926 FXUS64 KSHV 131806 AFDSHV Area Forecast Discussion National Weather Service Shreveport LA 106 PM CDT Sun Sep 13 2020 .AVIATION... For the 13/18z TAFs, scattered showers and thunderstorms are quickly developing over Southeast Arkansas/Northeast Louisiana and Deep East along a weak upper level trough. Convective coverage should continue to increase through the remainder of the daytime hours, mainly affecting KLFK, KSHV, KELD, and KMLU. The storms should gradually end by 14/02z. MVFR ceilings also persist across portions of Northern Louisiana and Southern Arkansas, but clouds should continue to lift into the VFR range. However, ceilings will once again lower into the MVFR/IFR categories during the early morning hours, with a slow improvement after daybreak Monday. CN && .PREV DISCUSSION... /issued 1054 AM CDT Sun Sep 13 2020/ UPDATE... Scattered convection has quickly developed over the last hours in Southern/Southeast Arkansas and North Central/Northeast Louisiana near a weak inverted upper trough. Coverage of the showers and thunderstorms should increase through the day as diurnal instability builds. The best rain chances will remain over Louisiana and Southern Arkansas. Overall, the forecast for today appears largely on track, and no updates are anticipated. CN PREV DISCUSSION... /issued 351 AM CDT Sun Sep 13 2020/ SHORT TERM.../Today through Monday Night/ The morning upper air analysis indicates a weak inverted trough extending from the NW Gulf NE across SW/Cntrl/NE LA and SE AR, which is depicted well in the latest Water vapor imagery. In fact, the latest 12.3-10.35 um RGB imagery indicates extensive AC cigs have developed this morning along this trough axis, as we await diurnal heating for sct convection to again develop later today as this trough slowly retreats W across the area. Thus, convection will develop and spread farther W across the region today than what occurred Saturday, with good agreement amongst the short range progs and CAMs with increasing convection from late morning through the afternoon. Have maintained high chance and likely pops this afternoon from Deep E TX across much of N LA/Scntrl AR, but did expand slight chance pops farther W across the remainder of SW AR/much of extreme NE TX based on the model/CAMs consensus with isolated convection developing over these areas later today. The increasing cloud cover and rapid development of convection today should also result in slightly cooler max temps, before they quickly cool in and near the convection later in the day. This convection should quickly diminish around or shortly after sunset with the loss of heating, although convective debris and low stratus hang tough/develop overnight over areas that see rain. Our focus will then turn to Sally, who will likely strengthen into a hurricane Monday as she shifts NW across the Nrn Gulf of Mexico. Much of the ensemble consensus has shifted the center slightly farther W as it nears the SE LA coast Tuesday morning, but the approach of this system will also begin to advect drier air WSW into the region, with the effects of subsidence expected as well NW of the center, and also near weak ridging aloft that will build over the area. Thus, have toned pops down to low chance across the far Ern zones Monday afternoon, with slight chance pops across the Srn parishes of Ncntrl LA as well as the SW and Wrn sections of E TX, which may still see an influence in isolated diurnal convection with the remnants of the weak inverted trough aloft as it continues to drift W into Ncntrl TX. Did bump up the NBM max temps Monday closer to the MET/MAVMOS blend to account for the strong insolation once the morning low stratus scatters out, with the pressure gradient expected to increase by afternoon across the Ern zones closer to the center of Sally as she moves inland across SE LA. Any isolated convection over the Ern zones should diminish during the early evening (where slight chance pops remain), as the convection becomes concentrated closer to the center over SE LA/Srn MS. 15 LONG TERM.../Tuesday through Saturday Night/ There is a model consensus that a mid-level trough will extend from west Texas northeastward into the Missouri Valley on Tuesday, becoming more amplified as it slides across Texas and into the ArklaTex Wednesday into Friday. It is this feature along with weakening in the ridge over the Southeast that currently look to be a saving grace for our region, helping keep Sally to the east of our area. At 12Z Tuesday, the latest National Hurricane Center advisory has Sally strengthening to a Category 1 hurricane progged to make landfall on the southeast Louisiana coast. The GFS/ECMWF/Canadian solutions are all fairly consistent with the track of Sally making landfall along the LA/MS coast and then taking a more northward track along the MS river before turning more further northeastward and tracking into central Mississippi and Alabama by Wednesday. Given the current forecast track of Sally, more widespread rainfall associated with the center of the system should stay east of the area with only some possible fringe outer bands bringing a chance of locally heavy rainfall to the ArkLaMiss Tuesday night into Wednesday. Even chances of heavy rain in the ArkLaMiss are diminishing with less than an inch of rain expected with Sally. Aside from moisture associated with Sally across the southeastern half of the forecast area, the area will be mostly dry Tuesday. The mid-level trough crossing Texas will then contribute to a range of a to a chance of thunderstorms each day Wednesday into Friday. By Saturday, the trough axis and a cold front are progged to shift south of the area with relatively higher pressure help to dry out the area for Saturday. For temperatures, forecast is closest to the National Blend of Models (NBM) with highs in the mid to upper 80s across the area Tuesday through Thursday. Friday into Saturday highs will range from the lower 80s in southeastern Oklahoma and southwestern Arkansas to the upper 80s in Deep East Texas and west-central Louisiana. Lows will range from the upper 60s to lower 70s through Thursday night with lows ranging from the lower 60s in SE OK/SW AR to the upper 60s in Deep East Texas and central Louisiana into the weekend. /04-Woodrum/ && .PRELIMINARY POINT TEMPS/POPS... SHV 74 90 72 88 / 20 10 10 30 MLU 73 91 73 89 / 20 30 20 50 DEQ 69 86 69 86 / 10 10 0 10 TXK 71 86 69 84 / 20 10 10 20 ELD 71 87 69 87 / 20 10 10 30 TYR 72 87 70 87 / 20 20 0 10 GGG 72 89 71 88 / 20 10 10 20 LFK 73 91 73 92 / 20 20 10 30 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 09/20