Flash Flood Warning 21, 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

Special Weather Statement
National Weather Service New Orleans LA
536 PM CDT Wed Apr 29 2026

LAZ037-039-071-MSZ069>071-292300-
Washington LA-St. Helena LA-Northern Tangipahoa LA-Pike MS-
Walthall MS-Amite MS-
536 PM CDT Wed Apr 29 2026

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF NORTHEASTERN ST.
HELENA, NORTHERN TANGIPAHOA AND NORTHWESTERN WASHINGTON PARISHES,
SOUTHWESTERN WALTHALL, PIKE AND EASTERN AMITE COUNTIES THROUGH 600 PM
CDT
...

At 536 PM CDT, Doppler radar was tracking a cluster of strong
thunderstorms along a line extending from 7 miles northeast of Mount
Herman to near Gillsburg. Movement was southeast at 25 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Mccomb, Franklinton, Magnolia, Kentwood, Summit, Tylertown, Osyka,
Smithdale, Mount Herman, Wilmer, Gillsburg, Tangipahoa, and Mccomb
Airport.

This includes the following Interstates...
 Interstate 55 in Louisiana between mile markers 52 and 66.
 Interstate 55 in Mississippi between mile markers 1 and 24.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

A Severe Thunderstorm Watch remains in effect until 900 PM CDT for
southeastern Louisiana...and southern Mississippi.

&&

LAT...LON 3121 9020 3082 8998 3079 9061 3135 9075
      3135 9046
TIME...MOT...LOC 2236Z 328DEG 22KT 3104 9022 3105 9063

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

HRL

Special Weather Statement
National Weather Service New Orleans LA
542 PM CDT Wed Apr 29 2026

LAZ039-MSZ071-077-292330-
Washington LA-Walthall MS-Pearl River MS-
542 PM CDT Wed Apr 29 2026

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF EASTERN WASHINGTON
PARISH, SOUTHEASTERN WALTHALL AND NORTHERN PEARL RIVER COUNTIES
THROUGH 630 PM CDT
...

At 541 PM CDT, Doppler radar was tracking a cluster of strong
thunderstorms along a line extending from near Rock Hill to 7 miles
northeast of Mount Herman. Movement was southeast at 35 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Bogalusa, Poplarville, Varnado, Crossroads, Dexter, and Angie.

This includes Interstate 59 in Mississippi between mile markers 22
and 42.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

A Severe Thunderstorm Watch remains in effect until 900 PM CDT for
southeastern Louisiana...and southern Mississippi.

&&

LAT...LON 3110 8993 3107 8992 3107 8984 3100 8983
      3101 8951 3100 8947 3098 8947 3098 8943
      3101 8942 3101 8935 3098 8934 3074 8934
      3072 8994 3106 9015
TIME...MOT...LOC 2241Z 308DEG 31KT 3104 8937 3101 9018

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

HRL

Special Weather Statement
National Weather Service New Orleans LA
559 PM CDT Wed Apr 29 2026

LAZ036-037-039-048-071-079-081-MSZ069>071-077-300000-
Washington LA-Central Tangipahoa LA-Northern St. Tammany LA-
St. Helena LA-Northern Tangipahoa LA-East Feliciana LA-
East Baton Rouge LA-Pike MS-Walthall MS-Amite MS-Pearl River MS-
559 PM CDT Wed Apr 29 2026

...STRONG THUNDERSTORMS WILL IMPACT PORTIONS OF ST. HELENA,
NORTHWESTERN ST. TAMMANY, EASTERN EAST FELICIANA, NORTHERN
TANGIPAHOA, NORTHEASTERN EAST BATON ROUGE AND WASHINGTON PARISHES,
WESTERN WALTHALL, PIKE, AMITE AND SOUTHWESTERN PEARL RIVER COUNTIES
THROUGH 700 PM CDT
...

At 559 PM CDT, Doppler radar was tracking a cluster of strong
thunderstorms along a line extending from near Tylertown to near
Gloster. Movement was southeast at 30 mph.

HAZARD...Wind gusts up to 50 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Mccomb, Bogalusa, Franklinton, Liberty, Greensburg, Amite, Amite
City, Magnolia, Kentwood, Summit, Tylertown, Roseland, Gloster,
Osyka, Montpelier, Smithdale, Enon, Darlington, Mount Herman, and
Wilmer.

This includes the following Interstates...
 Interstate 55 in Louisiana between mile markers 44 and 66.
 Interstate 55 in Mississippi between mile markers 1 and 24.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

A Severe Thunderstorm Watch remains in effect until 900 PM CDT for
southeastern Louisiana...and southern Mississippi.

&&

LAT...LON 3068 8978 3066 9094 3133 9104 3135 9102
      3133 9099 3135 9098 3135 9025
TIME...MOT...LOC 2259Z 334DEG 27KT 3110 9018 3115 9103

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

HRL