688
FXUS64 KMEG 171818
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
118 PM CDT Mon Aug 17 2026

...New DISCUSSION, AVIATION, FIRE WEATHER...

.KEY MESSAGES...
Issued at 118 PM CDT Mon Aug 17 2026

- An Extreme Heat Warning is in effect today across north
  Mississippi, much of eastern Arkansas, and southwest Tennessee
  with a Heat Advisory in effect for the rest of the Mid-South.

- A Marginal (level 1 out of 5) Risk for severe thunderstorms
  capable isolated damaging wind is in place for areas along and
  south of I-40 for this evening.

- Another Heat Advisory is in place for portions of eastern
  Arkansas and northern Mississippi Tuesday.

&&

.DISCUSSION...
(This evening through next Sunday)
Issued at 118 PM CDT Mon Aug 17 2026

Another day of dangerous heat is upon us as the tropical air mass
that has dominated the last week of our weather continues to
stubbornly lounge across the Mid-South. This is expected to lead
to heat index values between 105 F - 115 F through this afternoon
in most areas. However, surface and satellite observations show a
pronounced convectively-enhanced boundary moving across the
region, currently (18z)  analyzed across portions of north-
central MS and West TN. Moisture behind the front has pooled,
yielding dewpoints in the middle to upper 70s, which may offset
any cooling brought by the boundary through the day. Therefore,
no changes to the heat headlines were made, but heat indices
could drop below 105 F over northern portions of the region much
quicker than previous evenings.

Another aspect to today`s forecast is the potential for
convection through this afternoon and evening. Diurnally driven
MLCAPE values are expected to exceed 2500 J/kg with isolated
convection developing along the cool boundary across the region
by late this evening. Cells from this mode of convection will
likely be small, which will limit the amount of lightning and
impacts to heating from outflow. However, a second area of
convective potential exists with ongoing thunderstorms upstream
in AR. A relatively organized line of thunderstorms has been
producing severe wind through this morning, traveling east with
time and producing an area of strong outflow. Current CAMs
struggle to bring these storms into our region, but also have been
struggling to maintain the line at its current intensity for
several runs this morning, hence the new day 1 Marginal Risk from
SPC. Therefore, it is not out of the question that remnant
convection could last long enough to make it into the region this
evening. The only real road block will be some weak 850-700 mb
subsidence behind the preceding boundary across our area this
morning, which would decrease the available instability to the
line. So, isolated thunderstorms and an additional line from the
west are possible this afternoon, offering local heat relief and
the chance for isolated damaging winds.

More heat and humidity is expected tomorrow, but with the passage
of today`s front and increasing low-level subsidence, moisture
will begin to decrease. Mid-level dewpoints drop into the low
60s, which will help mix surface dewpoints in the afternoon down
towards the low 70s across much of the area. The only region that
is expected to remain hot enough to warrant heat headlines will
be the MS River Delta where a new Heat Advisory is now in effect
for Tuesday through 8 PM CDT. Wednesday will see the resurgence
of moisture as surface flow backs towards a southerly direction.
So, expect the expansion of heat headlines Wednesday with the
potential return of Extreme Heat Warnings to portions of the
area, especially in the MS River Delta. Some models depict the
troughing to our north nosing south with an increasing potential
for convection, but variance between models remains high on the
coverage and intensity of the convection.

By Thursday, high pressure to our north begins to strengthen in
earnest, gradually pushing the humidity south out of the region.
In turn, afternoon heat index values decrease to at or below
100 F for the first time in over a week for some areas. This
forecast is expected to continue through the end of the period
with relatively cooler, drier conditions through this weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 118 PM CDT Mon Aug 17 2026

TSRA potential will remain the primary aviation weather concern
through early evening. A well-organized TSRA cluster moved from
northeast OK into western AR this morning. This storm cluster
continued well into AR and spawned additional TSRA to the
southeast, toward LIT around midday.

KNQA and TMEM VWP products indicate winds have veered to the NNW
from the surface up through FL010. Given the trajectory of the
ongoing TSRA over AR, the favored downstream convective corridor
will likely set up south of MEM, toward UTA and points eastward
across north MS. TSRA may be in the dissipation phase if/when it
makes it to TUP around 00Z or later.

&&

.FIRE WEATHER...
Issued at 118 PM CDT Mon Aug 17 2026

Fire danger is expected to remain low through the period due to
light 20 ft winds, although minimum relative humidity values may
drop below 40% in some areas. Isolated showers are expected
across northern Mississippi this afternoon along a weak front,
which will shift winds to a more northwesterly direction after
passage. Fog potential remains low due to dry soils.

&&


.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory until 8 PM CDT this evening for ARZ009-018.

     Extreme Heat Warning until 8 PM CDT this evening for ARZ026>028-
     035-036-048-049-058.

     Heat Advisory from 9 PM this evening to 8 PM CDT Tuesday for
     ARZ049-058.

MO...Heat Advisory until 8 PM CDT this evening for MOZ113-115.

MS...Extreme Heat Warning until 8 PM CDT this evening for MSZ001>017-
     020>024.

     Heat Advisory from 9 PM this evening to 8 PM CDT Tuesday for
     MSZ007-010>012-020>022.

TN...Heat Advisory until 8 PM CDT this evening for TNZ001>004-019>022-
     050>055-090>092.

     Extreme Heat Warning until 8 PM CDT this evening for TNZ048-049-
     088-089.

&&

$$

PUBLIC FORECAST...JAB
AVIATION...PWB