Shenandoah, Louisianna 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

610
FXUS64 KLIX 130542
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1142 PM CST Tue Nov 12 2024

...New AVIATION...

.SHORT TERM...
(This evening through Thursday)
Issued at 423 PM CST Tue Nov 12 2024

It has been the dreary day today. All of this shower activity
appears to be associated with isentropic lift mainly around the
300-305k lvl and it would tend indicate that light showers would
continue to be possible through the evening eventually pushing
more to the northwest finally overnight.

As for tomorrow through Thursday, the bulk of the impact`s would be
tomorrow and look to really be between 16z through 00/01z Thursday.
SPC and WPC both have a Marginal Risk for severe weather and
excessive rainfall. Overall this is a very conditional threat as
storms would have some things to work with and storms could be very
cellular and not just a mess of convection. However, storms need to
develop early enough to really tap into the better shear and
kinematics. The sfc low will slowly work north to NNW overnight and
move inland across the central LA coast tomorrow morning. That said
it will be filling as it tries to merge with the approaching cold
front tomorrow and tomorrow evening. Initially this should help with
shear but winds may weaken considerably by tomorrow afternoon in the
BL as the sfc low fills with the sfc pressure over much of the CWA
either slightly rising or remaining steady. That said winds in the
rest of the column will respond as system moves through the Plains.

So why will convection fire. There are indications that a subtle
impulse could be moving northeast across the northwestern Gulf and
over the CWA during the late morning and afternoon hours tomorrow
and that may be the main antagonist leading to storms. This appears
to be the feature that is leading to convection trying to fire by
late morning and through the afternoon hours over the eastern
portions of the CWA. Given the subtleness of this possible feature
is likely why convection is appearing very cellular and not
congealing into a mess. That would promote a better chance of strong
to severe storms. The problem that is showing up is that a LL jet is
trying to respond over the CWA and central MS early tomorrow morning
and by early afternoon that jet could quickly be pulling out to the
northeast. This would mean our strongest LL convergence is mainly
during the mid and late morning hours possibly into the early
afternoon hours. In addition the stronger upper level diffluence
doesn`t really kick in till the afternoon hours so the optimized
window for any strong to severe storms may only be the midday
through early afternoon hours. Given the sfc low tracking north just
west of the CWA we will get into a the warm sector and have some
modest instability to work with.

With that there is a low risk for a few strong to severe storms
across the region but this could be during a very short window. in
addition this should only be along and east of I-55. Given the
development and location of the possible LL jet along with timing up
with the better upper level support and that subtle mid lvl
disturbance combining with the increasing instability we could see
storms develop after 16z. One thing to mention is that most of the
stronger convection could remain over the coastal waters. Main
concern from any severe storm would be damaging wind gusts and
possibly a tornado or two.

In addition to the threat for a few severe storms locally heavy rain
is possible. With PWs possibly abv 2" any convection would be very
efficient. If we measured 2" or greater tomorrow morning that would
easily break the record for PW on Nov 13th. Combine that with upper
lvl diffluence and instability and a few storms would be capable of
dropping quite a bit of rain in a short time. /CAB/

&&

.LONG TERM...
(Friday through Monday night)
Issued at 423 PM CST Tue Nov 12 2024

Forecast is much quieter after the first 36 hrs and we finally
cool off a little but we will moderate by Sunday and into next
week ahead of the next hopefully much stronger cold front mid/late
next week. That said confidence on strength and timing of a
potential cold front next week is low as models have not been in
great agreement and consistency has been low as well. Outside of
some temps adjustments mainly for lows this weekend no other
deviations made to the fcst from the NBM. NBM deterministic is
well abv the EC and GFS MOS and the median. For Friday and
Saturday morning the NBM is even above the 75th percentile. With
much drier air expected to be in place and light winds there is
now reason we should cool off more than what the NBM is currently
showing.

After our cold front moved through High pressure will filter in
behind it and dominate the region through the weekend. It will be
centered over the Mid and northern portions of the Lower MS Valley
Friday morning and by Friday night centered over IL/IN stretching
from the western Gulf and into Canada. This should help provide
lights winds especially Friday night. Thursday night winds just off
the deck may still be around 10-15kt out of the northeast and that
could help to mix things up a tad but not enough to keep us from
cooling off nicely. We will also see the ridge building aloft. This
should help keep skies generally clear both Thursday and Friday
night. That said there may be a chance some thin cirrus tries to
slide in overhead as the upper lvl jet streams across the southwest
and 4 corners region Friday night and a piece of it tries to break
off running ESE across the southern Plains and towards the Lower MS
Valley. However that may remain north of the area still providing a
nice radiational cooling setup Friday night and could lead to lows
back into the 40s to lower 50s for much of the area.

