-- Discussion containing changed information from previous version are highlighted. --
155
FXUS64 KLIX 201529
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
Issued by National Weather Service Jacksonville FL
1029 AM CDT Thu Jun 20 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 1025 AM CDT Thu Jun 20 2024

Current forecast on track. The morning sounding shows very moist
low level flow generally from the east and a PWAT value of 1.68
inches. PWAT is just shy of normal values for this time of year.
Low level RH was measured about 85 percent, which will make for
scattered to broken cumulus and enough moisture and low level
convergence to generate scattered showers and a few storms during
the daytime heating, mainly southern half of the forecast area.
Radar shows isolated to scattered shower activity over southeast
LA at this time, and is expected to increase in coverage and
intensity a bit through the afternoon and early evening before
fading. Given the fairly quick movement of the convection from
east to west, rainfall amounts will generally be light. Breezy
easterly winds continue today at 15-25 mph, with gusts up to
30-35 mph. No changes to the rest of the forecast package at this
time.
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&&

.SHORT TERM...
(Today through Friday)
Issued at 400 AM CDT Thu Jun 20 2024

Tropical Storm Alberto about to make landfall on the Mexican
coastline early this morning, and expected to weaken rapidly and
dissipate during the day today as it reaches higher terrain in
Mexico. As the pressure gradient weakens, the wind field should
relax somewhat. However, it will take time for the winds and swell
to abate. Additionally, with no significant change in the wind
direction, it will take some time for the higher water in the
tidal lakes to drain. Current plan is to replace the Coastal Flood
Warning with a Coastal Flood Advisory beyond today`s high tide
cycle for tomorrow`s high tide cycle. It can be cancelled later if
water levels fall quicker than forecast, but current guidance
indicates there may be at least some minor issues on Friday.

Upper ridging over the Mid-Atlantic States will build
southwestward over the next couple of days and be centered near
Memphis Friday afternoon. Water vapor imagery already shows drier
air moving westward through much of the local area. This was
noticeable in the 00z LIX sounding which showed a precipitable
water value of 1.6 inches, compared to the 2+ inches we`d seen for
the previous couple of days. Northern portions of the area may
already have precipitable water values nearer to 1 inch, if the
BMX sounding was any indication. We`ll continue to see drier air
filter into the area, with precipitable water values closer to 1.2
inches by Friday afternoon. However, there may still be enough
moisture both today and Friday to support at least a few showers
or storms. We are even seeing that early this morning with a few
echoes moving onshore from the Gulf. Most of that should be south
of the Interstate 10 corridor both days, and rain amounts should
be rather scarce. Have undercut the NBM PoPs somewhat, closer to
the global numbers, as they`ve been overstating things for the
last several packages.

With less precipitation, and likely less clouds, that argues for
going on the high end of temperature guidance, and the NBM
deterministic numbers support this. That should put pretty much
every one in the lower-middle 90s both today and Friday.

&&

.LONG TERM...
(Friday night through Wednesday)
Issued at 400 AM CDT Thu Jun 20 2024

Upper ridging will continue to build westward, and be centered
near the New Mexico-Arizona border on Sunday, where it will take
up residence for next week. For the weekend, and potentially
through Monday, there will be a southeastward extension of the
ridge into the northern Gulf of Mexico. Any convective development
over the weekend should remain on the isolated side and be limited
to primarily the afternoon hours from about Interstate 10
southward. As we move into early next week, the upper flow across
the area becomes northwesterly, which opens up the potential for
shortwaves moving through that flow to trigger clusters of
thunderstorms. Of course, timing those shortwaves at this time
range is going to be handled differently by the models. Can`t see
fighting the NBM PoPs for a target of opportunity beyond perhaps
Monday. With precipitable water values well in excess of 2 inches
for the middle of next week, certainly appears that storms could
be efficient precipitation producers.

NBM deterministic temperatures are generally on the high end of
the guidance envelope for highs this weekend and Monday, which
appears reasonable, as long as convection doesn`t develop too
early in the afternoon. At mid week, things should trend a bit
closer to normal, as the higher precipitable water values argue
for an earlier start to convective development. Some potential for
heat advisories for at least Sunday/Monday depending on timing of
convective development, with heat index values approaching 110F.

&&

.AVIATION...
(12Z TAFS)
Issued at 624 AM CDT Thu Jun 20 2024

Most terminals with VFR conditions ongoing, but there are
occasional MVFR ceilings as isolated showers move through the
southeasterly flow. Echo tops on the showers on KHDC radar were
only near the freezing level, so no large threat of TSRA in the
very near term. Will handle with VCSH to acknowledge there are
some out there.

May see somewhat better coverage later this morning or early
afternoon as heating gets involved. If there`s any real threat of
TSRA, it`d be at KHUM this afternoon, and VCTS is likely
overstating things. But there is a weak shortwave moving through
the easterlies, and moisture levels haven`t fallen off enough to
preclude it. With loss of heating toward sunset, most or all of
the limited amount of convection should dissipate, with vFR
conditions overnight tonight.

Easterly winds of 15 knots or greater may impact terminals south
of Interstate 10...KGPT/KNEW/KMSY/KHUM from mid-morning until
approximately 00z Friday.

&&

.MARINE...
Issued at 400 AM CDT Thu Jun 20 2024

As Tropical Storm Alberto makes landfall and weakens/dissipates
over Mexico, winds and seas should gradually subside today. Will
replace the Small Craft Advisory over the tidal lakes with
Exercise Caution headlines with forecast issuance. Will extend
Small Craft Advisory over the western open waters through this
evening, but allow it to expire on schedule at 21z elsewhere.
Can`t rule out needing brief Caution headlines on the back end of
the advisory this afternoon/evening, but will let the day shift
folks reassess that.

Winds could remain around 15 knots for a good portion of Friday,
but beyond that point, should be a much more benign period into
early next week, outside of the potential for thunderstorms.

&&

.PRELIMINARY POINT TEMPS/POPS...
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MCB  90  70  92  70 /   0   0   0   0
BTR  93  75  96  75 /  10   0  20   0
ASD  91  74  93  74 /  20  10  20   0
MSY  90  79  93  78 /  40  10  30   0
GPT  91  75  93  75 /  20  20  10   0
PQL  93  73  96  73 /  20  20   0  10
-- End Changed Discussion --

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
LA...Small Craft Advisory until midnight CDT tonight for LAZ068.

     Coastal Flood Warning until 4 PM CDT this afternoon for LAZ058-
     070-076-078-080-082-084-086.

     Coastal Flood Advisory from 4 PM this afternoon to 6 PM CDT
     Friday for LAZ058-070-076-078-080-082-084-086.

     Coastal Flood Advisory until 6 PM CDT Friday for LAZ060-066>069-
     077-087.

GM...Small Craft Advisory until 4 PM CDT this afternoon for GMZ532-
     536-538-555-557-575-577.

     Small Craft Advisory until midnight CDT tonight for GMZ550-552-
     570-572.

MS...Coastal Flood Warning until 4 PM CDT this afternoon for MSZ086.

     Coastal Flood Advisory from 4 PM this afternoon to 6 PM CDT
     Friday for MSZ086.

     Coastal Flood Advisory until 6 PM CDT Friday for MSZ087-088.

GM...Small Craft Advisory until 4 PM CDT this afternoon for GMZ536-
     538-555-557-575-577.

     Small Craft Advisory until midnight CDT tonight for GMZ552-570-
     572.
-- End Changed Discussion --

&&

$$

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