Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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331 FXUS64 KLIX 172058 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 358 PM CDT Mon Jun 17 2024 ...New SHORT TERM, LONG TERM, AVIATION, MARINE... .Key Messages...
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1. Scattered to numerous showers and thunderstorms are expected again Tuesday, but the heavy rain threat as a whole will be lower as the overall coverage and duration of heavier rain decreases. 2. Strong east-southeasterly winds across the northern Gulf will cause tide levels to rise above normal tonight, with minor coastal flooding expected Tuesday during the time of high tide and minor to potentially moderate coastal flooding during high tide Wednesday. A few low lying roads may become covered with water or impassable, especially during high tide Wednesday morning. 3. Winds will become quite gusty Tuesday and Wednesday and could blow around some light weight outdoor items. A wind advisory may be needed for some portions of the area, mainly south of the tidal lakes.
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&& .SHORT TERM...
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(This evening through Wednesday night) Issued at 244 PM CDT Mon Jun 17 2024 NHC has started advisories on Potential Tropical Cyclone (PTC) One in the Bay of Campeche. This system is not expected to have any direct impacts on the local area, but due to its large size and interaction with a strong high over the eastern US, some indirect impacts are likely. PTC One is forecast to become gradually better organized through the short term. As this happens, the pressure gradient will tighten across the local area, resulting in a strengthening wind field across the local area. Currently the wind and gust forecasts are still just below wind advisory criteria, but the next shift or two will need to continue taking a closer look. IF a wind advisory becomes necessary, it is most likely for areas south of the tidal lakes in southeast Louisiana. Strong east-southeasterly flow across the northern Gulf waters will cause tides to rise above normal by tomorrow morning and minor coastal flooding is likely during high tide. Water levels will be highest during high tide on Wednesday, and could result in a some low lying roads becoming impassable, mainly in the more vulnerable areas on the west/southwest side of Bay St. Louis. Based on the forecast, water could also cover some low lying portions of Hwy 1 between Port Fourchon and Grand Isle. Looking at the probabilistic water level guidance, there is still some potential that a coastal flood warning may be needed Wednesday morning, mainly for areas from Shell Beach to Bay St. Louis. Regarding water levels in the lake, will again hold off on any headlines around the lake shores for now as water levels in the lake are expected to lag those on the open coast by 1-2 days. The guidance at New Canal on the south shore does indicate an advisory may be needed by the high tide cycles late Wednesday and Thursday, though. The plume of deep tropical moisture that has been with us since yesterday will shift a bit to the west tomorrow. While there will still be plenty of moisture to support scattered to numerous showers and storms across the area, but rainfall rates should come down just a bit and the duration of heavier rain in any location should also limit the flood threat. Thus WPC continues to carry only a marginal risk of excessive rainfall leading to flash flooding on Tuesday. By Wednesday the bulk of the moisture shifts even further southwest with drier air moving into the local area. Generally scattered showers and storms are still in the forecast, with possibly higher coverage across coastal southeast Louisiana. With the precipitable water dropping back down closer to 1.75, which is above normal but not remarkably so, rainfall rates are not expected to be as dramatic as what we`ve seen today, and the flooding rain threat is fairly low. Afternoon temperatures will generally be near to below normal through the short term due to cloud cover and the higher rain chances. Morning lows will be above normal owing to the higher than normal dewpoints preventing the temps from dropping much below the mid 70s most places.
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&& .LONG TERM...
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(Thursday through Sunday night) Issued at 244 PM CDT Mon Jun 17 2024 Going into Thursday and the weekend the forecast is a little murky and kind of depends on where various moisture plumes end up. Currently, the NBM/consensus approach keeps the deeper tropical moisture out of our local forecast area, though there is quite a bit of uncertainty regarding the evolution of various vorticity features rotating through the central american gyre. With no confidence in any specific ensemble member solutions, see no reason to stray from the NBM at this point in the longer term forecast. This results in scattered to numerous POPs each day mainly across southern areas with lower POPs farther inland. Temperatures should be near to above normal based on the current forecast.