We start to moderate late Saturday and Sunday as high pressure
slides east and return flow starts to set back up. The next
disturbance that we will keep an eye on will be digging across the
western CONUS this weekend and by Sunday night may already begin to
kick out across the Baja. How that disturbances is handled could
make a lot of difference in the forecast later in the week as latest
models are trying to use it to significantly weaken the ridge that
builds across the Gulf and southeastern CONUS. If that ridge is not
as amplified it should allow the next deeper system to continue to
slide east which would bring us that much stronger cold front many
have been waiting on. If that lead disturbance doesn`t lift out as
fast allowing the ridge to build in a little strong and become more
amplified it would likely lead to more of a blocking setup and thus
keep everything out west and much slower.

As for the tropics, models continue to focus in on the western
Caribbean disturbance developing and meandering for a few days as
tomorrows trough finally passes across FL and the Bahamas. Once it
pushes far enough east ridging would build back behind it and should
help to drive this system west. All models show this developing over
the western Caribbean but how far south and west it moves before it
starts to turn more north is just a guessing game right now. That
said this system is not expected to have any impact on us. /CAB/

&&

.AVIATION...
(06Z TAFS)
Issued at 1137 PM CST Tue Nov 12 2024

IFR and LIFR ceilings will continue to impact the terminals
through daybreak, but some mixing after 12z will lift ceilings
into MVFR range of 1000 to 2000 feet for much of the day.
Thunderstorm probabilities have increased slightly, and are no
high enough to include TEMPO wording generally between 18z and 00z
at the terminals. Only GPT will see a later arrival of the
thunderstorm activity with the TEMPO wording in place after 00z.
The thunderstorms will most likely occur in the form of a broken
line moving from west to east across the region with IFR
visibilities and ceilings possible as the heaviest cells roll
through. Winds could also turn gusty at 25 to 35 knots with the
passage of the storms. Improving conditions are expected at all of
the terminals after 06z as drier air begins to feed in the west
and the threat of rainfall ends.

&&

.AVIATION...
(00Z TAFS)
Issued at 537 PM CST Tue Nov 12 2024

Weak isentropic forcing over a slightly cooler and more stable
airmass at the surface has led to widespread low stratus and light
rain development at all of the terminals this afternoon. These IFR
and LIFR conditions will persist through the overnight hours at
all of the terminals. Tomorrow morning, a bit of warm air
advection into the area will allow the ceilings to lift to a mix
of IFR and MVFR conditions at the terminals with ceilings variably
ranging between 800 and 1500 feet. Light rain showers will also
continue to produce periods of MVFR visibility restrictions.
After 18z, enough instability will be in place to support some
thunderstorm development. Thunderstorm probabilities are generally
between 30 and 50 percent, and have opted to include PROB30
wording to reflect the convective risk at at the terminals between
18z and 24z. Any storms passing over a terminal could produce
periods of IFR or lower visibilities and gusty winds over 25
knots.

&&

.MARINE...
Issued at 423 PM CST Tue Nov 12 2024

Offshore observations are still showing low end but areas of
small craft advisory conditions, especially east of the mouthy of
the MS.

The pressure gradient will gradually weaken tonight but whatever is
left of the surface low will work NNW to N towards the Louisiana
coast and this will keep modearate to strong onshore flow over most
of the coastal waters overnight. Wednesday the pressure gradient
should weakn enough to allow most if not all flags to be dropped
ahead of an approaching cold front. The cold front will come through
Wednesday night and bring offshore winds early Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  64  77  59  70 /  50  80  60   0
BTR  69  82  63  75 /  50  60  40   0
ASD  67  80  65  78 /  50  70  70  10
MSY  71  81  67  76 /  50  60  50  10
GPT  68  79  67  78 /  50  80  90  10
PQL  69  81  68  82 /  40  70  80  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 9 AM CST Wednesday for GMZ532-536-538-
     550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until 9 AM CST Wednesday for GMZ536-538-550-
     552-555-557-570-572-575-577.

&&

$$

SHORT TERM...CAB
LONG TERM....CAB
AVIATION...PG
MARINE...CAB