566
FXUS64 KLIX 170557
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1257 AM CDT Fri May 17 2024

...New UPDATE, AVIATION...

.UPDATE...
Issued at 1241 AM CDT Fri May 17 2024

High end convective wind event (75-80 mph gusts) in the New
Orleans Metro area over the last couple hours. Have cleared
portions of the Baton Rouge Metro area from Tornado Watch 251, but
with redevelopment of convection south of Interstate 10, not
clearing watch entirely behind the leading line.

&&

.SHORT TERM...
(This evening through Saturday)

We are heading into quite an active period of weather with multiple
rounds of storms through Saturday morning. This will bring us an
extended risk for flash flooding and severe weather during the short
term.

A warm front was located just off the LA coast this afternoon. This
boundary marks the leading edge of a very moist, unstable airmass.
While there is a temperature gradient across the boundary aloft, it
not very noticeable at the surface owing to much stronger boundary-
layer heating on land north of the it vs over the water.

Low-level convergence and isentropic lift along the warm front will
serve as a focus for convective development through tonight. Showers
and storms has so far today has been confined to coastal LA, but
this activity will increase this evening as the MCS that is
currently over eastern TX and northwest LA moves into the area. The
environment will become increasingly supportive of heavy rainfall
producers as the deeper moisture arrives behind the warm front
(PWATs increase from 1.2 to 2.1 inches this evening). Although this
system should be progressive as it is embedded in fast zonal flow
aloft, the west-east orientation of the convection on the southern
flank of the MCS will bring the potential for storms to track over
the same areas. Additionally, the northward progress of the surface
warm front may slow once it meets up with the cold pool on the
southern periphery of the complex. This will provide a favorable
setup for flash flooding across a narrow west-east corridor of the
area. The latest CAMs continue to highlight areas along and north of
the I-10/I-12 corridor to be under the axis of heaviest rainfall
tonight. The latest guidance continues to suggest a quick 2-3" with
isolated amounts of 4-5" with the storms. The Flood Watch was
expanded southward earlier in the day to include both the Northshore
and Southshore of LA and MS Coast. There is also a severe
thunderstorm threat this evening into the early overnight hours but
it is highly conditional on convection being able to become rooted
in the boundary layer. The opportunity for surface-based convection
is narrow and dependent on storms on the southern flank of the MCS
being able to develop south of the warm front.

A "relative" lull in showers and storms is still expected behind the
departing MCS during the day Friday from about mid morning through
early afternoon as warm front lifts just north of our area. Expect
additional storms to develop during the mid to late afternoon as the
boundary layer quickly destabilizes during peak heating. Plenty of
disagreement among the CAMs regarding how widespread the
convection will become later Friday afternoon and evening.
However, a highly unstable airmass fueled by a moist boundary
layer and steep mid- level lapse rates will support a risk of
damaging wind gusts and large hail with this second round.

But wait...there`s more. A third round is expected Friday night
(especially overnight) into Saturday morning. Convection will be
aided by favorable synoptic dynamics ahead of a sharpening
shortwave trough and upper jet streak. Accordingly, convection
should grow upscale, resulting in another round of heavy rainfall
and flash flooding.

&&

.LONG TERM...
(Saturday through Wednesday night)
Issued at 320 PM CDT Thu May 16 2024

The upper-level trough will be departing our area on Sunday and
northwest flow kicks in on the backside. Due to the upstream ridging
across the southern Plains, surface high pressure will filter in
across the area starting on Sunday. This will keep the area dry and
warm on Sunday.

The aforementioned ridging will slide east over our area by Monday.
This will cause temps to increase further throughout the week. The
suppression from the ridge will also keep us mostly dry, although the
onshore winds will pump moisture into the area.

&&

.AVIATION...
(06Z TAFS)
Issued at 1241 AM CDT Fri May 17 2024

Most forecast terminals VFR at issuance time, although thunder
still being reported in the vicinity of most. Should see TSRA end
at most terminals in the next hour or two, but expect ceilings to
deteriorate to MVFR or IFR prior to sunrise. MVFR ceilings may
remain at most terminals for much of the daytime hours. Main
question during the day will be how much, if any, convective
activity occurs. Most of the model guidance indicates convective
development primarily beyond 00z Saturday, with some holding it
off beyond 06z.

&&

.MARINE...
Issued at 103 PM CDT Thu May 16 2024

A warm front was located over the coastal waters of LA. A slight
wind shift from easterly to southeasterly is occurring with the
frontal passage. Wind speeds will also increase from around 10 kt
to 15 kt with occasional gusts to 20 kt. This boundary will
continue to lift northeastward through the rest of the waters
through the evening.

Storms have already developed just behind the surface boundary
across our far southwestern zones early this afternoon. Locally
strong wind gusts of 30-40 kt is possible with the strongest
convection.

Additional showers and storms are expected to move in this
evening and continue overnight. The highest coverage will be over
the lakes and MS Sound as convection becomes focused along the
warm front. Have ise SCA for tonight owing to the presence of a
wake low behind the storms. There is a potential for a brief 1-3
hour period of gales depending on where the wake low tracks and
how strong it is as it approaches our area.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  67  84  64  86 /  70  50  10   0
BTR  70  89  69  91 /  60  50  10   0
ASD  70  87  69  91 /  60  70  10   0
MSY  73  87  73  89 /  70  60  10   0
GPT  70  85  69  90 /  70  70  20   0
PQL  70  85  68  91 /  60  80  20  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Small Craft Advisory until 6 AM CDT Saturday for LAZ068.

     Flood Watch through Saturday morning for LAZ034>037-039-046>048-
     057-058-060-064-071-076>087-089.

GM...Small Craft Advisory until 6 AM CDT Saturday for GMZ530-532-534-
     536-538-550-552-555-557-570-572-575-577.

MS...Flood Watch through Saturday morning for MSZ068>071-077-083>088.

GM...Small Craft Advisory until 6 AM CDT Saturday for GMZ532-534-536-
     538-550-552-555-557-570-572-575-577.

&&

$$

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