Marine Weather Net

Boothville, LA to Southwest Pass of the Mississippi River Marine Forecast


OVERNIGHT

S
WINDS
15 - 20
KNOTS

THURSDAY

W
WINDS
10 - 15
KNOTS

THURSDAY NIGHT

N
WINDS
5 - 10
KNOTS

FRIDAY

N
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
GMZ555 Forecast Issued: 956 PM CST Wed Feb 08 2023

SMALL CRAFT EXERCISE CAUTION IN EFFECT UNTIL 6 AM CST THURSDAY
Overnight...South Winds 15 To 20 Knots, Diminishing To 10 To 15 Knots Late. Seas 4 To 6 Feet, Occasionally To 8 Feet. A Chance Of Showers And Thunderstorms Late This Evening And Early Morning, Then Showers And Thunderstorms Likely Late.
Thursday...West Winds 10 To 15 Knots With Gusts Up To 20 Knots, Becoming North 5 To 10 Knots In The Afternoon. Seas 3 To 5 Feet, Occasionally To 6 Feet. Showers And Thunderstorms, Mainly In The Morning.
Thursday Night...North Winds 5 To 10 Knots. Seas 2 To 4 Feet, Occasionally To 5 Feet. A Slight Chance Of Thunderstorms. A Chance Of Showers In The Evening, Then Showers After Midnight.
Friday...North Winds 10 To 15 Knots With Gusts Up To 20 Knots. Seas 2 To 4 Feet, Occasionally To 5 Feet. Showers Likely With A Slight Chance Of Thunderstorms In The Morning, Then A Chance Of Showers In The Afternoon.
Friday Night...Northwest Winds 15 To 20 Knots With Gusts Up To 30 Knots. Seas 2 To 4 Feet, Occasionally To 5 Feet. A Chance Of Showers.
Saturday...Northwest Winds 20 To 25 Knots With Gusts Up To 30 Knots. Seas 3 To 5 Feet, Occasionally To 6 Feet. A Slight Chance Of Showers.
Saturday Night...Northwest Winds 20 To 25 Knots, Diminishing To 15 To 20 Knots After Midnight. Seas 3 To 5 Feet, Occasionally To 6 Feet.
Sunday...Northwest Winds 10 To 15 Knots. Seas 2 To 3 Feet.
Sunday Night...Northwest Winds 5 To 10 Knots, Becoming Northeast After Midnight. Seas Around 2 Feet In The Evening, Then 1 Foot Or Less.
Monday...East Winds 5 To 10 Knots. Seas 1 Foot Or Less.
Monday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 3 Feet. Winds And Seas Higher In And Near Thunderstorms.
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Area Forecast Discussion
National Weather Service New Orleans LA
1132pm CST Wednesday Feb 8 2023

Issued at 732pm CST Wednesday Feb 8 2023

Scattered severe thunderstorms capable of producing tornadoes and damaging winds are moving across much of the northern and western CWA (County Warning Area) at this time and a tornado watch is in effect for this portion of the area until 11pm CST.

Thermodynamic profiles per the 00 UTC LIX sounding remain capable of supporting robust updrafts into the evening hours as these storms continue eastward. MLCAPE of 1300 j/kg, 0-3km lapse rates of 6.4 C/km and most notably 0-3km CAPE of 160 j/kg have fueled these storms thus far. Shear profiles that were marginal this afternoon, have gradually become more favorable with 0-1 km shear of 25-30kt and 0-3km SRH around 250 m2/s2 which has enabled more robust updraft development into supercellular structures. The main question into the late evening will be how quickly the favorable thermodynamic profiles wane which could induce weakening of convection into the overnight hours. This is particularly important with regards to the line of storms entering the CWA behind the warm sector convection as the corridor of recovery that has occurred is relatively narrow. With that being said, the linear structure of these storms and stronger 0-6km shear closer to the boundary will enhance the damaging wind threat along with the possibility of embedded tornadoes especially over SW MS and the Florida Parishes during the next 6 hours as this line progresses across the area.

Beyond the severe threat, training storms are already causing some areas to begin to exceed flash flood guidance and flash flood headlines could be required for parts of the Florida Parishes as the next round of storms approach the area in the coming hours.

.SHORT TERM... (This evening through Thursday night) Issued at 145pm CST Wednesday Feb 8 2023

The biggest concern in the short term is the potential for severe through the remainder of this afternoon and overnight tonight ahead of an approaching cold front.

Already seeing scattered to numerous showers and storms across portions of the area, especially west of I-55. 18z sounding indicated a good bit of instability with about 2100 J/kg of surface based CAPE with significant moistening having occurred in the low levels compared to the 12z sounding. The 12z sounding indicated a 3 degC inversion starting around 675mb. That inversion has weakened a bit (now 2 degC) and lowered slightly, starting around 700mb. Low level shear has decreased slightly from the 12z sounding as well with surface winds trending a bit more southerly than southeasterly compared to earlier this morning. As of the 18z sounding, surface to 1km shear was about 20kts with surface to 3km shear of 25kts. This is not overly impressive but should still be enough to sustain some longer- lasting updrafts, especially when considering that shear should increase a bit as the afternoon progresses. Still looks like the main threat from any storms that do become severe will be damaging wind gusts, but as usual with severe threats along the Gulf Coast, we cannot rule out a tornado or two either, especially if any discrete supercells develop ahead of the main line. Still looks like the greatest local threat of severe weather, especially tornadoes, will be across southwestern Mississippi and the adjacent portions of southeast Louisiana.

