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 261724 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 1224 PM CDT Sun May 26 2024 ...New AVIATION... .SHORT TERM... (Today through Monday) Issued at 340 AM CDT Sun May 26 2024 Upper ridging from the western Gulf of Mexico into Mississippi early this morning, with shortwaves over Oklahoma and Colorado. At the surface, high pressure was centered along the Atlantic Coast. Southerly winds continued to pump moisture into the area, but it is only being noticed in surface dew points in the 70s across the area. Temperatures were mainly in the 70s at 3 AM CDT, but there were several locations that have struggled to fall below 80 degrees. The 00z LIX sounding carried a precipitable water value of 1.37 inches, which is actually right at the climatologic median for the date. Not much in the way of moisture in the sounding beyond the lowest 4000 feet. Today is going to look a lot like Saturday across the area, with only some cumulus clouds during the day, as highs get into the 90 to 95 range across most of the area away from the immediate coastline. Dew points in the low to mid 70s will generally produce heat index values in the 100 to 105 range. There will be a bit more of a breeze this afternoon, which may take the edge off the heat a bit. A northern stream shortwave will push a frontal boundary close enough to the area to give the potential for a few showers or thunderstorms to southwest Mississippi prior to sunrise Monday. Monday (Memorial Day) could be a bit interesting, weather-wise. It currently appears that the main forcing from mid level shortwaves will be passing east of the area during the morning, with the frontal boundary near the north edge of the CWA before starting to become diffuse. For much of the area, precipitable water values never get much above 1.5 inches during the day Monday. Forecast soundings across the area generally show convective temperatures on Monday in the mid 90s or even a little higher. And we could get pretty close to mid 90s across much of the area. The main question is whether there is enough forcing to develop convection by late Monday afternoon. Most of the convection allowing mesoscale modeling shows no convection developing late Monday afternoon, but there are a few solutions that do. CAPE values run 3500-4000 J/kg or higher, steep low level lapse rates, DCAPE values near 1500, Lifted Indices near -10. Bottom line...it`s entirely possible that most or all of the CWA remains dry tomorrow, but if convection DOES develop, it will probably become severe, with damaging winds the main threat. Prior to storms developing (if they do), it`s going to be hot. Dew points and temperatures look to run a degree or two warmer than today, and there will be less wind. The current numbers in the forecast give heat index values pretty close to our 108F advisory criteria. Given that this is the first real hot spell of the season, and there will be a lot of people spending a lot of time out in that heat with holiday activities, have opted to issue a Heat Advisory for a large portion of the CWA for Monday afternoon. && .LONG TERM... (Monday night through Saturday) Issued at 340 AM CDT Sun May 26 2024 Northern stream shortwaves will gradually produce troughing over the Great Lakes and toward the Atlantic Coast during the early portion of the new week. That troughing will gradually force what is left of the frontal boundary toward the coast Tuesday and Wednesday. With the upper flow over the local area becoming more northwesterly over time, there will be the potential for weak shortwaves moving toward the mean trough position to develop convection during the heat of the afternoon each day. The operational GFS is much more bullish on this occurring than is the operational ECMWF, which has little or no convection beyond tomorrow until next weekend. The NBM PoP numbers favor a bit drier solution than the GFS operational, but not to the extent of the ECMWF. For now, that appears to be a decent compromise, with mainly afternoon convection on the isolated to scattered side. The slow moving boundary also means that the drier air will be a bit delayed compared to earlier forecasts, with dew points in the 60s probably not arriving until Tuesday night or Wednesday. Areas south of Interstate 10 may not see dew points fall below 70 all week. However, if convection does develop, the associated clouds may aid in holding temperatures below 90 degrees for much of the area beyond Tuesday. At this time, do not anticipate Heat Advisories beyond Monday. && .AVIATION... (18Z TAFS) Issued at 1202 PM CDT Sun May 26 2024 Most terminals currently in VFR condtions. Cumulus growth across the area may drop any given location to MVFR and at time of developing this discussion this is the case at KGPT. MVFR conditions will predominate overnight as ceilings lower, but return to VFR as tomorrow morning progresses. KMCB shows IFR with low ceiling and reduced visibility for several hours before sunrise. Slight chance for TSRA at KMCB around sunrise and KGPT just after sunrise worth mentioning here in discussion, but will wait for subsequent package issuance to see if inclusion in TAFs are needed. && .MARINE... Issued at 340 AM CDT Sun May 26 2024 May be brief periods this afternoon and overnight where winds creep up just above 15 knots over the open waters. This may necessitate Small Craft Exercise Caution headlines, probably overnight tonight. Beyond tonight, winds over the waters are likely to remain near or below 15 knots through the rest of the week. && .PRELIMINARY POINT TEMPS/POPS... MCB 72 92 70 91 / 20 20 10 20 BTR 78 96 75 95 / 10 20 0 20 ASD 76 94 74 95 / 10 20 10 20 MSY 78 93 77 93 / 10 20 10 20 GPT 77 91 74 93 / 0 20 10 20 PQL 76 91 73 95 / 0 20 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Heat Advisory from noon to 8 PM CDT Monday for LAZ034>037-039- 046>048-056>060-064-065-071-076>090. GM...None. MS...Heat Advisory from noon to 8 PM CDT Monday for MSZ068-077-083- 084-086-087. GM...None. && $$ SHORT TERM...RW LONG TERM....RW AVIATION...DS MARINE...RW