-- Discussion containing changed information from previous version are highlighted. --
186
FXUS64 KLIX 122046
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
346 PM CDT Wed Jun 12 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
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(This evening through Thursday night)
Issued at 335 PM CDT Wed Jun 12 2024

Invest 90L was over Florida this afternoon, and will move
northeastward into the Atlantic over the next couple days.

Otherwise, upper ridging was centered near El Paso this
afternoon, with troughing over southern Mississippi and Louisiana.
To the west of the ridge was an upper low southwest of San Diego.
At the surface, there is a boundary south of Lake Pontchartrain
and south of Interstate 10. Isolated convection has developed near
and south of the boundary, and one doesn`t have to go very far
south of the New Orleans Metro area to find it. Very little actual
cell movement, with propagation driving where storms occur. A few
lucky (or perhaps unlucky) spots could pick up 1 to 2 inches of
rain in less than an hour. Outside of convection, temperatures are
generally ranging from the mid and upper 80s across southwest
Mississippi to the lower 90s. Dew points range from the mid 60s
across southwest Mississippi to the mid and upper 70s south of the
boundary.

The shortwave over the local area will shift offshore overnight,
but it may take a good chunk of the daylight hours Thursday for
dry air to get to the south of Interstate 10. Precipitable water
values near 1.7-1.8 inches this afternoon will finally fall below
1.5 inches by late afternoon tomorrow, and range from 1.1 to 1.4
inches by Friday morning. Current convection should end with the
loss of surface heating in the next 4 hours or so. The drying of
the column will mean less areal coverage (probably 20 percent or
less) Thursday afternoon, and further south, if any develops at
all. Expect this to allow temperatures to be a couple degrees
higher on Thursday, with lower to middle 90s for most of the area,
although immediate coastal areas could be tempered slightly with a
weak sea breeze by mid-afternoon. MET guidance appears too cool,
and the NBM values also appear a bit too cool for low
temperatures, and will trend them up a degree or two.
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&&

.LONG TERM...
-- Changed Discussion --
(Friday through Tuesday night)
Issued at 335 PM CDT Wed Jun 12 2024

Continuing the trend of the previous forecast runs, the early
portion of the long term (Friday through Saturday night) is
fairly high confidence, before diminishing Sunday into early next
week. A piece of the upper ridge near El Paso breaks off and
shifts eastward to near Atlanta by Sunday and to the Atlantic
Coast early next week. Friday and Saturday should be primarily dry
and hotter than today, with much of the area in the mid and upper
90s. At this point, it appears that we will remain just short of
Heat Advisory criteria (108F) on Friday and Saturday, but we`ll
revisit that potential in later forecast packages.

The ridge moving eastward to our north will produce easterly flow
across the northern Gulf of Mexico from Sunday onward. Impulses
moving through that flow will produce periods of showers and
thunderstorms, but there is quite a bit of uncertainty, not only
in the timing of individual impulses, but in whether that
convection occurs over the Gulf or over land. ECMWF based guidance
including a majority of their ensemble members continue to be
primarily a non-event regarding heavy rainfall with the
operational run showing 7 day QPF of less than an inch across the
CWA, and the ensemble mean showing 1-2 inch mean totals from
Interstate 10 southward. Even the 12z GFS and ensemble has backed
off on the heavy rainfall threat, and wouldn`t be surprised if
these trends continue. Both families are tending toward a solution
where the Central American Gyre aids in the development of low
pressure near or over the Bay of Campeche early next week, which
would keep low level flow southeasterly and the deepest moisture
offshore. It certainly won`t be entirely dry early next week, but
we`re probably looking at more diurnally driven convection as
early as Sunday afternoon continuing through mid-week with
scattered areal coverage. High temperatures will be driven by
where and when convection occurs from Sunday onward with drier
solutions being hotter, not surprisingly. Didn`t depart from NBM
deterministic values from Sunday onward.
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&&

.AVIATION...
(18Z TAFS)
Issued at 1229 PM CDT Wed Jun 12 2024

Old frontal boundary continues to linger near the southeast
Louisiana coastline, where convection has bubbled up in the last
hour or so. Will carry TEMPO for KHUM this afternoon. Also seeing
deeper cumulus development much closer to the New Orleans
terminals of KMSY and KNEW than what was observed yesterday. With
a lake/sea breeze boundary near those terminals, will carry VCTS
at those terminals as well. Convection should weaken/dissipate by
00z Thursday, with primarily VFR conditions beyond that point
through the end of the forecast period.

&&

.MARINE...
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Issued at 335 PM CDT Wed Jun 12 2024

Only real impacts through at least Saturday would be the threat of
thunderstorms, and that would be mainly over the open waters
during diurnally favored hours. Convective threat likely to
increase from Sunday onward, again especially over the open
waters. If low pressure does develop over the Bay of Campeche
early next week, an increased pressure gradient would bring
stronger winds to the waters as early as Sunday or Monday. The
most likely forecast would be for Small Craft Exercise Caution
level conditions over the protected waters and Small Craft
Advisory conditions possible over the open waters by Monday or
Monday night. The persistence of southeasterly winds would likely
produce swell over shorelines facing that direction, but tide
ranges will be comparatively narrow over the weekend and early
next week, which should, at least for now, limit any coastal
flooding potential.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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MCB  64  91  67  94 /   0   0   0  10
BTR  70  95  72  98 /  10  10   0  10
ASD  71  95  72  96 /  10  10   0  10
MSY  77  92  77  95 /  10  20   0  20
GPT  72  94  74  94 /  10  10   0  20
PQL  69  97  72  98 /   0  10   0  10
-- End Changed Discussion --

&&

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

$$

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