-- Discussion containing changed information from previous version are highlighted. --
758
FXUS64 KLIX 240448
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1148 PM CDT Mon Sep 23 2024

...New AVIATION...

.SHORT TERM...
(This evening through Wednesday night)
Issued at 316 PM CDT Mon Sep 23 2024

Model agreement is high through the short term period and shows a
deepening positively tilted trough axis tonight into tomorrow that
takes a more neutral tilt by Tuesday night. At the same time, a
fairly potent upper level low embedded within the larger trough
will descend from the northern Plains and become detached from the
northern jet stream on Wednesday. This low will continue to deepen
over the Mid-Mississippi Valley into Wednesday night. In the low
levels, a weak frontal boundary will gradually sink southeastward
in advance of the trough axis. However, the parent low for this
front will quickly advance to the east, and the front is expected
to stall over the area on Wednesday. Although moisture values are
marginal, enough forcing associated with increasing positive
vorticity advection from the approaching trough axis and weak
convergence along the front should be enough to produce scattered
convective activity Wednesday into Wednesday night. Before
Wednesday, dry mid- level conditions and lower than normal PWATS
will greatly limit the convective potential on Tuesday. At most,
an isolated shower or storm may develop across the far northwest
portion of the CWA in southwest Mississippi along the weak frontal
boundary. Temperatures will continue to run above average over
this period with highs rising into the upper 80s and lower 90s
both Tuesday and Wednesday and lows only dipping to around 70.

&&

.LONG TERM...
(Thursday through Sunday night)
Issued at 316 PM CDT Mon Sep 23 2024

By Thursday, the tropical system moving through the eastern Gulf
will drive the cold front over the area offshore resulting in
significantly cooler high temperatures in the lower 80s. There is
also expected to be a fairly sharp moisture gradient in place as
the outer rain bands of the tropical system brush the Mississippi
Coast and parts of Lower Plaquemines Parish. The result is POP of
less than 20 percent for areas west of I-55 and 30 to 60 percent
for locations further to the east. The highest POP values are
across coastal Mississippi where some outer rain bands on the
western periphery of the tropical system could pass through.
Thursday will also be a breezy day with north winds of 15 to 20
mph and gusts up to 30 mph at times.

As the system moves inland and away from the area Thursday night,
strong negative vorticity and dry air advection will take hold of
the forecast area. The end result will be a very dry and very
stable airmass dominating the region from Friday through Sunday.
PWATS will be well below normal and cloud development will be
limited. Temperatures will also remain mild as northwest flow
aloft ushers in a cooler airmass with lows falling into the 60s
and highs only warming into the lower 80s on Friday and Saturday.
Some warming back into the mid 80s is expected on Sunday as winds
turn more southwesterly. Overall, have stuck with the NBM for
forecast temperature and POP values in the extended period given
the small spreads in the model solutions.

&&

.AVIATION...
-- Changed Discussion --
(06Z TAFS)
Issued at 1142 PM CDT Mon Sep 23 2024

VFR conditions in place this evening, and likely to be for much of
the forecast period. Frontal boundary remains to the northwest of
Louisiana. Potential does exist for patchy fog development around
sunrise Tuesday, but only areas that I feel any confidence in
mentioning are at KMCB and KHUM, and will mention brief MVFR to
IFR visibilities there. If any fog does develop, it`ll improve
quickly by mid morning. Only last day of only scattered cumulus on
Tuesday before the front approaches overnight Tuesday night into
Wednesday. Not expecting much in the way of convection prior to
sunrise Wednesday, so there won`t be any mention in this package.
-- End Changed Discussion --

&&

.MARINE...
Issued at 316 PM CDT Mon Sep 23 2024

The main concerns for the marine forecast are directly related to
Potential Tropical Cyclone 9. As this system intensifies into a
tropical cyclone tonight into tomorrow and begins to move into the
Gulf on Wednesday the pressure gradient over the coastal waters
will begin to increase. Initially, benign conditions will persist
over the waters through tomorrow, but winds will begin to increase
from the northeast and east tomorrow night into Wednesday. By
Wednesday night, small craft advisories will be needed as
northeast winds increase to 20 to 25 knots over the open Gulf
waters and sounds.  These stronger winds will persist into
Friday morning before finally easing as the tropical cyclone moves
inland and weakens. The larger impact will be very high seas of 15
to 20 feet impacting the open Gulf waters east of the Mississippi
River Thursday into Thursday night due to a combination of wind
wave and swell activity. Seas of 10 to 15 feet can be expected
west of the river and waves of 4 to 6 feet will impact the sounds
over this period of time.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  69  91  69  88 /   0  20  30  50
BTR  72  91  72  89 /   0  20  20  40
ASD  71  90  71  89 /   0   0  10  50
MSY  75  89  75  88 /   0  10  10  40
GPT  73  88  73  90 /   0   0  10  60
PQL  72  89  72  90 /   0   0  20  70

&&

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

$$

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