Marine Weather Net

Southwest Pass of the Mississippi River to Port Fourchon, LA 20 - 60 NM Marine Forecast


TODAY

SW
WINDS
5 - 10
KNOTS

TONIGHT

SW
WINDS
10
KNOTS

THURSDAY

W
WINDS
5 - 10
KNOTS

THURSDAY NIGHT

W
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
GMZ572 Forecast Issued: 421 AM CDT Wed Apr 08 2020

Today...Southwest Winds 5 To 10 Knots. Seas 1 To 3 Feet. Dominant Period 5 Seconds.
Tonight...Southwest Winds Near 10 Knots. Seas 1 To 3 Feet. Dominant Period 5 Seconds.
Thursday...West Winds 5 To 10 Knots. Seas 1 To 3 Feet. Dominant Period 6 Seconds.
Thursday Night...West Winds 5 To 10 Knots Becoming North 10 To 15 Knots After Midnight. Seas 1 To 2 Feet. Dominant Period 5 Seconds. Slight Chance Of Showers After Midnight.
Friday...Northeast Winds 15 To 20 Knots. Seas 2 To 4 Feet. Dominant Period 4 Seconds. Chance Of Showers Through The Day.
Friday Night...East Winds 15 To 20 Knots. Seas 3 To 5 Feet. Dominant Period 5 Seconds.
Saturday...Southeast Winds 15 To 20 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 5 Seconds. Chance Of Showers And Thunderstorms.
Saturday Night...South Winds 15 To 20 Knots. Seas 4 To 7 Feet With Occasional Seas To 9 Feet. Dominant Period 7 Seconds. Slight Chance Of Showers And Thunderstorms Through The Night.
Sunday...Southwest Winds 15 To 20 Knots. Seas 6 To 10 Feet With Occasional Seas To 11 Feet. Dominant Period 8 Seconds. Chance Of Showers And Thunderstorms.
Sunday Night...West Winds 10 To 15 Knots. Seas 5 To 8 Feet With Occasional Seas To 10 Feet. Dominant Period 9 Seconds. Slight Chance Of Showers And Thunderstorms In The Evening.
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Synopsis for Pascagoula to SW Pass Mississippi - GMZ501
Synopsis for SW Pass Mississippi River to Atchafalaya River- GMZ500
421 AM CDT Wed Apr 8 2020

High pressure will remain through Thursday morning. A cold front will settle into the coastal waters late Thursday, followed by a surge of cool high pressure Friday. This front is then expected to surge northward as a warm front Saturday, then another cold front is expected to push through the central Gulf coast region Sunday night.
Area Forecast Discussion
National Weather Service New Orleans LA
429am CDT Wednesday April 8 2020

Glancing at the surface maps this morning, the weak surface high axis off the east coast of Florida has subtly pressed west into the eastern Gulf, combined with a recent weak warm frontal passage (now undergoing frontolysis in central MS/AR) has allowed for a very noticeable surge in surface dewpoints. Many locations have seen a 8-12 degree rise in Td's, and will notice a summer-like early morning feel to the air with plenty of dew to go around. In such a moist airmass, it won't take much to produce a few isolated areas of drizzle this morning, primarily in and around marine areas (model soundings indicating a nearly saturated, moist adiabatic profile in the 0-1km layer, below a subsidence inversion around 900mb. Have added a few isolated drizzle/showers to accommodate this. Otherwise, the main story for today will be continued very warm conditions. Main focus in regards to this will be forecast highs and the relation to the larger surge in surface to low-level moisture. This may yield afternoon heat indicies in the lower to mid 90's for some, especially west of I-59 and including the southshore - which will feel more like early summer today. The Storm Prediction Center does have our NW counties and parishes in a Marginal Risk for severe thunderstorms, however diving deep into CAM's and Global models does not really illustrate much of a widespread risk. One run of the HRRR (High-Resolution Rapid Refresh) tonight did show one small cell skimming our SW MS counties later this afternoon. While there will be plenty of instability to go around today thanks to the recent surge in low-level moisture, the missing item here is a clear dynamic trigger (weak impulse more to our north), and the threat appears to be too isolated to mention much today. Following this afternoon, the next feature to focus on will be to our north, with a fast moving storm system and attendant cold front sparking a widespread severe weather event across the mid- mississippi valley to ohio valley regions. This front and ongoing convection across north-central MS and northern AL early Thursday morning will progressively slide south. Even though we are just talking ~24 hours from now, models are not handling the speed and PoP coverage of this front well at all. Such a large suite of models (including Global ECMWF/GFS solutions) keep the front well back to the north at or before 12Z THU (even the extended 36hr 06Z HRRR (High-Resolution Rapid Refresh) is lagging with almost zero coverage) Not anticipating any severe weather risks IF the front OR cells form along the front early Thursday morning.

