523 FXUS64 KBMX 251029 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 429 AM CST Wed Nov 25 2020 .SHORT TERM... /Updated at 0359 AM CST Wed Nov 25 2020/ Today through Thursday. Currently this AM we have a retreating surface ridge over New England and extending southward down the Atlantic Seaboard with S-SE flow into C AL around the back side of it. Pressure gradients have increased ahead of our next system to the west. Some wind gusts will continue today at times. Shower activity will increase today (along with a few thunderstorms) ahead of a cold front moving across AR and TX toward us. Warm and moist air will increase across C AL ahead of it with dew points increasing to the low to mid 60s today and warm highs mainly in the 70s (except for some upper 60s far N/NE). We will have warm, moist and marginally unstable air to greet the convection. PW's of 1.2-1.5", 0-6km bulk shear values of 45-60kts, and 0-1 km mucape of 300-600 j/kg are indicated by guidance. I see no reason to pull back on the marginal severe messaging already mentioned since the timing of the system has activity in the afternoon and evening instead of later in the overnight. Damaging straight line winds along with a brief tornado still apply. In fact, parameters look to be high enough to expand the marginal to a little more of the area in the E/NE, generally along and N of a Selma to Alexander City line. The front is expected to make it through much of the area to near the I-85 corridor by Thursday morning. Unfortunately, the upper SW flow will not be helpful to pushing it through. The main surface low will push across the Ohio Valley tonight and into New England by Thursday morning causing the southern tier of the front to stall across Alabama. This will necessitate keeping some rain chances in the SE counties for Thursday. Across the N/NW counties cloudiness should decrease during the morning and clear during the afternoon. However, the colder air progress into the area will be hampered due to the SW upper flow. 08 .LONG TERM... /Updated at 0359 AM CST Wed Nov 25 2020/ Thursday night through Tuesday. The frontal boundary is stalled across Central AL and becomes more diffuse, but still present. Lingering showers along the front can be expected across the southernmost portions of our area Thursday night. Rain should subside briefly Friday morning as slight ridging slides across Central AL before our next shortwave approaches from the west Friday afternoon and evening. Synoptically, an upper level low pressure system becomes cut-off over the Desert Southwest. The timing of this second shortwave is uncertain, which means it's difficult to know exactly how long of a break in the rain we'll see on Friday morning, but by the afternoon to evening hours, we should see numerous to widespread showers generally south of I-20. There could be a few thunderstorms, but instability is lacking overall, so I've only added mention for isolated thunderstorm coverage. The cut-off low builds eastward over the Central Plains on Saturday, leading to slight amplification of a ridge over the Gulf States. This will likely lead to another break in the shower/thunderstorm activity over most of Central AL through the day on Saturday. I've kept lower PoPs in the forecast for our far southern counties due to the timing differences in these shortwave passages. Rain chances increase substantially on Sunday as the cut-off low slowly becomes phased with the upper trough and lifts eastward through the Ozarks and Mid-MS Valley. Guidance suggests a surface low could develop around this time and push a cold front through our area during the day on Sunday. Due to the numerous rounds of rain that move through just prior to this, it will be very difficult for the atmosphere to destabilize, so I've largely removed any mention of thunderstorms with the activity on Sunday. A secondary upper level low pressure system drops southward from Canada through the Upper Midwest Sunday afternoon through evening. This low quickly deepens, pulling in a much colder air mass southward along with it. Right now, the cold front and low pressure system should push to our east Monday morning, meaning the cold air will advect into Central AL through the day on Monday. Because of this, we'll likely see temperatures drop during the day. The upper level low continues to strengthen over the Great Lakes region, becoming occluded, but will continue pulling in cold air advection into Central AL for most of the day on Tuesday. Low temperatures Tuesday morning and again Tuesday night/Wednesday morning could be in the 20s for most of Central Alabama. As a couple of examples, probabilistic guidance shows around a 70% chance Birmingham drops below 30 degrees Tuesday morning, and increases to an 80% chance for Tuesday night/Wednesday morning. Montgomery is showing an 80% chance for Tuesday morning and a 90% chance by Tuesday night. 25/Owen && .AVIATION... 06Z TAF Discussion. An approaching frontal system will bring an end to VFR conditions by mid morning Wednesday. Surface winds will become more southerly and gusty, ceilings will lower to MVFR, and rain showers will move in from the west. A few thunderstorms are possible, and those along with any heavier showers could lead to brief IFR conditions. Rain showers will continue through tomorrow evening with ceilings lowering to IFR by Midnight at least for the northern terminals. 19 && .FIRE WEATHER... Rain chances increase today as a cold front pushes into our area. Expect winds to increase along and ahead of the front as well, shifting from the south to west-northwest as the front passes. There could be a few thunderstorms with this system, but they will likely remain more isolated. The frontal boundary stalls across the area tonight and into Thursday, leading to at least isolated to scattered showers across the southern portions of Central AL Thursday through Friday. The wet pattern should continue through the weekend with a few brief breaks in the rain. Much cooler and drier air builds in for the first part of next week. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 68 49 67 42 68 / 80 80 0 10 30 Anniston 71 56 70 48 71 / 60 80 10 10 30 Birmingham 71 52 68 48 69 / 80 80 10 10 40 Tuscaloosa 73 49 70 48 70 / 80 70 10 10 50 Calera 71 55 69 49 68 / 70 80 10 10 40 Auburn 72 62 72 55 71 / 30 60 50 20 30 Montgomery 77 62 74 56 74 / 40 80 30 20 50 Troy 77 63 76 58 75 / 20 60 50 20 50 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$