Another pleasant day for a walk among the Bald Cypress Trees (Taxodium distichum) along the St. Johns River. The temperature was about 70° F. (21° C.).
The weather will be changing, again. A powerful arctic cold front will move through North Florida Monday afternoon, January 27, 2014. The front will bring strong northerly winds and subfreezing temperatures into North Florida Monday night through Wednesday morning. A series of strong upper level disturbances will then move from west to east over the Florida Panhandle to Jacksonville through Wednesday morning.
With cold air in place most of North Florida can expect a mix of freezing rain and sleet throughout the day Tuesday. The mixed precipitation is then expected to transition to all snow north of a line from Hattiesburg, Mississippi to Andalusia, Alabama, Tuesday evening and south of that line all the way to the Gulf Coast after midnight Tuesday night. The track of the upper level disturbance indicates the heaviest snow amounts will be southeast of a line from Wiggins, Mississippi to Greenville, Alabama. The heavier snow area includes the cities of Biloxi, MS, Mobile, AL, Pensacola, Destin, and Ft. Walton Beach, Florida.
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| Freezing precipitation moves south across the Florida panhandle, January 28, 2014 |
A significant amount of frozen rain is falling in the Pensacola area today, and up to an inch of snow may accumulate overnight, according to the National Weather Service.
The temperature is expected to reach a high of 37° (3° C) in the early afternoon, before dropping to around 32° (0° C) by 3 p.m. Wind chill values will be between 20° and 25° (-4° to-7° C), and wind gusts may reach as high as 30 mph.
Historical Florida Snows
Snowfall is rare in Florida because freezing temperatures in Florida are generally caused by the cold and dry winds of anticyclones (high pressure, clear skies). Frost is more common than snow. Frost formation requires temperatures of 45 °F (7 °C) or less at 2 m (7 ft) above sea level, a cloudless sky, and a relative humidity of 65% or more. In a normal winter we experience dozens of episodes of frost but no snow. This winter has produced only 2 nights of patchy frost making it a rather warm winter overall across Central Florida.
In general, for snow to occur, the polar jet stream must move southward through Texas and into the Gulf of Mexico, with a stalled cold front across the southern portion of the state curving northeastward to combine freezing air into the frontal clouds. This scenario happens rarely.
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| Timing of winter weather in the Big Bend area of Florida, January 28, 2014 |
In the current event, arctic air will surge into the Deep South on Monday, January 27. In the wake of the cold frontal passage the airmass is forecast to become progressively colder. At the same time, deep layer moisture may remain adequate to present the potential for winter weather precipitation. Atmospheric lift will be maintained or enhanced Monday night through Wednesday morning as the right rear quadrant of a strong 120 to 140 knot high level Jet Streak (a point or area of relative maximum wind speeds within a jet stream) within the base of a long wave upper level trough (storm) will remain in place, supporting the possibility of winter weather precipitation.
The January sun at noon (at 29° N. latitude) appears approximately 40° above the horizon. . . casting long shadows through the cypress trees.
FLORIDA SNOW FORECAST
FLORIDA SNOW FORECAST
Confidence is fairly high that very cold air will arrive Monday night, January 27, 2014, and that there will be at least some light precipitation in the Panhandle of Florida east to Jacksonville. Confidence is rather low in the timing of the cold air being collocated with the precipitation, which is the critical part of the forecast.
Early in the event, when the precipitation may be heaviest, there will likely be warm layers at different levels of the atmosphere, resulting in different types of precipitation (ranging from rain, to freezing rain and/or sleet). Snow is more likely later in the event, though the precipitation may taper off by that time.
Potential impacts include snow/sleet accumulation of up to an inch possible. Freezing rain up to a quarter of an inch is possible. Travel problems are possible Tuesday night through Wednesday, January 29. Elevated surfaces (bridges) will be most prone to freezing. Even small accumulations of snow and ice can create significant travel impacts for the Deep South.
The last official measurable snowfall for Tallahassee - Panama City was December 22-23, 1989.
Further south, across Central Florida, the arctic front is not forecast to have as big an impact as the cold air mixes with very warm and pleasant air currently over the peninsula.
The woody projections rising from the base of the cypress trees (below) are cypress knees. In the biology of trees, a cypress knee is a distinctive structure in a root of a cypress tree of any of various species of the subfamily Taxodioideae. Their function is unknown, but they are generally thought to help in providing oxygen to the tree and assist in anchoring the tree in the soft, muddy soil.
Below: A stand of water poppies (Hydrocleys nymphoides) near the shoreline.
Below: More cypress knees.
Below: The nearshore waters are very still and clear, which is very unusual.
Below: Looking southwest along the St. Johns River at Highbanks, Debary, Florida.
Below: Looking northeast along the St. Johns River at Highbanks, Debary.
Note that the river banks are neither high nor wide along this part of the river. High banks refers to the ancient bank of the river 1 mile to the east which is 50-100 feet higher than the waters of the St. Johns.
