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447 FXUS64 KLIX 120908 CCAAFDLIXArea Forecast Discussion...CORRECTEDNational Weather Service New Orleans LA408 AM CDT Wed Jun 12 2024...New SHORT TERM, LONG TERM, MARINE....SHORT TERM...(Today through Saturday) Issued at 400 AM CDT Wed Jun 12 2024Overall the forecast as a whole is a tale of two scenarios. Firstpart, high confidence, mostly dry, and HOT. Second part of the forecast, highly uncertain, increasing rain chances and possibly very wet, and thus cooler than the first part of the forecast. Because of that the short term will actually cover through the first half of the weekend and then we will delve into the abyss known as the Long Term portion. Stalled boundary is still apparent in the sfc field and is draped right along almost the entirety of the northern Gulf coast. High pressure dominates pretty much all of the eastern CONUS. The other sfc feature is the weak trough over the eastern Gulf associated with the heavy rainfall that plagued the srn half of the FL peninsula. This area has been highlighted by NHC as having a low probability of developing into a tropical system but it will have zero impacts on our area as it will move across FL and enter the Atlantic. Aloft we are still seeing the slight impacts of the weak disturbance moving across the Lower MS Valley with a L/W trough just off the east coast. The main drivers of the weather for the short term (well actually probably most of the forecast) is the strengthening ridge currently centered over the Mexican states of Sonora and Chihuahua along the AZ and NM. The ridge axis stretches north across the 4 corners. The other main feature is the closed low that is in the Pacific west of the Baja and how it evolves as it lifts to the northeast. So those are the players for the next week and the main one to watch is how the ridge evolves. It is specifically the feature we will focus on in the short term as it builds to the east across the southern Plains, the Lower MS Valley and into the southeastern CONUS by Saturday afternoon, likely centered over the TN/MS/AL/GA border. With that track along with hghts of around 592dm this should provide more than enough subsidence to keep convection over much of the land at bay. This will also occur with an increase in LL temps with h925 temps rising from 23-24C today to 27-29C by Saturday. We got slightly warmer than expected yesterday and see little reason why we won't be as warm today. The one slight hiccup that could occur today is that disturbance coming across the region today. It will cool off mid lvl temps about a degree or two and with h5 temps possibly around -8C there is a very small chance that a few storms could try to develop today. PWs are sufficient enough up to I-12 but thedeeper richer moisture is still locked in along the coast and if convection can fire inland it will likely be the same areas that saw it yesterday. That said we will continue to hold on to 15-20% between I-12 and just south of I-10 for isolated storms. This should not be an issue the next few days as that feature will continue to push to the southeast into the eastern Gulf and acrossthe southeastern CONUS (but keep en eye on the base of this feature as it moves into the southeastern and southern Gulf and could help determine where the rain goes Sunday and next week). LL moisture doesn't really start to recover till Friday and more so on Saturday and these two days will be ones to watch for possible heat products. LL temps as mentioned earlier will be on the rise and by Friday h925 temps of 26-28C should easily yield highs in the mid to upper 90s and can not rule out isolated 100s Friday. Highs could be a degree or two hotter on Saturday with probably more than a few sites testing the century mark. With the ambient temperature getting that warm, any increase in LL moisture will make for an oppressive environment and by Friday we should start seeing widespread heat index values of 100 to the mid 100s. Saturday though we will finally see light to moderate onshore flow and that will finally see a surge of LL moisture push in. With the ridge overhead likely keeping convection out of the area we will heave little problems heating up and combine that with a very humid airmass and we will see quite the oppressive airmass and Heat Adv are beginning to look likely for Saturday and can not rule that out for Friday. /CAB/&&.LONG TERM...