Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
628 FXUS64 KLIX 281036 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 536 AM CDT Mon Sep 28 2026 ...New AVIATION... .KEY MESSAGES... Updated at 535 AM CDT Mon Sep 28 2026 - During the latter part of this week, a period of more active weather appears likely. While there is still significant uncertainty regarding the specifics, heavy rain could become a concern mainly Friday into the weekend. && .SHORT TERM... (Now through Thursday) Issued at 1022 PM CDT Sun Sep 27 2026 Most, if not all, of this fcast can be seen by splicing together the upper and mids level sections of the synoptic picture. We will stay on the H3 level for this section of the fcast to get a cleaner pic of what`s occurring. The upper trough over the east CONUS is bringing one more shot of dry air down into the SE part of the country. This is located currently over Kentucky moving south. The upper trough extends down the east coast to near the Yucatan. The trough will remain stalled where it is. Other features such as the upper high over northern Mexico will then move NE over the next few days causing this upper trough over the east coast/gulf to sharpen as the next upper trough digs into the inner-mountain west. Knowing what we know about upper/mid level troughing, textbook troughing scenarios tells us that there is subsidence in the axis(not always the base) of the upper trough with pooling moisture and best lift on their east(pva) side. So putting this together, one can easily see there will be a sinusoidal difference in the moisture fields which will unfold in a zonal orientation starting Thu. By the way, the atmosphere is rarely textbook. The setup will look like this in the layered RH fields across the CONUS by Thu, dry over the west coast transitioning to moist over the TX panhandles back to relatively dry down the southern Miss River valley, back to wet over the SE CONUS then back to dry again over the Atlantic. This is the basic build up of what we will see as time moves toward the weekend. Between the two deep moisture areas(the east side of each trough) there has to be highs, which is going to be the case. The high over our area will become sharply ridged as it gets squeezed between the upper troughs. This sets up two fairly distinctive air masses. One of these is continental and the other is tropical. By Wed, sfc moisture will stream back into the area, but the upper/mid ridging will keep the area capped with mostly showers forming and maybe a storm or two. But as the sharp upper troughing moves west, this will change as it will allow the deep tropical moisture to move into the gulf coast. Where that occurs is still in question. For that answer, we will need to look at which model is initializing the best currently and the winner to that one goes to the Euro. We will see some strong differences in solutions for the upcoming days as the jet energy that produces this will be over the open Pacific, but eventually, as the jets move over the upper air network again, we will get more of a consensus in the solutions. The earliest that this looks to occur will be Wed. By the way, the hurricanes over EASTPAC will also play a role as they are, as always, responsible for delivering a tremendous amount of heat energy to the mid/upper levels of the atmosphere, which in turn drives and strengthens the winds at these levels causing flow differences as well. So this will continue to be a moving target until we get next to it. && .LONG TERM... (Thursday night through Sunday) Issued at 1022 PM CDT Sun Sep 27 2026 Lingering continental dry air will continue to suppress development of afternoon convection keeping PoPs limited through Tuesday. Seasonable dew points and PWATs of the short-term period will give way to increasing moisture with a return flow regime advecting gulf air into the area on Wednesday. This will begin the conditioning process of the atmosphere headed into the latter part of the week with increasing PoPs each day. Global model guidance continues to support the arrival of a tropical wave into the area by Friday which will bring a surge of deeper tropical moisture sending PWATs toward daily record maximums (>2.3 inches). This will promote widespread, daily afternoon convective activity with storms capable of highly efficient rainfall rates exceeding 2 to 3 inches per hour. This will increase the risk for localized to areas of flash flooding, especially for urban and poor drainage areas. However, one thing this set up lacks is the mid-upper level support and lift to promote widespread convection and thus a higher risk for excessive rainfall. Something to watch over the coming days will be trends with the stalled trough over the central CONUS that is delivering ample lift over deep tropical Pacific moisture from the remnants of Hurricane Polo. As this trough lifts out, its propagation and remnants of any shortwave that linger near the Gulf Coast could align to produce a period of higher lift and more favorable dynamics for excessive rainfall over the area. At this time, there is disagreement on what, if any, remnants of this shortwave sticks around through the weekend. The main window for the excessive rainfall risk will be Friday through Sunday. It`s favored that elevated moisture and the wetter pattern will persist into the following week as we don`t see a strong frontal passage clearing out this moisture field just yet. && .AVIATION... (12Z TAFS) Issued at 535 AM CDT Mon Sep 28 2026 VFR through this cycle. && .MARINE... Issued at 1022 PM CDT Sun Sep 27 2026 Winds over all coastal waters will remain light and sometimes variable through today. Winds will become predominantly SE by Tuesday at around 10 knots then rise further into mid next week to around 15 to 20 knots as a cold front approaches the coast. && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$ SHORT TERM...TE LONG TERM....TJS AVIATION...TE MARINE...TE