Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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777 FXUS64 KLIX 281721 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 1221 PM CDT Tue May 28 2024 ...New UPDATE... .UPDATE... Issued at 1131 AM CDT Tue May 28 2024 Forecast update sent to increase PoPs and highs. Yes that is odd to do both but we are running warmer a little faster than yesterday and with slightly warmer LL temps. In addition not expecting a lot of convection till 20z or later so the only real issue with temps not getting as warm if not warmer than yesterday will be the cirrus trying to push south. By 1630z it had just entered southwest MS and should continue to steadily push south but if it thins out anymore the impact from it will be fairly minimal. With h925 temps about 1.5 degrees warmer than yesterday and BTR got to 98 see little reason to think they won`t get at least 98 again today but it would not be a surprise if BTR peaked out at 99 and even a very remote shot at 100 (but not willing to bite on that yet). The one positive thing with respect to temps is the northern half (almost 2/3rds) of the CWA is mixing in drier air and dewpoints have fallen into the 60s to lower 70s for those aforementioned areas. However to the south dewpoints are still in the mid 70s and even a few lower 80s and those places are already quite miserable with heat index readings running from 100 to 108. Now that said it does appear that convection may be a good bit easy to come by today than yesterday. Much of the same parameters we saw yesterday are still in place and from a sounding standpoint we have a very favorable environment for strong to severe storms. The key is can we get anything to pop and yesterday that was the problem with no real boundaries moving in/colliding or any subtle lift transiting the area. Now with a boundary draped over the area, a LL convergent axis shown at h925 and h85 draped over the area from the Southshore to Opelousas to the northwest into west-central LA. This also coincides with an instability gradient. In addition we could see a seabreeze move north from the Gulf and collide with a developing lake breeze over the southshore. This is now providing multiple areas of convergence/forcing to possibly get a few storms to pop. Once and if we get some to develop it is likely that storms would then develop along the line along and just south of I-10 this afternoon. Last there is a lot of convection upstream crossing Toledo Bend and this could continue to surge southeast down that gradient and into the western fringes of the CWA around 19/20z. There is another even larger area of convection back behind the previously mentioned one that may catch up to the first. Both of these have the potential to race down that gradient/convergent line into the CWA. The most likely timing appears to be from 19z through 22z with convection possibly spreading out from there to the ENE right up along the northshore and maybe eventually into coastal MS. Mid level lapse rates of greater than 8C suggest large hail is possible and DCAPE values currently around 1350-1550 over western/southwestern portions of the CWA highlight a rather impressive damaging wind potential. One other little concern could be heavy rain. If storms start to pop along the line we have reference multiple times isolated locations could see multiple storms before then main threat gets here. That could add quick bouts of locally heavy rain then add strong/severe storms with even heavier rain on top and there could be isolated pockets of flash flooding. One last thing noticed over the past hour is the southern edge of the first line of convection is starting to hang up and drift back to the west towards the 2nd line of convection. If we have that happen as it moves into the region then the risk for heavy rain will greatly increase. Keep an eye out for possibility of a Severe Thunderstorm watch and the potential for localized flash flooding. /CAB/ && .SHORT TERM... (Today through Wednesday) Issued at 323 AM CDT Tue May 28 2024 We will start out with an important feature in the form of a front. Can`t legitimately call this a cold front since temps are as warm behind it as ahead of it but by definition it would be because there is an air mass change across its boundary via dew pts. This front currently(2am) is located where the storms are ongoing this morning along the Miss coast. The front is just off the coast south of Pascagoula coming onshore just east of Gulfport to just north of Hammond then snakes its way into west central LA and on into TX south of Dallas. This boundary will help a very large complex of elevated storms develop later today near the Red River Valley. This complex should do two things, one is massively cold pool southward toward the sfc boundary causing all kings of severe wx over central TX today as it becomes sfc based. Smaller disturbances from this will be able to use the frontal boundary