Area Forecast Discussion
Issued by NWS Lake Charles, LA
Issued by NWS Lake Charles, LA
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051 FXUS64 KLCH 160418 AFDLCH Area Forecast Discussion National Weather Service Lake Charles LA 1118 PM CDT Sat Jun 15 2024 ...New AVIATION... .SYNOPSIS... Issued at 330 PM CDT Sat Jun 15 2024 A disturbance is expected to move gradually west across the southern Gulf of Mexico through mid week. If this system remains rather weak as far as low pressure goes as expected, than an inverted trough will extend north from this system and help bring a plume of deep highly anomalous moisture into the forecast area that will bring about a potential for heavy rainfall and flooding. Both high rainfall rates and duration may be factors through mid week, along with high tide levels along the coast not allowing for proper drainage of river systems. Reasonable rainfall totals of 6 to 10 inches along and south of the I-10 corridor through Wednesday night, with 3 to 6 inches north of the I-10 corridor. A Slight Risk (level 2 out of 4) Potential for Excessive Rainfall leading to flooding is outlined for a majority of the forecast area staring on Monday into Wednesday. Stay tuned. If confidence in the the heavy rainfall potential increases and the heavy rainfall regions become more fine tuned, the Risk Potential may increase and a Flood Watch may be needed. There will also be increased winds and seas over the coastal waters, along with increased in tides and potential for coastal flooding. Please see the marine section for more details. Rua && .SHORT TERM... (Tonight through Monday night) Issued at 330 PM CDT Sat Jun 15 2024 Drier air aloft is helping to keep any widespread shower activity from forming this afternoon. Just a few showers are noted near the sea breeze so far in Cameron Parish. The upper level ridge over the northwest Gulf will continue to weaken on Sunday with the upper level ridge becoming centered over the southeast US. This will develop a broad east to west wind flow across the Gulf of Mexico, and this will push the inverted trough and associated deep tropical moisture that has been over the northwest Caribbean into the Florida area to the west. The deep moisture and trough will begin to reach eastern portions of the forecast area late Sunday to allow some diurnal and sea breeze shower and storm activity to get going, especially over the lower Atchafalaya Basin. The deeper moisture plume will over take the forecast area on Monday. The air mass will definitely have a tropical origin to it with highly anomalous moisture values. Precipitable Water values will range from 2.2 to 2.5 inches which is well above the 90th percentile for this time of year of around 2 inches, and closer to max moving averages and daily highs. Also, 1000-500 mean layer relative humidity values will be over 90 percent and warm cloud layer will be between 14k-16k feet, which all means that convection will be highly efficient warm process rain makers. Usually in these air masses, plenty of nocturnal activity will occur over the Gulf and right along the coast. Therefore, expect by Monday morning to see plenty of showers and a few storms over the coastal waters and just inland. With low convective temperatures, this activity will spread quickly inland through the morning hours and continue into the afternoon before some decrease in activity during the evening with loss of any daytime heating. With the expected high rainfall rates in the convection, any cell mergers or training along mesoscale boundaries, would quickly bring about a heavy rain and flood threat. A Slight Risk (level 2 out of 4) Potential for Excessive Rainfall leading to flooding will be outlined for the entire forecast area on Monday. If there is some good news, high temperatures should be a little below normal and stay in the 80s. Rua && .LONG TERM... (Tuesday through next Friday) Issued at 330 PM CDT Sat Jun 15 2024 Long range pattern begins with a very stout SEly regime building in with a notable low level jet max ~ 850mb filtering from the central Gulf across SWLA and SETX before continuing into the Southern Plains. Confidence has increased in seeing an active wet pattern throughout the week as low pressure troughing continues to persist in the western Gulf with signs of gradual deepening into the midweek. Beyond that, the pattern remains unsettled in terms of further organization of a closed low pressure center in the SW Gulf. Signals for active weather along the Gulf Coast persist beyond the long range which is congruent latest CPC analysis indicating 40 / 50 % chance of above normal precipitation continuing into the following week. Locally, regardless of any tropical development along the SW Gulf of Mexico, excessive rainfall potential continues for greater portions of SETX and SWLA given the above mentioned strong LLJ of humid air with little inversion signals to prevent shower/storms developing along coastal and later, further inland portions of the CWA. Naturally, this pattern creates more uncertainty with diurnal maximum in temperatures with some suites indicating precipitation and thicker cloud cover to remain more prevalent during the daytime hours. Meanwhile some guidance consolidates the moisture according to purposed solutions in the SW Gulf. With decent low level moisture profiles in the forecast, confidence leans toward a wetter and slightly milder surface conditions through Wednesday. Marine interests should closely monitor this pattern through the upcoming week, as headlines regarding winds and/or seas are likely for Tuesday / Wednesday barring any major change to the current forecast trend. Winds will have strong E - SE components making for difficult channel navigation for large profile vessels while sea heights may propose a threat to safe navigation to smaller vessels along coastal waters as well. By Thursday, overall guidance continues to keep a fairly tight gradient of pressure along the central and western Gulf of Mexico indicating heavier rainfall to shift NW inland toward central TX and Southern Plains, however, despite weak lapse rates in the mid levels remaining under 6.5C opportunities for surface based CAPE to initiate scattered showers / storms continues, albeit to weaker POPS trending into the weekend. Kowalski/30 && .AVIATION... (06Z TAFS) Issued at 1113 PM CDT Sat Jun 15 2024 VFR conditions will continue through the night. Showers and thunderstorms will be forming in the afternoon. Winds will be calm tonight becoming south to southeast after sunrise. && .MARINE... Issued at 330 PM CDT Sat Jun 15 2024 Weak high pressure will bring about mainly light easterly winds through the night into Sunday. A trough will gradually move west across the southern Gulf of Mexico from early to mid week. The gradient between the trough and high pressure to the northeast will bring moderate to strong east to southeast winds at or above 20 knots by Monday, that will continue through mid week. This prolonged wind field will allow for a significant increase in wave heights and swells. Wave heights are expected to be 4 to 8 feet on Monday increasing to 6 to 12 feet on Tuesday and Wednesday. Small craft advisories will be needed during this period. Also, with the long duration and fetch of the easterly winds, Ekman spiral affects will allow for water piling along the coast increasing tide levels. Tides will be 1 to 2 feet above astronomical predicted levels. P-ETSS guidance shows actual tide levels during high tide times staring late Monday night through Wednesday at 1.5 to 2.0 Mean Higher High Water (MHHW) which are in coastal flood advisory category, with 10 percent exceedance, reasonable highest tide levels possible, in the 2.5 to 3.5 MHHW which would be over coastal flood warning criteria. Deep moisture will also be associated with this system that will bring widespread shower activity across the coastal waters starting Sunday night through mid week. Rua && .PRELIMINARY POINT TEMPS/POPS... AEX 71 94 73 86 / 0 30 30 90 LCH 74 92 75 85 / 0 60 50 90 LFT 75 92 75 86 / 0 80 50 90 BPT 75 92 76 87 / 0 40 50 90 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$ SHORT TERM...07 LONG TERM....30 AVIATION...14