Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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293 FXUS64 KLIX 171145 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 645 AM CDT Mon Jun 17 2024 ...New AVIATION... .UPDATE... Issued at 348 AM CDT Mon Jun 17 2024 A final look at marine observations required an adjustment to the Small Craft Advisory over western waters to initiate the advisory immediately. No other changes made. && .SHORT TERM... (Today through Tuesday) Issued at 338 AM CDT Mon Jun 17 2024 Upper ridging centered over the Carolinas this morning, with a second ridge over Baja California. A weakness between the two is combining with the Central American Gyre to pump deep moisture northward across the local area. An area of low pressure is expected to develop over the Bay of Campeche over the next couple of days associated with the Gyre. The impulse that produced showers and storms across the area on Sunday has moved north of the area, but the next impulse is already noted on water vapor imagery over the central Gulf of Mexico moving northward. The 00z LIX sounding last evening already showed precipitable water values in excess of 2 inches, which is above the 90th percentile climatologically. Already seeing radar returns on LCH radar over their coastal waters, and expect to start seeing them on the HDC radar over the next hour or so. Deep moisture is expected to remain in place today with precipitable water values remaining in the 1.9 to 2.2 range, which will be in the top 10 percent climatologically for mid June. Expect pretty widespread areal coverage of precipitation today, which will produce locally heavy downpours (2 inches per hour possible). Not everyone will see rainfall that heavy, but if one occurs over an urban or poor drainage area, it will have the potential to cause localized flash flooding. Over the course of the day, areal average rainfall of 1 to 2 inches appears likely, with spot higher totals. However, don`t expect widespread totals heavy enough to justify a Flood Watch at this time. Similar to Sunday, expect a significant decrease in areal coverage of showers/storms toward sunset this evening, through the overnight hours. Another surge of showers and storms is expected on Tuesday, with precipitable water values similar to today. However, the impulse driving that round is expected to be further west, more toward western Louisiana, where the axis of heavier rainfall is expected. The pressure gradient between the expected low pressure over the Bay of Campeche and high pressure over the Carolinas will bring an increase in surface winds across coastal areas, especially on Tuesday. A Wind Advisory may be necessary across coastal areas near and to the south of Interstate 10 on Tuesday. The persistent southeast winds expected will cause higher tide levels along east and south facing shorelines as early as late tonight, and don`t see a need for adjustments to the Coastal Flood Advisory at this time. Regarding temperatures, can`t rule out a few spots touching 90 degrees today or tomorrow, but the high areal coverage of showers and storms should hold highs in most areas in the 80s. With the deep moisture remaining in place, overnight lows are going to have a tough time dropping below the mid 70s tonight. && .LONG TERM... (Tuesday night through Sunday) Issued at 338 AM CDT Mon Jun 17 2024 Wednesday and Thursday are expected to be comparatively dry as upper ridging builds back in from the east briefly. The airmass only dries out somewhat with precipitable water values falling to about 1.8 inches and no large scale forcing. We should be back to more of a summertime convective regime with overnight/early morning marine convection and isolated to scattered afternoon precipitation over land. Beyond Thursday, details remain uncertain regarding an inverted trough to our east. At this point, it appears that significant precipitation associated with the trough should remain to the east of the local area for the weekend. Even with the drier weather Tuesday night/Wednesday, the southeasterly winds will continue pushing water toward the coast, with water levels somewhat higher Wednesday than Tuesday. At this point, it appears that we should stay at advisory levels, but can`t entirely rule out the need for a Coastal Flood Warning in a few of the more vulnerable locations. The tidal lakes will probably need to be added in a later forecast package, as they may have issues by Wednesday or Wednesday night. High temperatures Wednesday and Thursday will creep up a bit from today and tomorrow to around 90, then into the lower and middle 90s over the weekend. Overnight lows will continue to be above normal. && .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... Issued at 338 AM CDT Mon Jun 17 2024 Have noted a few locations seeing sustained winds near or just above 20 knots this morning. Small Craft Exercise Caution headlines will be replaced with Small Craft Advisories over most waters at 12z, although it may take until midday for some waters to get near 20 knots sustained. Advisory level conditions expected to continue overnight tonight into at least Tuesday morning. Not out of the question that we could reach gale levels over portions of the waters Tuesday or Wednesday, but we will allow oncoming shift to take another look. The long fetch of these winds will produce a swell train over the open waters which is likely to push seas to at least 9 to 12 feet over the open waters by Tuesday night into Wednesday. Hazardous to dangerous conditions should be anticipated for much of the work week, especially over the open waters, with not much improvement expected until perhaps 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 as issued previously, and will likely eventually need extended into Thursday. Coastal Flood Warnings may be necessary for more sensitive spots by Tuesday night or Wednesday. Will hold off on tidal lakes for this run, as it appears their main water concerns may hold off until Wednesday night or Thursday. && .PRELIMINARY POINT TEMPS/POPS... MCB 86 72 84 72 / 80 30 40 10 BTR 88 77 87 76 / 90 30 60 10 ASD 87 76 87 76 / 90 40 60 20 MSY 87 80 87 81 / 90 40 80 30 GPT 88 77 88 77 / 80 40 60 30 PQL 90 76 91 76 / 80 40 40 30 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...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 GMZ536-538-555- 557-575-577. Small Craft Advisory until 7 AM CDT Thursday for GMZ550-552-570- 572. 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 GMZ538-555-557- 575-577. Small Craft Advisory until 7 AM CDT Thursday for GMZ552-570-572. && $$ SHORT TERM...RW LONG TERM....RW AVIATION...RW MARINE...RW