Port Fourchon, LA to Lower Atchafalaya River, LA out 20 - 60 NM Marine Forecast
|Tonight...South Winds 15 To 20 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds.|
|Monday...South Winds Near 15 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds. Slight Chance Of Showers And Thunderstorms Early In The Afternoon.|
|Monday Night...South Winds 10 To 15 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds.|
|Tuesday...Southeast Winds 10 To 15 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds.|
|Tuesday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Dominant Period 6 Seconds. Slight Chance Of Showers And Thunderstorms After Midnight.|
|Wednesday...East Winds 10 To 15 Knots. Seas 2 To 4 Feet. Dominant Period 6 Seconds. Chance Of Showers And Thunderstorms In The Morning, Then Showers And Thunderstorms Likely In The Afternoon.|
|Wednesday Night...Northeast Winds 15 To 20 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 5 Seconds. Showers And Thunderstorms Likely In The Evening, Then Chance Of Showers And Slight Chance Of Thunderstorms After Midnight.|
|Thursday...Northeast Winds 15 To 20 Knots. Seas 3 To 6 Feet. Dominant Period 5 Seconds. Chance Of Showers And Thunderstorms.|
|Thursday Night...Northeast Winds 15 To 20 Knots. Seas 3 To 6 Feet. Dominant Period 5 Seconds. Slight Chance Of Showers In The Evening.|
|Friday...Northeast Winds 15 To 20 Knots. Seas 3 To 6 Feet. Dominant Period 6 Seconds.|
|Friday Night...East Winds 15 To 20 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 6 Seconds.|
| Synopsis for Pascagoula to SW Pass Mississippi - GMZ501|
Synopsis for SW Pass Mississippi River to Atchafalaya River- GMZ500
330 PM CDT Sun May 9 2021
A series of low pressure systems will pass north of the waters through Wednesday. A cold front will then sweep through the region Wednesday night into Thursday. High pressure will build over the waters on Friday and remain in place through the weekend.
| Area Forecast Discussion|
National Weather Service New Orleans LA
317pm CDT Sunday May 9 2021
Short Term - Tonight Through Tuesday Night
A zonal flow regime will be in firm control of the area through Tuesday night. A series of fast moving upper level jet streaks and associated vorticity maxima will sweep through the Lower Mississippi Valley on the back of this zonal flow pattern. In the low levels, onshore flow will continue to advect moisture into the region. Lapse rates on the order of 6.0C/km should be sufficient to produce a fair degree of instability through the period, and expect to see mixed layer CAPE values of 1500 to 2000 J/KG each day. Given the forcing and instability in place, several rounds of convective development are anticipated through Tuesday night and fairly high Probability of Precipitation in the likely to categorical range is forecast each day.
The primary concern from the multiple rounds of convective activity through the period will be locally heavy rainfall and have storm total Quantitative Precipitation Forecast values of 2 to 3 inches forecast through Tuesday night. If storms begin to train over the same area, some locally higher amounts will be possible. A flash flood watch has not been issued yet as there is still some uncertainty in exactly where the highest threat will set up, but a watch will likely be issued by tomorrow or Tuesday. There will also be a limited risk of an isolated severe storm forming, but shear profiles remain weak through the period. Model soundings do indicate a favorable setup for a few downburst events during the afternoon hours both tomorrow and Tuesday, and an isolated damaging wind event cannot be ruled out. Given the weaker lapse rates and limited directional shear anticipated, the threat of hail and tornadoes will be very low.
.LONG TERM (Wednesday through Saturday Night)...The zonal flow pattern will continue to bring rounds of thunderstorms to the area on Wednesday, but a northern stream trough axis and associated front will bring about a pattern change from Thursday onward. Initially, the pattern will be little different from that seen on Monday and Tuesday with rounds of convection being driven by upper level jet dynamics and passing regions of increased omega. Precipitable water values will remain elevated and instability will be in place to support the convection. The only significant change on Wednesday is that a more stable cold pool(a region of relatively cold air) will likely be in place in the low levels. As a result, the convection should remain largely elevated and the risk of severe storms will be greatly diminished. However, with precipitable water values running around 2 inches, locally heavy rainfall will continue to be a concern. An additional 1 to 2 inches of rain could fall Wednesday into Wednesday night and this will keep a risk of flash flooding in place.
Fortunately, the period of unsettled weather will begin to end on Thursday as the northern stream trough axis and attendant cold front sweep east of the area. As northwest flow develops, a drier and much more stable airmass will begin to advect into the area. The dry air will initially advect into the mid and upper levels, and some lingering post-frontal stratus is expected through Thursday afternoon. By Thursday night, this stratus deck should clear out as deep layer subsidence develops. These clear skies will then persist through Saturday night as a deep layer ridge axis builds over the Gulf South. Weak cold air advection into the region will also occur and this will keep a few degrees cooler than average on Thursday and Friday. Given the clear and dry conditions in place, a large diurnal range is anticipated. Highs should warm into the upper 70s and lows should dip into the 50s. By Saturday, some modification of the airmass is expected with highs climbing back to more normal levels in the lower to middle 80s and lows dipping into the 60s.
Onshore flow will be the rule through Tuesday night as the region remains sandwiched between a low to the northwest and a high to the east. Winds will likely remain elevated in exercise caution range of 15 to 20 knots tonight, but should ease back to 10 to 15 knots tomorrow through Tuesday as the high to the east weakens. A front will push through the waters on Wednesday and winds will shift to the northeast. This northeast flow will persist through Friday and will likely increase to 15 to 20 knots as slightly cooler air advects over the warmer Gulf waters. Seas will turn choppy at 3 to 5 feet as these winds persist. PG
NOAA New Orleans LA Office: Watches - Warnings - Advisories
LA...None. GM...None. MS...None. GM...None.