Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 222037

Area Forecast Discussion
National Weather Service Memphis TN
337 PM CDT Sat Jul 22 2017

.DISCUSSION...Water Vapor Satellite trends this afternoon centers
an upper level ridge axis over portions of the Middle and Lower
Mississippi Valleys. This has resulted in temperatures rising into
the middle to upper 90s with high surface dewpoints in the 70s. A
combination of the very hot temperatures and high surface
dewpoints has produced heat index values between 105-112 today
with the highest values occurring again along and west of the
Mississippi River.

KNQA/KGWX WSR-88D radars this afternoon indicate isolated to
scattered showers and thunderstorms across the Mid-South this
afternoon coincident with convective temperatures being reached.
Overall shear remains weak with surface based CAPE values in
excess of 4000 J/kg. An isolated strong thunderstorm or two may be
possible until early evening. Temperatures will remain quite warm
tonight in the middle 70s to approaching 80 degrees.

Another hot day is expected across the Mid-South on Sunday but
some relief will arrive later in the day as the upper level ridge
axis breaks down and a weak cold front drops into the region later
Sunday night into Monday. Latest short term models indicate a
majority of the convective chances may hold off until convective
temperatures are reached Sunday afternoon. A combination of these
hot temperatures and surface dewpoints will push heat index values
to 105 to 110 degrees on Sunday and will continue the Heat
Advisory for tomorrow. One potential uncertainty for tomorrow will
be the amount of moisture pooling that could occur across the
area. An Excessive Heat Warning may need to be considered by the
evening/overnight shifts if surface dewpoints are forecast to
increase more than forecast or remain up through the day.

A combination of a hot, humid, and very unstable airmass will
increase the potential for strong to severe pulse type
thunderstorms across the Mid-South on Sunday. Damaging winds will
remain the predominant threat along with a secondary threat for
heavy rainfall. Shower and thunderstorm chances will continue into
Monday with slightly cooler temperatures in the lower 90s.

Long term models indicate the upper level ridge axis will attempt
to build back in across the Mid-South for mid to late next week
bringing a potential return of advisory criteria heat index
values. This will continue to be monitored in subsequent
forecasts. In addition, isolated to scattered shower and
thunderstorm chances are anticipated to persist into much of next



/18z TAFs/

Generally VFR conditions will continue across the Mid-South over
the next 24 hours. Expect a scattered Cu field through 00z with
occasional ceilings between 4-5 kft. In addition, isolated showers
and thunderstorms will be possible, primarily along and south of
I-40. Any convection that develops will dissipate after sunset.
Southwest winds may gust to around 15 kts at times this afternoon
across AR/MO/TN, but wind speeds will be lighter over north MS.



AR...Heat Advisory until 8 PM CDT Sunday for Lawrence-Lee AR-Phillips-

     Excessive Heat Warning until 8 PM CDT this evening for Clay-

     Heat Advisory from 8 PM this evening to 8 PM CDT Sunday for Clay-

MO...Excessive Heat Warning until 8 PM CDT this evening for Dunklin-

     Heat Advisory from 8 PM this evening to 8 PM CDT Sunday for

MS...Heat Advisory until 8 PM CDT Sunday for Alcorn-Benton MS-Calhoun-
     Chickasaw-Coahoma-Itawamba-Lafayette-Lee MS-Marshall-Monroe-

     Excessive Heat Warning until 8 PM CDT this evening for DeSoto.

     Heat Advisory from 8 PM this evening to 8 PM CDT Sunday for

TN...Heat Advisory until 8 PM CDT Sunday for Benton TN-Carroll-

     Excessive Heat Warning until 8 PM CDT this evening for Dyer-Lake-

     Heat Advisory from 8 PM this evening to 8 PM CDT Sunday for Dyer-


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