to ride eastward as well. This will act as a conduit for our area. The problem is stability even with this boundary over the area. Numbers show where stability quickly erodes as one moves west today so the marginal risk of severe looks well placed as west of I55 is where downburst numbers and the most severe wx producing numbers are highest relative to our area. This scenario will play out over the next few if not several days and it will be important to know where this or any other boundaries are located on a daily basis. Instability numbers rise for Wed and again they are indicating that if something can actually break the cap and produce lightning it will likely become severe. Again, with upper NW flow regimes, it is always a daily struggle to find the processes in the mesoscale environment that will cause trouble. So today is most visible vs. tomorrow. The current storms moving along the cold pool boundary to the west from coastal Miss and over the gulf will eventually modify and stall with the storms gradually weakening. There is not one CAM that is showing any of this activity, but the GFS did pick up on this convective burst developing along this frontal boundary but it did not hang on to it past midnight. Regardless, this is also the only model that is keeping this modified cold pool near the western part of the CWA later today. At least one disturbance should develop near the Toledo Bend area and move east along the frontal boundary later today as well. It is this activity that should collide with this modified cold pool late this afternoon to cause at least some storms over the western half of the area. The reason we can put a bit more confidence in this is the existence of the features that will allow it to occur and provide the travel path. Cloud cover and somewhat slightly lower dew pts as this front will be near the coast later today will help keep heat index numbers in check. But it will still be hot. One can easily tell in this forecast where we and our neighbors are placing the frontal boundary as the highest precip numbers will be located along and south of its axis, for us this mainly be the afternoon/evening hours. Areas to the north of these higher precip numbers will get somewhat lower heat index values while cloud cover along and ahead of it will keep others from those numbers as well. As a side note, BTR broke the record for the warmest low temp yesterday(Monday). Also, this record of 82F has not been reached(with respect to our records) for any day since January 1st until *JULY 5th*. Yes, July 5th is the first time a low of 82F was hit for the first time since Jan 1st of any year since records began in 1892. And the record value of 82F on July 5th was set in 2016. This record high(low) was not reached for more than another month away. The odds of this occurring this early is insane. && .LONG TERM... (Wednesday night through Monday) Issued at 323 AM CDT Tue May 28 2024 If it is difficult to tell what is going to occur tomorrow, it is almost impossible to give an extended fcast in this kind of environment. But we can see where the synoptic features should be located, which gives us a better handle on areas that could be most vulnerable to these MCS features. Looking at the extended through the next several days, it looks as if there will be endless MCS features develop daily and move east along either the sfc boundary or the 850 boundary which will both be in flux on a daily basis as these disturbances push and pull it each day. The sfc part of this boundary fades by late Wed and is somewhat located along the Miss River Valley by Thu and is out of the picture Fri. The only thing steering these disturbances later in the week will be ThetaE gradients or old outflow boundaries. && .AVIATION... (12Z TAFS) Issued at 323 AM CDT Tue May 28 2024 VFR will be found at all terminals through this taf period with the exception of one or two. The most at risk terminal for IFR will be BTR late today. The next would be HUM. There is a chance to get some TSRA for these two locations and if this occurs, IFR conditions could quickly develop for a short time. && .MARINE... Issued at 323 AM CDT Tue May 28 2024 There is a chance for temporarily getting a northerly brz over waters to the east of the Miss River. This would be short lived and would not be an issue as speeds should remain around 5kt. Southerly winds of 10-15kt will remain over waters to the west of the river and after today, all areas will be back in return flow at these levels for the remainder of the week. Any storms that are capable of developing or moving offshore will be able to produce erratic and much higher wind speeds. && .PRELIMINARY POINT TEMPS/POPS... MCB 92 68 87 66 / 10 10 30 20 BTR 96 73 90 72 / 20 20 30 10 ASD 95 72 91 71 / 10 10 20 10 MSY 94 76 90 76 / 10 10 20 10 GPT 94 73 90 72 / 0 10 10 10 PQL 96 70 92 69 / 0 10 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...TE LONG TERM....TE AVIATION...TE MARINE...TE