Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
982 FXUS64 KLIX 131818 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 118 PM CDT Sun Sep 13 2026 ...New SHORT TERM, LONG TERM, AVIATION, MARINE... .KEY MESSAGES... Updated at 116 PM CDT Sun Sep 13 2026 - Lower rain chances and warmer temps return first half of the week. Heat indices could approach Heat Advisory Criteria. - Stronger easterly winds may result in small craft advisory conditions for the latter half of the week in the coastal waters. && .SHORT TERM... (Now through Wednesday night) Issued at 116 PM CDT Sun Sep 13 2026 The mid-level shortwave that moved across the Lower Mississippi Valley yesterday is now well east of the local area (already crossing the Appalachian Mountains). Meanwhile, 500mb heights are rising from the west as an upper level ridge axis that extends from south Texas to Canada begins expanding toward the region. Today is been the start of a transition toward a drier pattern than recent days as subsidence increases from that ridge and column moisture drops a bit. Storms that do develop increasingly tied to the sea breeze, differential heating, and leftover outflow boundaries. We`re seeing that now with minimal coverage outside of capped showers south of I-10 in Louisiana. In addition, increasing heights along with less shower/storm activity will allow temps to moderate solidly into the 90s. The upper ridge becomes centered across the Tennessee Valley region Monday and should remain the dominant feature across the southern US through at least the middle of the week. Increasing subsidence beneath the ridge will result in a noticeable reduction in convective coverage compared with last week, although enough boundary-layer moisture should remain for isolated to scattered afternoon storms along the sea breeze and other mesoscale boundaries. So think along the lines of 20-40% coverage Monday with highs generally in the lower to mid 90s. Will be watching heat index forecast closely as a few locations should be approaching advisory criteria. Biggest question is if enough of the area will be warm enough to justify even a targeted advisory. Tuesday currently appears that it will be the hottest and relatively driest day this forecast period as the 596-598DM ridge remains strongest overhead or just to the north. Afternoon highs in the mid 90s combined with dewpoints generally in the lower to middle 70s should yield heat indices largely in the 100 to 107 degree range. So again, right at the cusp of Heat Advisory criteria. A few localized locations could reach just above 108 if temperatures reach the warmer end of guidance while dewpoints remain elevated. Conversely, greater mixing or an isolated afternoon storm would knock apparent temperatures down quickly. Strong subsidence from that ridge will really stunt POPs as well during this timeframe. Rain chances may start to creep up along coastal areas of the CWA as trough the north flattens the northern side of the nearby upper ridge and also causes it to weaken some. MEFFER && .LONG TERM... (Thursday through Saturday night) Issued at 116 PM CDT Sun Sep 13 2026 Global models continue to favor continued weakening of the portion of the upper ridge aloft as an upper low approaches from the Florida/western Atlantic region. One interesting feature to watch with this synoptic evolution is dry slot on the northwestern side of the upper low coming across the Gulf. Models suggest it may be pulling in dry air caught underneath the ridge into the CWA, effectively keeping rain chances down quite a bit inland with most of the convection along the coast and in the open Gulf waters. From the temps side, you`d think lower 500mb heights means cooler temps. In this particular situation, as drier air mixes to the surface, dewpoints crater. That`ll result in a wider diurnal range in temps with lower lows and higher highs. The great thing is that even though air temp still reaches mid 90s, those mid aftn sub-70 dewpoints will keep heat indicies drastically lower than earlier in the week. Somewhere on the order of 10-15 degrees cooler for those max heat indices. MEFFER && .AVIATION... (18Z TAFS) Issued at 116 PM CDT Sun Sep 13 2026 VFR conditions will dominate the forecast period outside of convection. Subsidence from upper level ridge moving into and across the Lower Mississippi Valley is really stunting shower/storm development today. Radar shows only isolated to scattered showers south of KMSY/KNEW and that activity is so capped that showers have been struggling to mature into thunderstorms. This activity should dissipate as daytime heating drops off this afternoon into the early evening hours. Light and variable winds will persist through the period. MEFFER && .MARINE... Issued at 116 PM CDT Sun Sep 13 2026 A broad surface high over the area will keep benign conditions in place across the waters through Tuesday with light and variable winds of less than 10 knots and seas of less than 2 feet expected. A few showers or storms will pop up in the morning hours with some locally higher winds and waves, but these impacts will be short- lived each day. The pressure gradient will begin tightening Wednesday and remain that way as an amplifying surface ridge draped along the Eastern Seaboard expands southwestward and takes over the high currently over the northeastern Gulf. This will create an easterly flow regime with strengthening winds. Latest forecast calls for winds to increase to at least 20 to 25 knots with gusts approaching gale force Wednesday into Thursday. Seas will respond to these higher winds and increase to 8 to 10 feet. Some minor coastal flooding may also impact east facing shorelines over this period. MEFFER && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...ME LONG TERM....ME AVIATION...ME MARINE...ME