Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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931 FXUS64 KLIX 272124 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 424 PM CDT Thu Jun 27 2024 ...New SHORT TERM, LONG TERM, AVIATION, MARINE... .SHORT TERM... (This evening through Sunday night) Issued at 406 PM CDT Thu Jun 27 2024 Quiet the day today for most of the region. Convection quickly refired overnight between 6-7z across much of the coast with widespread storms across the SELA coast and near shore waters through the early morning time frame with rather heavy rain in some of the river parishes. This appears to be from the seabreeze/lake breeze finally dissipating and the land breeze beginning to develop while at the same time the s/w was finally beginning to move in providing some subtle dynamics and cooler mid lvl temps. Given how water the coastal waters are making the coastal areas the most unstable region over the area storms were able to tap into the better dynamics finally and quickly developed over those areas. The problem is by the time the s/w axis moved into the CWA which was around and shortly after sunrise it had pushed most everything south and as feared yesterday the northern half of the CWA really struggled to see any precip. Tomorrow and through the weekend the forecast problems are PoPs and temps. Where will storms fire and even if they can in some regions along with how much rain will occur. If storms do develop how widespread will it be and what impact will that then have on afternoon highs. The ridge currently over west TX will continue to build to the east while our disturbance currently centered over central AL/MS border will continue to slowly drop into the north- central Gulf for tomorrow. This would suggest that we could still have some mid lvl support from the disturbance even as it fills in. One problem is PW, currently 1.4-1.5 across the northern 3rd/half of the CWA but this could recover quickly tomorrow. But the biggest negative is the ridge and mid lvl temps. The ridge is going to continue to build into the area and both the GFS and ECMWF show h5 temps warming back to around -2 to -3C across the northwestern 3rd of the CWA. Combine that what appears to be LL diffluence/divergence and the northwest could have a very difficult time seeing much if any convection. Now along the coast of both LA and MS that is a different question. Winds will be light so once again we should have little problems getting the seabreeze and lake breeze to develop, very rich moisture in place and closer to being directly underneath the weakening disturbance should be more than enough to get numerous showers and thunderstorms tomorrow. With this we have made some rather big deviations from the NBM in the northwest going much closer to the MAV and ECS MOS values which is about 20-30% lower. As for the temperatures the convection across the southeastern half should help keep most of the area cool enough to not be concerned with heat issues where as the northwest that may remain rain free will likely have lower humidity values and thus also remain just below heat advisory status. This weekend the forecast is a little more tricky. The ridge still looks like it will continue to build to the east but models are now showing it not quite as stout yet and in fact actually show the h5 temps cooling a tad -3 to -5 (cooling is relative) and typically that is usually too warm to get much convection still. However, we will have a plethora of moisture available with PWs ranging from 2 to possibly 2.3" at times. Even with what looks like LL high pressure sitting over the region very light winds through the column again will allow diurnal fluctuations in the wind filed to dictate convection, especially on Sunday. Portions of southwest MS may struggle again to see much rain as it will be closer to the center of the ridge. LL temps begin to very slowly inch up this weekend with mid 90s and possibly some isolated 90s for highs on Saturday and then may be a few more upper 90s on Sunday. These two days provide a better chance of seeing heat index values in the 104 to 112 range. The most likely day for a heat advisory looks like Sunday and that should continue into next week. Again the biggest question is convection as timing and coverage will have significant impacts on the eventual outcome. More coverage especially around midday and early afternoon would keep the heat at bay some however very early convection (which I`m not seeing that as the seabreeze should not become active quickly with the very light wind field) or very late convection like after 19/20z would both allow for peak heat index values to be achieved. /CAB/ && .LONG TERM... (Monday through Wednesday night) Issued at 406 PM CDT Thu Jun 27 2024 The northern stream upper level trough moves through the Great Lakes Sunday evening and continue eastward into the Atlantic Ocean Monday. The base of this trough doesn`t reach much farther south than the Appalachian Mountains. This is why a weak backdoor front comes in from the northeast just ahead of the trailing ridge. The upper ridge in the wake of this trough will be sliding east across the entire Mississippi Valley Monday afternoon into Tuesday. Global models are still in good agreement that this 596/7dm high pressure will be centered near the Akrlatex region Monday afternoon. Excluding rain potential, increasing 500mb heights will bring already above normal weekend temps up even more. Guidance spread through the forecast period is fairly minimal and as of 12z runs, Monday has the potential to be the warmest with highs mid/upper 90s to 100 degrees. Convective coverage will probably be the bigger deciding factor on max temps. That previously mentioned weak backdoor front looks to stall near the Gulf Coast, which combined with forecast temps, would support scattered to numerous showers and storms. If convective initiation is early enough, heat indicies will get knocked down quickly. However, if not too early, widespread upper 70 to 80 degree dewpoints with hot temps may bring heat indicies into Excessive Heat Warning issuance. Tuesday will virtually mirror with the same heat/convection timing challenges as the center of the upper ridge will be progressing eastward fairly slowly. As the rest of the week progresses, the upper ridge aloft will begin to flatten out and spread across the entire Gulf Coast. This is in response to repeated northern stream troughs/shortwaves weakening the ridge. As the subsidence slowly fades, should eventually see some less extreme temps and more widespread daily convection. /MEFFER/ && .AVIATION... (00Z TAFS) Issued at 406 PM CDT Thu Jun 27 2024 VFR condition will persist across the region unless impacted by convection and this has been very difficult most of the day. Convection may still imapct GPT/NEW/MSY/HUM this evening but should be scattered and not persistent all evening and overnight. Convection may be an issue again right along coastal sites tomorrow morning. /CAB/ && .MARINE... Issued at 406 PM CDT Thu Jun 27 2024 High pressure will be in control through the weekend. This will continue to provide mostly light winds across the coatal waters. The biggest issues will be conveciton as rather decent coverage of storms is possible tomorrow and Saturday over the coastal waters, especially during the early morning hours. Very rich low level mositure, light winds, and convection during the overnight/early morning hours should lead to decent wterspout potential. /CAB/ && .PRELIMINARY POINT TEMPS/POPS... MCB 72 92 74 93 / 10 40 10 50 BTR 77 94 79 96 / 10 50 10 50 ASD 76 91 78 94 / 30 80 20 60 MSY 78 91 81 93 / 30 80 20 60 GPT 76 91 78 92 / 50 70 40 60 PQL 76 93 77 95 / 50 70 40 50 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...CAB LONG TERM....ME AVIATION...CAB MARINE...CAB