Southwest Pass of the Mississippi River to Port Fourchon, LA 20 - 60 NM Marine Forecast
|Tonight...Southeast Winds 5 To 10 Knots. Seas 1 To 2 Feet. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms After Midnight.|
|Wednesday...Southeast Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms Through The Day.|
|Wednesday Night...South Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms After Midnight.|
|Thursday...South Winds 5 To 10 Knots. Seas 1 To 2 Feet. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms.|
|Thursday Night...Southwest Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Slight Chance Of Showers And Thunderstorms After Midnight.|
|Friday...West Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms Through The Day.|
|Friday Night...West Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds.|
|Saturday...West Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Slight Chance Of Showers And Thunderstorms Through The Day.|
|Saturday Night...Southwest Winds 5 To 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds.|
|Sunday...Southwest Winds Near 10 Knots. Seas 1 Foot Or Less. Dominant Period 4 Seconds. Chance Of Showers And Thunderstorms Through The Day.|
|Sunday Night...Southwest Winds 10 To 15 Knots. Seas 1 To 2 Feet. Dominant Period 4 Seconds. Slight Chance Of Showers And Thunderstorms After Midnight.|
| Synopsis for Pascagoula to SW Pass Mississippi - GMZ501|
Synopsis for SW Pass Mississippi River to Atchafalaya River- GMZ500
327 PM CDT Tue Jul 27 2021
High pressure will remain centered over the Southern Plains. A weak front will continue to try to move toward the Gulf coast but will stall just inland for the remainder of next week.
| Area Forecast Discussion|
National Weather Service New Orleans LA
433pm CDT Tuesday July 27 2021
Main forecast concern is the heat. Today it took a little longer than expected to really get those higher heat index values but we finally started to around 19/20z. Looking at the morning sounding there was a little more dry air in the lower 3-5k feet and that obviously mixed down some drier air in the boundary layer for many locations, but some places recovered, especially coastal MS once the seabreeze somewhat kicked in bringing dewpoints back up. It doesn't look like we will have that dry air over the coming days so the heat could be a little worse, especially at the end of the work week and into the weekend.
Lets be honest, yes it is Summer, yes it is the South, and yes it is suppose to be quite warm and muggy. Many times we have either just met or even stayed just below criteria for our Heat Advisory but with the Summer we have so far the recent heat has put a few things into perspective a little.
This Summer has actually been slightly cooler than normal thanks to ALL OF THE RAIN and when dealing with "Heat Illness/Casualty" it is very much a cumulative issue. Many people probably haven't acclimated completely to the heat thanks to the rain and clouds we have seen so even if the afternoon heat index struggles to get abv 108 degrees (which is the criteria for the advisory) it is still oppressive and dangerous for numerous people. Combine that with morning lows in the upper 70s and even a few lower 80s and for any of the vulnerable population that can not find a way to artificially cool off, the body will not have a chance to recover. With that, the prolonged nature of the warm temps, and high moisture content we will continue to see these issues and it could actually become worse Friday and Saturday.
There is some conflicting forecast concerns for tomorrow and into Thursday. Moisture does look like it will return a little earlier than anticipated as was the concern yesterday. Currently looking at GOES16 and the total precipitable water is actually quite dry over a good portion of the area but it isn't moving and is actually moderating some. The ridge over the Rockies will try to build east into the Central Plains and Mid/Lower MS Valleys. This will try to build in across the southeastern CONUS leading to warming mid level temps and rising hghts. At the same time a backdoor weak cold front will slide towards the coast tomorrow. and moisture will build ahead of it. This boundary could provide enough to overcome the building ridge but with possibly northerly or even northeasterly flow in the mid levels, convection will struggle to develop and likely hold off till late afternoon and possibly into the evening hours. These storms could also be on the strong side so we will need to watch that. What does that mean for our heat, well it doesn't look like we will see much in the way of relief during the day which will allow the region to heat up again and with increasing moisture and possibly even some slight compressional heating, tomorrow afternoon will be quite miserable. With that we have issued another heat advisory for all but extreme coastal LA. Coastal MS has been added to the advisory and could see some of the highest heat index values tomorrow afternoon.
Thursday whatever is left of the boundary will likely be right over the CWA. Moisture will be readily available with PWs likely above 2". Mid level flow will become more easterly as the ridge continues to build southeast. That shouldn't hold back convective initiation like the northerly/northeasterly flow would but mid level hgheights will be rising and h5 temps could be warmer than -5C and that will absolutely hurt thunderstorms potential. The combination of a boundary, very rich moisture, and h925 temps around 26C suggest another hot day. If convection can develop then it will help to provide some relief but if storms struggle then our current heat index values are too low. /CAB/
Heading into the extended portion of the forecast models and ensembles continue to be in agreement with the back end of the work week and into the weekend looking H O T. However, quite a bit suggest we could see some relief early next week but that also means the return of..................rain. Hey beggars can't be choosers. Overall only adjustments made to the NBM were to raise highs a degree or two across the northern half of the CWA and some minor adjustments to raise morning lows mainly around New Orleans.
Friday and Saturday could be the hottest days of the Summer so far, both from a temperature standpoint but also a heat index standpoint. The ridge will absolutely be in charge Friday and mid level hgheights could be around 595-596dm and h5 temps may approach -4C. That should really but the lid on rain chances across at least the northern half of the CWA. Coastal sections of LA may still see some storm development as it could be on the southern periphery of the ridge and if an easterly wave is moving under the ridge we could see some convection down there. Dry air will not move in, so the lack of rain will combine with very humid conditions and that will have the region primed for another oppressive day. The question now is how hot do we get. Quite surprisingly the operational models aren't overly impressive with the h925 or h85 temps. The one location that does impress me is coastal MS and just across the Pearl River into LA. H925 temps by at least some of the models are approaching 28C and that mixed down would be around 37C and add another degree or two F for the super-adiabatic skin layer and upper 90s possibly approaching 100 is not out of the question. I AM NOT showing that yet. Not much is advertising that potential but I think models may have to catch up a lot on that. If that actually comes to fruition then some locations may very well need an Excessive Heat Warning. That would not be for the entire area but some locations will flirt with that.
Saturday will likely be quiet similar to Friday so SSDD...Same Sh...I mean Stuff Different Day. Yes it looks hot and humid with heat advisories likely to continue. Convection will continue to be hard to come by thanks to the warm mid level temps. Sunday may see a little bit of a change as the ridge will begin to weaken across the western CONUS and suppressed some over the northern Gulf.
A full on pattern change continues to be advertised heading into next week with a rather deep L/W trough setting up over the eastern CONUS. This could lead to a few days of heavy rain but if it continues to develop as strong as being shown it could actually send a front through with slightly cooler temps but much drier air. /CAB/
Typical Summer like conditions over the water. Winds will be quite light over the region but with the lack of winds it will be quite miserable over the water as well. Thunderstorms will be a little harder to come by until Thursday and maybe Friday over the waters as we move back under the easterlies. Convection will probably become diurnally driven then with storms more likely early in the morning and far more isolated during the day. /CAB/
NOAA New Orleans LA Office: Watches - Warnings - Advisories
LA...Heat Advisory until 7pm CDT this evening for LAZ034>037-039- 046>050-056>061-063>065-071-072-075>078.
Heat Advisory from 9am to 7pm CDT Wednesday for LAZ034>037-039- 046>050-056>061-063>065-070>072-075>078.
GM...None. MS...Heat Advisory until 7pm CDT this evening for MSZ068>071-077-080.
Heat Advisory from 9am to 7pm CDT Wednesday for MSZ068>071-077- 080>082.