Buckle up those chin straps!
The normally slow-changing Florida Keys weather pattern will become highly volatile during the next 24 hours.
The polar jet stream has dipped unusually far south, even for winter, producing a highly energetic upper flow pattern across the subtropical Gulf of Mexico basin, including the Florida Keys. The cold front which moved through Keys island communities Thursday night, stalled over the Gulf Stream, and is inching northward at present. Meanwhile, a vigorous upper-atmospheric disturbance currently moving quickly across old Mexico, will accelerate eastward overnight and Sunday, inducing the birth of a low pressure system very near the Florida Keys by Sunday evening. What this means first and foremost is that our confidence in the timing and numerical values for wind velocities, rain chances, thunderstorm severity, and air temperatures is well below average from later tonight through Sunday night. At the same time, the potential for significant to severe marine weather is higher than average.
Given this scenario, we recommend checking marine weather observations and forecasts frequently, as they are likely to change.
Here are the primary potential marine weather hazards tonight through Sunday night:
Tonight -- Small Craft Advisory currently is in effect for the extreme southeastern Gulf of Mexico beyond five fathoms. NNE ranging from 15-20 knots, highest west of Key West.
Sunday -- Volatile wind character expected. ESE becoming S, becoming SW, becoming W. Wind speeds could be below 10 knots or above 30 knots depending on low pressure system development and evolution.
Sunday night -- Higher confidence in NNW 20-30 knots developing.
Tonight -- Isolated; a few severe storms possible after 3:00 a.m., mainly over the Straits of Florida.
Sunday -- Marginal risk for severe storms.
Sunday night -- Non-severe storms mainly along an eastward-moving squall line.
Periods of heavy rain are likely through Sunday night.
Seas will depend on wind and thunderstorms.
Please consult the following sources for Florida Keys marine weather.
Florida Keys Coastal Waters Forecasts:
Hourly Marine Weather Graphs:
NOAA/NWS Florida Keys Marine Weather Page:
Chip Kasper and Chris Rothwell