Switching gears to the potential for heavy rain, the 18z sounding also indicated precipitable water has increased to 1.14 inches, which already puts us around the 25th percentile for this time of year. With continued onshore flow and moisture return, expect that value to continue increasing through the evening. Model soundings continue to indicate PW values (Precipitable Water values) of 1.5-1.6 inches by this evening which is above the 90th percentile for this time of year and nearing the daily maximum PW. That being said, efficient rainfall rates are expected from some of the stronger storms and if any one area sees multiple storms in a short period, these higher rainfall rates could easily lead to ponding of water in low lying and poor drainage areas. Still not enough confidence in specific areas to go ahead with a flood watch, but certainly there is at least some threat of isolated flash flooding and the marginal risk highlighted by WPC seems warranted.

Going into this evening and overnight, the upper trough becomes negatively tilted and lifts northeastward toward the Great Lakes. In response, the cold front will push into our local area. However, deeper layer flow will become more parallel to the front at the same time as forcing lifts northeastward. This will cause the front to slow down or stall somewhere near the coast. Where exactly the front stalls will have a fairly significant effect on what can be expected, especially across portions of far southeastern Louisiana and coastal Mississippi. Currently, it looks like the surface boundary should have enough push to make it through the local area by daybreak, with all land-based locations having north/northwesterly winds by about midday Thursday.

However, mid/upper winds will remain southwesterly/westerly until a stronger upper level impulse arrives. With that being said there could still be some lingering elevated showers/storms on the back side of the surface boundary. Uncertainty in exactly where the boundary stalls and thus the amount of lingering shower/thunderstorm activity makes for a somewhat tricking temperature forecast through the short term also. Cold air advection behind the front should result in cooler afternoon temperatures topping out in the 60s, especially if clouds linger. However, in areas where clouds move out, temperatures could easily rise to near or just over 70s degrees. Overnight lows will be similarly affected by clouds Thursday night. In areas where there are few to no clouds, efficient radiative cooling should allow temperatures to drop into the 40s. Where clouds linger, temperatures will be a bit warmer, bottoming out in the 50s.

Long Term
(Friday through Tuesday night) Issued at 145pm CST Wednesday Feb 8 2023

A northern stream trough currently located over the northwestern CONUS will dive southward toward Texas Thursday. As the base of the trough moves into northern Louisiana, guidance continues the trend of developing a cutoff low over Mississippi/Alabama. As mentioned in this morning's AFD, this would likely result in a bit more lingering cloud cover and light drizzle across the area through at least midday Saturday until the upper low moves east of the local area. That being said, Saturday looks pretty uncomfortable by most southern standards for outdoor activities. Highs will struggle to reach the mid 50s and these temperatures will be accompanied by 10-15 mph winds and possibly on and off drizzle.

Sunday will still be cool as the high passes overhead, with highs around 60. However, with full sun and less wind, it won't be nearly as uncomfortable even after a chilly start in the 30s that morning. Warming trend begins on Monday as the high shifts eastward ahead of the next system on Tuesday. Expect another cold frontal passage on Tuesday with accompanied high rain chances and a cool down following.

Marine
Issued at 145pm CST Wednesday Feb 8 2023

Expect scattered to numerous showers and storms this evening and overnight as a cold front moves through the waters. Ahead of the front, a tight gradient will keep winds in the 15 to 20 kt range through at least the first part of the evening and have extended the exercise caution headline accordingly. Winds stay elevated across eastern areas through around daybreak before easing as the front stalls in the vicinity. Will mention that there is some potential that winds will briefly reach advisory criteria across the eastern waters mainly between 00z and 06z. It is very borderline (sustained winds forecast right at 20 kts) and low confidence, so given the likely short duration, have held off on an advisory for now, but if winds trend any higher than currently forecast, will need to hoist a short-notice headline. The front is expected to stall in the vicinity of our southeastern waters with lingering showers and a few storms continuing through Friday. A stronger upper low finally kicks the front out of the area Friday and strong cold air advection will cause winds to strengthen again, likely reaching advisory criteria after sunset Friday evening. The elevated winds persist through the first half of the weekend, but should ease on Sunday as high pressure moves into the area. The high moves eastward on Monday with return flow kicking in by Monday afternoon ahead of another cold front.

NOAA New Orleans LA Office: Watches - Warnings - Advisories
LA...Flood Watch through Thursday morning for LAZ039-058>060-064-065- 070-071-076>082-087>090.

GM...None. MS...Flood Watch through Thursday morning for MSZ070-071-077-080>082.

GM...None.