Severe Thunderstorm Warning 45, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
103 PM CDT Wed Apr 29 2026

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

.KEY MESSAGES...
Updated at 102 PM CDT Wed Apr 29 2026

- There is a Marginal to Slight Risk of severe weather with the greatest
  potential in southwest MS and adjacent LA parishes this
  afternoon and evening.

- There is a Marginal Risk for heavy rainfall this afternoon and
  evening and a Marginal to Slight Risk of heavy rainfall Friday night.
  For the Friday night evening, the greatest potential sill be in
  southwest Mississippi and Baton Rouge Metro.

&&

.SHORT TERM...
(Now through Thursday night)
Issued at 102 PM CDT Wed Apr 29 2026

Upper level analysis shows a ridge centered over Mexico by flattened
on its northern side due to a trough axis coming across the mid and
upper Mississippi RIver Valley. A cold front along the southern edge
of the trough has pushed into Texas and extends across northern LA
and MS. As storms develop along this focal point, cold pool will
likely drive the activity southeastward towards the CWA. Model
soundings are similar in some facets but also quite different when
looking at KBTR vs KMCB. In southwest MS, storms should be surface
based as 700-850mb layer cools quite a bit between late morning and
early afternoon. That'll support more robust updrafts as CAPE values
jump to the 2000+j/kg realm. Low level shear not much to speak of
but do have decent 0-6km shear at 50kts or so. Hail and damaging
winds will be the main threats. When it comes to flash flooding, not
the biggest concern but worth noting. Depending on the strength
of the cold pool dragging storms south, if its not strong enough,
could get some W/E training to produce upwards of 3 to 4 inches of
rainfall. Generally, it takes more than this to produce flash
flooding in southwest MS, but not in the isolated more urbanized
areas there. Looking farther south in the CWA, lack of low level
cooling will really limit instability comparatively and stunt
updraft potential.

As the main trough axis passes east of the CWA Thursday, the base of
it pulls northward. That puts the CWA in more of a zonal flow
pattern. So wherever the cold front ends up by then is probably were
it will stay for the time being. High temp gradient across the local
area will be much higher than typical, ranging from mid/upper 70s
north of the boundary to mid 80s south of it. Moisture convergence
along this boundary will probably aide in development of scattered
showers and possibly some thunderstorms throughout the day.

MEFFER
&&

.LONG TERM...
(Friday through Tuesday night)
Issued at 102 PM CDT Wed Apr 29 2026

Southwesterly flow increases in the mid and upper levels overhead
Friday as an upper level low comes into the southwestern US,
reaching the 4 Corners region late in the day. This setup will first
lead to a fairly substantial cirrus deck over the CWA Friday. That,
combined with east to northeast surface flow will yield even cooler
highs. Will be the first time in about a week that highs struggle to
reach climatological normal.  Friday night into Saturday though,
rain chances come up considerably as a shortwave coming across AZ
through TX merges with broad upper trough to the north. As the
track of this feature nears the local area, frontogenesis will be
taking place over the northern Gulf Coast. That setup with lead
to both surface and upper level height falls. Combine that with
PW's 1.75-2" along with W/E orientation of convective
development/movement, and you've got a decent setup for heavy
rain/flash flooding potential.

Sharpening of the main trough Saturday morning will drive the cold
front well into the Gulf and bring much cooler air to the local area
through Monday. Look for highs in the 70s this weekend and lows 40s
to near 50. Early next week looks to be non-impactful characterized
by moderating temps as the upper level trough lifts and slight
ridging builds in to the region from the south.

MEFFER
&&

.AVIATION...
(18Z TAFS)
Issued at 102 PM CDT Wed Apr 29 2026

MVFR to VFR conditions will prevail this afternoon with modest winds
gusting in the teens. Main impact tonight is a few terminals seeing
MVFR visibilities and IFR decks as the night progresses. Early
evening storms could push into KMCB area but confidence is not
particularly high with that coming to fruition.

&&

.MARINE...
Issued at 102 PM CDT Wed Apr 29 2026

Persistent onshore flow of 10 to 15 knots will remain in place
through this with high pressure generally centered east of the local
coastal waters. Seas will remain well below any hazardous limits at
1 to 3 feet through this period. As we move into the back half of
the week, we will see a weak cold front drift south towards the
coast and stall along the northern Gulf Coast. That'll lead to both
weaker winds overall as well as north or south winds depending on
coastal zone's location in related to the boundary. A stronger upper
level trough moves through the region Saturday morning. Expect to
see at least Exercise Caution, possibly low in Small Craft Advisory,
conditions behind this front.

MEFFER
&&

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

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