Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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FXUS64 KLIX 201835
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
135 PM CDT Sat Apr 20 2024

...New AVIATION...

.UPDATE...
Issued at 1141 AM CDT Sat Apr 20 2024

A fairly broad upper level trough is currently moving east through
the Great Lakes. The southern side of this feature is relatively
flat at this time which is why the associated cold front draped
across central Louisiana and southern Mississippi is struggling to
make southward progression. The cold front will be basically
crawling south into the CWA this afternoon. Current visible
satellite shows only partly cloudy skies south of the boundary
across the Florida Parishes and coastal Mississippi. This will allow
for decent warming which should increase CAPE in the lower to mid
levels. As that boundary reaches this region later this aftn, a few
thunderstorms could develop along and north of I-12 in LA and
southern portions of LA. Latest CAMs show various versions of this
and am in agreement with this. Severe potential not particularly
high due to weak shear but fairly steep mid level lapse rates
could be enough for a few marginally severe storms with hail.

&&

.SHORT TERM...
(Today through Sunday Night)
Issued at 307 AM CDT Sat Apr 20 2024

A cold front currently draped just north of the forecast area
along the I-20 corridor will continue to drift south and will move
through the northern third of the CWA by this evening. This
southward drift will be entirely driven by density differentials
between the cooler airmass to the north and the warmer and more
humid airmass to the south as no strong synoptic scale forcing
mechanisms are forecast to pass through the region today. As the
cold pool moves into the northern third of the CWA, weak
isentropic forcing over the cold pool will combine with broad
region of increasing positive vorticity advection in advance of a
shortwave trough kicking out of the Four Corners. This will
support the development of scattered showers and possibly a weak
thunderstorm by this afternoon. Overall, rainfall should not be
excessive with this event with rainfall totals of less than half
an inch expected. Temperatures will be slightly cooler behind the
front in the upper 70s while readings ahead of the front will
climb back into the mid 80s.

The shortwave energy kicking out of the Four Corners will sweep
through the Lower Mississippi Valley tonight into tomorrow
morning. At the same time, the development of a weak mid-level low
pressure system along the 850mb frontal boundary will allow the
surface front to sweep southward toward the Louisiana coast by
tomorrow morning. The combination of continued isentropic forcing
over the cooler low level airmass behind the front and stronger
deep layer forcing in the mid and upper levels will support the
development of numerous showers and a few elevated thunderstorms,
especially after midnight. PoP values will peak out in the 70 to
80 percent range from midnight through Noon tonight into tomorrow
morning, and QPF should peak out around an inch. A few spots may
see locally higher amounts of up to 2 inches, but overall flood
risk is low with this event as most of the rainfall will be
stratiform in nature. Temperatures will be cooler as the front
sweeps to the south with temperatures ranging from the mid 50s in
Southwest Mississippi to the upper 60s along the Louisiana coast.
Overall, have stuck with a blend of the NBM 50th and 75th
percentiles for tonight as rain cooled air dips down toward the
dewpoint.

By tomorrow afternoon, rapidly improving conditions are
expected as upper level trough axis pulls to the east and the
front is driven further offshore. Mid-level flow will turn
northwesterly, and this will cut off isentropic forcing and also
usher in a drier airmass by tomorrow evening. Fully expect to see
dry conditions over all land based zones by Sunday evening as well
as clearing skies. Temperatures will be significantly cooler as
the heart of a 925mb thermal trough axis advects into the area
behind the front. Highs will only warm into 60s and lows will
upper 40s and lower 50s.

&&

.LONG TERM...
(Monday through Friday)
Issued at 307 AM CDT Sat Apr 20 2024

Monday and Tuesday will see a deep layer northwest flow regime
dominate the Gulf South, and this will keep conditions clear and
dry each day. With dry air in place, temperatures will see a
larger diurnal range. Highs will warm into the lower 70s on Monday
and the upper 70s on Tuesday, and lows will fall into the low to
mid 40s north of I-10 and the low to mid 50s south of I-10 Monday
night. Overall, have went with NBM 75th percentile values for
highs and NBM 50th percentile values for overnight lows.

Wednesday will see a northern stream shortwave trough axis slide
through the area, and weak attendant front will slip into the
area and dissipate. This system will be moisture starved as PWATS
remain around an inch, and do not expect to see much more than
some passing cirrus as this system moves into the region.
Temperatures will continue to modify and highs are forecast to
climb back into the lower 80s by Wednesday afternoon. The large
diurnal range will also persist with temperatures cooling into the
50s Tuesday night. By Wednesday night, the return of onshore flow
will support rising dewpoints, and expect to see lows only dip
into the upper 50s and lower 60s. Boundary layer flow is expected
to below 10 knots, and some radiation fog could develop over
inland areas Wednesday night with this increase in low level
humidity.

A strong longwave ridge will build over the area on Thursday and
Friday, and the deep layer subsidence associated with this ridging
will keep conditions dry both days. Temperatures will also
continue to warm beneath this strong ridge with highs climbing
back into the mid to upper 80s. Continued onshore flow will also
keep pushing dewpoints up into the upper 50s and lower 60s, and
this will result in lows only dropping into the 60s for Thursday
night. However, boundary layer winds look to increase enough to
keep fog development at bay on Thursday night.

&&

.AVIATION...
(18Z TAFS)
Issued at 111 PM CDT Sat Apr 20 2024

A cold front is slowly moving south through the area, currently
between KHDC and KMCB. Terminals continue to see a mix of MVFR
and VFR conditions as ceilings range from 1000ft north of the cold
front to 3500 feet south of the front. Scattered thunderstorms
will be possibly this afternoon and evening, mainly along and
north of a KBTR to KPQL line. Post-frontal scattered shower
activity is also expected to become more pronounced after 06Z and
have included VCSH wording at terminals. The front will continue
to move south and a broad area of IFR stratus and more persistent
stratiform rainfall will overspread the area through the overnight
hours and into early Sunday morning. Most shower activity should
begin to wane by midday Sunday.

MEFFER
&&

.MARINE...
Issued at 307 AM CDT Sat Apr 20 2024

A cold front will push through the waters tonight into tomorrow,
and northerly winds of 15 to 20 knots will develop after the front
moves through. These winds will persist through Monday morning
before easing as high pressure builds over the waters. Seas will
respond to the stronger winds and could build to high as 5 feet
over the open Gulf waters by Monday morning. As the high pulls to
the east on Tuesday, a return to southeast winds of around 10
knots is expected. This southeasterly flow regime will persist
through Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  54  62  44  71 /  70  60  10   0
BTR  61  66  48  74 /  50  50  10   0
ASD  62  68  48  75 /  50  70  20   0
MSY  66  68  55  73 /  50  70  20   0
GPT  63  69  50  74 /  40  70  20   0
PQL  63  69  48  74 /  40  70  20   0

&&

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

$$

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


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