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228 FXUS64 KLIX 172036AFDLIXArea Forecast DiscussionNational Weather Service New Orleans LA336 PM CDT Sat Aug 17 2024...NEW SHORT TERM, LONG TERM, MARINE....SHORT TERM...(This evening through Monday Night) Issued at 336 PM CDT Sat Aug 17 2024Another hot day across the CWFA with most if not all sites runningat heat advisory criteria this afternoon. And if they haven'tgotten there they will...outside of maybe MCB? Those lucky onesare far and few...(although this forecaster questions whether or not 105 degree heat index values is really lucky vs 108+?). Aftera few low topped showers earlier today, a mostly dry scan on KHDC. This will gradually change later this evening as a few isolated to scattered showers and thunderstorms develop, which will provide at least a few of us with some heat relief closer to sunset or perhaps even shortly after. The best potential for activity will be along and north of the I10 corridor with the mainfocus on interior south MS and MS Gulf Coast...closer to a surface boundary we will be following going through much of the short term period and into the start of the long term. Think most of this activity will remain rather benign outside of the typical summer time convection, however, DCAPE is running at or above 1000J/kg. SBcape from an instability side of things looks to also be moderate or around 2500 J/kg. Although for this time of year instability could be better. That said, a more robust updraft may have the potential to end with a strong wind gust or two out there...again best potential MS both interior and Gulf Coastthrough this evening. Going into Sunday, surprise surprise another hot one. As Imentioned there will be a surface boundary or a backdoor coldfront that will try to move into the region with the upper levelflow mostly from the north. Along and ahead of this feature, lowlevel moisture pooling will be able to counter and BL mixing fromstrong surface heating...meaning dew points will remain very high.With that, temperatures are forecast to increase back into the upper 90s to even above 100 in some places which will result in heat index values exceeding the 113 degree heat index criteria foran Excessive Heat Warning...so covered the region with this headline for Sunday. Now, similar there will be a shot of showers and storms on Sunday, but again more isolated to scattered in variety and once again the best chances will be across south MS and the Florida Parishes later in the evening. Now the differencein today and Sunday will simply be the higher instability (almostdouble that of today with a bit cooler air working into the upperlevels) as well as a slight uptick in wind shear as well, which is very "interesting" for this time of year. Nonetheless, the parameters along with robust DCAPE suggest the potential for a severe wind gusts or hailstone or two in the strongest activity. Again, coverage appears to still be limited to isolated/scattered.SPC has delineated a marginal risk but a categorical upgrade to slight will not be impossible for the far north and eastern portions of the CWFA if parameters continue to reflect a slightly higher damaging wind and hail potential respectively.Quickly, for the short term relied heavily on CAMs. Global QPF signals have been running relatively high, which is causing consensus models to over compensate with POP/QPF forecasts. Kept POPs and QPF manageable based on verification over the last cycle or two and again weighted today and tomorrow heavily on mesoscale model data.By Monday, the surface backdoor cold front will have moved southacross the northern Gulf waters and stretching NW and eventually Ncrossing through the middle of Louisiana. The dry northerly flowwill keep the eastern two-thirds of the forecast areas dry aloft and even some help from mixing some of the drier conditions to thesurface. However, along the boundary out close to the Atchafalaya, conditions will remain more on the moist side. An impulse or two on the eastern periphery of the ridge center well to our west will work with the diurnal cycle as well as the surface boundary that is stalled under the mean upper level flow. So, this is enough evidence to keep at least some mention of convection with again winds and perhaps a small hailstone or two looking possible in the wider updrafts. Otherwise, heat index values along and north of 10 look to be below headline criteria...sadly along and south look to required heat headlines along with locations closer to surface boundary since those areas again will hold onto low level moisture a bit longer. (Frye)&&.LONG TERM...(Tuesday through Friday night) Issued at 336 PM CDT Sat Aug 17 2024The region will reside under a mostly northerly or northeasterlyflow to start the long term period. The old backdoor front thatstalled out north to south of the center part of Louisiana willeventually move west as a stronger upper level impulse moves southward and advances the boundary further away from the region. Much drier air at the surface can be expected. Although surface temperatures will still be well above average, the dry surface conditions will help make things slightly more comfortable. Rain chances will mostly be offshore closer the stalled surface trough/boundary so rain chances midweek will be tough to find. Going into the 2nd half of the week, a mid/upper level low beginsto pinch off from the east coast trough. A weak surface trough develops and both move west. At the surface our winds will transition to a more east or southeast direction with time helpinglow level moisture creep back into the region. With the proximityto the upper low and surface trough, POPs will begin to creep back up as well late in the period. Temperatures late in the period will remain hot, but there is a bit of a confidence factorin there depending on timing of convective initiation, which is unclear at this range. (Frye) &&.AVIATION...(18Z TAFS)Issued at 1216 PM CDT Sat Aug 17 2024VFR conditions are largely expected through the cycle. Cannot ruleout some evening convection this evening generally before 06z andthe best potential being for terminals along and north of I10.Outside of convection, MCB may have limited VIS around sunrise,especially if rain occurs. Otherwise, light and variable windsexpected. (Frye)&&.MARINE...Issued at 336 PM CDT Sat Aug 17 2024Overall favorable marine conditions this weekend outside of anypotential nocturnal showers or storms. Naturally, convection willincrease winds and seas locally. Otherwise, a surface front willeventually push into the local waters to start the new workweek.Outside of the chance of additional shower and thunderstormactivity, winds will turn more to the north or northeast Mondayand into Tuesday. Cautionary headlines will be possible early nextweek, especially for the MS Sound areas. High pressure willeventually take back over late in the period and allow winds toshift back to a more southeasterly direction. (Frye) &&.PRELIMINARY POINT TEMPS/POPS...MCB 75 99 74 92 / 20 10 30 30 BTR 80 101 80 96 / 20 10 20 30 ASD 77 100 79 96 / 20 10 30 30 MSY 80 98 80 95 / 10 10 20 30 GPT 78 97 79 96 / 30 10 30 30 PQL 77 101 78 98 / 30 20 40 30 &&.LIX WATCHES/WARNINGS/ADVISORIES...LA...Heat Advisory until 7 PM CDT this evening for LAZ034>037-039- 046>048-056>060-064>071-076>090. Excessive Heat Warning from 10 AM to 7 PM CDT Sunday for LAZ034>037-039-046>048-056>060-064>071-076>090.GM...None.MS...Heat Advisory until 7 PM CDT this evening for MSZ068>071-077- 083>088. Excessive Heat Warning from 10 AM to 7 PM CDT Sunday for MSZ068>071-077-083>088.GM...None.&&$$SHORT TERM...RDFLONG TERM....RDFAVIATION...RDFMARINE...RDF
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Topic: [Alert]LIX issues Area Forecast Discussion (AFD) at Aug 17, 3:36 PM CDT ...NEW SHORT TERM, LONG TERM, MARINE... (Read 522 times)
