315
FXUS64 KLIX 131203
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
703 AM CDT Mon May 13 2024

...New UPDATE...

.UPDATE...
Issued at 607 AM CDT Mon May 13 2024

All interests over SELA should be alert to future updates and
warnings issued today; this includes marine, flight terminals,
and inland interests.

There has been a concerning trend in model runs mainly from the
GFS over the last several days that show a very fast moving MCS
type feature(most likely a squall line/wake low) moving either
along the coast or just inland entering our area from the west
around 6pm today. The GFS was the first to show this but since
then, the NAM, Euro and now the HRRR is starting to show this very
same scenario. If this is going to actually occur, this feature
should begin to develop over south central TX around or just after
noon today. One can easily see that development of this system
over south central TX around noon then only 6 hours later entering
our area(~400 miles) would show this is a very fast moving feature
which puts it moving east at around 70mph. The wind speeds
associated with this should be 50-60kt but much higher gusts could
be entirely possible.

The majority of the weather associated with this feature may stay
over marine areas. The problem with setting any long fused
warnings out at the moment is very dependant on exactly where this
forms and how fast it actually moves. Since we don`t know these
specifics until after it forms, the timing and placement could be
off quite a bit.

&&

.SHORT TERM...
(Today through Tuesday)
Issued at 324 AM CDT Mon May 13 2024

The upper flow is now supportive and subsequent lower level flows
are also lining up to support the training of heavy rainfall. Models
did show a very weak system moving through late this morning but
this mornings system is a bit earlier than what previous model runs
were showing but the main thing is, the system is much stronger than
what any model was showing. The second system coming in late today
is still expected but we will contend with the first one then start
on the next. To show just how large the errors are in the 00z model
runs, the HREF has >5% of its members showing >5" rain between 1am
and 7am today in an area from Gonzalez to Mandeville. This will not
be occurring in that time frame but could later. The area to the
north, where the heavy rainfall is actually occurring, this same
model has no members showing a chance of getting >5" of rainfall.
This is what we expected with all of these models trying to handle
mesoscale solutions. They will simply be all over the place. We
will choose the models that are closest to where the activity has
developed this morning(best initialization). One of these is the
NAM Nest. This model develops this area into a line to the NW of
the area this morning and swings it into the area well before
daylight and slowly sinks it southward. This looks to be the most
logical conclusion at the moment, so we will move more along these
lines. This model, and the others still bring another system
through the area this evening into the overnight hours. This first
system could cause some flooding and severe weather issues, but
if it does not cause any issues, it will at the very least prime
the area ahead of the next. Both of these systems will be capable
of flooding rainfall and severe storms. The Flood Watch will
remain as this should verify for several locations. Rainfall
amounts are still coming in from 3 to 6 inches with the highest of
these numbers over coastal Mississippi through 7am Tuesday. Once
the second system moves to the east, it will clean the
area(clearing skies and stable conditions). This should occur by
Tue afternoon.

&&

.LONG TERM...
(Tuesday night through Sunday)
Issued at 324 AM CDT Mon May 13 2024

The frontal boundary that is helping to cause all of this will have
sunk back into the gulf by late Tue. The next upper troughing will
then move out into the plains by mid week with sfc return flow
forcing this boundary back to the north moving back over the area
possibly as early as Thu and this whole thing looks to play out
again similar to this event. The first disturbance moves through mid
day Thu and may hug the coast. This should be associated with the
warm front. The next main system will move along the cold frontal
interface as it stalls across the area with an abundance of deep
moisture Fri. This is at least one solution, but as one can clearly
see with the current system, this will almost surely change several
times before we get there. The general synoptic structure looks
valid, but we will definitely need to get closer to even think of
resolving the smaller scale features.

&&

.AVIATION...
(12Z TAFS)
Issued at 324 AM CDT Mon May 13 2024

Cigs will mainly be between two levels, MVFR and IFR. There is a
small window of VFR cigs by afternoon, but this will be temporary.
All terminals will have two systems impact their locations today.
The first will move through this morning and the second this
evening. Each of these will cause IFR and even LIFR conditions for
short to moderate term durations(1-3hrs).

&&

.MARINE...
Issued at 324 AM CDT Mon May 13 2024

The first of two systems will move through the area this morning.
Some of these storms will impact some of the coastal waters
mainly the nearshore waters. A second system will move thorugh
this evening to impact a greater portion of the gulf waters. Both
of these systems could have strong to severe storms associated
with them. Gradient flow winds will be southerly while convective
winds will be from the direction of the nearest storm. Basically,
wind direction will be all over the compass at times and could be
quite strong. Tuesday looks to see these conditions ease but
storms could be an issue once again toward the end of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  81  65  84  62 / 100  80  30   0
BTR  87  69  89  66 /  90  70  20   0
ASD  85  69  89  66 /  90  80  50   0
MSY  85  72  89  71 /  90  90  50   0
GPT  83  69  87  68 / 100  90  60  10
PQL  84  69  88  66 / 100  90  70  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flood Watch through Tuesday morning for LAZ034>037-039-046>048-
     071-076-079>086.

     Flood Watch through Tuesday morning for LAZ056>060-064>070-077-
     078-087>090.

GM...None.
MS...Flood Watch through Tuesday morning for MSZ068>071-077-083>088.

GM...None.
&&

$$

SHORT TERM...TE
LONG TERM....TE
AVIATION...TE
MARINE...TE