Flash Flood Warning 86, NWS New Orleans, LA

Area Forecast Discussion
National Weather Service New Orleans LA
215 PM CDT Thu Jun 18 2026

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

.KEY MESSAGES...
Updated at 144 PM CDT Thu Jun 18 2026

- Potential for Life Threatening Flash Flooding. A Particularly
  Dangerous and Life Threatening Flash Flood Situation exists with
  a High Risk of Flooding across portions of south Mississippi and
  southeast Louisiana, especially east of Interstate 55.
  Considerable Flash Flooding is likely and Catastrophic Flash
  Flooding is possible today.

- A Flood Watch is in effect through Friday morning for most of
  southeast Louisiana as well as all of southwest and coastal
  Mississippi.

- A Tornado Watch remains in effect until 5 PM for areas along and
  east of the Pearl River.

- Dangerous conditions for mariners of small craft and minor
  coastal flooding on south facing shores west of the Mississippi
  River will persist through tonight as Post Tropical Cyclone
  Arthur moves into southwest Louisiana.

- Extreme heat is expected this weekend. Heat advisories will
  likely be issued for heat index values of around 110 degrees.

&&

.SHORT TERM...
(Now through Sunday night)
Issued at 144 PM CDT Thu Jun 18 2026

Conditions will greatly improve as we move into tonight and rest
of the short term period in terms of the heavy rainfall threat. A
broad deep layer ridge axis will expand northward across the Gulf
South resulting in lower overall rain chances as we move into
Friday and Saturday, but the side-effect will be significantly
warmer temperatures. Highs will easily climb into the low to mid
90s and very high dewpoints in the upper 70s and lower 80s will
produce heat index readings of around 110 degrees Friday through
Sunday. A heat advisory has been issued for much of the area for
tomorrow and additional heat advisories may be issued for the
weekend. Ample instability will accompany these warm temperatures
with MLCAPE of 2000 to 2500 J/KG both days. As a result,
diurnally induced convection will form each day with the highest
probabilities north of I-12 where the influence of the mid to
upper level ridge will be lower. Although PWATS will fall to more
average levels by Saturday and Sunday, the wet antecedent
conditions could lead to isolated flash flooding incidents as
rainfall rates still average 1 to 2 inches per hour.

&&

.LONG TERM...
(Monday through Wednesday night)
Issued at 144 PM CDT Thu Jun 18 2026

The influence of the ridge will grow as we move into next week
with lower overall rain chances and continued warm temperatures.
Highs will easily continue to climb into the low to mid 90s each
day and overnight lows will only cool into the upper 70s and lower
80s. Heat index values will continue to rise to between 105 and
110 degrees, so more days of heat advisory conditions can be
expected. The growing influence of the ridge will lead to a strong
mid-level capping inversion and overall lower rain chances from
Sunday through Tuesday with only isolated to widely scattered
afternoon showers and storms anticipated. Rain chances will be
highest over the northern third of the forecast area where the
capping inversion will be slightly weaker.

The ridge will begin to weaken on Wednesday as a shortwave trough
axis moves in from the northwest. This will allow for steeper
lapse rates in the mid-levels and overall increased rain chances
for Wednesday afternoon. This is reflected by increased PoP values
fo 30 to 50 percent. Sounding review indicates some potential for
an isolated strong to severe thunderstorms, mainly wind, due to
some linger mid-level dry air.

&&

.AVIATION...
(18Z TAFS)
Issued at 144 PM CDT Thu Jun 18 2026

Gradually improving conditions will occur at most of the terminals
in terms of thunderstorm threat as the storms move east of the
region. Lingering MVFR ceilings will be in place at all of the
terminals through tonight and into tomorrow morning. At MCB, a
period of low stratus and fog could develop around 10 to 14z in
the morning as a weak inversion tries to develop. This could
produce a period of IFR conditions at this terminal. VFR
conditions should return to the all of the terminals after 15z as
drier air begins to feed in.

&&

.MARINE...
Issued at 144 PM CDT Thu Jun 18 2026

Strong southerly winds of 20 to 25 knots with gusts of 30 knots will
remain in place over the coastal waters through this afternoon in
the open Gulf waters.  Small craft advisories remain in effect due
to these conditions.  Moving into the weekend and early next week, a
broad area of high pressure will build back over the eastern Gulf
waters. Persistent onshore winds of 10 to 15 knots and seas of 2 to
4 feet can be expected from Friday through early next week.

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Flood Watch through Friday morning for LAZ034>037-039-046>048-
     056>058-064-071-076>087-089-090-092-094-096-098>100.

     Heat Advisory from 10 AM to 7 PM CDT Friday for LAZ034>037-039-
     046>048-056>058-064-070-071-076>087-089>100.

GM...Small Craft Advisory until 6 AM CDT Friday for GMZ529-531>536-
     541-543-551-553-554-557-570-572-575-577.

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

     Heat Advisory from 10 AM to 7 PM CDT Friday for MSZ068>071-077-
     083-086.

GM...Small Craft Advisory until 6 AM CDT Friday for GMZ531>536-541-
     543-551-553-554-557-570-572-575-577.

&&

SHORT TERM...PG
LONG TERM....PG
AVIATION...PG
MARINE...PG

Preliminary Local Storm Report
National Weather Service New Orleans LA
135 PM CDT Thu Jun 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1205 PM     Tstm Wnd Gst     2 SW Gulfport           30.37N 89.10W
06/18/2026  M78 MPH          Harrison           MS   Mesonet

            The Weatherflow mesonet in Gulfport measured
            a thunderstorm wind gust of 78 mph.

&&

MEFFER

Preliminary Local Storm Report
National Weather Service New Orleans LA
152 PM CDT Thu Jun 18 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0135 PM     Marine Tstm Wind 2 ENE Bay Saint Louis   30.32N 89.29W
06/18/2026  M56 MPH          Harrison           MS   Mesonet

            A Weatherflow Tempest station on Sandy Hook
            Dr measured a thunderstorm wind gust of 56
            mph.

&&

MEFFER

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