Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
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559 FXUS64 KLIX 132235 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 535 PM CDT Mon May 13 2024 ...New UPDATE... .UPDATE... Issued at 534 PM CDT Mon May 13 2024 Developing squall line over southwest LA has already had a history of producing a few tornadoes and widespread wind damage. This line is expected to accelerate some moving into the CWA between 6 and 7 and then across most of the area before midnight. It will also likely remain severe and thus SPC has issued Severe Thunderstorm Watch 239 until midnight tonight for the entire area. Main concern is damaging winds possibly greater than hurricane force force along with large hail and even a few tornadoes. /CAB/ && .SHORT TERM... (This evening through Tuesday night) Issued at 342 PM CDT Mon May 13 2024 Key Messages: 1. A flood watch remains in effect for areas along and south of the I-10/12 corridor due to the threat for heavy rainfall that could result in localized flash flooding primarily in urban and poor drainage areas. 2. An enhanced risk for severe weather remains primarily along and south of the I-10/12 corridor for the threat of a secondary round of storms moving into the area this evening with damaging winds and hail being the primary threat, but a tornado cannot be ruled out. The morning convection has surged southeast into the coastal waters putting down a decent cold pool that has moderated temperatures and stabilized the air mass overhead for now. SPC mesoanalysis and LCH 18z special sounding have indicated that ample instability (CAPE >5000 j/kg and ML lapse rates >7.5 C/km) and sufficient 0-6km bulk shear (~45-50kt) lay just to our southwest which has initiated the second round of deep convection over coastal Texas. This second round is anticipated to continue to deepen and organized as it traverses southwest LA and surges east into our area. Timing of this MCS has sped up to the earliest arrival into the Atchafalaya Basin to be by 6-7PM CDT. Given the strength of the developing cold pool with this MCS, 12z HREF guidance, and latest CAMs the expectation is for this system to be more progressive though will pack a punch with damaging winds and hail being the primary severe threat. Locally heavy rainfall (rainfall rates of 2-3"/hr) will be another concern for urban and poor drainage areas along and south of the I-10/12 corridor. Once this squall line pushes through over the course of 4-6 hours, we`ll be monitoring the progression of the cold pool boundary to ensure it clears coastal LA and diminishes the flooding threat. The current thinking is all severe and flooding threat should be over by sunrise on Tuesday. Clearing skies by Tuesday afternoon will allow us to rapidly warm up back into the upper 80s, and we should see temps follow strong diurnal curves through midweek thereafter. Warmest day of the week appears to be Wednesday which is collocated best with an amplifying shortwave ridge and as well as mostly fair skies. && .LONG TERM... (Wednesday through Sunday night) Issued at 342 PM CDT Mon May 13 2024 The next upper troughing will then move out into the plains by mid week with sfc return flow forcing this boundary back to the north moving back over the area possibly as early as Thu and this whole thing looks to play out again similar to this event. The first disturbance moves through mid day Thu and may hug the coast. This should be associated with the warm front. The next main system will move along the cold frontal interface as it stalls across the area with an abundance of deep moisture Fri. This is at least one solution, but as one can clearly see with the current system, this will almost surely change several times before we get there. The general synoptic structure looks valid, but we will definitely need to get closer to even think of resolving the smaller scale features. TE && .AVIATION... (18Z TAFS) Issued at 1252 PM CDT Mon May 13 2024 MVFR to IFR CIGs will prevail through the remainder of the daylight hours. Some breaks to scattered coverage can be expected with the wake of the morning showers and storms, but expect redevelopment of VCTS through the afternoon primarily along and north of I-10/12 corridor. Another complex of strong to severe thunderstorms are expected to move in from the west after 00 UTC tonight with TEMPOs noted for windows of highest confidence of TSRA impacts. However, timing is still somewhat uncertain with exact evolution of these storms. After this line of storms clears the area through 06-09 UTC timeframe, expect SHRA to persist into sunrise in the morning with gradual improvement of CIGS/VIS as the day progresses on Tuesday. && .MARINE... Issued at 342 PM CDT Mon May 13 2024 Higher winds (15-25 knots) and seas (3-7 feet) are expected through the overnight hours tonight. Strong thunderstorms moving through the area could result in locally higher winds and seas which will be dangerous for small crafts. Winds become more west to southwesterly and decrease to less than 10 knots through the afternoon on Tuesday where hazards to small crafts will decrease. Southerly component to light winds remains intact through midweek but becomes more easterly with time by later in the week. && .PRELIMINARY POINT TEMPS/POPS... MCB 64 84 61 86 / 70 20 0 0 BTR 68 89 65 91 / 70 20 0 0 ASD 68 87 66 91 / 90 50 0 0 MSY 71 87 71 89 / 90 30 0 0 GPT 69 86 67 89 / 90 60 0 0 PQL 68 87 66 91 / 90 60 0 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Flood Watch through late tonight for LAZ046>048-056>060-064>070- 076>090. GM...Small Craft Advisory from 1 AM to 10 AM CDT Tuesday for GMZ530- 532-534-536-538-555-557-575-577. MS...Flood Watch through late tonight for MSZ083>088. GM...Small Craft Advisory from 1 AM to 10 AM CDT Tuesday for GMZ532- 534-536-538-555-557-575-577. && $$ SHORT TERM...TJS LONG TERM....TJS AVIATION...TJS MARINE...TJS