Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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423 FXUS64 KLIX 062041 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 341 PM CDT Mon May 6 2024 ...New SHORT TERM, LONG TERM, AVIATION, MARINE... .SHORT TERM... (This evening through Wednesday night) Issued at 243 PM CDT Mon May 6 2024 The region will continue to feel the influence of a shortwave ridge axis extending in a southwest to northeast orientation across the Gulf South through the middle of the week. Ample subsidence in the mid and upper levels beneath this ridge will continue to produce a strong mid- level capping inversion, and this will effectively limit any convective potential tomorrow and Wednesday. At most, an isolated shower may develop over portions of Southern Mississippi, but deep convection and thunderstorm activity will be hard pressed to occur tomorrow. By Wednesday, the strength of the ridging aloft will be so substantial that no convective activity is expected. Skies will start off mostly cloudy to overcast as another inversion forms around daybreak both tomorrow morning and Wednesday morning, but warming temperatures into the upper 80s and lower 90s will lead to skies turning partly cloudy by the late morning hours. Overall, a warm and benign period of weather is expected through Wednesday night. && .LONG TERM... (Thursday through Sunday night) Issued at 243 PM CDT Mon May 6 2024 There is little spread in the ensemble members concerning the passage of a cold front Thursday night into Friday, but there continues to disagreement and larger spread in the solutions heading into the weekend. Given the large disagreement in the forecast solutions over the weekend, have largely stuck with the NBM deterministic output for the time being. Initially, a deepening northern stream trough axis will start to dig into the eastern third of the CONUS. As this trough digs southward, a southern stream vorticity max will slide out of Texas and across the Gulf South. This southern stream energy will tap into a highly unstable airmass as noted by MLCAPE values Thursday afternoon and evening of 2500 to 3000 J/KG across the CWA. These high MLCAPE values are being driven by extremely steep mid-level lapse rates approaching 7.0 C/km. This instability will tap into a very moist airmass with PWATS expected to climb to to between 1.75 and 2 inches by Thursday evening. Another factor to watch for will be just how much speed shear develops in response to the passage of an 100 knot jet streak co-located with the vort max. Effective layer speed shear values of 50 to 60 knots could occur just as the convection begins to develop, and this will support tilted updrafts and the prospect of scattered strong to severe thunderstorms Thursday afternoon into Thursday evening. Based on the model sounding profiles, large hail and damaging wind gusts will be the primary severe weather concern. Later in the night, generally after midnight Thursday night, the jet streak will pass to the east and a surface front will begin to push across the area. Overall shear values will decrease substantially and the threat of severe convection should diminish. In addition to the thunderstorm risk Thursday afternoon into Thursday evening, compressional heating in advance of the front should allow highs to warm into the low to mid 90s across much of the forecast area. Only coastal regions should remain in the upper 80s due to the influence of the seabreeze cycle. The area will be post-frontal by Friday morning as a prevailing west-northwest flow regime develops in the mid and upper levels and a northerly wind takes hold in the low levels. A cooler and drier airmass will move into the area with rain chances coming to an end over the eastern third of the CWA by late Friday morning. Temperatures will be closer to average on Friday with highs warming into the low to mid 80s. The warmest temperatures will be along the Mississippi coast where a weak downslope component will induce some mild subsidence and warming. The strength of the northerly wind will be sufficient to suppress seabreeze development, thus allowing the temperatures to warm on the coast Saturday and Sunday will see the flow pattern aloft turn more zonal, and a series of weak and fast moving vorticity maxima should slide across the northern Gulf of Mexico over this period. Unfortunately, there are significant differences in the timing of these systems between the ensemble members of the GFS and ECMWF, and thus forecast confidence over the weekend is lower. Given the uncertainty, have opted to stick with NBM forecast values. This solution results in largely coastal PoP values of 20 to 30 percent and drier conditions further inland. Temperatures will be largely near average with highs in the lower 80s and lows in the upper 50s and lower 60s. && .AVIATION... (18Z TAFS) Issued at 243 PM CDT Mon May 6 2024 VFR conditions will be found at all of the terminals through the evening hours. There may be an isolated shower that develops near MCB this afternoon, but the risk to low to include in the forecast. Tomorrow morning, generally between 08z and 14z, some boundary layer decoupling will occur as temperatures cool and winds decrease. Another round of IFR and MVFR stratus development is expected with the most prevalent IFR conditions expected at MCB where decoupling will be greatest. The remainder of the terminals should see ceilings of 1000 to 1500 feet in the early morning hours. After 15z, increased thermal mixing of the boundary layer will allow the stratus deck to begin breaking and lifting into VFR range. && .MARINE... Issued at 243 PM CDT Mon May 6 2024 A persistent south to southeast flow of 10 to 15 knots and seas of 1 to 3 feet will continue across the coastal waters through Wednesday as the region remains on the southwest periphery of a broad surface high pressure system. However, the approach of a cold front Wednesday night into Thursday will lead to a slightly tighter pressure gradient over the waters, and subsequently a period of stronger onshore flow between 15 and 20 knots. Seas will increase to 3 to 5 feet in response to these higher winds. After the front moves through the waters Thursday night, winds will shift to the north at 10 to 15 knots on Friday and Saturday. && .PRELIMINARY POINT TEMPS/POPS... MCB 69 87 71 90 / 20 20 0 10 BTR 73 88 74 91 / 10 10 0 0 ASD 72 88 73 89 / 10 10 0 0 MSY 75 87 75 88 / 10 10 0 0 GPT 74 84 75 85 / 10 10 0 0 PQL 73 84 74 86 / 10 10 0 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...PG LONG TERM....PG AVIATION...PG MARINE...PG