Flash Flood Warning 24, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
325 AM CDT Wed May 7 2025

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

.SHORT TERM...
(Today through Thursday)
Issued at 310 AM CDT Wed May 7 2025

Upper troughs near Lake Ontario and over the southwestern states
early this morning. Evening convection has pushed a surface
boundary to the south of Interstate 10, and that convection has
contributed to a surface pressure fall/rise couplet that has
produced wind gusts in excess of 30 knots around the New Orleans
Metro Area in the past 90 minutes. One band of thunderstorms will
be moving into Alabama around 4 AM CDT, with another cluster
moving across the Lower Atchafalaya River Basin. This cluster will
move into the New Orleans area over the next few hours, enhancing
a threat for flooding. This area may also impact the Mississippi
coastal counties later this morning. Considering that quite a few
areas have already seen 2 to 4 inches of rain, tolerance for
another round of heavy rain is fairly low.

In the wake of that cluster of storms, we anticipate a relative
lull in showers and storms during the late afternoon hours and
most or all of the overnight hours tonight. Another wave is
expected to move along the surface boundary late tonight and
Thursday with potential for another round of heavy rainfall. At
this point, it appears that the greatest threat with that round
will be near or south of Interstate 10, but confidence isn't
strong enough quite yet to make significant adjustments to the
Flood Watch. Can't rule out a few strong to severe storms either
today or Thursday, but the larger threat is the heavy rain
potential.

Will run with the NBM numbers on temperatures today and Thursday,
with Thursday being a bit warmer than today, assuming we don't get
much sunshine this afternoon behind the thunderstorm cluster.

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 310 AM CDT Wed May 7 2025

Potential for an additional round of showers and storms on Friday
with the trailing portion of the trough currently near Las Vegas.
The main question with that round is whether it occurs offshore or
over coastal Louisiana. Considering the rain that's fallen over
the last 12 hours, and what's expected later today and Thursday,
any convective complex over land on Friday would exacerbate
hydrologic concerns. We won't extend the Flood Watch at this time,
but will likely message that there is potential for that to occur
in later forecasts.

Upper troughing or even a closed low are being depicted across the
Lower Mississippi River Valley through at least the Mother's Day
weekend. That's certainly not going to aid in improving hydrologic
conditions. Timing of individual spokes of energy at those time
steps is problematic, but suffice it to say that predicting any
specific periods of dry weather prior to about Monday or Tuesday
is a low confidence forecast. That also means there's not really
a target of opportunity to make significant beneficial adjustments
to temperature forecasts at this time.

&&

.AVIATION...
(06Z/12Z TAFS)
Issued at 310 AM CDT Wed May 7 2025

Any terminals not being impacted by SHRA/TSRA are currently at VFR
conditions, but another round of SHRA/TSRA is expected this
morning, which will produce IFR or lower conditions, at least
briefly, this morning into the early afternoon hours. The meso-low
producing gusty winds over the southern terminals early this
morning should shift east of the area by sunrise, but another
round of gusty winds will be possible with the second round of
storms later this morning. Do anticipate a window of MVFR to VFR
conditions late this afternoon and for much of the evening. Low
clouds (MVFR to IFR or lower) are expected to develop between 08z
and 14z Thursday, even if TSRA remain offshore.

&&

.MARINE...
Issued at 310 AM CDT Wed May 7 2025

Current plan is to allow Small Craft Advisory to expire on
schedule, as most of the stronger winds are currently associated
with thunderstorms and the meso-low. With a frontal boundary in
the area, and potentially over the coastal waters, the surface
pressure gradient should be weak enough to not necessitate
advisories. However, marine interests should plan for numerous
rounds of showers and thunderstorms over the next several days
that could produce rapidly changing conditions.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  78  63  81  63 /  90  60  80  40
BTR  80  66  82  66 / 100  70  80  40
ASD  81  65  82  65 / 100  70  90  50
MSY  80  70  80  69 / 100  70  90  60
GPT  79  67  80  66 / 100  70  90  60
PQL  81  65  81  65 / 100  60  90  60

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flood Watch through Thursday evening for LAZ034>037-039-046>048-
     056>060-064>071-076>090.

GM...Small Craft Advisory until 7 AM CDT this morning for GMZ530-532-
     534-536-538-550-552-555-557-570-572-575-577.

MS...Flood Watch through Thursday evening for MSZ068>071-077-083>088.

GM...Small Craft Advisory until 7 AM CDT this morning for GMZ532-534-
     536-538-550-552-555-557-570-572-575-577.

&&

SHORT TERM...RW
LONG TERM....RW
AVIATION...RW
MARINE...RW

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