426 FXUS64 KBMX 071710 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1110 AM CST Sat Dec 7 2019 .UPDATE... For 18Z Aviation. && .SHORT TERM... /Updated at 0551 AM CST Sat Dec 07 2019/ The Dense Fog Advisory has been cancelled. Despite decreasing cloud cover since 3 am CST, visibilities have also improved with most areas above 3 miles. A few locations were still below 1 mile, but certainly not enough fog to continue dense fog advisory. Previous short-term discussion: /Updated at 0355 AM CST Sat Dec 07 2019/ Through Tonight. The combination of a rain cooled air mass and partial clearing of clouds in some areas has led to the formation of patchy dense fog. Even though the dense fog is not widespread in areal coverage, there are several metropolitan areas that are experiencing very low visibilities. A dense fog advisory has been issued for all counties in central Alabama thru 9 am this morning. The advisory may be lifted in some counties where cloud cover has persisted overnight. A large cyclonic flow below 850 mb will keep moisture levels high enough for mostly cloudy skies to prevail, but with breaks in the clouds at times. The breaks in the clouds will allow for enough sunshine to push afternoon temperatures into the lower to middle 60s. Much drier air aloft will advect into the area and keep rain free conditions. Low level pressure gradient will increase tonight as a surface high pushes down the mid-Atlantic states. This should hinder fog formation. 58/rose .LONG TERM... /Updated at 0355 AM CST Sat Dec 07 2019/ Sunday through Friday. Relatively active weather is expected across the CONUS for the upcoming work week as a result of several mid/upper-level shortwaves to traverse the country. This will produce a period a wet weather to begin overnight Sunday in the form of isolated light rain showers via the onset of low-level WAA across Central Alabama. This activity will gradually peak in coverage/intensity on Tuesday, and eventually clear the area to the southeast on Wednesday ahead of a stout cold front. Thereafter, a second round of wet weather is possible for the late Thursday through early Saturday timeframe. By Sunday morning a rather complex upper-level pattern is progged to continue evolving across the country. A sharp trough is forecast to begin digging across the West Coast with a low amplitude/downstream jet streak positioning across the souther tier of the country. Through time the trough is expected to become more amplified with southwesterly flow aloft overspreading the Southeast with a sub- tropical ridge near the northern Caribbean. By Tuesday morning this places favorable synoptic scale lift via the right entrance region of the jet streak to our north, as well as continuation of low-level WAA. Peak coverage of rainfall is forecast through Tuesday evening as additional forcing from the advancing shortwave provides PVA and a deformation axis from the TX Gulf Coast northeastward through the southern Appalachians. PWs are expected to rise to the 1.3-1.5" range during this time, which is plenty to support widespread rain chances. However, totals are forecast to remain at or below an inch at this time as convection remains quite limited due to little instability, even aloft. With the cold front forecast to continue southeastward across Central Alabama through the afternoon, aforementioned forcing aloft will provide needed support for over- running rain showers through the evening. However, the Canadian airmass will not bring sub-freezing temperatures into the area until early Wednesday morning. By this time the trough axis passes to our east & associated subsidence will signal the end of rainfall as the much cooler/drier airmass takes over with high pressure. Forecast details with this system will continue to be tweaked in the coming days. For now, any wintry precipitation that may occur in the cold airmass will be negligible (as with the last case of isolated flurries). After frontal passage on Wednesday, highs in the 40s/50s are forecast through the end of the forecast period. High pressure will keep weather conditions relatively quiet through around Friday whereas another potent shortwave is expected to approach from the west. This will support another period of wet weather as an associated low pressure system develops across the region. For now, PoPs have been truncated to <40% as forecast certainty remain low this far out. 40/Sizemore && .AVIATION... 18Z TAF Discussion. VFR conditions are expected through Sunday morning at all TAF sites. Due to the winds remaining light...and increasing cloud coverage...fog development is not expected at this time. After sunrise Sunday...introduced MVFR ceilings at KMGM and KTOI due to increasing moisture and chance for scattered showers through the rest of the TAF period. Only included VCSH for now due to uncertainty in coverage and timing. 24 && .FIRE WEATHER... Overnight clearing of overcast ceilings led to many areas of fog to develop across Central Alabama. This should improve throughout this morning. Otherwise, mostly cloudy skies are expected to continue through today with best coverage across the south. A slight chance of light rain showers is forecast again on Sunday with more widespread rainfall expected Monday night into Wednesday. There are no fire weather concerns at this time. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 62 44 58 49 68 / 0 10 20 50 40 Anniston 65 46 59 50 70 / 0 10 20 50 30 Birmingham 63 47 61 53 68 / 0 10 20 40 30 Tuscaloosa 64 48 64 53 70 / 0 10 20 30 30 Calera 65 47 61 52 69 / 0 10 20 40 20 Auburn 63 46 58 52 69 / 10 10 20 40 30 Montgomery 67 50 64 55 74 / 10 10 20 30 20 Troy 65 49 64 55 74 / 10 10 20 30 20 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$