here because the western panhandle exchanges less moisture, both on the surface and in the air, for a colder air mass.

In general, this region may see isolated light mixing or snowfall Tuesday morning, with the heaviest snow occurring Tuesday afternoon and evening. In general, snow totals of 1 to 2 inches inland are the best bet, but local snow totals of 3 inches or more would not be surprising.

Snow is likely on the beach in the western panhandle, but there will be less snow on the coast. The record for snowfall in a single storm in Florida is 4 inches, set on March 6, 1954 in Milton. Snowfall was expected to taper to thunderstorms and end early Wednesday morning.

Eastern Panhandle, including Tallahassee: On the edge of snow and ice

The forecast is most uncertain for Big Bend and Eastern Panhandle, the most likely region with overlap between deeper moisture and temperatures one to two miles up in the atmosphere, around freezing during the peak of the storm.

The colder trend in the models over the past 24 hours has further reduced the likelihood of significant precipitation in the Capitol Region, at least east of the Suwannee River.

Tallahassee, which means we should see a combination of freezing rain, sleet and snow. A few aesthetic upsets (or mixes) are possible on Tuesday morning, with the main event starting on Tuesday evening, continuing into the overnight hours and tapering off before dawn on Wednesday.

Since the freezing line above likely runs right through the Big Bend, I hesitate to make a specific statement on the type of precipitation and the amounts forecasted.

If the precipitation manages to leave snow most of the time, the potential for 1-3 inches of snow totals (or more? Am I really writing that???) are available – especially closer to the Apalachicola River or the Florida-Georgia line.

Realistically, some snow is a good possibility at the beginning and end of the storm, particularly in the eastern Big Bend, but a period of freezing rain or sleet is likely overnight as surface temperatures will be below freezing but warm above Nose The surface is above freezing.

In this case, up to 0.25 inch icing or ice pellets are possible. Basically, the Eastern Panhandle is going to be all over the precipitation type, so please manifest and visualize snow. Let’s hope for more Snolepocalypse, less Tallahassee or ice cream.

Northeast Florida, including Jacksonville

Further south and west toward Gainesville and Jacksonville, rainfall totals will be around 0.75 inches or more, while airborne temperatures will likely be above freezing during most of the storm.

This means rainfall is likely to start with some rain on Tuesday evening, with freezing rain likely to be more prominent in the back half of the winter event early tonight into Wednesday, and possibly some snow as the event begins late Wednesday morning comes to an end.

Amounts of glaze or ice of 0.1 to 0.25 inches are likely here, especially farther north and west. Don’t expect significant frozen precipitation far south of the Gainesville to Saint Augustine line, although only a fool could rely on a Gulf Coast precipitation forecast.

A winter dream with some big limitations

Finally, a few forecast reservations.

Make ALL the precipitation forecasts first before the actual storm starts with giant grains of salt that we don’t need to sprinkle on our roads.

Big forecast changes in who gets what are certainly possible. As a snow lover, writing this forecast feels like I’m writing weather fanfiction, but this forecast is simply my best and hopefully unbiased guess at the general outcome of the winter storm at midday Monday.

I could very well be wrong. For current information, contact the National Weather Service forecast offices in Mobile, Tallahassee and Jacksonville.

Overall, however, all signs point to a historic winter storm on its way to the Panhandle. Temperatures will be over 30°C during the day on Wednesday and will rise back to 20°C on Wednesday evening. This means there will be hazardous travel conditions from west to east from Tuesday, including hard-to-see black ice, which may last until Thursday morning.

Let’s stay off the road as much as possible and just all enjoy a nice cup of hot cocoa if you’re an adult, or the sacrament of youth that is a snow day if you’re a kid (or a kid at heart). .

In general, I wouldn’t expect the company to operate on Tuesdays and Wednesdays along the Gulf Coast from Houston to Tallahassee, even taking into account recent low standards.

Stay safe, stay warm and keep watching the skies… for flakes!

Dr. Ryan Truchelut is chief meteorologist at WeatherTiger, a Tallahassee startup that provides advanced weather and climate analysis, forensic meteorology and expert consulting, as well as subscription services for agricultural and hurricane forecasts. For more information, visit Weathertiger.com or contact us at [email protected].

This article originally appeared on Tallahassee Democrat: Florida winter storm: Forecast calls for historic amounts of ice and snow