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Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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323 FXUS64 KLIX 171718 AAC AFDLIX Area Forecast Discussion...UPDATED National Weather Service New Orleans LA 1218 PM CDT Sat Aug 17 2024 ...NEW AVIATION... .UPDATE... Issued at 1017 AM CDT Sat Aug 17 2024 Just after 10am and temperatures already soaring into the 90s across the CWFA this morning. Needless to say there will not be any changes to the ongoing heat headlines this afternoon/evening. Otherwise, POPs this morning will remain on the lower side across the CWFA. Over the last hour or so a couple of very isolated narrow/weak updrafts have developed for a few out there. This should remain very limited as upper levels are a bit on the warm side and instability will be lackluster...at least initially. Convection odds increase later this evening and closer to midnight CAMs are suggesting convection to occur over southern MS, MS Gulf Coast, and Florida Parishes. Respectively made the change to add at least lower end POPs. Instability again will be there with 2500 J/KG of SBCAPE to work with and DCAPE in excess of 1000 J/KG suggest that a wind potential will certainly be there in updrafts that are a bit wider and more robust. Outside of the adjustment in POPs this evening no other forecast changes with this midpoint. (Frye) && .SHORT TERM... (Today through Sunday) Issued at 358 AM CDT Sat Aug 17 2024 Typical Summer night across the region. Convection that fired yesterday afternoon persisted into the evening a little before tapering off with mostly clear skies but still mild and rather humid conditions. Temperatures by 7z were generally in the upper 70s to lower 80s and we should continue to see a slow fall till sunrise. Two biggest questions through the weekend remain how hot and oppressive do we get followed by how much and especially when can convection fire. The large mid lvl ridge that has dominated the area continues to slide west and will amplify over the Rockies. This is in response to a deep Pac low digging south off the west coast and the L/W trough digging over the eastern CONUS. This eventually places us under northerly and northwesterly flow which will have some rather strong implications on convection and more so timing. The ridge will still have a rather strong influence over the area today as it is still building to the west. Finally by mid/late afternoon today it should be centered over northern NM which we will finally move under northwest flow but it will be very weak today. Nothing else though will be much different from what occurred yesterday. PWs will still be hovering just abv 2" and with temperatures expected to quickly rise into the 90s once again instability will not be in question. DCAPE may not be as high today as it has been in previous days but it will likely be abv 1000 j/kg for much of the area. Given the slowly developing and very weak northerly/northwesterly flow today given is likely going to be initially driven by the sea/lake breeze and the boundary collisions. As for timing, high pressure at the sfc which is expected to dominate the region through the weekend, will not greatly help things to kick off. The very weak synoptic wind field would also suggest sea/lake breeze and other boundaries (outflow/differential heating) as the driving factor today. LL winds will be light as well and with h85 winds chaotic or even out of the north, not expecting the seabreeze to get going quickly either. Fcst sndgs suggest the convective temp will be around 93-95 and with that storms will likely hold off on initiation till mid afternoon say 19/20z. That does bring into question of the current Heat Adv and whether some areas need to be upgraded to an Excessive Heat Warning. First thought was we probably needed to upgrade a few locations mainly around the title lakes, immediate coast of MS, and possibly up the MS and Pearl River valleys but digging in a little more and things look far more borderline. Main issues is looking at what occurred yesterday. With no glaring changes in conditions or setup why should things be much different. Almost all of our official obs remained just below Warning criteria and with that decided to hold off on any upgrade at this time. That isn`t to say we won`t hit Excessive Heat anywhere today and it is probably a good but that we will reach that in a few areas. Either way it is still going to be rather miserable and if you are outside during the late morning to mid afternoon hours, drink plenty of water and have a way to cool off. As for the strong to severe aspect we are probably looking a very similar setup to yesterday although we may not see quite as much of that mid lvl drier air which is leading to the slightly lower DCAPE values. As for Sunday though that may have a much better chance of strong to severe storms. So why does Sunday look like it may have a better chance of strong to severe storms. On Sunday our ridge will be firmly entrenched over the continental divide with our L/W trough digging through the southeastern CONUS. Northwest flow will be in place and there is strong agreement from most of the model solutions that the mid lvl flow could be rather impressive for this time of the year. H5 winds will increase to 20kts and there are some indications that it could be up to 25kts. Mid lvl northerly/northwesterly of 15 kts is good enough to add a punch to Summer thunderstorms but 20-25kts definitely makes it more interesting. Also as has been mentioned numerous times northerly/northwesterly flow leads to convection developing late in the day. What does this mean then, we will have no issues warming up and becoming quite unstable and all guidance is indicating MLCAPE values around 3K j/kg. Lastly we will see a surge of mid lvl dry air moving in as well and this will enhance the risk for damaging winds. Ok all that makes it sound like a rather decent chance of seeing severe storms but and yes there is usually always a but, are we too far west. There is a chance and maybe a decent chance that the convection that develops which will likely become an strong to severe MCS could move right on the periphery of our CWA across southeastern MS and into coastal AL and coastal MS. The potential is there for severe weather Sunday but it may only occur across the northeastern 3rd of the CWA. /CAB/ && .LONG TERM... (Sunday night through Friday) Issued at 358 AM CDT Sat Aug 17 2024 As we head into the next work week its the old saying, as much as some things change they stay the same. We will see a push of drier air and slightly lower rain chances but we will look to be hot. No adjustments made from the NBM as it appears to be a good blend of the medium range guidance. With the ridge still in place to our west and the L/W trough remaining over the east coast through Wednesday we will remain under northerly flow. This does try to send a week front through the area overnight Sunday or early Monday. Pressure and wind field would suggest probably overnight but LL moisture suggest Monday morning. The drier air will be a welcome touch but LL temps will not drop and afternoon highs will continue to climb into the mid to upper 90s. Even morning lows don`t really cool much until mid to late in the week as we start to see the pattern shift with the ridge beginning to build back to the northeast. As for rain potential, Monday has the highest chance through much of the week as we will still have enough moisture in place to get some afternoon convection but it would likely be the southern half of the CWA. Drier air continues to work into the area driving the moisture south and that likely keep much of the area rain free Tuesday through Thursday. /CAB/ && .AVIATION... (18Z TAFS) Issued at 1216 PM CDT Sat Aug 17 2024 VFR conditions are largely expected through the cycle. Cannot rule out some evening convection this evening generally before 06z and the 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 winds expected. (Frye) && .MARINE... Issued at 358 AM CDT Sat Aug 17 2024 High pressure remains in place through the weekend and even with a weak front pushing towards the coast Monday conditions will remain rather benign outside of any thunderstorm. Daily isolated to scattered rain chances remain mainly during the early morning timeframe each day. Expect slightly elevated northerly winds with the front before slacking off when the following surface high settles over later in the week. && .PRELIMINARY POINT TEMPS/POPS... MCB 75 99 74 93 / 20 10 30 30 BTR 80 101 80 96 / 20 10 20 40 ASD 77 100 79 96 / 20 10 30 40 MSY 80 98 80 96 / 10 10 20 40 GPT 78 97 79 96 / 30 10 30 30 PQL 77 101 78 99 / 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. GM...None. MS...Heat Advisory until 7 PM CDT this evening for MSZ068>071-077- 083>088. GM...None. && $$ UPDATE...RDF SHORT TERM...CAB LONG TERM....CAB AVIATION...RDF MARINE...CAB