(Saturday night through Tuesday) Issued at 400 AM CDT Wed Jun 12 2024Now the not so clear part of the forecast, Sunday through Tuesday.Medium range models all suggest at least some rain moving in Sunday. The increase in cloud cover along with rain helps to cool things off a tad but how much rain, when does it arrive, and how long does it stick around is quite uncertain. With so much uncertainty and rather low confidence we will stick with the NBM for now but that said personally I am leaning to a drier western solution and we will get into that. There appears to be 2 camps, 1 with a better chance of rain over the 3 days, and the other which keeps the bulk of the rain to our west and southwest. The ensembles aren't a great deal of help either as they are kind of washing things out and broad brushing rain across the western half of the Gulf. A lot of this appears to hinge on the ridge and how it evolves/moves. The camp with the better rain chances and even possibility of heavy rain for the north-central Gulf coast shows the ridge continuing to push east-southeast across the southeastern CONUS and nudging into the Atlantic. This causes the western edge of the ridge to slide far enough east allowing for a path NNW towards the north-central and northwestern Gulf. This also cuts off the base of the weak trough over the eastern Gulf that is currently moving through us right now. That would allow allow the weak mid lvl feature to work NNW and it along with a deep and rich plume of tropical moisture could bring about widespread rain to the area by Sunday and possibly through Tuesday. This would also be capable of producing very heavy rain as was evident in FL yesterday. If this scenario plays out even trying to pinpoint where the heaviest rain would occur is still too difficult at this time. Scenario 2 which seems like the operational models were trying to trend towards would be a drier set up for our area and the bulk of the rain likely going into TX if not southern TX and Mexico. Why is that, again it is the ridge that will bring us our hot temps. In this scenario the ridge doesn't shift as far east and the Pacific low we mentioned earlier, as it lifts to the northeast it wouldn't eroded the western periphery of the ridge as much and right up over it. If that occurs the ridge would basically be a blocking setup for us. The ridge is not extremely large and even centered in that TN/MS/AL/GA area we would be on the southern Periphery. This would at the least allow some moisture to move north providing an increase in cloud cover and some convection Sunday and Sunday night but after that we probably get shut down. With the s/w riding up and over the ridge, the ridge is going to want to expand back to the west and this would keep any disturbance and deep tropical moisture well off to our west and southwest. Even though we didn't make any adjustments away form the NBM this scenario feels like the more probably solution. Ridges are stubborn and the Pacific low as it opens up and lifts to the northeast will likely ride up and over it as there doesn't appear to be anything blocking it from driving that direction. This would also allow the western portion of the ridge axis to quickly push back to the west and basically blocking things from moving to far to the northwest. This mainly the OP ECMWF solution and it doesn't have a ton of support right now as the the GFS and GEM are both well off to the east and the ensemble means are in between with the ECS having the greatest dispersion ofsolutions. /CAB/&&.AVIATION...(06Z TAFS)Issued at 1153 PM CDT Tue Jun 11 2024VFR conditions are expected for most terminals with HUM havingMVFR due to visibility. That should clear up early tomorrowmorning after sunrise. Terminals should then be VFR throughout theday with a low chance of some showers/storms near the southernterminals during the afternoon hours. -BL&&.MARINE...Issued at 400 AM CDT Wed Jun 12 2024Boundary is still stalled along the coast and should start to washout Thursday night and Friday. Until then light and variable windsto northernly winds of 5-10 kts will continue. After the frontwashes out looks for winds to become more easterly and then byFriday night and more so this weekend onshore flow will developand could become moderate times. A decent fetch out of thesoutheast may develop this weekend and into next week and that could bring an increase in the potential for swells. Convection isstill possible over the coastal waters through the week but muchhighs rain chances will be in place Sunday and into next week andwith any convection locally higher winds and seas are to be expected. /CAB/&&.PRELIMINARY POINT TEMPS/POPS...MCB 90 63 92 67 / 10 0 0 0 BTR 94 69 96 72 / 10 10 10 0 ASD 94 70 95 72 / 10 10 10 0 MSY 94 77 94 77 / 20 10 10 0 GPT 93 71 94 75 / 10 10 10 10 PQL 95 69 97 73 / 10 10 10 10 &&.LIX WATCHES/WARNINGS/ADVISORIES...LA...None.GM...None.MS...None.GM...None.&&$$SHORT TERM...CABLONG TERM....CABAVIATION...BLMARINE...CAB
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Topic: [Alert]LIX issues Area Forecast Discussion (AFD) at Jun 12, 4:08 AM CDT ...New SHORT TERM, LONG TERM, MARINE... (Read 399 times)
