Stake Island, LA to Southwest Pass of the Mississippi River out 20 - 60 NM Marine Forecast
|Rest Of Today...Southeast Winds 15 To 20 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds. Chance Of Showers And Thunderstorms Through The Day.|
|Tonight...South Winds 15 To 20 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds. Chance Of Showers And Thunderstorms.|
|Thursday...West Winds 10 To 15 Knots Becoming Northwest Late In The Afternoon. Seas 3 To 5 Feet. Dominant Period 6 Seconds. Chance Of Thunderstorms In The Morning. Chance Of Showers Through The Day. Chance Of Thunderstorms In The Afternoon.|
|Thursday Night...North Winds 10 To 15 Knots Becoming East In The Late Evening. Seas 3 To 5 Feet. Dominant Period 6 Seconds.|
|Friday...Southeast Winds 10 To 15 Knots. Seas 3 To 5 Feet. Dominant Period 6 Seconds. Slight Chance Of Showers And Thunderstorms Through The Day.|
|Friday Night...South Winds Near 15 Knots. Seas 2 To 4 Feet. Dominant Period 5 Seconds. Slight Chance Of Showers And Thunderstorms After Midnight.|
|Saturday...Southwest Winds 10 To 15 Knots Becoming North In The Afternoon. Seas 3 To 5 Feet. Dominant Period 5 Seconds. Chance Of Showers And Thunderstorms.|
|Saturday Night...Northeast Winds 15 To 20 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 6 Seconds. Chance Of Showers In The Evening. Slight Chance Of Thunderstorms Through The Night. Showers Likely After Midnight.|
|Sunday...Northeast Winds 15 To 20 Knots. Seas 3 To 6 Feet. Dominant Period 5 Seconds. Showers Likely In The Morning. Chance Of Thunderstorms Through The Day. Chance Of Showers In The Afternoon.|
|Sunday Night...Northeast Winds 15 To 20 Knots. Seas 3 To 6 Feet. Dominant Period 5 Seconds. Slight Chance Of Thunderstorms In The Evening. Chance Of Showers Through The Night.|
| Synopsis for Pascagoula to SW Pass Mississippi - GMZ501|
Synopsis for SW Pass Mississippi River to Atchafalaya River- GMZ500
1107 AM CDT Wed Apr 14 2021
A stalled frontal boundary near the coast will remain in place through the end of the week. Showers and thunderstorms will impact the marine areas through this afternoon with locally strong winds near and in the wake of the thunderstorms. Another round of thunderstorms may affect the waters during the day Thursday. A cold front is expected to move through the northern Gulf by the weekend.
| Area Forecast Discussion|
National Weather Service New Orleans LA
647pm CDT Wednesday April 14 2021
SHORT TERM...(through Saturday) Another MCS embedded in the zonal flow aloft is currently moving through the Lower MS region this afternoon. The back end of the convective activity that is currently over the northern half of the forecast area has been 50-75 miles farther north and a bit more organized than what was depicted by 12Z CAMs and in our forecast this morning. Luckily this activity is progressing fast enough to the east to limit the threat of flash flooding across the North Shore of LA and coastal MS. Probability of Precipitation decrease from NW to SE across the region this evening when a relative lull in precipitation is expected.
Yet another MCS is expected to pass nearby just to our north (Mid South states) late tonight into Thursday morning. With a frontal boundary stalled along the Gulf coast and low-level flow backing out of the southwest ahead of the MCS, isentropic lift will lead to additional showers and storms developing overnight. The highest Probability of Precipitation will be during the morning hours on Thursday. The severe threat looks limited with convection predominately elevated and modest on the cool side of the boundary. The main threat with this round of storms will be locally heavy rainfall. An additional 1-2 inches of rainfall is expected with this next round with locally higher amounts to 3" possible. The Flash Flood Watch will remain in effect for the entire area through noon Thursday. There's still some uncertainty regarding exactly where the heaviest rain falls Thursday morning as the guidance has been wavering north-south somewhere between the SE LA-S MS and coast
There looks to be another relative lull in the precipitation Thursday afternoon (especially late) through at least Friday morning. Then the last round of potentially heavy rainfall appears to be late Friday afternoon through Saturday morning. Depending on how much rainfall occurs early Thursday (and where), a more targeted Flash Flood Watch may be needed for Friday night.
LONG TERM (Saturday night through Wednesday)... The boundary that has been parked over the area for much of the week will finally progress south and east of the region Saturday night. This will allow us to finally dry out by Sunday after the recent wet spell. A broad area of high pressure will build over the Southern Plains and Gulf Coast region through much of the week, which should keep the area mainly dry during the long term. The one exception may be coastal LA depending on exactly how close the aforementioned frontal boundary drifts back northward toward the coast Sunday- Wednesday. Temperatures will generally be 5-10 degrees below normal owing to a northerly component to the winds on the cool side of the front.
AVIATION... Conditions so far this afternoon have generally been MVFR (Marginal Visual Flight Rules) or IFR with showers and storms and VFR outside of precip. The greatest coverage of TSRA through about 20-21Z will be north of BTR-HDC, east of ASD, and from the NOLA terminals especially southward. The trend will be for this activity to weaken and drift southward toward the LA coast. While a break in the convection is anticipated this evening, CIGs looks to gradually lower to MVFR and IFR with northerly flow and stratus developing on the cool side of the front.
Showers and storms are expected to redevelop tonight toward C LA and move southward across the area overnight and into the early morning hours. Thunderstorm coverage should be limited initially during the overnight, but increase (scattered coverage) in the morning as elevated instability increases. Mainly IFR or low-end MVFR (Marginal Visual Flight Rules) CIGs should be prevailing through the morning hours. CIGs may improve gradually in the afternoon with some breaks in the cloud cover that allow for modest daytime mixing. N-NE winds 5-15 kt are expected.
A SCA (Small Craft Advisory) has been expanded this afternoon to include the MS sound and coastal waters. Latest marine observations show an enhanced SE wind just offshore with winds 20-25 kt, gusting to 30 kt. The onshore surge is expected to rather short lived and weaken toward sunset. Accordingly, the SCA (Small Craft Advisory) is only in effect through 7 PM. Additionally, the SCA (Small Craft Advisory) for the LA coastal waters was extended until midnight. Although the stronger winds were slow to develop today, the have over the past few hours. While there were some gusts of 35-40 kt a few miles off the SE LA coast, this looked to be convectively driven with N-NE winds caused by an outflow boundary from earlier thunderstorms. However, S-SE winds are expected to strengthen this evening to around 20 kt.
Winds and seas should remain below SCA (Small Craft Advisory) criteria Thursday through the weekend.
NOAA New Orleans LA Office: Watches - Warnings - Advisories
LA...Flash Flood Watch through Thursday morning for LAZ034>037-039- 046>050-056>061-063>072-075>078.
GM...Small Craft Advisory until 1am CDT Thursday for GMZ550-552-555- 570-572-575.
Flash Flood Watch through Thursday morning for GMZ530.
Small Craft Advisory until 7pm CDT this evening for GMZ532-536- 538-557-577.
MS...Flash Flood Watch through Thursday morning for MSZ068>071-077- 080>082.
GM...Small Craft Advisory until 1am CDT Thursday for GMZ552-555-570- 572-575.
Small Craft Advisory until 7pm CDT this evening for GMZ536-538- 557-577.