McComb, Mississippi 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

218
FXUS64 KLIX 252324 AAA
AFDLIX

Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
624 PM CDT Sat Jul 25 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 619 PM CDT Sat Jul 25 2026

- Impactful heat conditions will persist well into next week. Mid
  week will be the most intense days with heat indices 110-115
  degrees.

&&

.SHORT TERM...
(Now through Tuesday night)
Issued at 1234 PM CDT Sat Jul 25 2026

A broad mid/upper-level ridge is currently draped across the
Rockies, extending northward into Canada, southward into Mexico, and
eastward into the Lower Mississippi Valley. The ridge will continue
building toward the region through the weekend, with 500 mb heights
rising into the middle and upper 590dm range. Warming through the
850-700 mb layer will strengthen subsidence and the mid-level cap,
suppressing the usual summertime afternoon convective relief despite
strong surface heating. This is supporting the development of a hot
and remarkably dry late-July pattern across the region.

Visible satellite imagery shows a cirrus deck across northern
portions of the CWA along with an isolated fair-weather cumulus
field. The 12Z KLIX sounding measured a PW of 1.25", even lower than
yesterday and between the late-July 10th percentile and observed
minimum. Much of the additional drying compared to yesterday
occurred above 500 mb. Although there`s some boundary-layer moisture
beneath the dry air aloft, strong subsidence, the strengthening cap,
and a lack of meaningful forcing will make convective initiation
very difficult. Light west to northwest low-level flow around a
surface ridge centered along the northern Gulf Coast will become
increasingly important through this weekend and into early next
week. This land-based flow regime should allow temperatures to rise
rapidly each day before the sea and lake breezes can penetrate very
far inland. Highs will climb into the middle 90s this afternoon,
with upper 90s becoming more prevalent Sunday as the upper ridge
edges slightly closer to the CWA.

The main factor limiting the upper bound of heat indices today will
be the extent to which drier air aloft mixes into the boundary
layer. The decrease in dewpoints may not be dramatic, but even a
small reduction can lower apparent temperatures by several degrees.
By Sunday, the anomalously dry mid and upper-level air currently
over the area will gradually shift away as flow around the eastern
side of the central U.S. ridge carries somewhat higher moisture into
the column from the northeast. Meanwhile, the surface ridge will
drift southward into the Gulf, allowing low-level flow to become
more westerly. This should maintain the existing shallow moist
boundary layer and may deepen it slightly, but does not represent a
classic deep southerly Gulf moisture return.

The current forecast still doesn`t support enough of a large area of
heat index values over 108 degrees Sunday to warrant a Heat Advisory
at this time. The principal uncertainty remains afternoon dewpoints.
Some guidance mixes dewpoints into the lower 70s over inland areas,
which would keep heat indices somewhat lower. However, if dewpoints
instead remain in the middle to upper 70s through peak heating,
apparent temperatures could rise rapidly and produce more localized
advisory-level values. Overnight lows will remain in the middle and
upper 70s, with readings around 80 degrees across the New Orleans
metro, near the tidal lakes, and along the immediate coast.
Overnight recovery will consequently become increasingly limited as
the heat event continues.


&&

.LONG TERM...
(Wednesday through Friday night)
Issued at 1234 PM CDT Sat Jul 25 2026

The broad upper-level ridge centered to the northwest will remain
the dominant feature across the south-central United States during
at least the first half of next week. Mid to upper 590dm heights,
strong subsidence, and a warm 850-700 mb layer will extend across
southeast Louisiana and southern Mississippi. The primary driver of
the heat will therefore be the combination of deep-layer warming,
abundant sunshine, suppressed convection, and a persistent west to
northwest low-level flow that delays meaningful marine influence
during the hottest part of the day.

