Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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650 FXUS64 KLIX 020458 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 1158 PM CDT Wed May 1 2024 ...New UPDATE, AVIATION... .UPDATE... Issued at 1144 PM CDT Wed May 1 2024 Earlier isolated convection near Baton Rouge has finally dissipated, so have removed mention from the overnight forecast. No other changes. && .UPDATE... Issued at 1004 PM CDT Wed May 1 2024 Convection near Baton Rouge has persisted longer than anticipated and have gone ahead and updated that area for isolated showers and storms. A very small area may be seeing heavy rain as cells aren`t moving much. Anticipating that we should see a diminishing trend prior to midnight CDT. No other changes made at this time. && .SHORT TERM... (This evening through Thursday night) Issued at 211 PM CDT Wed May 1 2024 A fairly strong mid to upper level shortwave ridge axis continues to dominate the Gulf South today and this will continue into the overnight hours. Beneath this mid to upper level ridge, southeast flow off the Gulf of Mexico will continue. This onshore flow regime will continue to pump Gulf moisture into the low levels, and dewpoints will remain elevated in the 60s. This will also limit overnight cooling with lows only falling into the upper 60s and lower 70s tonight. These values are 5 degrees warmer than average. Although conditions do not look as favorable for fog development tonight due to stronger boundary layer winds of around 15 knots and increasing cirrus coverage from storms over Texas, some patchy fog development could occur right around daybreak over inland areas. Tomorrow will see a fast moving shortwave trough axis push in from Texas. The majority of the forcing with this system will be shunted to the north of the CWA due to the strength of the ridge axis aloft, but weakening band of showers and thunderstorms could push into the northwest third of the CWA tomorrow afternoon. Have bumped PoP values to 50 to 60 percent for areas to the north and west of Baton Rouge where the combination of higher upper level omega and enough cooling aloft to weaken the strong mid-level cap should be in place to support updraft development. Away from this region, the influence of the ridge and resultant subsidence will be strong enough to keep the mid-level cap in place. This is evident by weak mid-level lapse rates of around 5.5-5.7 C/km tomorrow afternoon across coastal Louisiana and coastal Mississippi. Fortunately, for the areas that could see some convective activity tomorrow afternoon, shear values will remain weak, and severe storms are not expected. By tomorrow evening, the convective threat will diminish as the shortwave trough pulls to the northeast and a brief period of increased ridging and negative vorticity takes hold of the northwest third of the CWA. Temperatures will be closer to average tomorrow into tomorrow night as increased cloud cover reduces overall solar insolation. && .LONG TERM... (Friday through Tuesday night) Issued at 211 PM CDT Wed May 1 2024 Another shortwave trough will quickly move through the region on Friday, and this trough is expected to impact the area more effectively. This will be due to both the lingering weakness in the ridge from the previous system on Thursday, but also a more southern origination over the Texas coast that will push the core of the shortwave trough the Lower Mississippi Valley. With the core of the shortwave moving more over the region, the mid-level cap will break down more easily, and this will allow for greater MLCAPE of 500-1000 J/KG in the afternoon hours when temperatures rise into the upper 70s and lower 80s. Have went with fairly high PoP of 50 to 70 percent for areas along and north of the I-10 corridor in Southeast Louisiana and Southwest Mississippi where overall forcing and instability will be maximized. A fairly sharp cut-off in convective activity is expected to the south, and have only went with a 20 to 30 PoP for areas around New Orleans and the River Parishes Friday afternoon. PWATS will surge to around 1.75 inches, so some locally heavy downpours will be the primary concern with the deeper convection that develops. Shear values will remain limited, so severe storms are not anticipated on Friday. The trough axis will pull east of the area Friday evening, and a rapid reduction in convective activity is expected during the evening hours. The mid to upper level ridge will intensify over the region on Saturday and continue to build in strength through early next week. As this occurs, subsidence and warming aloft will begin to greatly limit convective potential over the area and also lead to very warm temperatures for this of year. Saturday will be the last day with any convective threat as another fast moving shortwave feature slides through the Mid-Mississippi Valley, but only isolated storms are expected as mid-level lapse rates start to weaken with the strengthening cap in place. By Sunday, any rain chances will be finished with the ridge fully dominating the region. Temperatures will warm into the mid 80s on Saturday, and will further warm into the upper 80s and lower 90s by Monday. With onshore flow and higher dewpoints persisting through the extended period, lows will only cool into the upper 60s and lower 70s each night. It will be a very Summer-like feel out there early next week, and extra caution is advised for those working outdoors due to a lack of acclimation. A few record highs could be approached or broken. && .AVIATION... (06Z TAFS) Issued at 1144 PM CDT Wed May 1 2024 Over the last hour or so, have seen MVFR ceilings...near FL012...develop at several terminals. Combining that with the NBM probabilities of visibilities of a mile or less around sunrise coming in lower than earlier in the evening, it appears this will be more of a low stratus event. Will be carrying IFR ceilings at most terminals from 08 or 09z through about 14z, before improvement to MVFR. Still seeing widely varying solutions regarding convective expectations on Thursday. That includes the amount of areal coverage, timing, and how far east storms make it before dissipating. Primary threat appears to be during the afternoon hours from about noon to 5 pm, mainly west of Interstate 55 and north of Interstate 12. With the uncertainty, will carry VCTS at KMBC/KBTR/KHDC. Beyond 00z Friday, MVFR ceilings likely for much of the night. && .MARINE... Issued at 211 PM CDT Wed May 1 2024 A persistent surface ridge centered over the Southeast CONUS will keep southeast winds of around 10 knots in place through the weekend and into early next week. Seas will also be fairly persistent at 1 to 3 feet through the period. Overall, no significant concerns to maritime operations are anticipated through early next week. && .PRELIMINARY POINT TEMPS/POPS... MCB 63 84 66 80 / 0 50 40 60 BTR 70 85 70 81 / 10 50 30 50 ASD 67 84 69 83 / 0 30 20 30 MSY 71 84 72 82 / 0 30 20 20 GPT 68 81 71 81 / 0 20 10 20 PQL 65 82 69 82 / 0 10 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...PG LONG TERM....PG AVIATION...RW MARINE...PG