Zachary, Louisianna 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

712
FXUS64 KLIX 031047
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
447 AM CST Tue Dec 3 2024

...New AVIATION...

.SHORT TERM...
(Today through Wednesday)
Issued at 333 AM CST Tue Dec 3 2024

Upper trough remains along the East Coast this morning, with
ridging from New Mexico to British Columbia. A trough was off the
California coast to the west of the ridge. At the surface, high
pressure extended from Iowa to the northern Gulf of Mexico. There
were a few reports of fog near water sources, but this doesn`t
seem to be widespread at this time. Temperatures at 3 AM CST were
generally from the mid 30s to lower 40s, except Lakefront Airport
(56F), where the warmer water of Lake Pontchartrain held the
temperatures up.

The high pressure over Iowa this morning will sink southeastward
to Florida by Wednesday afternoon. This will keep winds northerly
to northeasterly today and most of tonight. By midday Wednesday,
surface flow will become southeasterly, allowing moisture to
finally return to the area. Precipitable water values were near
0.30 inches on the 00z LIX sounding, and those values won`t change
much until the daytime hours on Wednesday. We`ll start to see
mid-level (near 700 mb) clouds arrive prior to sunrise Wednesday,
gradually saturating the lower levels during the daytime hours
with precipitable water values climbing to about 1.5 inches. Could
see a few patches of light rain or showers arrive in northwest
areas, west of McComb and Baton Rouge prior to sunset Wednesday.

Forecast temperatures don`t look unreasonable. Cold advection will
hold temperatures down from yesterday`s levels today. Overnight
lows will be chilly again with a few of the normally colder spots
potentially hitting freezing again. The mid level clouds could
mean temperatures starting to rise shortly before sunrise
Wednesday, depending on just how quickly they arrive. Warm
advection on Wednesday will bring warmer temperatures to the area
with most locations in the 60s.

&&

.LONG TERM...
(Wednesday night through Monday)
Issued at 333 AM CST Tue Dec 3 2024

A southern stream shortwave will move across the area Wednesday
night and Thursday, aided by the East Coast trough. This will push
a cold front across the area Thursday, arriving in the
northwestern portions of the area around sunrise, and moving into
Alabama around midday. Rain and a few elevated thunderstorms will
accompany the front. While the shear would be sufficient for
severe weather, instability is almost non-existent. Rain amounts
of 1 to 2 inches will be possible with this system, mainly in
northwestern portions of the CWA.

The medium range modeling continues to struggle with just how far
offshore the frontal boundary makes it on Thursday. The ECMWF runs
have been pretty consistent in pushing the front well offshore,
while the GFS has trended close enough to the Louisiana coast to
hold the potential for at least some rain over the local area for
Friday and Saturday. The ECMWF has essentially a dry forecast for
the area from Thursday afternoon into the daytime hours on Sunday.
This will also have a significant effect on temperatures, as the
drier solution also means more cold air advection across the area.
Regardless, high temperatures Thursday are likely to occur prior
to noon. Thursday night through Friday night temperatures will be
tied to the progression of the front. If the ECMWF verifies, sub-
freezing temperatures will be possible across a significant
portion of the area both Friday and Saturday mornings. The GFS
solutions are 10-15 degrees warmer due to cloud cover. The NBM
deterministic is essentially a compromise between the two, but
would expect that those numbers will start drifting toward the
preferred modeling over the next couple days. Highs on Friday will
also be a struggle, but would note that the GFSBufr soundings
would actually be somewhat more appropriate for the ECMWF
solution, with most of the area not getting much warmer than
52-53F at best, and some may not get out of the 40s. Saturday
should see some improvement in temperatures, getting into the 60s.

High pressure will be off to the east of the area by Saturday
night and Sunday with winds gradually turning onshore as a
southern stream shortwave (the one off the West Coast now)
approaches the area. The GFS is considerably quicker with this
system, with some light precipitation possibly arriving prior to
sunrise Sunday, while the ECMWF solution is more like Sunday
night. Of course, at that time range, the NBM deterministic is
somewhat of a compromise, and would expect PoPs to eventually
focus on a shorter time span for precipitation chances. We`ll have
to keep an eye on that system for excessive rainfall, as the
medium range models indicate a very moist airmass with dew points
in the mid 60s, and GFSBufr soundings show anomalously high
precipitable water values between 1.75 and 2 inches Sunday night
through Monday night.

Temperatures from Sunday until frontal passage, which could be as
late as next Wednesday (12/11) will likely get into the 70s for
highs, normal is mid 60s. Overnight lows could be as much as 15
to 20F above normal.

&&

.AVIATION...
(12Z TAFS)
Issued at 446 AM CST Tue Dec 3 2024

VFR conditions expected through the forecast period. We could
start to see some ceilings around FL100 toward sunrise Wednesday
as moisture arrives ahead of the next weather system.

&&

.MARINE...
Issued at 333 AM CST Tue Dec 3 2024

Will carry Small Craft Exercise Caution headlines for the far
western waters today. Wind field should relax later this evening
through the daytime hours Thursday. Cold advection behind the
front may necessitate Small Craft Advisories Thursday night into
Friday, especially if the farther south solution for the frontal
position in the ECMWF operational verifies.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  56  31  62  51 /   0   0  20  90
BTR  64  39  68  58 /   0   0  20  90
ASD  61  36  67  57 /   0   0   0  60
MSY  61  45  67  60 /   0   0   0  60
GPT  59  37  64  57 /   0   0   0  60
PQL  62  31  67  55 /   0   0   0  50

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

$$

SHORT TERM...RW
LONG TERM....RW
AVIATION...RW
MARINE...RW