Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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310 FXUS64 KLIX 201757 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA Issued by National Weather Service Jacksonville FL 1257 PM CDT Thu Jun 20 2024 ...New AVIATION... .UPDATE... Issued at 1025 AM CDT Thu Jun 20 2024 Current forecast on track. The morning sounding shows very moist low level flow generally from the east and a PWAT value of 1.68 inches. PWAT is just shy of normal values for this time of year. Low level RH was measured about 85 percent, which will make for scattered to broken cumulus and enough moisture and low level convergence to generate scattered showers and a few storms during the daytime heating, mainly southern half of the forecast area. Radar shows isolated to scattered shower activity over southeast LA at this time, and is expected to increase in coverage and intensity a bit through the afternoon and early evening before fading. Given the fairly quick movement of the convection from east to west, rainfall amounts will generally be light. Breezy easterly winds continue today at 15-25 mph, with gusts up to 30-35 mph. No changes to the rest of the forecast package at this time. && .SHORT TERM... (Today through Friday) Issued at 400 AM CDT Thu Jun 20 2024 Tropical Storm Alberto about to make landfall on the Mexican coastline early this morning, and expected to weaken rapidly and dissipate during the day today as it reaches higher terrain in Mexico. As the pressure gradient weakens, the wind field should relax somewhat. However, it will take time for the winds and swell to abate. Additionally, with no significant change in the wind direction, it will take some time for the higher water in the tidal lakes to drain. Current plan is to replace the Coastal Flood Warning with a Coastal Flood Advisory beyond today`s high tide cycle for tomorrow`s high tide cycle. It can be cancelled later if water levels fall quicker than forecast, but current guidance indicates there may be at least some minor issues on Friday. Upper ridging over the Mid-Atlantic States will build southwestward over the next couple of days and be centered near Memphis Friday afternoon. Water vapor imagery already shows drier air moving westward through much of the local area. This was noticeable in the 00z LIX sounding which showed a precipitable water value of 1.6 inches, compared to the 2+ inches we`d seen for the previous couple of days. Northern portions of the area may already have precipitable water values nearer to 1 inch, if the BMX sounding was any indication. We`ll continue to see drier air filter into the area, with precipitable water values closer to 1.2 inches by Friday afternoon. However, there may still be enough moisture both today and Friday to support at least a few showers or storms. We are even seeing that early this morning with a few echoes moving onshore from the Gulf. Most of that should be south of the Interstate 10 corridor both days, and rain amounts should be rather scarce. Have undercut the NBM PoPs somewhat, closer to the global numbers, as they`ve been overstating things for the last several packages. With less precipitation, and likely less clouds, that argues for going on the high end of temperature guidance, and the NBM deterministic numbers support this. That should put pretty much every one in the lower-middle 90s both today and Friday. && .LONG TERM... (Friday night through Wednesday) Issued at 400 AM CDT Thu Jun 20 2024 Upper ridging will continue to build westward, and be centered near the New Mexico-Arizona border on Sunday, where it will take up residence for next week. For the weekend, and potentially through Monday, there will be a southeastward extension of the ridge into the northern Gulf of Mexico. Any convective development over the weekend should remain on the isolated side and be limited to primarily the afternoon hours from about Interstate 10 southward. As we move into early next week, the upper flow across the area becomes northwesterly, which opens up the potential for shortwaves moving through that flow to trigger clusters of thunderstorms. Of course, timing those shortwaves at this time range is going to be handled differently by the models. Can`t see fighting the NBM PoPs for a target of opportunity beyond perhaps Monday. With precipitable water values well in excess of 2 inches for the middle of next week, certainly appears that storms could be efficient precipitation producers. NBM deterministic temperatures are generally on the high end of the guidance envelope for highs this weekend and Monday, which appears reasonable, as long as convection doesn`t develop too early in the afternoon. At mid week, things should trend a bit closer to normal, as the higher precipitable water values argue for an earlier start to convective development. Some potential for heat advisories for at least Sunday/Monday depending on timing of convective development, with heat index values approaching 110F. && .AVIATION... (18Z TAFS) Issued at 1250 PM CDT Thu Jun 20 2024 Most of the generally weak convection has moved off to the south and southwest, with activity near KNEW, KMSY, KHUM, and KBTR. Best chance of TSRA look to be near KHUM in the next 1-4 hours. Mainly MVFR cigs around KNEW at this time, but should improve a bit later this afternoon to VFR clouds. With the loss of heating in the evening hours, the cumulus clouds will diminish. Could be some light fog in a few spots but by and large maintained VFR at this time, given the low level winds will tend to keep low levels mixed. Easterly winds of 15 knots or greater will impact terminals south of Interstate 10...KGPT/KNEW/KMSY/KHUM through the late aftn hours. Lighter winds expected tonight. Mainly easterly flow again Friday to about 8-12 kt and a few higher gusts possible with generally scattered cumulus and a low threat of a shower but kept out for now in the TAFs given low probabilities. && .MARINE... Issued at 400 AM CDT Thu Jun 20 2024 As Tropical Storm Alberto makes landfall and weakens/dissipates over Mexico, winds and seas should gradually subside today. Will replace the Small Craft Advisory over the tidal lakes with Exercise Caution headlines with forecast issuance. Will extend Small Craft Advisory over the western open waters through this evening, but allow it to expire on schedule at 21z elsewhere. Can`t rule out needing brief Caution headlines on the back end of the advisory this afternoon/evening, but will let the day shift folks reassess that. Winds could remain around 15 knots for a good portion of Friday, but beyond that point, should be a much more benign period into early next week, outside of the potential for thunderstorms. && .PRELIMINARY POINT TEMPS/POPS... MCB 70 92 70 94 / 0 0 0 10 BTR 75 96 75 98 / 0 20 0 10 ASD 74 93 74 95 / 10 20 0 10 MSY 79 93 78 93 / 10 30 0 20 GPT 75 93 75 93 / 20 10 0 10 PQL 73 96 73 96 / 20 0 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Small Craft Advisory until midnight CDT tonight for LAZ068. Coastal Flood Warning until 4 PM CDT this afternoon for LAZ058- 070-076-078-080-082-084-086. Coastal Flood Advisory from 4 PM this afternoon to 6 PM CDT Friday for LAZ058-070-076-078-080-082-084-086. Coastal Flood Advisory until 6 PM CDT Friday for LAZ060-066>069- 077-087. GM...Small Craft Advisory until 4 PM CDT this afternoon for GMZ532- 536-538-555-557-575-577. Small Craft Advisory until midnight CDT tonight for GMZ550-552- 570-572. MS...Coastal Flood Warning until 4 PM CDT this afternoon for MSZ086. Coastal Flood Advisory from 4 PM this afternoon to 6 PM CDT Friday for MSZ086. Coastal Flood Advisory until 6 PM CDT Friday for MSZ087-088. GM...Small Craft Advisory until 4 PM CDT this afternoon for GMZ536- 538-555-557-575-577. Small Craft Advisory until midnight CDT tonight for GMZ552-570- 572. && $$ SHORT TERM...RW LONG TERM....RW AVIATION...ARS MARINE...RW