Heat Advisory 21, NWS New Orleans, LA

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Hancock County, MS, Pearl River County, MS, Pike County, MS, Walthall County, MS, Wilkinson County, MS

Area Forecast Discussion
National Weather Service New Orleans LA
129 PM CDT Mon Aug 18 2025

.UPDATE...
Issued at 127 PM CDT Mon Aug 18 2025

Retransmitting earlier product which did not send properly.

&&

.SHORT TERM...
(This afternoon through Tuesday night)
Issued at 1244 PM CDT Mon Aug 18 2025

Not a whole lot to discuss that hasn't already been said in the
last few days. Local area will remain loosely under the influence
of high pressure aloft which will result in somewhat delayed onset
of convective initiation of scattered afternoon showers and
thunderstorms.

Afternoon temperatures are forecast to rise into the mid to upper
90s, with maximum heat index values forecast to peak in the
106-109 degree range most places. Have seen a few mesonet sites
reach criteria today, but lower dewpoints have started to mix down
from aloft and that should help bring the heat index down as
well. Between the drier air mixing down and the fact that we're
starting to see convection popping up, will not issue a short-
fused heat advisory for the remainder of this afternoon. However,
with similar conditions expected tomorrow, will go ahead with a
heat advisory from 10a-7p tomorrow for most of the forecast area.

The one good thing about this set up is that overnight lows have
generally been in the mid 70s aside from areas along the immediate
lakeshore and coast of SE LA, and that will provide overnight
relief from the heat, helping limit the cumulative effects of
heat impacts as well.

&&

.LONG TERM...
(Wednesday through Sunday)
Issued at 1244 PM CDT Mon Aug 18 2025

Overall pattern will remain generally unchanged through Wednesday
as the upper high gradually retreats westward in response to a
trough moving into New England and hurricane Erin recurving
northward over the western Atlantic. This will begin the
transition to a more active pattern for the second half of the
work week. Some question regarding exactly how much coverage we'll
see on Wednesday. With the ridge's influence waning, should see
at least a slight increase in coverage, but likely still in the
scattered category.

By Thursday and into Friday, the high should be solidly centered
near the four corners region with an overall weakness or even weak
troughing in the upper levels across the local area allowing for
more typical summertime coverage of scattered to numerous showers
and storms each afternoon. The increase in convective coverage
should also result in a slight decrease in afternoon temperatures,
with highs falling a couple degrees back into the low 90s most
places.

Going into the weekend, biggest question continues to focus on
exactly how far south a weak frontal boundary will move before
stalling and dissipating. Ensemble guidance has been fairly
consistent with the front stalling somewhere near the local area,
and this will enhance rain chances by providing a convective
focus. Moisture pooling ahead of the front will also raise
precipitable water to over 2 inches across much of the area, with
some model soundings indicating values of around or just over 2.2
inches across areas just ahead of the front. This would be around
or just above the 90th percentile for this time of year, and
suggests potential for efficient rainfall processes. That being
said Will need to monitor trends to keep an eye on heavy rain
potential going into the weekend - especially if the front does
indeed make it into the area, providing a focus for more sustained
convection.

&&

.AVIATION...
(18Z TAFS)
Issued at 1244 PM CDT Mon Aug 18 2025

Outside of scattered showers and storms, conditions will remain
VFR through the period. Have tried to target PROB30 and TEMPO
groups to most likely locations and timing this afternoon.
Convection should die down around sunset with light and variable
winds overnight.

&&

.MARINE...
Issued at 1244 PM CDT Mon Aug 18 2025

No significant marine concerns through the period with generally
benign conditions outside of convection. Isolated to scattered
daily showers and storms will continue through midweek. Expect to
see a fairly typical diurnal convective cycle with storms
developing over the Gulf waters during the late night and and
early morning hours, and transitioning farther inland by
afternoon. Showers and thunderstorms will become more numerous
late in the week as a weak frontal boundary stalls near or just
north of the area. Winds will remain light at 10 knots or less
with waves/seas 2 feet or less outside of thunderstorms.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  73  94  73  95 /  30  30   0  30
BTR  74  96  74  96 /  30  40  10  30
ASD  72  94  73  95 /  20  30  10  30
MSY  79  96  79  95 /  20  30  10  30
GPT  75  93  75  93 /  20  20  10  30
PQL  73  94  73  94 /  20  20  10  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Heat Advisory from 10 AM to 7 PM CDT Tuesday for LAZ034>037-039-
     046>048-056>060-064-065-070-071-076>090.

GM...None.
MS...Heat Advisory from 10 AM to 7 PM CDT Tuesday for MSZ068>071-077-
     083-086.

GM...None.
&&

SHORT TERM...DM
LONG TERM....DM
AVIATION...DM
MARINE...DM

Preliminary Local Storm Report
National Weather Service New Orleans LA
903 AM CDT Mon Aug 18 2025

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

0738 PM     Marine Tstm Wind 12 SSW Mandeville       30.20N 90.12W
08/17/2025  M43 MPH          GMZ530             LA   Mesonet

            Mid-lake Pontchartrain measured a
            thunderstorm wind gust of 43mph.

&&

JZ

Preliminary Local Storm Report
National Weather Service New Orleans LA
909 AM CDT Mon Aug 18 2025

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

0710 PM     Tstm Wnd Dmg     3 E Madisonville        30.40N 90.12W
08/17/2025                   St. Tammany        LA   Public

            Public call of limbs up to 2 inches broken
            along with power outages in the Woodridge
            neighborhood in Mandeville. Time estimated
            by radar.

&&

JZ

Special Weather Statement
National Weather Service New Orleans LA
Issued by National Weather Service Jacksonville FL
120 PM CDT Mon Aug 18 2025

MSZ068-181845-
Wilkinson MS-
120 PM CDT Mon Aug 18 2025

...A STRONG THUNDERSTORM WILL IMPACT PORTIONS OF WEST CENTRAL
WILKINSON COUNTY THROUGH 145 PM CDT
...

At 120 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Fort Adams, or 25 miles northeast of Simmesport,
moving southwest at 10 mph.

HAZARD...Winds in excess of 40 mph.

SOURCE...Radar indicated.

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

This storm will remain over mainly rural areas of west central
Wilkinson County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3124 9141 3118 9138 3112 9139 3109 9160
      3110 9161 3114 9162 3118 9159 3121 9159
      3122 9158 3122 9152 3123 9151 3123 9149
TIME...MOT...LOC 1820Z 058DEG 10KT 3119 9146

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

SHASHY