-- Discussion containing changed information from previous version are highlighted. --
838
FXUS64 KLIX 271536
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1036 AM CDT Thu Jun 27 2024

...New UPDATE, MARINE...

.UPDATE...
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Issued at 1015 AM CDT Thu Jun 27 2024

Just sent a mid morning forecast update for the rest of today. The
focus was on hourly PoPs and Wx. A convective complex that
resulted in heavy rain overnight and early this morning across the
lower Atchafalaya - Thibodaux area is quickly decaying as a weak
impulse rotating around the based of the upper trough lifts out.
This will yield a lull in precipitation through early afternoon
until diurnally-driven convection develops during peak heating.
In addition to the lake- and sea-breezes, outflow boundaries north
of the earlier convection will provide a focus for scattered
showers and storms across the Atchafalaya, Florida Parishes, and
Coastal MS.
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&&

.SHORT TERM...
(Today through Friday)
Issued at 325 AM CDT Thu Jun 27 2024

Upper ridging centered near El Paso this morning, with a trough
extending from eastern Kentucky to near Lake Charles. A stronger
trough was over the Pacific Northwest. A weak frontal boundary
extended from Tennessee into north Texas. Scattered showers and
thunderstorms were noted on radar with most of the activity south
of Interstate 10. The greatest areal coverage was over the lower
portions of the Louisiana coastal parishes. A few of these showers
and storms could produce wind gusts of 30 to 40 mph and brief
heavy rain. early morning temperatures ranged from the mid 70s
over southwest Mississippi to the mid 80s near Lake Pontchartrain.

Main forecast issue for this package will be the areal coverage
and timing of showers/thunderstorms, both today and Friday.
Mesoscale modeling hasn`t been particularly helpful over the last
couple of days, but does seem to be in somewhat better agreement
this morning. The ongoing convection is being depicted, albeit a
bit slow. Most solutions eventually build this convection offshore
later this morning and then eventually redevelop storms around
the Interstate 10/12 corridor by mid to late afternoon, where
differential heating, as well as lake/sea/outflow boundary
interaction, will help to produce lift. Current indications are
that these storms should dissipate by mid to late evening.

The troughing that is moving into the area this morning is
expected to become strung out near or just off the coast over the
next 36 hours. This is likely to provide a focus for convective
development again tomorrow, although there is some question as to
how far northward convection can develop, considering the very
warm mid level temperatures (500 mb of -2C to -4C).

The additional cloud cover and precipitation potential should
prevent high temperatures from getting much hotter than 90 to 95
today and Friday. This should alleviate the need for Heat
Advisories, but we`ll continue to monitor each day.

&&

.LONG TERM...
(Friday night through Wednesday)
Issued at 325 AM CDT Thu Jun 27 2024

The troughiness along the coast in the short term will eventually
wash out as the upper ridge takes up residence between Interstate
20 and Interstate 40 to our north through at least the middle of
next week. Forecast soundings show that there won`t be a lot of
day to day change in moisture levels with precipitable water
values generally remaining between 2 and 2.3 inches, which is near
or above the 90th percentile for late June. No real indications of
any capping mechanism, so we will likely see at least isolated to
scattered thunderstorm development each day once the convective
temperature is reached. Considering the high precipitable water
values, any cell could produce locally very heavy rain if it lasts
long enough.

Daily highs are going to be driven by convective development.
Areas that see development will have trouble getting much higher
than the 90 to 95 range, but if an area remains dry, they could
reach upper 90s. We`ll have to go day by day, but Heat Advisories
may be necessary if convection fails to develop, or if the upper
ridge axis moves closer to the coast than currently expected.

&&

.AVIATION...
(12Z TAFS)
Issued at 636 AM CDT Thu Jun 27 2024

At forecast issuance time, all terminals were VFR with the
exception of KMCB, where IFR ceilings were occurring. Those
ceilings at KMCB should improve to MVFR in the next hour or two,
then to VFR by midday. Scattered TSRA were generally south of
Interstate 10 at 11z, but it appears that in the short term, the
only forecast terminal(s) that would be impacted would be KHUM,
and possibly KMSY. Direct impacts would be IFR or lower
visibilities, MVFR ceilings, and wind gusts to perhaps 35-40
knots. The current round of convection is likely to move offshore
or dissipate prior to 17z. A second round of TSRA will be possible
for most terminals by late afternoon as the airmass will have had
time to destabilize with surface heating. The exceptions would be
KMCB/KBTR/KHDC, where subsidence behind the shortwave may limit
development. That round should dissipate by mid-evening, roughly
03z Friday.

&&

.MARINE...
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Issued at 1015 AM CDT Thu Jun 27 2024

Issued a Small Craft Advisory for all of the waters through 1 PM
with a W-NW winds 15-25 kt. This surge in winds is due to a
tightening pressure gradient between a mesohigh (1014 mb south of
Terrebonne Bay) in wake of offshore convection and surface trough
near the MS-AL border (1010 mb). The winds should fall below SCA
threshold from west to east across the waters between 11 AM and 1
PM.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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MCB  89  72  91  74 /  40  20  50   0
BTR  93  77  94  79 /  50  20  70   0
ASD  91  76  92  78 /  70  40  70  10
MSY  91  78  92  81 /  80  40  80  10
GPT  91  76  91  78 /  80  60  70  30
PQL  92  76  93  78 /  80  60  70  40
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&&

.LIX WATCHES/WARNINGS/ADVISORIES...
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LA...Small Craft Advisory until 1 PM CDT this afternoon for LAZ068.

GM...Small Craft Advisory until 1 PM CDT this afternoon for GMZ530-
     532-534-536-538-550-552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until 1 PM CDT this afternoon for GMZ532-
     534-536-538-550-552-555-557-570-572-575-577.
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&&

$$

UPDATE...JK
SHORT TERM...RW
LONG TERM....RW
AVIATION...RW
MARINE...JK