Marine Weather and Tide Forecast for Metairie, LA

FXUS64 KLIX 122047 AFDLIX

Area Forecast Discussion National Weather Service New Orleans LA 247 PM CST Sun Jan 12 2025

New SHORT TERM, LONG TERM, MARINE

SHORT TERM
(This evening through Monday night)
Issued at 224 PM CST Sun Jan 12 2025

Starting off with mid/late afternoon, as mentioned in the morning update, our next weather maker is getting itself together offshore coastal SE TX as a weak surface low. This is in association with a weak shortwave impulse riding progressive SW/NE flow aloft from the Mexican Plateau into the far NW GOMEX.
Downstream divergence/attendant lift as well as low/mid-level moisture advection has led to widespread clouds across the region, with a few light echoes from KHDC radar trends. The 12Z KLIX RAOB was very telling about where the moisture layer resides (roughly around H8 to H7) sandwiched between two very distinct dry layers in the troposphere. Meaning, as greater dynamic ascent approaches the area (corresponding with slow/steady sfc low strengthening), this layer will precipitate greater as we go on into the evening hours helping to wetbulb the dry layer below it by evaporative cooling. All models are in agreement that we'll continue to see stratiform precipitation spread across the region this evening into tonight, and had no trouble going 90-100% PoPs timed by NBM hourly guidance which looks good overall. Given the northern proximity of SE LA/S MS in correlation with the northern Gulf low, not anticipating any thunderstorm activity and in fact, with the airmass largely stable and non-convective (over land, could see thunderstorms near the coast and marine areas), rain totals could land more towards the lower side of forecast QPF. Noticed this trend recently in the HRRR today compared to yesterday.
Thinking rain totals of 0.5-0.75" will be pretty common but some 1-1.25" (isolated higher) totals can't be ruled out. Generally speaking, a quiet, chilly rainy night is ahead with very little impact. Otherwise, as for temperatures, went colder for highs today from the morning update but it looks like it wasn't cold enough, as another drop was required given temperature trends.
It'll be chilly tonight, with lows in the 40's (north) to 50's (south) but didn't adjust temperatures going into daybreak much as this looks on track.

Getting into early Monday, the rain will become lighter with time, perhaps from a light rain to drizzle going into mid-morning from west to east, as the surface low departs the area. As the low continues east, our winds will transition more from the NE and increase becoming occasionally breezy during the daytime. Next to closely monitor will be the low stratus deck overnight into tomorrow. Model soundings/guidance strongly suggests remnant 925mb layer moisture on the back side within persistent CAA regime.
While the exact degree of cloud cover is in question (for example, more spotty stratocumulus versus solid-deck stratus), feeling confident that clouds will hang around and with the aforementioned CAA pattern. Felt obligated to nail MaxT's lower yet again towards a 1/3 10th percentile and 2/3 25th percentile blend putting many areas topping out in the upper 40's to low 50's.
We'll have to just keep a close eye on cloud cover trends if any further adjustments are needed but overall, wanted to go ahead and get on board with atleast a 5-6F drop in suggested NBM deterministic values.

Eventually clouds to thin out some going into Monday and into Monday night, but it'll be turning cold yet again with lows dropping back again to freezing for mainly the Florida Parishes north of I-10/12 and SW MS. While we'll see radiational cooling at work that morning, sfc/low-level winds may remain just enough elevated to allow mixing to offset maximized radiational cooling processes (and to a smaller degree, high clouds). Thus, didn't make any notable adjustments to lows as everything looks plausible given the meteorological setup. Only adjustment was a notch to MinT's down slightly in the Pascagoula/Pearl River Drainage basins more protected from the winds. Additionally, due to winds remaining a bit more elevated (displaced from the surface high still to the NW), min wind chills do get down into the upper 20's to mid 30's for the I-10/12 corridor, with low/mid 20's possible for SW MS. Not within Cold Advisory criteria with just yet, but will keep an eye on guidance. KLG
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