Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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523 FXUS64 KLIX 270902 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 402 AM CDT Mon May 27 2024 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (Today through Tuesday) Issued at 350 AM CDT Mon May 27 2024 Upper ridge remains over Mexico early this morning but has been suppressed southward by a shortwave extending from the Great Lakes to Texas. A cold front was just ahead of this trough extending from the Great Lakes to near Shreveport to central Texas. Scattered thunderstorms continued in a couple of bands with the closest to the local area extending from near Meridian to Natchez to Alexandria at 3 AM CDT. Temperatures at that time across the local area ranged from the upper 70s to lower 80s with dew points in the mid and upper 70s. Dual concerns for today will be thunderstorms and heat related issues. Ongoing convection should be somewhat elevated, if forecast soundings are any indication. Low level winds just ahead of the band approaching the northwest corner of the CWA have become a bit more southwesterly, making us question the strength of low level convergence. Most of the mesoscale modeling has the western portion of the line weakening or dissipating prior to sunrise, with only scattered activity potentially impacting areas from McComb to the Mississippi coast prior to noon. The boundary looks to become rather diffuse over the northern portion of the CWA later this morning or afternoon with very little in the way of low level convergence indicated by forecast wind fields. Diurnal heating is likely to be the main trigger if any convection is to develop. With forecast soundings indicating convective temperatures in the mid 90s by the middle of this afternoon, it is rather questionable as to whether convection will develop at all. If it does, strong to severe storms with damaging winds would become a significant concern with all the mid-level drier air available. Any convection that does develop should wind down pretty quickly after sunset. Prior to the convective development, hot and humid weather will be in place. Heat index values generally topped out in the 100-105 range yesterday, and both temperature and dew point values will be a degree or two higher, nudging values today to right around 108 in the advisory area. With it being early season heat and outdoor activities higher than normal, keeping the advisory in place is the preferred path. For Tuesday, with the weakening boundary still hanging around, can`t eliminate at least isolated thunderstorm development, although the GFS based solution is the only one really advertising much in the way of storms. Will hold onto the previous PoPs for Tuesday, but confidence isn`t particularly high. Somewhat drier air should slowly filter into the area tomorrow, lowering heat indicies somewhat, even though high temperatures will remain in the lower and middle 90s. The highs on the Mississippi coast may be a bit tricky depending on whether a sea breeze develops or not. If winds remain offshore, they could reach well into the middle 90s. && .LONG TERM... (Tuesday night through Sunday) Issued at 350 AM CDT Mon May 27 2024 Quite a bit of disagreement in medium range rain chances between the GFS based and ECMWF based guidance. The area will be in northwesterly mid level flow for Wednesday through at least Friday. With the exception of agreement on a shortwave producing thunderstorms Wednesday afternoon, the ECMWF solutions are much drier than the GFS solutions. With the trough axis to the east of the area, there`s a tendency to downplay any convective threat, but I`ve seen too many times that convection around the periphery of a ridge tends to "overperform". We`ll keep some mention of afternoon convection in the forecast. By the weekend, the model families flip with the ECMWF solutions the wetter choice. High temperature forecast will obviously be tied to precipitation chances, with the drier model solution the hotter one. For now, will go with the NBM deterministic, hoping for better agreement between the model families. Overnight lows should be at least slightly more comfortable beyond Tuesday night with slightly drier air in place. && .AVIATION... (06Z TAFS) Issued at 1204 AM CDT Mon May 27 2024 Intermittent MVFR CIGs are likely to extend through the overnight hours with more BKN coverage mixing in and southerly winds will remain near 10 knots. Will be monitoring latest guidance for trends in SH/TS activity headed into the morning hours. Uncertainty exists regarding extent of coverage of stronger thunderstorms starting late morning into evening and will likely need to add and refine timing of these storms for terminals in subsequent forecasts. Have added more emphasis on TSRA impacts to ASD and HDC as well as highest confidence of impacts being to GPT in the 1400-1800 UTC timeframe. && .MARINE... Issued at 350 AM CDT Mon May 27 2024 With the boundary to the north expected to weaken, the weaker pressure gradient should allow winds to diminish a bit later this morning. Current plan is to let Small Craft Exercise Caution headlines expire. Once that occurs, we should be in a pattern that will be driven by diurnal heat processes with onshore/offshore diurnal trends. This usually doesn`t result in wind speeds strong enough to require headlines. && .PRELIMINARY POINT TEMPS/POPS... MCB 92 69 92 67 / 20 10 20 10 BTR 96 75 95 72 / 30 10 30 10 ASD 94 74 94 71 / 30 10 10 10 MSY 93 77 93 75 / 40 10 20 10 GPT 90 74 93 72 / 40 10 10 10 PQL 91 72 95 69 / 30 10 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Heat Advisory from noon today to 8 PM CDT this evening for LAZ034>037-039-046>048-056>060-064-065-071-076>090. GM...None. MS...Heat Advisory from noon today to 8 PM CDT this evening for MSZ068-077-083-084-086-087. GM...None. && $$ SHORT TERM...RW LONG TERM....RW AVIATION...TJS MARINE...RW