Mandeville, Louisiana Weather Forecast Discussion

682
FXUS64 KLIX 061721
AFDLIX
Area Forecast Discussion
National Weather Service New Orleans LA
1221 PM CDT Sat Sep 6 2025
...New SHORT TERM, LONG TERM, AVIATION, MARINE...
.SHORT TERM...
(This afternoon through Sunday Night)
Issued at 1116 AM CDT Sat Sep 6 2025
Few items to discuss right off the bat early this Saturday
afternoon. The long-waited front has drifted into the area, with
GOES-16 Ch2 VIS trends and KHDC radar illustrating where the front
is generally located approaching the I-10/12 corridor. For now,
what is left of this boundary following scattered showers earlier
over far NW areas is just a cloud line, representing primarily a
air density difference without a well-defined wind shift. This
boundary is separating post-frontal/subsident and drier air behind
it with a well-developed Cu field ahead of the front within
slightly deeper available moisture. Ahead of this moisture
boundary (front) shows noticeably lower Tc per 12Z HRRR proximity
soundings indicating enough diurnal destabilization coupled with
weak frontogenetic lift will support scattered showers/storms
mainly over the I-10/12 corridor on south. 13Z NBM brought in some
plausible numbers ranging in the 15-25% range, with no changes
needed here. Not seeing anything stand out significantly with the
tropospheric thermal profile representing any threat for locally
strong to severe storms with this activity later today, but a few
could become locally strong and dump brief heavy rainfall. All
activity diminishes after the front sweeps SE and we lose the
diurnal support tonight, revealing a quiet night as dry air
continues to progressively pump into the region from the north.
Sunday is looking rather nice with some low/mid-level
stratocu/altostratus around. No adjustments needed to temperatures
as all guidance is coming in looking in line with thoughts. KLG
&&
.LONG TERM...
(Monday through Friday)
Issued at 1116 AM CDT Sat Sep 6 2025
By Monday and into Tuesday, the main story is  another
reinforcing shot of the drier/cooler air builds into the region.
Took a very close look at two items here:
Min temperatures Monday and Tuesday morning and dewpoints Monday
and Tuesday afternoon. For lows, deterministic 13Z NBM is coming
in already on the low side of the ensemble spread, generally in
the 25th-10th percentile so did not adjust suggested lows much in
this case, other than massaging traditionally cooler locations
across the Pascagoula and Pearl River drainage basins. Next, did
apply a noticeable target of opportunity to dewpoints both Monday
and Tuesday afternoons during peak diurnal mixing, as model
soundings illustrate a well-mixed PBL/adiabatic thermal profile to
1) support occasionally breezy winds and 2) likely mix down well
below suggested deterministic NBM guidance. Introduced a steady
transition to 25th to eventual 10th percentile dewpoints both
afternoons, bringing MinRH`s into the 30`s for most areas. This
will without a doubt make it feel much, much more comfortable both
days. As mentioned yesterday, something to remember is the sun
angle is still pretty high, and in the direct sunlight it`ll still
feel hot (and a much drier atmosphere will likely spike UV index
making for a risk for sunburn). Something to consider, otherwise
it`ll be a nice change in the hot summer we`ve been through so far
and a nice reminder that Fall is almost here! Beyond Tuesday into
the middle to later parts of the week, moisture steadily returns
back to the region underneath a building upper-level weakness
(broad SE US troughing pattern) that`ll bring back a few scattered
shower/storm chances. For now, best chances are looking across
the coastal areas of SE LA and MS, within greatest total column
moisture, but will monitor how far north moisture return builds to
support shower activity within this upper-level weakness with
time. Temperatures remain seasonal, with no excessive heat
concerns over the next 5-7 days. KLG
&&
.AVIATION...
(18Z TAFS)
Issued at 1116 AM CDT Sat Sep 6 2025
Expect VFR conditions for all area terminals through the TAF
cycle. A few ISO/SCT TSRA is possible this afternoon, primarily
for central/coastal terminals but impacts are expected to remain
limited to only brief VIS/CIG reductions with VFR outside of any
activity. Otherwise, we`ll see a FROPA sweeping across the region
today into early tonight, which will primarily introduce a steady
increase in NE surface winds mainly by mid/late morning Sunday
into Sunday afternoon. Winds look to be ranging 06-09ts generally
bearing 010 to 030 with gusts 10-12kts, higher for KNEW across the
lake. Otherwise, no impacts to area terminals are expected thru
the TAF cycle.
&&
.MARINE...
Issued at 1116 AM CDT Sat Sep 6 2025
A cold front is expected to progress south across marine waters
later this afternoon into tonight, introducing a steady wind shift
from the NNE to NE and drier air to progressively filter into the
region into the day on Sunday. Winds will be delayed to respond
increasing primarily 12-18kts for Gulf waters during the morning
thru afternoon hours on Sunday, with another reinforcing push of NE
winds expected overnight into early Monday. During this time period
(primarily 12AM thru 3PM Monday), winds may reach sustained upwards
of 15-20 knots, especially for outer Gulf zones south of the MS
sound including Chandeleur and Brenton sounds. Exercise caution
headlines are expected, but could briefly touch Small Craft Advisory
for portions of these areas during this time frame. Waves/seas will
respond into the 3-5ft range generally. Mid/late week, winds shift
more easterly but remain slightly elevated in the 10-15kt range,
especially for eastern zones which will keep waves/seas also slightly
elevated in the 2-4ft range for outer waters, 1-2ft for protected
waters. KLG
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB  87  68  85  62 /  30  10  10   0
BTR  91  71  88  66 /  20  10  20   0
ASD  90  69  89  63 /  20  10  10   0
MSY  92  76  90  73 /  20  10  10   0
GPT  90  70  90  66 /  20  10  10   0
PQL  92  69  90  64 /  20  10  10   0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
SHORT TERM...KLG
LONG TERM....KLG
AVIATION...KLG
MARINE...KLG

NWS LIX Office Area Forecast Discussion