794
FXUS64 KLIX 272340
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
640 PM CDT Thu Jun 27 2024

...New AVIATION...

.SHORT TERM...
(This evening through Sunday night)
Issued at 406 PM CDT Thu Jun 27 2024

Quiet the day today for most of the region. Convection quickly
refired overnight between 6-7z across much of the coast with
widespread storms across the SELA coast and near shore waters
through the early morning time frame with rather heavy rain in
some of the river parishes. This appears to be from the
seabreeze/lake breeze finally dissipating and the land breeze
beginning to develop while at the same time the s/w was finally
beginning to move in providing some subtle dynamics and cooler mid
lvl temps. Given how water the coastal waters are making the
coastal areas the most unstable region over the area storms were
able to tap into the better dynamics finally and quickly developed
over those areas. The problem is by the time the s/w axis moved
into the CWA which was around and shortly after sunrise it had
pushed most everything south and as feared yesterday the northern
half of the CWA really struggled to see any precip.

Tomorrow and through the weekend the forecast problems are PoPs and
temps. Where will storms fire and even if they can in some regions
along with how much rain will occur. If storms do develop how
widespread will it be and what impact will that then have on
afternoon highs. The ridge currently over west TX will continue to
build to the east while our disturbance currently centered over
central AL/MS border will continue to slowly drop into the north-
central Gulf for tomorrow. This would suggest that we could still
have some mid lvl support from the disturbance even as it fills in.
One problem is PW, currently 1.4-1.5 across the northern 3rd/half of
the CWA but this could recover quickly tomorrow. But the biggest
negative is the ridge and mid lvl temps. The ridge is going to
continue to build into the area and both the GFS and ECMWF show h5
temps warming back to around -2 to -3C across the northwestern 3rd
of the CWA. Combine that what appears to be LL diffluence/divergence
and the northwest could have a very difficult time seeing much if
any convection. Now along the coast of both LA and MS that is a
different question. Winds will be light so once again we should have
little problems getting the seabreeze and lake breeze to develop,
very rich moisture in place and closer to being directly underneath
the weakening disturbance should be more than enough to get numerous
showers and thunderstorms tomorrow. With this we have made some
rather big deviations from the NBM in the northwest going much
closer to the MAV and ECS MOS values which is about 20-30% lower. As
for the temperatures the convection across the southeastern half
should help keep most of the area cool enough to not be concerned
with heat issues where as the northwest that may remain rain free
will likely have lower humidity values and thus also remain just
below heat advisory status.

This weekend the forecast is a little more tricky. The ridge still
looks like it will continue to build to the east but models are now
showing it not quite as stout yet and in fact actually show the h5
temps cooling a tad -3 to -5 (cooling is relative) and typically
that is usually too warm to get much convection still. However, we
will have a plethora of moisture available with PWs ranging from 2
to possibly 2.3" at times. Even with what looks like LL high
pressure sitting over the region very light winds through the column
again will allow diurnal fluctuations in the wind filed to dictate
convection, especially on Sunday. Portions of southwest MS may
struggle again to see much rain as it will be closer to the center
of the ridge. LL temps begin to very slowly inch up this weekend
with mid 90s and possibly some isolated 90s for highs on Saturday
and then may be a few more upper 90s on Sunday. These two days
provide a better chance of seeing heat index values in the 104 to
112 range. The most likely day for a heat advisory looks like Sunday
and that should continue into next week. Again the biggest question
is convection as timing and coverage will have significant impacts
on the eventual outcome. More coverage especially around midday and
early afternoon would keep the heat at bay some however very early
convection (which I`m not seeing that as the seabreeze should not
become active quickly with the very light wind field) or very late
convection like after 19/20z would both allow for peak heat
index values to be achieved. /CAB/

&&

.LONG TERM...
(Monday through Wednesday night)
Issued at 406 PM CDT Thu Jun 27 2024

The northern stream upper level trough moves through the Great
Lakes Sunday evening and continue eastward into the Atlantic
Ocean Monday. The base of this trough doesn`t reach much farther
south than the Appalachian Mountains. This is why a weak backdoor
front comes in from the northeast just ahead of the trailing
ridge. The upper ridge in the wake of this trough will be sliding
east across the entire Mississippi Valley Monday afternoon into
Tuesday. Global models are still in good agreement that this
596/7dm high pressure will be centered near the Akrlatex region
Monday afternoon. Excluding rain potential, increasing 500mb
heights will bring already above normal weekend temps up even
more. Guidance spread through the forecast period is fairly
minimal and as of 12z runs, Monday has the potential to be the
warmest with highs mid/upper 90s to 100 degrees. Convective
coverage will probably be the bigger deciding factor on max temps.
That previously mentioned weak backdoor front looks to stall near
the Gulf Coast, which combined with forecast temps, would support
scattered to numerous showers and storms. If convective
initiation is early enough, heat indicies will get knocked down
quickly. However, if not too early, widespread upper 70 to 80
degree dewpoints with hot temps may bring heat indicies into
Excessive Heat Warning issuance. Tuesday will virtually mirror
with the same heat/convection timing challenges as the center of
the upper ridge will be progressing eastward fairly slowly. As the
rest of the week progresses, the upper ridge aloft will begin to
flatten out and spread across the entire Gulf Coast. This is in
response to repeated northern stream troughs/shortwaves weakening
the ridge. As the subsidence slowly fades, should eventually see
some less extreme temps and more widespread daily convection.

/MEFFER/

&&

.AVIATION...
(00Z TAFS)
Issued at 636 PM CDT Thu Jun 27 2024

Outside of a few showers and thunderstorms across coastal
Louisiana, VFR conditions will prevail all all terminals tonight
and into tomorrow. high-res models depict thunderstorm development
tomorrow morning, mainly along the coast and spreading inland by
the afternoon. Thus the most likely terminals to see thunderstorms
are south of I-10/12. Have only kept VCTS since these storms will
be scattered and confidence on exactly where they will go is
uncertain due to that.

&&

.MARINE...
Issued at 406 PM CDT Thu Jun 27 2024

High pressure will be in control through the weekend. This will
continue to provide mostly light winds across the coastal waters.
The biggest issues will be convection as rather decent coverage
of storms is possible tomorrow and Saturday over the coastal
waters, especially during the early morning hours. Very rich low
level moisture, light winds, and convection during the
overnight/early morning hours should lead to decent waterspout
potential. /CAB/

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  72  92  74  93 /  10  40  10  50
BTR  77  94  79  96 /  10  50  10  50
ASD  76  91  78  94 /  30  80  20  60
MSY  78  91  81  93 /  30  80  20  60
GPT  76  91  78  92 /  50  70  40  60
PQL  76  93  77  95 /  50  70  40  50

&&

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

$$

SHORT TERM...CAB
LONG TERM....ME
AVIATION...JZ
MARINE...CAB