045 FXUS64 KBMX 050948 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 348 AM CST Tue Jan 5 2021 .SHORT TERM... /Updated at 0345 AM CST Tue Jan 05 2021/ Today through Wednesday. Fog has developed across west Alabama this morning where temperatures have cooled faster than other areas. Many areas were reporting visibilities less than one mile, and satellite imagery shows areal coverage of fog increasing fairly quickly. A dense fog advisory will be issued for west Alabama. A digging upper trof over the eastern United States will bring cold air advection to Alabama today, and highs today will average about five degrees cooler than yesterday. Plenty of sunshine today as a drier air mass advects into the region. The dry air mass will remain in place through Wednesday, but there may be an increase in mid to high level clouds Wednesday afternoon from the west. Clear skies and calm winds tonight will allow for temperatures to fall into the upper 20s to lower 30s. Slightly warmer afternoon temperatures on Wednesday as 1000-850mb flow becomes east-southeast. 58/rose .LONG TERM... /Updated at 0345 AM CST Tue Jan 05 2021/ Wednesday night through Thursday. The overall concept with the forecast mid-week wasn't changed as we anticipate a stout shortwave to dive southeast and become more dynamic & negatively tilted Wednesday night/Thursday morning. Its presence across the Southern Plains and Lower Mississippi River Valley will coincide with a strong cold front pushing through the ArkLaTex and a narrow area of pre-frontal moisture return/synoptic lift along a corridor of warm air advection and nearby PVA. As a result, clusters of light to moderate rain showers will become more numerous as the system nears Central AL after midnight and into Thursday morning, though this activity will have to deal with a little dry air as well. However, I kept PoP trends generally the same and truncated to 70% with west-to-east progression. I also maintained the lagging departure of rain chances across the north and northeast as moisture wraps into the occluded disturbance early Friday morning. Wintry precipitation was not included with this system Friday morning despite a few runs of the NAM suggesting this possibility. General model consensus suggests surface temperatures in the upper 30s along with 1000-850 mb thickness values too far above 1300 m to support snowfall. It appears the NAM is more robust with components of vertical velocity near the 500 mb low and is yielding heavier precip & more dynamic cooling despite lack of and/or weakening mesoscale lift in these areas. Friday through Monday. After departure of this system on Friday, high temperatures are forecast to remain in the 40s and 50s for the remainder of the long- term. However, we're continuing to monitor trends for the next potential weather maker on Sunday and Sunday night. The evolution and trajectory of the parent mid/upper-level trough and how it interacts with antecedent dry/cool air will ultimately dictate our respective rain/snow chances during this time. Due to very limited forecast confidence this far out I've continued a conservative approach with PoPs (10-30%) and only kept slight chance mentioning of light rain/snow for areas generally along and north of I-20. Until forecast details become more clear I'll forego speculation on potential impacts and any updates to the HWO. 40/Sizemore && .AVIATION... 06Z TAF Discussion. MVFR cigs are possible during the pre-dawn across the northern portions portions of C AL (BHM) in the morning hours behind a front. The latest guidance is very meager with the low stratus. I have pulled back on the mention. Patchy fog will be possible generally W of I-65 and mostly likely only affect TCL and maybe EET briefly. I'm not confident enough to add fog at the other TAFs for now. As of now, no precipitation is expected with this system. NW winds 5-10kts (maybe a few gusts) will commence on Tuesday behind the system. Winds should relax some on Tuesday evening as ridging builds. 08 && .FIRE WEATHER... Relatively dry and stable conditions should continue through Wednesday evening with minimum RH values dropping to 40-50% this afternoon, and 30-40% tomorrow afternoon. Winds are forecast to slowly veer from NW this afternoon to NNW this evening. Moisture will increase by Wednesday night and Thursday ahead of a storm system approaching the region. This will veer winds to a more southeasterly direction Thursday afternoon. This system will yield light to moderate rain showers from Thursday into early Friday morning. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 51 27 55 34 49 / 0 0 0 10 60 Anniston 54 30 58 37 51 / 0 0 0 10 60 Birmingham 53 31 56 39 50 / 0 0 0 20 60 Tuscaloosa 54 31 57 39 52 / 0 0 0 40 70 Calera 54 31 57 39 50 / 0 0 0 20 60 Auburn 58 33 57 39 52 / 0 0 0 10 70 Montgomery 60 32 59 39 57 / 0 0 0 10 70 Troy 61 33 59 40 57 / 0 0 0 10 70 && .BMX WATCHES/WARNINGS/ADVISORIES/... Dense Fog Advisory until 9 AM CST this morning for the following counties: Bibb...Chilton...Dallas...Fayette...Greene...Hale... Jefferson...Lamar...Marengo...Marion...Perry...Pickens... Shelby...Sumter...Tuscaloosa...Walker...Winston. && $$