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&& .AVIATION... (18Z TAFS) Issued at 244 PM CDT Mon Jun 17 2024 Outside of showers and storms, expect prevailing VFR to MVFR conditions. Scattered to numerous showers and storms will bring occasional restrictions to the terminals today as deep tropical moisture moves through the area. High rainfall rates will temporarily reduce visibility to ifr conditions as showers and/or thunderstorms move over the terminals. Convection should wane somewhat after sunset, but will increase in coverage again by mid to late morning Tuesday. Winds will also strengthen Tuesday in response to a tightening pressure gradient. && .AVIATION... (12Z TAFS) Issued at 634 AM CDT Mon Jun 17 2024 Most terminals VFR at issuance time this morning, with the exception of KMCB, where IFR ceilings were in place. Convection was rather isolated at 11z, but expect areal coverage to blossom in the next few hours as surface heating kicks in. MVFR ceilings may become predominant by 15z. SHRA will be main weather for the next few hours with the threat of TSRA at pretty much all terminals by midday. Areal coverage should be sufficient for TEMPO during the afternoon at all terminals with IFR or lower visibilities and MVFR ceilings. While wind gusts in excess of 30 knots are possible with the strongest cells, not high enough confidence to carry in most terminals. Areal coverage will diminish toward 00z Tuesday, with little or no precipitation between about 02z and 10z. MVFR to IFR ceilings may return toward sunrise Tuesday. Sustained winds near 15 knots possible during much of the daytime hours today before diminishing this evening. With low pressure expected to develop over or near the Bay of Campeche later today or tomorrow, stronger sustained winds are anticipated during the daytime hours tomorrow, with gusts of 25 to 30 knots not out of the question by mid-morning. && .MARINE...
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Issued at 244 PM CDT Mon Jun 17 2024 No significant change to the marine forecast with this package. Generally still expecting advisory conditions across most of the coastal waters through midweek as winds respond to a tightening pressure gradient between low pressure in the Bay of Campeche and high pressure centered over the east coast. Latest forecast does have a period of potentially gale conditions, mainly in the form of gusts from Tuesday night through Wednesday, but confidence is low enough that we will hold off on any gale watch for the time being. Regardless of whether winds reach gale conditions, a long fetch combined with a swell train emanating from the low in the SW Gulf will likely push seas to at least 9 to 12 feet over the open waters by Tuesday night into Wednesday. Hazardous to dangerous conditions will persist through much of the work week, especially over the open waters, and are not likely to see any significant improvement until Thursday night or Friday. As noted above, with the prolonged southeasterly winds, east and south facing shorelines will see increased water levels beginning overnight tonight, and a Coastal Flood Advisory will remain in effect and will likely eventually need extended into Thursday. Coastal Flood Warnings may be necessary for more sensitive spots by Tuesday night or Wednesday. Will again hold off on tidal lakes for now, as it appears their main water concerns may hold off until Wednesday night or Thursday.
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&& .PRELIMINARY POINT TEMPS/POPS...
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MCB 72 85 71 90 / 30 40 0 30 BTR 76 88 76 92 / 40 60 10 50 ASD 75 87 76 90 / 60 60 10 50 MSY 79 88 81 90 / 50 70 10 60 GPT 77 87 76 90 / 30 50 20 40 PQL 75 91 75 92 / 30 40 20 30
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&& .LIX WATCHES/WARNINGS/ADVISORIES...
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LA...Small Craft Advisory until 7 AM CDT Thursday for LAZ068. Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday for LAZ066>070-076-078. GM...Small Craft Advisory from 7 AM Tuesday to 7 AM CDT Thursday for GMZ530-532-534. Small Craft Advisory until 7 AM CDT Thursday for GMZ536-538-550- 552-555-557-570-572-575-577. MS...Coastal Flood Advisory from 1 AM Tuesday to 4 PM CDT Wednesday for MSZ086>088. GM...Small Craft Advisory from 7 AM Tuesday to 7 AM CDT Thursday for GMZ532-534. Small Craft Advisory until 7 AM CDT Thursday for GMZ538-550-552- 555-557-570-572-575-577.
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&& $$ SHORT TERM...DM LONG TERM....DM AVIATION...DM MARINE...DM