Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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700 FXUS64 KLIX 302054 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 354 PM CDT Tue Apr 30 2024 ...New SHORT TERM, LONG TERM, AVIATION, MARINE... .SHORT TERM... (This evening through Wednesday night) Issued at 259 PM CDT Tue Apr 30 2024 A fairly strong mid to upper level ridge axis will remain in firm control of the area through Wednesday night. Ample subsidence in the mid-level will lead to warmer and drier conditions aloft, and this will help keep a mid-level capping inversion and weak mid- level lapse rates in place. The end result will be a proliferation of fair weather cumulus development tomorrow, but PoP values will be at 5 percent or less through the entire short term period. Temperatures will be warmer than average due to the deep layer subsidence in place, and have highs climbing into the upper 80s over inland areas and the low to mid 80s along the coast. These values are around 5 degrees above normal. Onshore flow in the low levels will also keep dewpoints elevated, and this will result in overnight lows only dipping into the 60s tonight and tomorrow night. NBM deterministic values were used for temperatures. && .LONG TERM... (Thursday through Monday night) Issued at 259 PM CDT Tue Apr 30 2024 A series of weak and fast moving shortwave troughs will ride up and over the mid to upper level ridge axis from Thursday through Monday. Most of the strongest forcing associated with these troughs will remain displaced to the north of the CWA, but enough cooling and forcing aloft should support the development of some isolated to scattered convection each day. Initially, the ridge will still be the most dominant feature over the area on Thursday, and this will greatly limit convective potential as mid-level lapse rates remain weak at around 5.5 C/km. The main impact from this system will be an increase in high level cloud cover and slightly cooler daytime highs in the mid 80s. The only area that may see an isolated shower or storm pop up will be in areas to northwest of Baton Rouge where just enough cooling aloft could help weaken the cap and allow for deeper updraft development. Friday will have the highest convective potential over the area as another shortwave trough slides through the region. This trough will be stronger than the one on Thursday, and will break down the ridge axis more efficiently. The result will be a weaker mid-level capping inversion, steeper mid-level lapse rates of around 6.0 C/km, and higher convective potential over the forecast area. There will be a north to south gradient with the highest PoP values for areas along and north of the I-10/12 corridor where scattered to numerous showers and thunderstorms could develop. To the south, more isolated convective activity is expected as the ridge axis will be more pronounced. PWATS also increase to around 1.5 to 1.75 inches, and this will support some locally heavy rainfall rates of 1 to 2 inches per hour with the deepest convection. The convection will be fairly progressive in forward motion, so any flood threat will be limited. Fortunately, wind shear will also be very limited on Friday, so strong to severe thunderstorm activity is not expected. The increased convective activity and cloud cover will keep temperatures near average in the lower 80s. The convective threat will quickly end Friday evening as the shortwave moves to the east and the deep layer ridge axis rebuilds back over the area. Rain chances decrease over the weekend and into early next week as the mid to upper level ridge axis becomes more dominant and the ridge riding shortwave troughs shift more toward the mid- Mississippi Valley. At most, an isolated shower or storm could develop over the northern third of the CWA on Saturday as the ridge continues to reassert itself, but dry conditions are expected for Sunday and Monday. As the ridge builds in, temperatures will rise in response to the increased subsidence aloft, and expect to see daytime highs climb a good 10 degrees above average into the upper 80s and possible the lower 90s by Sunday and Monday. Persistent onshore flow in the low levels will keep dewpoints in the 60s and lows will be warmer than average in the upper 60s and lower 70s. && .AVIATION... (18Z TAFS) Issued at 259 PM CDT Tue Apr 30 2024 Drier air has mixed down into the boundary layer this afternoon, and this has allowed for prevailing VFR conditions to take hold at all of the terminals. These VFR conditions will persist through around 10z tomorrow, but another inversion will result in boundary layer decoupling once again after 10z. Fog probabilities are highest at GPT, NEW, and MSY, and have included prevailing IFR ceilings of 300 to 500 feet and MVFR visibilities of 3 to 5 miles in the forecast from 10z to 14z at these terminals. At MCB, fog probabilities are lower, but have opted to include a period of IFR conditions between 11z and 13z. After 14z, drier air will mix into the boundary layer, and a return to VFR conditions at all of the terminals is expected. PG && .MARINE... Issued at 259 PM CDT Tue Apr 30 2024 No significant weather concerns are expected for the maritime zones through the end of the week. A persistent southeast flow of around 10 knots and seas of 1 to 3 feet can be expected through the weekend on the southwest periphery of a surface high dominating the Southeastern CONUS. && .PRELIMINARY POINT TEMPS/POPS... MCB 60 89 64 85 / 0 0 0 10 BTR 64 89 67 86 / 0 10 0 20 ASD 65 87 66 85 / 0 0 0 10 MSY 68 85 70 84 / 0 10 0 10 GPT 67 83 68 82 / 0 0 0 0 PQL 65 84 65 83 / 0 0 0 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...PG LONG TERM....PG AVIATION...PG MARINE...PG