527 FXUS64 KBMX 041719 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1219 PM CDT Sat May 4 2019 .UPDATE... For 18Z Aviation. && .SHORT TERM... Today and Tonight. There are two separate systems to our west this morning. The first is a mesoscale convective vortex (MCV) sliding through the ArkLaMiss. The second is another MCV pushing through Southeastern Texas, which at this time is the more robust system of the two. Across Central AL, we've got a remnant boundary stretched just south of the I-20 corridor, which will likely be the dividing line between the two MCV tracks as they slide eastward/northeastward today. Synoptically, an upper level trough is swinging through, which will help provide some larger-scale lift due to the height falls and weaker positive vorticity advection. Otherwise, there's not much forcing synoptic forcing associated with these MCVs. The first MCV will lift northeastward through Central MS and into North-Central AL, generally along and north of the I-20/59 corridor before 10am. This is on the north side of the remnant boundary, where the dewpoints are in the low to mid 60s and surface instability is generally below 500 J/Kg. Therefore, expect some thunderstorms with this morning round to produce some isolated gusty winds, but I do not expect there to be any severe storms with the first MCV. There will likely be a break in the late morning to around noon where there won't be much rain or thunderstorms in the area, but the second MCV is expected to move east-northeastward into South-Central AL in the early afternoon. This round will likely track south of the remnant boundary, generally south of the I-20/59 corridor. This is the area that is already seeing dewpoints in the upper 60s to near 70. With daytime heating, instability will likely increase to 1000- 2000+ J/Kg in this area, leading to the more robust storms of the day, some of which could be severe. High resolution guidance has not handled the evolutions of these MCVs very well, giving drastically different data in each run, which isn't a surprise given the weak forcing and mesoscale nature of the propagation. With that said, some guidance keeps hitting on the more robust line of thunderstorms moving through Southern AL during the mid-afternoon. If this were to take place, it would have the better chance to produce damaging winds when compared to the more disorganized thunderstorms. Therefore, I'll increase the risk for severe storms capable of producing damaging winds to a "slight" risk generally along and south of the Hwy 80 corridor in South-Central AL. Locations north of this could still see strong to severe thunderstorms, but confidence in the coverage is relatively lower. At this time, the tornado potential is extremely low given the unfavorable low level wind profiles. By roughly 10pm, any thunderstorm activity should be east of our area, ending any severe threat for Central AL. 25/Owen .LONG TERM... /Issued at 0300 AM CT/ Sunday through Saturday. Low level ridging builds in across much of the Southeastern CONUS with zonal flow aloft Sunday through early Tuesday. This will keep the area mostly dry with a gradual warming trend. Afternoon highs on Tuesday could reach into the upper 80s to near 90 degrees. A persistent trough remains over the Western US through mid-week and into the second half of the week. Several impulses move through the base of the trough, each bringing increased chances of thunderstorms for at least the northern half of Central AL through Saturday. For now, will not add any mention of severe potential with these systems as timing of any individual impulse remains uncertain. 25/Owen && .AVIATION... 18Z TAF Discussion. Active afternoon and evening in store across central Alabama with the majority of the TAF sites impacted. Currently most locations are experiencing MVFR ceilings except the far south which have cleared and lifted to VFR conditions. Isolated TSRA was noted just east of KBHM at 17z with more organized convection across Mississippi. This convection will increase in coverage and overspread the TAF sites this afternoon/evening. Have included a period of TSRA at all areas roughly between 21z and 01z with more widespread light precipitation after that time period. Ceilings will lower to the IFR range overnight before slowly improving late Sunday morning. 15 && .FIRE WEATHER... Showers and thunderstorms expected today across Central AL. Gusty winds may become erratic in proximity to the thunderstorms. There are no fire weather concerns at this time. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 61 79 57 84 59 / 80 20 10 0 0 Anniston 62 80 58 85 60 / 80 20 10 0 0 Birmingham 63 80 60 87 63 / 80 20 0 0 0 Tuscaloosa 62 82 59 88 63 / 70 20 0 0 0 Calera 62 80 60 86 62 / 80 20 0 0 0 Auburn 63 79 62 85 63 / 70 40 10 0 0 Montgomery 65 83 62 88 64 / 80 30 10 0 0 Troy 64 82 62 87 64 / 80 40 10 0 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$