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282 FXUS64 KLIX 171926AFDLIXArea Forecast DiscussionNational Weather Service New Orleans LA226 PM CDT Fri May 17 2024...New UPDATE, SHORT TERM, LONG TERM, AVIATION, MARINE....UPDATE...Issued at 200 PM CDT Fri May 17 2024Updated forecast through Saturday with a focus on timing of severe wx and heavy rainfall threat for the next event. Convection has struggled to develop so far today (and we aren't complaining). A special 18Z RAOB sounding from KLIX shows a subsidence inversion near 850 mb in wake of last night's MCS that has helped to cap convection thus far. We are closely monitoring for convection to initiate along the quasi-stationary frontal boundary that is located just south of a line from Lafayette to Baton Rouge to Hattiesburg. This boundary has become increasingly better-defined as differential heating has magnified the temperature gradient (upper 60s/lower 70s on the cool side of the boundary and mid 80s in the warm sector). Low-level convergence has also strengthened near the front and this will provide a source of lift, but appears to be too shallow for convective updrafts to reach the LFC. Recent satellite trends show the CU field is building just south of the warm front along the Southshore, Coastal MS, and parts of coastal southeastern LA. This is the area where storms are most likely to initiate through mid afternoon. Expect coverage of storms to be widely scaterred given the absence of deeper forcing. However, any storms that to break the cap has the potential to quickly become severe with an EML overhead and strong instability rooted in the boundary layer. These storms will be capable of producing locally damaging winds (favorable wet microburst environment with high instability and mid-level dry air) and large hail (steep mid-level lapse rates). &&.SHORT TERM...(Today through Saturday)Issued at 235 AM CDT Fri May 17 2024Although there are a few storms remaining early this morning, anysevere threat likely limited to borderline hail as main portion ofshortwave is east of the area. Quite a bit of uncertaintyregarding severe threat and heavy rain threat over the next 24hours. Deepest moisture remains just offshore where dew points arein the mid and upper 70s, but drier air is over the northernportion of the area, where dew points are in the lower 60s. Nextshortwave actually won't approach the area until the overnightperiod tonight into Saturday morning when precipitable water values will again approach 2 inches, as southerly surface winds pull moisture back into the area. Quite a bit of mid level dry airfor much of the area until perhaps 06z Saturday, and would anticipate that instantaneous areal coverage during the day today should remain on the scattered side, with a significant increasein areal coverage during the mid to late evening hours. Drier airreturns during the day Saturday.Will keep the Flood Watch in place, as there was a fairly sizeablearea of 1.5 to 3 inch rainfalls, and another inch or two on top ofthat overnight tonight could cause runoff issues. Will not move off the NBM temperature forecast at this time, butthe main question for high temperatures today will be cloud cover.&&.LONG TERM...(Saturday night through Thursday)Issued at 235 AM CDT Fri May 17 2024Upper ridging builds from Mexico into the Lower Mississippi RiverValley beginning Saturday evening through much or all of the workweek. At present, it appears that any significant chance ofprecipitation beyond tomorrow morning is likely to wait untilbeyond the end of the forecast package, with at least somepotential to remain dry through next weekend. Temperatures areexpected to remain above normal through the forecast period. &&.AVIATION...(18Z TAFS)Issued at 108 PM CDT Fri May 17 2024A stationary boundary was drapped across the region thisafternoon. Low clouds and fog has been socked in north of theboundary at KBTR and KMCB. Expected IFR conditions to continuethrough most of the afternoon although eventual improvement toMVFR should occur late in the day (between 21Z and 00Z). South ofthe boundary, CIGs are higher but a CU field has developed andkept the other TAF sites in MVFR CIGs. Expect bases to graduallyincrease through the rest of the afternoon and eventually VFR CIGswill become increasingly common south of the front. Coverage ofshowers and storms will be too isolated to mention in 18Z TAFsbefore about 02Z this evening. Showers and storms will becomebetter organized late this evening and especially overnight as a disturbance approaches. This activity will be focused along thefront which will progress slowly southward through the area.Confidence in heavy rain and an extended period of IFR/LIFRconditions increases farther south. This is reflected in the 18ZTAFs with the greatest restrictions and longest period of TSRAmentioned for HUM, MSY, NEW, and GPT. &&.MARINE...Issued at 108 PM CDT Fri May 17 2024The strongest winds thus far today has been present across the farsoutheastern coastal waters, but even here observations marginallysupport a SCA with occasional gusts to 20 kt. Winds have actuallybecome light over the lakes where the pressure gradient is lightnear a stationary boundary. Isolated thunderstorms are expected to develop near the coast latethis afternoon and early evening. Although coverage will belimited, any of these storms have the potential to produce locally strong winds in excess of 34 kt, large hail, heavy downpours, lightning, and higher seas. The risk of hazardousconditions on the waters will increase overnight and continuethrough Saturday morning as storms organize along the front andmove southward. Some of our model guidance is showing thepotential for intense convective wind gusts in excess of 50 kt, perhaps locally to hurricane strength.&&.PRELIMINARY POINT TEMPS/POPS...MCB 66 84 65 88 / 60 30 0 10 BTR 70 87 70 93 / 60 30 0 0 ASD 69 84 69 92 / 70 70 0 10 MSY 71 84 73 90 / 80 70 0 10 GPT 69 81 69 89 / 80 80 10 10 PQL 69 82 67 91 / 70 80 10 10 &&.LIX WATCHES/WARNINGS/ADVISORIES...LA...Small Craft Advisory until noon CDT Saturday for LAZ068. Flood Watch through Saturday morning for LAZ034>037-039-046>048- 057-058-060-064-071-076>087-089.GM...Small Craft Advisory until noon CDT Saturday for GMZ530-532-534- 536-538-550-552-555-557-570-572-575-577.MS...Flood Watch through Saturday morning for MSZ068>071-077-083>088.GM...Small Craft Advisory until noon CDT Saturday for GMZ532-534-536- 538-550-552-555-557-570-572-575-577.&&$$UPDATE...JKSHORT TERM...JK LONG TERM....RW AVIATION...JK MARINE...JK
