616
FXUS64 KLIX 072059
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
359 PM CDT Tue May 7 2024

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

.SHORT TERM...
(This evening through Wednesday night)
Issued at 330 PM CDT Tue May 7 2024

The forecast area will remain embedded beneath a fairly stout deep
layer ridge axis that is oriented in a southwest to northeast
fashion across the Gulf South. Ample subsidence and dry air aloft
will keep a potent mid-level capping inversion in place, and this
will greatly limit convective development through Wednesday night.
At most, a scattered to broken strato-cumulus field is expected to
develop each day in the moist and unstable airmass beneath the
mid-level cap, but deeper updrafts and rainfall are not expected.
The other impact of this highly subsident regime will be continued
warmer than normal temperatures with near record high temperatures
in the upper 80s and lower 90s and very warm overnight lows in
the 70s.

&&

.LONG TERM...
(Thursday through Monday night)
Issued at 330 PM CDT Tue May 7 2024

A fast moving southern stream vorticity max and associated 125
knot jet streak will move into the area by Thursday evening. In
advance of this system, continued subsidence associated with a
departing ridge axis will allow daytime highs to once again climb
into the upper 80s and lower 90s, and a few record highs will
likely be tied or broken. These warm surface temperatures will
combine with cooling temperatures aloft to induce very steep mid-
level lapse rates in excess of 7.0 C/km by the afternoon and
evening hours. The primary result of these steep lapse rates will
be very high MLCAPE values of 2500 to 3000 J/KG Thursday afternoon
into Thursday evening. Additionally, a surge of Pacific based
upper level moisture will also rapidly feed into the area as the
jet streak moves in. This will increase PWATS by nearly half an
inch over the course of Thursday, and values will be approaching 2
inches by the evening hours. The combination of deeper moisture,
ample instability, and deep layer forcing from the passing vort
max will result in deeper convective updrafts and eventually
shower and thunderstorm activity. As a result, fairly high rain
chances of 50 to 70 percent are forecast Thursday evening into
Thursday night. Another factor to review is the wind field and
shear parameters in place. Low level winds are expected to be from
the south and south-southwest at 10 to 15 knots. However, mid-
level winds will be more southwesterly at 30 to 40 knots, and
this will push storm relative helicity values upward to between
150 and 200 m2/s2. The strong jet streak moving through will also
push effective bulk wind shear values to between 50 and 60 knots.
The combination of these factors will support both tilting and
splitting updrafts, and a few discrete supercells may form within
a larger convective complex. All severe threats will be possible
including large hail, strong damaging wind gusts, and a few
tornadoes Thursday evening into Thursday night.

Conditions will begin to improve on Friday as the jet streak moves
to the east and increasing upper level subsidence takes hold of
the area. Lingering convection over eastern zones in the morning
will give way to clearing skies and dry conditions by the
afternoon hours. A cooler airmass will also begin to move into the
area, and highs will be closer to average in the low to mid 80s
Friday afternoon. The warmest readings will be along coastal
Mississippi where downslope compressional heating on the back of a
northerly wind flow can is expected. Saturday and Sunday will be
mainly clear and dry as a very stable ridge of high pressure
dominates the Gulf South, and temperatures will be largely near
average. Overall, have stuck with the NBM deterministic output
over this period.

Heading into Monday, model guidance has come into better agreement
that a southern stream shortwave trough will begin to impact the
area. A broad area of increasing positive vorticity advection and
favorable jet dynamics will support higher rain chances and the
threat of some elevated convection along a weakening frontal
boundary Monday into Monday. Greater confidence in this solution
will occur if subsequent model runs continue to remain in good
agreement. Overall, have stuck with the NBM output until
confidence increases further.

.AVIATION...
(18Z TAFS)
Issued at 330 PM CDT Tue May 7 2024

Moist boundary layer conditions will continue through the entire
forecast period, and this will keep a scattered to broken deck of
strato-cumulus ranging between 2000 and 3000 feet in place through
the afternoon hours. Later tonight, mainly between 08z and 14z,
another weak inversion will form within the boundary layer. The
development of this inversion will allow for lower stratus of 1000
to 1500 feet to develop at the majority of the terminals. However,
at MCB, further stratus build down could occur due to a stronger
inversion layer, and period of IFR ceilings ranging from 300 to
800 feet is in the forecast between 09z and 13z. Increased thermal
mixing after 15z will allow the stratus deck to mix back out into
the scattered to broken MVFR deck much as seen today.

&&

.MARINE...
Issued at 330 PM CDT Tue May 7 2024

Southeast flow of 10 to 15 knots will persist on the southwest
periphery of a high pressure system through tomorrow. Winds will
briefly increase on Thursday as frontal boundary increases the
pressure gradient over the Gulf with values of 15 to 20 knots and
seas of up to 5 feet expected. There will also be the risk of
convection producing strong wind gusts Thursday night in advance
of the front. After the front moves through on Friday, winds will
shift to the north and gradually decrease back to 10 to 15 knots
by Friday night. Fairly benign conditions are then expected for
the upcoming weekend with light winds of 10 knots or less and calm
seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  72  89  73  91 /  10  10  10  30
BTR  75  90  76  93 /   0  10   0  10
ASD  74  89  74  91 /   0   0   0  10
MSY  76  88  77  91 /   0  10   0  10
GPT  75  85  76  87 /   0  10   0  10
PQL  74  85  75  87 /   0  10   0  20

&&

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

$$

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