252
FXUS64 KLIX 042158
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
358 PM CST Wed Dec 4 2024

...New SHORT TERM, LONG TERM, AVIATION, MARINE...

.SHORT TERM...
(This evening through Thursday night)
Issued at 332 PM CST Wed Dec 4 2024

Starting things out with this afternoon, main focus is on an
approaching, subtle shortwave impulse riding progressive NW flow
aloft into the area. Attendant lift and low-level moisture
advection has led to increasing mid/upper-level clouds, ontop of a
very dry post-frontal arctic airmass in place (per the 12Z KLIX
RAOB). Already seeing some light radar returns from KHDC well to
the west, with some light rain reports nudging into the
AtchafalayaBasin. Most of the leading edge of the precipitation
is not making it to the ground as virga, but will continue to
moisten with time leading to showers increasing this
evening/overnight. Forcing ahead of this system is mainly by
isentropic ascent causing the rain to be will be light/stratiform,
but greater dynamic and frontal forcing increases overnight
leading to this QPF shield becoming more heavy, oriented from SW
to NE per recent HREF runs. It is possible (some) subtle warm
sector attempts to drift north into SE LA (generally along/south
of I-10/12) with dewpoints creeping into the low to mid 60`s.
While instability is limited (MUCAPE in the 250-350 J/kg range),
some claps of thunder could be possible by a small slither of
elevated instability. Additionally, H5 temperatures around -12 to
-13C could support small hail in any stronger storm, just not
confident enough to see enough lift offset the lack of instability
to provide a notable risk. Thus, should mainly see just a
moderate to heavy swath of rain progressing WNW to ESE throughout
the night. Rain totals will vary, with area average totals in the
0.5 to 1 inch range, but some folks could see upwards of 1 to
1.5"+ in isolated swaths before all said and done. Additionally,
adjustments to temperatures were made beginning this afternoon,
coming in lower thanks to clouds which will progress into the
overnight remaining chilly.

Some light showers/drizzle could remain after daybreak Thursday,
mainly associated with the lagging front but will quickly see a
drying trend going into the rest of the afternoon. Cold air
advection builds in strong going through the rest of the day as
the front slams south, keeping winds breezy. KLG

&&

.LONG TERM...
(Friday through Tuesday night)
Issued at 332 PM CST Wed Dec 4 2024

We see the brunt of the air change overnight Thursday into early
Friday as temperatures bottom out into the mid to low 30`s
along/north of I-10/12. Temperature spread in guidance is not too
bad, looking meteorologically plausible given the persistent
CAA/wind overnight allowing mixing to reduce any extreme cold
temps. Having said that, it is looking likely we`ll still see a
freeze for areas just north of the I-10/12 corridor into SW MS
including parts of the drainage basins with no deviation from
deterministic. We wont warm up at all Friday, with highs in the
low to mid 50`s underneath partly cloudy skies. However, by early
Saturday, that`ll be when winds back down enough to see the best
chance of radiational cooling proving the coldest morning. With
deterministic just a notch above the 75th percentile, decided to
introduce the 50`s to edge slight colder. This may be a bit of a
stretch though, regardless, another freeze will be possible mainly
for the same areas again, just will need to monitor
guidance/spread with time. Also, did want to briefly mention from
earlier saying how the winds were backing down (somewhat) however,
could remain up just enough to allow for wind chills into the
20`s for I-10/12 on north. Nothing extreme, but could prompt the
issuance of our first Cold Advisory for these locations (for wind
chills), should the forecast hold together. It is urged to read
more about these cold weather product changes on our web page
headline at the top on www.weather.gov/lix.

As we progress into the weekend, our sights shift back to the
west again and a more potent, closed low meandering over the for
corners region. This low is in no hurry as it becomes caught
underneath a building ridge pattern over the western US, slowing
it`s eastward progression, however it`s an additional embedded
shortwave impulse, or "kicker" that dives south over the western
US plus a stronger NW trough axis diving into the Pac NW that
helps to give it the push it needs east into the southern/central
plains. What both in turn do to the upper-low is allow it to
broaden out as a shortwave trough, digging ENE into the southern
MS valley region. Reflection at the surface is rather mess, with
the main greatest downstream divergence over the Great Lakes
owing to eventual surface cyclogenesis, then a cold front trails
to the SW into Texas. The front that passed the area on Thursday,
slowing to a crawl into the north-central Gulf, returns back north
as a warm front ahead of a building WAA regime downstream of the
shortwave over Texas. We`ll see what likely will be a messy line
of storms, perhaps multiple waves over east Texas, building into
the ArkLaTex region and given the SW flow aloft oriented with the
frontal boundary, could lead to a flash flood risk in this region.
Eventually, the trough gets enough momentum to press east
overnight Sunday into early Monday, but poses the risk 1) for
Flash Flooding, with at this time, the greatest risk west of I-55,
and 2) The risk for severe weather, in a low instability/modest
shear environment overnight Sunday into early Monday. This could
pose a risk for perhaps a QLCS with an embedded weak tornado risk
overnight, but more will become clearer as we get past this
current system going into later this week.

Beyond that, it gets even more messy as another impulse dives
southeast into the central US following that system, resulting in
another chance for active weather somewhere in the SE. Peeking at
some cluster analysis fields reveals an extremely low-confidence
range in CMC, EPS and GEFS solutions provided unclarity with this
trough location and amplification, so caution is advised in the
long-range where adjustments may likely follow in the next several
days forecasts. So check back. KLG

&&

.AVIATION...
(00Z TAFS)
Issued at 332 PM CST Wed Dec 4 2024

Main focus for this evening will be cloud cover increasing, and -SHRA
building in from the west overnight into early Thursday. At this
time, low CIG`s and periods of reduced VIS caused by SHRA can be
expected for all terminals, timed for each TAF site ending from NW
to SE into daybreak Thursday. Lower flight categories can be
expected, and may persist with low clouds early Thursday
regardless of a general drying trend expected. Thereafter,
conditions will continue to improve during the day, but winds will
remain breezy out of the N to NNE at times, ranging around
10-14kts with gusts to 18-22kts and VFR prevailing (mid/upper-
level clouds likely persisting). KLG

&&

.MARINE...
Issued at 332 PM CST Wed Dec 4 2024

A quick-moving disturbance and attendant frontal boundary will
swing through coastal waters tonight into early Thursday, leading
to a switch in wind direction from onshore to offshore, and
becoming gusty at times. At this time, winds will likely reach
small craft criteria late Thursday into Friday, with waves/swells
responding for offshore waters reaching 5-7ft with time. Winds
back down later in the day on Friday, remaining calm with
waves/seas responding. The next frontal boundary and associated
active weather arrives late Sunday into early Monday, with
dangerous marine conditions possible. KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  49  57  27  50 / 100  30   0   0
BTR  56  64  34  56 / 100  30   0   0
ASD  53  67  32  55 / 100  60   0   0
MSY  58  67  40  53 / 100  70  10   0
GPT  55  66  33  54 / 100  70   0   0
PQL  52  68  31  56 /  90  80   0   0

&&

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

$$

SHORT TERM...KLG
LONG TERM....KLG
AVIATION...KLG
MARINE...KLG