Area Forecast Discussion
Issued by NWS Lake Charles, LA
Issued by NWS Lake Charles, LA
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098 FXUS64 KLCH 120445 AFDLCH Area Forecast Discussion National Weather Service Lake Charles LA 1145 PM CDT Sat May 11 2024 ...New AVIATION... .UPDATE... Wx map shows weakening surface high pressure over the SE U.S. with a tightening pressure gradient across the Western Gulf of Mexico. East northeast winds around 5-10 mph along and south of I-10 across SW LA/SE TX, less than 5 mph further north and east. Previous forecast of increased chances of showers and thunderstorms verified. Main updates this evening involved the latest guidance catching up with the observed radar, which moved up the timing onset about 3 hours or so. Still expecting the highest chances north of I-10 this evening through the early overnight hours with this first impulse moving through. Many more impulses expected through Monday. Remainder of forecast parameters on track. 08/DML && .SHORT TERM... (Tonight through Monday night) Issued at 415 PM CDT Sat May 11 2024 A generally pleasant afternoon across the forecast area this afternoon, with surface high pressure centered north of the region underneath weak ridging aloft yielding light to modest easterly winds and a fair amount of sun, though the trend of increasing cloud cover is already underway. Temperatures across the area are generally in the lower to mid 80s, with dew points in the upper 50s to around 60 keeping humidity levels in the 40% range away from the coast. Water vapor satellite imagery clearly shows our upstream trouble maker swirling over the Four Corners this afternoon. This upper trof is progged to progress slowly EWD across the central CONUS over the next 72 hours or so, eventually resulting in a frontal passage heading into the long term forecast. Until then, however, a warm air/moisture advection regime coupled with perturbations translating through an increasingly active W/SW flow aloft will produce rounds of showers and thunderstorms. The devil as they say is in the details, and those are difficult to pin down. An initial bout of showers and thunderstorms is possible as early as tonight as the low level ridge axis continues to slide off to the east, strengthening the warm air advection/MSTR influx across E/SE TX as one of the aforementioned weak impulses traverses the TX Coastal Plain into the NW Gulf. Confidence on convective initiation and eventual evolution is low with a wide variation in solutions offered by guidance, thought the bulk depict little more than isolated/scattered showers and thunderstorms. Any activity that does develop will lift north with time such that it would likely be north of the area by SUN morning. Attention then shifts to a more substantial impulse progged to pivot through the ARKLATEX SUN afternoon/evening. If an organized/widespread rainfall event is to transpire tomorrow, this would be the catalyst, though once again there is decent spread in guidance. With that in mind, chose to defer on a flood watch at this time to allow subsequent shifts to monitor observational and guidance trends. With that said, do not begrudge my western/northern neighbors for issuing at this time as there is better consensus for an axis of heavy rain within the WPC Moderate Risk of excessive rainfall to our NW. Something of a reprieve is expected SUN night into MON morning, with generally good guidance consensus on a period of severe and flash flood potential arriving MON afternoon as the combination of another lead impulse plus the shortwave trof axis itself and associated SFC front near the region. Strong forcing for ascent coupled with ample MSTR/instability will yield widespread convection ahead of and along the frontal boundary. SPC and WPC have outlined the entire forecast in a SLGT risk of severe and of excessive rainfall respectively. The SFC front will progress through the area during the evening/overnight hours. 13 && .LONG TERM... (Tuesday through next Friday) Issued at 415 PM CDT Sat May 11 2024 Moving forward into Tuesday morning, remaining showers and thunderstorms will continue to shift east of the Mississippi with a broad region of subsidence developing over the Southern Plains into Central Texas throughout the day. Despite the cold front dropping dewpoints, there will be now CAA behind the front. Thus while conditions clear and dry out at the surface, temperatures will rise toward upper 80s toward 90 for many locations across SETX / SWLA. That trend follows through Wednesday. The upper level pattern continues to develop a week ridge across the Southern Plains while low level subsidence is more amplified along the central Plains. Meanwhile, looking upstream across the Four Corners region, there is a large mass of convergent air aloft begins to increase the magnitude of the subtropical Jet over Baja and northern Mexico. Naturally, divergence aloft over western Plains begins to develop precipitation along a frontal boundary. Concurrently, the sfc- 850mb lower troposphere layer continues indicate southerly onshore flow from the ridge now shifting over Appalachia while extending south into the eastern Gulf. Overnight Wednesday into Thursday, a frontal boundary develops under this scenario near the TX/LA Gulf Coast before lifting inland. Surface troughing deepens eastward over the central plains into the Tennessee Valley throughout the day. Thus, as this next shortwave setups to the west, numerical guidance has held a degree continuity of heavy precipitation potential along Eastern TX and Central LA over the past couple days. However, the variability of warm front will determine the placement of the heaviest or excessive rainfall across SETX and SWLA. The National Blend of Models has shifting some of the heavy precip over central portions of the state, but there is much time for the evolution of the shortwave to keep this frontal boundary further south over the CWA. Thus, while POPs modestly increase, do expect some variability of projected QPF until the shortwave begins to take shape upstream during the early work week. Trend later Friday the cold front signals the end of the precipitation for this system with drier air moving in as yet another ridge builds west of the Mississippi along the central Plains. Kowalski/30 && .AVIATION... (06Z TAFS) Issued at 1143 PM CDT Sat May 11 2024 Rain with a few thunderstorms will be possible tonight which may cause temporary lower vis. Ceilings will also gradually become MVFR through the morning hours. Additional convection is anticipated Sunday/Sunday evening leading to periods of lower vis and ceilings. && .MARINE... Issued at 415 PM CDT Sat May 11 2024 Moderate easterly flow this gradually diminish and shift more southeast tonight. Onshore flow will become better established on Sunday as surface high pressure moves off to the east, and strengthen with lower pressure developing over the plains. Onshore flow will persist through midweek until passage of a cold front. Shower and thunderstorm chances will increase tonight into Sunday, with off and on rain chances expected through midweek. 13 && .PRELIMINARY POINT TEMPS/POPS... AEX 64 77 66 87 / 40 70 80 60 LCH 68 82 73 85 / 10 70 50 60 LFT 68 85 74 86 / 10 60 60 60 BPT 71 82 74 86 / 20 70 30 50 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$ SHORT TERM...08 LONG TERM....30 AVIATION...05