438
FXUS64 KLIX 211856
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
156 PM CDT Tue Jul 21 2026

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

.KEY MESSAGES...
Updated at 1236 PM CDT Tue Jul 21 2026

- Hot and mostly dry today, and across northern sections on
  Wednesday. Highs in the mid 90s to near 100 with heat indices
  105-112. An Extreme Heat Warning has been issued for Wednesday
  as heat indices look to increase to 110-115 degrees.

- Tropical Storm Bertha is forecast to move westward toward our
  general area through midweek. Impacts are still low confidence,
  but an increase in rainfall (mainly south of I-10) with breezy
  conditions along with potential coastal flooding are more and
  more possible with time. Tropical Storm Watches and Warnings are
  in place for coastal areas along and south of I-10.

&&

.SHORT TERM...
(Now through Friday night)
Issued at 1236 PM CDT Tue Jul 21 2026

The primary forecast challenges through Thursday will be the track
and structure of Tropical Storm Bertha, the extent of its rainfall
footprint, coastal flooding, and dangerous heat across areas that
remain outside of cloud cover.

As of early Tuesday afternoon, Bertha was located over the
northeastern Gulf and beginning its turn towards the west. A
continued west-northwest to west motion is expected tonight
through Thursday as a mid-level ridge builds southeastward towards
the Gulf Coast. The current track of Bertha brings the center near
the Mississippi and southeast Louisiana coastal waters on
Wednesday, near or just south of lower Plaquemines Parish
Wednesday evening, and west of the coastal waters during the day
on Thursday. However, small track or structural changes will
significantly affect the placement of the strongest winds and
heavier rain bands, especially since there`s a chance that the
low-level center and mid-level center becomes detached due to
increasing wind shear and dry air tomorrow. If that were to occur,
the low-level center would track more north until a new low-level
center forms under the heaviest convection pushed to the south of
the low-level center.

For the remainder of today, much of the area should remain hot
and relatively dry beneath subsidence northwest of Bertha.
However, most of the CAMs and some of the latest radar trends
point to a convective band developing across the river and bayou
parishes this afternoon. With the mid-level dry air in the
vicinity and ample instability (4000+ j/kg SBCAPE), damaging
winds will be the primary concern with these storms. Although,
with the localized forcing and vorticity of Bertha, very isolated
and brief tornadoes can`t be ruled out with this activity through
sunset across mainly East Baton Rouge Parish southward through
Terrebonne Parish. Outside of the convective development, highs
are expected to peak out in the mid to upper 90s, which when
combined with dewpoints in the mid to upper 70s, will support heat
indices from 108-112 degrees this afternoon.

Conditions will begin deteriorating from the east to west over the
coastal waters and immediate coast tonight into Wednesday as
Bertha approaches. Persistent northerly vertical wind shear is
keeping the storm asymmetric, with most of the organized
convection, strongest winds, and heaviest rainfall displaced south
and east of the center. Consequently, the greatest rainfall totals
should remain offshore or close to the immediate coast. Much of
the inland CWA may receive less than one inch of rain, although
locally higher amounts will remain possible where individual bands
move repeatedly across coastal areas. Any heavier band could
produce rapid ponding or localized urban flooding, but the overall
flash flood threat appears to be limited compared to previous
forecasts.

Tropical storm conditions will be most likely over the open Gulf
waters and portions of the immediate Louisiana and Mississippi
coast Wednesday and into Wednesday night. Farther inland,
including the New Orleans metro area and tidal lakes, sustained
winds should generally remain below tropical storm force, but
gusts 30-40 mph will be possible, with locally higher gusts near
exposed coastal locations and within heavier rain bands. The
tornado threat on Wednesday currently appears low given the
displaced convection and limited overlap of stronger low-level
shear with surface-based instability over land.

Coastal flooding will likely be the most significant local impact.
Inundation of 2-4 feet above normally dry ground is possible along
the Mississippi Coast and the more vulnerable portions of lower
Plaquemines, lower St. Bernard, eastern Orleans, and southeast St.
Tammany Parishes. Water levels of 1-3 feet above ground will be
possible elsewhere along the southeast Louisiana coast and around
portions of Lake Pontchartrain. Numerous low-lying coastal roads
could become flooded or impassable Wednesday through early
Thursday.

Because much of Bertha`s rainfall shield is expected to remain
offshore Wednesday, dangerous heat will continue across a large
portion of the CWA due to the compression of the ridge and Bertha
overhead. Inland locations are expected to see highs in the upper
90s with heat indices from 110-115, thus an Extreme Heat Warning
has been issued for all of SE LA and SW MS. A more southerly wind
component across the MS Coast is expected to keep high temps in
the low 90s with subsequent heat indices in the 108-110 range. So,
please do not let the extreme heat sneak up on you even though a
tropical system is passing by.