Next area to focus on will be the strong, upper-level low out west as the next shortwave impulse/stretched area of vorticity advances east downstream of the trough then spinning its way across southern NV/CA. This will send the next rain mass our way late Thursday evening into Thursday night/Friday morning. Pretty much all of our land areas will be in a much cooler, post-frontal airmass with the aforementioned front slowing/stalling just along the SE LA coastline. With this impulse racing east on top of this stable airmass, there may be a few elevated thunderstorms generally along/south of I-10/12. Marine areas may need to be monitored closely either along the stationary front or in the warm sector between 06Z and 15Z Friday, as a few strong to possible severe storms may be possible (Storm Prediction Center has the Day 2 MRGL as west as the LCH/LIX CWA border, but will still need to be monitored). Once this disturbance passes, we will deal with one more dry day on Friday with generally mostly cloudy skies and mild, yet comfortable temperatures.

Then comes the upper-low from the west by this weekend. The slow movement of the upper-low is due to the subtle blocking pattern and how it's more off on its own, however the next Henry kicker trough dives across the Pac NW in the progressive NW to SE flow dominating the northern US. This will pick up the strong upper- low, open it more to a neutral trough across central Texas on Saturday, and press east our way early Sunday, and become negatively tilt in this process. Even though we are talking about Saturday and/or Sunday - this needs to be analyzed closely and lets go ahead dive deep. The negative tilted nature of the trough will yield explosive cyclogenesis downstream across the ARKLATEX/lower to mid-MS valley of the region (Euro targeting in on a sub 990mb low across central AR). Comparing the GFS and EURO show similar solutions and overall dynamics, but mostly with timing differences (GFS faster/Euro slower). Will hold back on leaning towards either one's timing, however know that a slower solution like the Euro would place a significant severe weather event somewhere in our CWA due to peak daytime heating and impressive shear/instability profiles. Even if it is faster, and the (what would appear by storm mode to be a QLCS) is earlier in the day on Sunday, and instability is somewhat on the low side, it may still be enough to cause widespread severe weather. Storm Prediction Center did in fact add our area in a Day 5 outlook, and mention the points previously made here as well as calling this a potential "substantial severe thunderstorm event". Look for more details as we get closer and may be subject to change, but getting the word out is the main focus at this point in time.

Won't dive into much in regards to the days beyond this system, but prognostic guidance continues to clearly hint at more of a cool down through early to the middle part of next week, back to near to slightly below normal temperatures for a change! We'll take it! KLG

Marine
SW winds around 10kt today will become more variable by Thursday and a cold front could push into the northern gulf early Friday bringing northerly winds at 15-20kt shifting to easterly by early Saturday. The front will stall and quickly return as a warm front during the day Saturday bringing southerly winds back to the area. There will be times of sh/ts Thursday through the weekend. A cold front should move through by the start of the new week bringing northerly winds at around 20kt.

NOAA New Orleans LA Office: Watches - Warnings - Advisories
LA...None. GM...None. MS...None. GM...None.