Marine Weather Net

Port Fourchon, LA to Lower Atchafalaya River, LA out 20 - 60 NM Marine Forecast


REST OF TODAY

E
WINDS
15
KNOTS

TONIGHT

E
WINDS
15 - 20
KNOTS

TUESDAY

E
WINDS
15 - 20
KNOTS

TUESDAY NIGHT

SE
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
GMZ570 Forecast Issued: 837 AM CST Mon Mar 08 2021

Rest Of Today...East Winds Near 15 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 6 Seconds.
Tonight...East Winds 15 To 20 Knots. Seas 3 To 5 Feet With Occasional Seas To 6 Feet. Dominant Period 7 Seconds.
Tuesday...East Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 7 Seconds.
Tuesday Night...Southeast Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 7 Seconds.
Wednesday...Southeast Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 7 Seconds.
Wednesday Night...Southeast Winds 15 To 20 Knots. Seas 4 To 7 Feet With Occasional Seas To 9 Feet. Dominant Period 8 Seconds.
Thursday...Southeast Winds 15 To 20 Knots. Seas 4 To 7 Feet With Occasional Seas To 9 Feet. Dominant Period 8 Seconds.
Thursday Night...Southeast Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 8 Seconds.
Friday...Southeast Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 8 Seconds.
Friday Night...Southeast Winds 15 To 20 Knots. Seas 3 To 6 Feet With Occasional Seas To 8 Feet. Dominant Period 8 Seconds.
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Synopsis for Pascagoula to SW Pass Mississippi - GMZ501
Synopsis for SW Pass Mississippi River to Atchafalaya River- GMZ500
837 AM CST Mon Mar 8 2021

High pressure over the coastal waters will gradually shift eastward through the week.
Area Forecast Discussion
National Weather Service New Orleans LA
1112am CST Monday Mar 8 2021

.MORNING

SHORT TERM (Today through Wednesday Night)... Starting off the new week a bit chilly across the area early this morning. Surface high pressure has steadily drifted south and east into the southeastern US which has promoted a steady lowering in surface winds compared to 24 hours ago. Many locations will end up in the upper 30's to lower 40's to start the day, with some traditionally colder areas (drainage locations northshore to coastal MS) possibly reaching the mid 30's. Blends also came in a bit too warm for the southshore as winds have finally become calm enough for radiational cooling to take over, as some areas in this region likely reaching the lower to mid 40's as we start the day. Confident on this lower bias against blends as short-range guidance illustrates very strong subsidence in the mid to low- level troposphere, with HRRR (High-Resolution Rapid Refresh) and RAP13KM guidance coming in around 0.10 to 0.14" PW by 12Z this morning. Will be interesting to see the 12Z KLIX RAOB (Radiosonde Observation or Upper-Air Observation) shows as it will be well below the lowest PW for this day according to Storm Prediction Center Sounding Climatology (March 8th 12Z Min of 0.23") which goes to show just how dry the air truly is that has settled in with this surface high. Otherwise, we moderate quickly later today as the aforementioned surface high continues to drift east across the southern Atlantic states, with winds becoming more from the southeast. Going to keep this trend going of a few degrees above blends for highs today, as many areas reaching right at or just above 70 for a high. Plenty of PBL mixing later today from surface heating will drop afternoon dewpoints fast, similar to yesterday and have introduced a RAP13KM/HRRR (High-Resolution Rapid Refresh) blend into afternoon dewpoints, which better handles PBL mixing generally along and north of I-10/12. Additionally, with SE winds cranking back up off marine areas, we will likely see a seabreeze/lakebreeze boundary from Lake Pontchartrain, east to the MS coast which following the boundary passage will pull Td's back up, along with more of a transition of southerly winds to follow. No clouds in the forecast but cant rule out some friendly contrails for later today.

Going into tonight, persistent (but light) southeasterly winds will continue to steadily drag moisture back into the area which will prevent any radiational cooling similar to what we saw this morning. Lows will not be as cold across the region, still may be a bit chilly east of I-55 with lows reaching the lower 40's, especially in typical colder areas. Rinse and repeat for Tuesday with us warming up a few degrees warmer into the mid 70's as southeasterly moist return flow continues to deepen across the region. This will help moisten the PBL just enough at the base of a strong subsidence inversion to get some patchy low-level cumulus (or cloud streets) to develop. In addition, some patchy upper-level clouds will be advecting east across the region in response to a deepening west coast trough (UL moisture stretching east then southeast over a southern US ridge) but overall, a very nice day!

Going into Wednesday, temperatures continue this moderation trend with highs getting comfortably into the mid to upper 70's. Will not be surprised to see a few 80's here and there making for another very nice day. However, clouds begin to thicken at both the low-levels with widespread Cu, and in the mid to upper-levels making for a partly to mostly cloudy day. Not seeing any shower chances regardless of strengthening/deepening moist southerly return flow, as the same aforementioned strong subsidence inversion continues anchored in place helping to keep a cap on any potential activity. To summarize...it'll be nice through mid- week. KLG

LONG TERM (Thursday and beyond)... Surface pattern going into the end of the week resembles a Bermuda High setup. Both the GFS and ECMWF (European Centre for Medium-Range Weather Forecasts) feature upper ridging over the Gulf of Mexico at that time. With the low level flow becoming onshore, low level moisture will increase. So we can't rule out a few, emphasis on few, showers as early as perhaps Friday afternoon. Starting to see a little bit of agreement between the medium range models, as the GFS solutions have been coming in somewhat slower over the last few runs. Any frontal passage, likely occluded, looks now to hold off until Sunday night or Monday. Since there's still quite a bit of uncertainty regarding timing, don't see a particular benefit to making changes to the blended Probability of Precipitation grids at this time.

Will continue to trend high temperatures above the blended numbers by a couple degrees, close to the operational numbers, for Thursday into the weekend, with temperatures around 80 pretty common. If the timing on the latest GFS/ECMWF holds regarding frontal passage, currently forecasted high temperatures Sunday, and even moreso on Monday, will need to be raised. Sunday's would need raised at least 3-5 degrees, and perhaps as much as 5 to 10 degrees on Monday. 35

Marine Discussion
Surface high pressure will continue to drift east across the southern Atlantic states, with persistent easterly to transitioning southeasterly winds expected today. Not anticipating any hazards weather concerns through late week. However, continued southeasterly flow/longer fetch will begin to slowly increase waves/seas with time, especially by Wednesday through late week with waves increasing to 4 to 6 feet south of the MS delta, climbing close to 7ft through late week. Next potential storm system later in the upcoming weekend to possibly early next week with a cold front and some showers and thunderstorms possible. However, confidence on timing at this time remains low KLG

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