566 FXUS64 KBMX 121921 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 121 PM CST Wed Jan 12 2022 .UPDATE... Midday Update and 18Z Aviation. && .SHORT TERM... /Updated at 1228 PM CST Wed Jan 12 2022/ Through Thursday. Fairly tranquil weather continues across Central Alabama this afternoon. A broad surface ridge exists generally across the Carolinas, and we're seeing surface winds in our western counties shifting to the south and southwest. A weak upper level shortwave continues to move eastward along the central Gulf Coast, while another shortwave is progged to dive southeastward into the area overnight tonight through Thursday. Both features are still expected to only bring in some high clouds across the forecast area with very dry air still in place. Forecast highs today are in good shape and on track, with mid to upper 50 expected later on this afternoon. Flow at the surface will be from the west during the day on Thursday following frosty temperatures during the morning. We'll have some pressure gradient winds kick up a little bit in response to the digging longwave trough over the eastern conus and surface ridging over the western Gulf of Mexico. Prevailing westerly winds of 10 to 15mph with gusts 20 to 25mph will be common through Thursday afternoon under partly cloudy to mostly sunny skies and highs ranging from the upper 50s north to the mid 60s south. 56/GDG .LONG TERM... /Updated at 0332 AM CST Wed Jan 12 2022/ Thursday night through Friday night: A shortwave trough will continue to push eastward across the Carolinas Thursday night, with surface cyclogenesis taking place off the coast of Cape Hatteras. Northwest winds behind this system will bring another round of cold air advection, though winds will be a limiting factor for radiational cooling Thursday night. One more dry day is expected Friday with cool northerly winds. Winds then shift to east-southeasterly Friday night ahead of the next system. Saturday through Sunday night: Models seems to be coming into better agreement on the synoptic scale regarding this weekend's system, though some mesoscale details at this lead time remain unresolved. A shortwave trough in northwest flow sinks down into the Plains Friday, with an upper low forming within the initially positively tilted trough in the Kansas/Oklahoma vicinity by Saturday morning. The upper low and associated trough will begin take on more of a neutral tilt as it crosses the Lower Mississippi Valley Saturday night, moving across Alabama on Sunday before taking on more of a negative tilt over the Carolinas by Sunday night. At the surface, a 1040mb high over Ontario will induce a cold air damming wedge along the lee of the Appalachians. A weak surface low will move from the Southern Plains Friday night to the Lower Mississippi Valley on Saturday, before deepening/undergoing cyclogenesis as it moves across Alabama Saturday night and eventually up the East Coast Sunday/Sunday night. Main point of uncertainty with the forecast is whether there will be more of a double barrel low structure along both sides of the Appalachians or a single low moving along the southeast side of the wedge. Strong southerly flow/warm air advection should result in widespread soaking rainfall Saturday afternoon and Saturday evening, with thermal profiles only supportive of liquid precipitation. The air mass is too stable to support thunder at this time. After midnight the exact track of the surface low becomes critical to the forecast. If the track of the surface low is far enough to the south, increased easterly winds could bring the CAD air mass into our far northeast counties late Saturday night into early Sunday morning. With warm air advection and a possible warm nose aloft, this could be a wintry mix of snow, sleet, or possibly freezing rain if temperatures are cold enough. Also if the low track is far enough to the south, colder air behind it could bring a changeover to snow late Saturday night into Sunday morning in our far northwest counties. While the above scenarios represent reasonable worst case scenarios, the most likely scenario according to the guidance consensus at this time is that temperatures remain warm enough for only rain Saturday night. Then on Sunday, models indicate the dry slot of the developing mid-latitude cyclone moving through the area, with drying aloft in the snow growth zone. This is then followed by an area of wraparound moisture/the commahead of the cyclone, with moisture returning aloft in the snow growth zone (though a bit lower than the optimal dendritic growth zone). Strong cold air advection aloft will then result in a better chance of rain and snow showers during the day on Sunday with potentially falling temperatures during the afternoon. Forecast temperatures are in the mid 30s, but some light accumulations could occur in any heavier bursts of precipitation. So to recap, at this time the best chance of light snow accumulations will be generally along and north of I-20 on Sunday. This could cause limited impacts if rates are high enough to counteract above freezing temperatures. This is the most likely scenario represented in our forecast at this time based on more of a northern track of the surface low. On the other hand, there is a minority of guidance members with the southern track which would result in higher impacts from a potential wintry mix, especially in some of our northeastern counties. This is a reasonable worst case scenario and will be monitored as we get closer to the event. Either way, will also have to watch for re-freezing of any remaining moisture on roadways Sunday night when temperatures fall below freezing which could end up being the main impact. Monday through Wednesday: Cool/dry conditions are expected for Monday and Tuesday. A weak shortwave in fast quasi-zonal flow may approach the area Tuesday night/Wednesday, but at this time expect any precipitation to hold off until after temperatures warm above freezing next Wednesday. 32/Davis && .AVIATION... 18Z TAF Discussion. VFR conditions will continue through the forecast period with light to variable surface winds. Westerly surface winds are expected to increase after 18z on Thursday and will be incorporated in future TAF issuances. Note: AMD NOT SKED is appended at KBHM due to ASOS power loss until further notice. 56/GDG && .FIRE WEATHER... Fire weather elements remain below critical thresholds over the coming days. Wednesday afternoon should have the lowest RH values in the 30 percent range, with higher afternoon minimum RH values thereafter. Rain perhaps changing to rain/snow or snow is expected over the weekend. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 31 58 33 52 32 / 0 0 0 0 0 Anniston 34 60 35 54 34 / 0 0 0 0 0 Birmingham 36 59 35 52 37 / 0 0 0 0 0 Tuscaloosa 34 62 36 54 37 / 0 0 0 0 0 Calera 36 60 36 54 37 / 0 0 0 0 0 Auburn 34 59 36 55 37 / 0 0 0 0 0 Montgomery 33 63 36 58 37 / 0 0 0 0 0 Troy 33 64 37 59 37 / 0 0 0 0 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$