Flash Flood Warning 81, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
403 AM CST Fri Dec 30 2022

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

.SHORT TERM...
(Today through Saturday)
Issued at 349 AM CST Fri Dec 30 2022

A line of strong to severe thunderstorms has formed to our west and
is approaching our area this morning. This line has a history of
producing severe wind gusts, small hail, and flash flooding. It will
start to  move into western parts of our CWA within the next few
hours. As this line moves into our area it will continue to be
favorable for producing severe winds gusts as well as possibly
producing a couple short lived tornadoes. While this line was not
moving too fast early on in its formation, it has been picking up
and will continue to do so as it enters our area becoming cold pool
dominated. If it races across the area the way models are
anticipating, we likely will see less of a flash flooding risk.
While it will be producing high rainfall rates that may cause a few
areas of localized flooding, the fast moving nature of it will help
keep us from seeing any widespread flooding issues. Showers and
thunderstorms should clear the LA/MS border sometime in the
afternoon, moving out of coastal MS late in the afternoon through
the evenings hours.

Following this line of storms, we will start to see conditions
become favorable for dense fog Friday Night into Saturday as we see
winds shift SW and advect in a higher RH field. Not going to jump
the gun on putting out a dense fog advisory just yet, going to let
the next shift take a close look and evaluate the situation.
Conditions look favorable for this to continue again Saturday night
into Sunday.

With all the active weather moved out by late Friday we expect to
see nice conditions for New Years Eve as clouds clear out and high
temperatures warm into the low 70s. Similar conditions are expected
into Sunday, but clouds start to build in later in the day ahead of
our next weather-maker. &&

.LONG TERM...
(Monday through Thursday)
Issued at 349 AM CST Fri Dec 30 2022

Our next big weather maker is expected to move into the region
Monday into Tuesday. The main focus will be a cold front that
swings through bringing showers and thunderstorms along with it,
some storms looking to be on the stronger side. This comes as a
deep trough digs down through the western CONUS on Sunday and into
Monday before moving eastward into the Central Plains and
eventually up into the Upper Midwest. As of now the convection
associated with the frontal boundary will move into our CWA
sometime Monday night into Tuesday. Ahead of the front, southerly
winds will increase moisture and instability over the area. Heavy
rain may be a threat with this system if there is any slowing or
stalling of the convection over the area. PWs will be on the
order of 1.50-1.70, showing plenty of available moisture in the
environment. It is still to far out to know any specific details
of possible severe weather, but SPC has thrown a 15% risk area
over us on Tuesday. Just pulling a few model soundings does show
plenty of CAPE (1500-2000J/Kg), vertical wind shear, and SRH
values shows most parameters looking favorable for this threat.
Will dive into this more once we get through this first system
today.

&&

.AVIATION...
(06Z TAFS)
Issued at 1152 PM CST Thu Dec 29 2022

Categorical impacts to terminals are beginning to show up with IFR
or MVFR ceilings noted at KBTR, KHUM, KMCB, and KASD. Areas of
sea fog and low stratus have been observed over Lake Pontchartrain
which is causing LIFR ceilings and reduced visibilities at KNEW.
Some periods of MVFR to IFR ceilings will be possible at terminals
through the remainder of the overnight hours. By 1200 UTC,
impacts to terminals will begin from west to east associated with
a line of showers and storms. The majority of thunderstorm
activity associated with this line will clear the terminals
between 1800-2000 UTC. Lingering showers and low ceilings will
remain into the evening hours and with winds weakening and
shifting to be out of the southwest. This will yield favorable
conditions for dense fog to develop Friday night. TJS

&&

.MARINE...
Issued at 349 AM CST Fri Dec 30 2022

Exercise caution headlines will continue through 12z this morning,
then increasing to Small Craft Advisory that continues through 12z
Saturday. Winds and seas will continue to increase throughout the
day as a cold front approaches the area. Along with this front
also comes a line of strong to severe thunderstorms that will
bring thunderstorm wind gusts and elevated seas. Winds briefly
turn to a westerly direction following the front, before
returning southerly into Sunday. Winds very briefly come down on
Saturday before picking back up a bit into Sunday, though likely
remaining below Exercise Caution headlines until into the day on
Monday. Our next system moves in late Monday into Tuesday,
bringing elevated winds and seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  68  57  70  48 / 100  30  10   0
BTR  71  58  73  51 / 100  20   0   0
ASD  71  58  73  50 / 100  30  10   0
MSY  70  60  72  53 / 100  30  10   0
GPT  69  58  71  53 / 100  40  10   0
PQL  71  58  71  52 / 100  60  20   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...Small Craft Advisory until 6 AM CST Saturday for GMZ536-538-550-
     552-555-557-570-572-575-577.

MS...None.
GM...Small Craft Advisory until 6 AM CST Saturday for GMZ538-550-552-
     555-557-570-572-575-577.

&&

SHORT TERM...HL
LONG TERM....HL
AVIATION...TJS
MARINE...HL

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