Bertha should continue westward along the Louisiana coast
Thursday, with lingering bands most likely across coastal
Louisiana and west of I-55. Winds, rain coverage, and coastal
water levels should gradually improve from east to west Thursday
afternoon and evening. By Friday, the circulation should remain
well west of the area, although residual tropical moisture will
support isolated to scattered mainly afternoon thunderstorms with
temperatures back in the lower 90s.


&&

.LONG TERM...
(Saturday through Monday night)
Issued at 1236 PM CDT Tue Jul 21 2026

Surface and upper-level ridging should expand across the central
Gulf Coast during the weekend as Bertha and its remnants move
farther west and dissipate. Increasing subsidence and somewhat
lower deep-layer moisture should reduce the shower/storm coverage
compares with the middle of the week. However, sufficient moisture
will remain for isolated to scattered afternoon convection along
the sea breeze, lake breeze, and any remnant outflow boundaries.
Rain chances should generally remain in the 20-40 percent range
Saturday and Sunday, the with greatest coverage during peak
afternoon heating. With weak steering flow, any storm that
develops could produce locally heavy rainfall, frequent lightning,
and brief gusty winds, but there is no current signal for
organized severe weather or a widespread heavy rainfall event.

Heat will again become the primary concern during the weekend and
early next week. High temps should generally reach the low to mid
90s, with locally upper 90s possible across northern and western
portions of the area, Persistent dewpoints in the upper 70s could
produce afternoon heat indices between 105 and 110, potentially
requiring additional heat headlines.

The ridging may strengthen even further on Monday and Tuesday,
which would favor slightly lower rain chances and continued
above-normal temperatures. Confidence is moderate in the overall
hot and mainly diurnal-driven convective pattern, but lower
regarding daily thunderstorm coverage and whether the center of
the ridge is strong enough to largely suppress convection.

&&

.AVIATION...
(18Z TAFS)
Issued at 1236 PM CDT Tue Jul 21 2026

VFR conditions are expected to prevail at most terminals through
the period, with northerly winds generally around 5-10 knots this
afternoon and tonight. Isolated to scattered convection may
briefly affect MCB, HDC, NEW, MSY, and especially HUM through the
early evening, producing short-lived visibility reductions, gusty
winds, and MVFR ceilings beneath heavier showers and
thunderstorms. Conditions should remain largely quiet overnight,
but winds generally veer north-northeasterly and increase
Wednesday morning as Tropical Storm Bertha approaches from the
east. The greatest aviation impacts are expected at GPT beginning
around 12-14z Wednesday, where gusts of 20-25 knots and periods of
MVFR to IFR ceilings and visibility will become possible in rain
bands and thunderstorms. Lower-confidence restrictions may spread
toward ASD and NEW later Wednesday morning.

&&

.MARINE...
Issued at 1236 PM CDT Tue Jul 21 2026

Tropical Storm Bertha will meander over the northeast gulf for the
next day or so. It is forecast to move westward along or off the
north central gulf coast. As the system moves over our local waters,
expect winds and seas to increase with tropical storm conditions
possible for most if not all the local waters. The system will move
west of the region later Thursday and conditions should improve
going into the upcoming weekend.

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...Tropical Storm Watch for LAZ058-064-077-087-089-090-092-094-
     096>100.

     Tropical Storm Warning for LAZ070-076-078-091-093-095.

     Heat Advisory until 7 PM CDT this evening for LAZ034>037-039-
     046>048-056>058-064-070-071-076>087-089>100.

     Extreme Heat Warning from 10 AM to 8 PM CDT Wednesday for
     LAZ034>037-039-046>048-056>058-064-070-071-076>087-089>100.

     Coastal Flood Advisory until 4 AM CDT Thursday for LAZ058-080-
     082-093-095-097-098.

     Coastal Flood Warning until 4 AM CDT Thursday for LAZ070-076-078-
     091.

GM...Tropical Storm Watch for GMZ529-531-533-541-551-570.

     Tropical Storm Warning for GMZ532-534>536-543-553-554-557-572-
     575-577.

MS...Tropical Storm Watch for MSZ083>085.

     Tropical Storm Warning for MSZ086>088.

     Heat Advisory until 7 PM CDT this evening for MSZ068>071-077-
     083>088.

     Extreme Heat Warning from 10 AM to 8 PM CDT Wednesday for
     MSZ068>071-077.

     Coastal Flood Warning until 4 AM CDT Thursday for MSZ086>088.

     Heat Advisory from 10 AM to 8 PM CDT Wednesday for MSZ083>088.

GM...Tropical Storm Watch for GMZ531-533-541-551-570.

     Tropical Storm Warning for GMZ534>536-543-553-554-557-572-575-
     577.

&&

$$

SHORT TERM...JZ
LONG TERM....JZ
AVIATION...JZ
MARINE...JZ