Tuesday through Thursday (a slight delay from previous forecasts)
appear to be the hottest portion of the forecast period. Inland
highs will commonly reach the upper 90s, with some locations near
100 degrees. Did glance at record highs for early next week and
forecast temps are right at to just below depending on location.
Low-level moisture may become somewhat deeper early in the week even
as the mid-level cap remains strong. This is the more concerning
heat scenario, as dewpoints holding in the middle or upper 70s
during peak heating would combine with temperatures in the upper 90s
to produce heat indices of 108 to 115 degrees. Widespread Heat
Advisory criteria appears increasingly likely Monday through at
least Thursday. Portions of the I-10/12 corridors in LA and MS
could approach or exceed the 113-degree Extreme Heat Warning
threshold Tuesday and Wednesday. Similar values remain possible
Thursday, but confidence decreases as the ridge begins to weaken.

The duration of the event will become increasingly important.
Overnight lows will remain in the upper 70s across much of the area
and near or above 80 degrees around New Orleans, the tidal lakes,
and the immediate coast. Looking at previous similar events,
locations around the tidal lakes sometimes get such little relief
overnight. Have seen periods where KNEW`s lowest heat index doesn`t
even drop below 100! The poor nighttime recovery across the CWA will
allow heat stress to accumulate as this event progresses. We see
this in the HeatRisk guidance which shows Extreme for about 25% of
the CWA Monday, ~70% of the CWA Tuesday, and 80-90% Wednesday. This
is consistent with the combination of hot afternoons, warm nights,
and very limited convective relief. And speaking of convection,
strong subsidence from upper ridging aloft should hold rain chances
to near 10% Monday through Wednesday. A rogue storm could still
briefly develop along a sea breeze, lake breeze, or remnant boundary
late in the afternoon, but meaningful or widespread relief is not
expected. Most locations will remain dry each day.

Changes should begin gradually around Wednesday as the ridge center
starts shifting farther west and troughing deepens over the eastern
United States. The Mississippi coastal counties and adjacent coastal
waters will be closest to the weakening southeastern edge of the
ridge and may see isolated/scattered afternoon convection return
first. Rain chances around 20-30% are warranted there Wednesday,
with substantially lower chances farther west beneath stronger
subsidence. The eastern trough should exert a greater influence
Thursday and Friday, lowering heights, weakening the cap, and
allowing the sea breeze and other mesoscale boundaries to generate
more typical afternoon convection. Rain chances increase into the 30
to 40 percent range. The increased clouds and convection should
gradually lower daytime temperatures and heat indices, although
Thursday could remain dangerously hot if the ridge breaks down more
slowly than currently forecast. A faster erosion would provide
earlier relief, while a slower transition would extend widespread
heat hazards through Thursday and potentially into Friday.


&&

.AVIATION...
(00Z TAFS)
Issued at 623 PM CDT Sat Jul 25 2026

A shower/storm has developed over MSY this evening, so starting
with a tempo for this locations. Elsewhere it remains dry and VFR
conditions are anticipated through the period, again outside of
the one cell over MSY. Expect winds to remain light and variable
as well. (Frye)

&&

.MARINE...
Issued at 1234 PM CDT Sat Jul 25 2026

Surface high pressure centered near the northern Gulf Coast will
maintain relaxed conditions through today, with winds generally 5 to
10 knots and seas around 2 feet or less. The ridge will gradually
settle southward Sunday and eventually become positioned near the
Florida Keys by the middle of the week. This will establish a
predominantly westerly flow regime across the local coastal waters.
A typical summertime diurnal cycle will develop Sunday and carrying
on through the forecast period. West to southwest winds will
increase to around 10 to 15 knots during the evening and overnight
hours, especially over the outer waters, then relaxing to 5 to 10
knots during the day. Seas will respond similarly, occasionally
building to 2 to 4 feet offshore overnight and subsiding to around 1
to 2 feet during the afternoon. Strong subsidence will keep
thunderstorms very limited through Tuesday. Storm coverage should
begin increasing Wednesday near the Mississippi coastal waters and
become more noticeable across the marine area Thursday and Friday as
the upper ridge aloft weakens. Locally higher winds and seas will be
possible near any late-week thunderstorms.


&&

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

$$

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