Our days of basking in the sunshine and 80 degree weather are over. This morning's water vapor loop is showing a potent trough in the middle and upper troposphere plowing through Texas, Oklahoma, and Kansas. Moisture at low-levels is streaming northward from the Gulf of Mexico into our region. Interestingly enough, the leftover moisture from what was once Tropical Storm Olga is lifting northward from the western Caribbean and Eastern Gulf of Mexico, and will play a noticeable role in this developing storm system. Broad warm and moist advection will result in mostly occasional light rain showers for much of the daylight hours. In fact, the morning balloon launch from Tallahassee still shows a very strong capping inversion up at around 15,000 feet, with very dry air above that. As the middle and upper trough translates eastward, increasing large-scale lift will act to remove the cap and gradually push the dry air aloft toward saturation tonight. The wind field will be increasing and become favorable for rotating updrafts once the cap breaks. As is usually the case with severe weather systems in the winter, the question of instability is always tougher to resolve. Widespread cloud cover will keep instability from getting out of control, but even modest instability (as forecast by the numerical models) would be enough to enhance the tornado and damaging wind potential. If anything, the latest high-resolution models are trending a little stronger with the instability. Our in-house computer models (the WRF and RPM) predict the first thunderstorms to initiate to our west over Southeast Alabama and the Panhandle after 3 o'clock. A broken squall line is then forecast to gradually organize and our WRF model is explicitly showing a mix of short line segments and supercells within this line. The estimated time of arrival is between 8 and 10 PM for areas closest to the Apalachicola and Chattahoochee Rivers; between 10 PM and 2 AM for areas along U.S. Highway 319 (including Apalachicola, Tallahassee, Thomasville, Moultrie and Tifton); and then between Midnight and 5 AM for South-Central Georgia, the Eastern Florida Big Bend and Suwannee River Valley (including Valdosta, Perry, Madison, Live Oak, Mayo and Jasper). The strongest weather should exit our entire area by dawn on Sunday as a cold front marches through.
Temperatures will be substantially colder behind the front Sunday through Wednesday. In fact, highs are not expected to get out of the 50's on Sunday or Monday. At this time, we anticipate a light freeze early Monday morning, but a moderate or hard freeze is possible early Tuesday morning. We will delve into more details on the colder weather once the severe weather threat passes us tonight.
Stay tuned to WCTV and wctv.tv for additional severe weather information later today and tonight. You can also sign up for our Mobile Text Alerts. One of our staff meteorologists will send these when watches and warnings are issued. Go to: WCTV Text Alerts web page. The service is free and only standard text message fees from your provider would apply.