Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 250445
AFDMEG

Area Forecast Discussion
National Weather Service Memphis TN
1145 PM CDT Mon Jul 24 2017

.UPDATE...

Updated to include 06z aviation discussion.

&&

.PREV DISCUSSION... /issued 925 PM CDT Mon Jul 24 2017/

UPDATE...
Scattered showers and isolated thunderstorms continued over north
MS at midevening, having decreased in coverage and intensity from
earlier. Convection in this region was aided by divergences aloft,
associated with the right entrance region of the upper jet.
Precipitable water values averaged near 2 inches over north MS.

To the north, isolated showers and storms were noted on radar over
southeast MO and western KY. These activity was occurring along a
stalled front, aided by a weak midlevel shortwave.

For the area in between the above mentioned areas, including the
I-40 corridor, there appeared to be little forcing to overcome the
gradually-strengthening convective inhibition. Where clouds
remain thin, patchy appears likely to form during the overnight.

PWB

PREV DISCUSSION... /issued 353 PM CDT Mon Jul 24 2017/

DISCUSSION...
Convection is struggling to develop across the Mid-South this
afternoon. Mesoanalysis suggests 3 PM MLCAPE values exceed 2500
J/kg with little/no MLCIN, but the environment is likely still a
little worked over from the widespread convection yesterday
evening. In addition, the weak, large-scale subsidence in the wake
of the departing shortwave trough isn`t really helping matters.
We do still expect some storms to form through the early to mid-
evening hours and a few storms could be strong, capable of
producing gusty winds. Slow storm motions will also lend to a
potential for localized heavy downpours. Otherwise, temperatures
are generally in the upper 80s and lower 90s with heat indices
near 100 degrees in most locations.

The heat will return on Tuesday. We anticipate a slightly warmer
air mass with afternoon highs in the low to mid 90s. Dewpoints
will again be in the mid 70s across the Mid-South, resulting in
heat indices of 105-107 degrees during the afternoon and early
evening hours. The primary area of concern includes most of the
counties adjacent to and west of the Mississippi River. This
includes the Memphis metro area and Jonesboro. A Heat Advisory has
been issued from 1 PM Tuesday through 8 PM Wednesday. Diurnal
showers and thunderstorms will be possible once again, but
coverage doesn`t look to be more than 30-35%.

The hot and humid conditions will persist across the area on
Wednesday, but may affect a greater area and may necessitate an
expansion of the current Heat Advisory. Similar conditions on
Thursday may warrant a temporal extension of the Heat Advisory.
However, at this time we do not anticipate a widespread area of
heat indices exceeding 110 degrees. Diurnal convection on
Wednesday and Thursday is not expected to be very widespread. In
fact, rain chances are limited to 20-30% during this period with
generally dry conditions during the overnight hours. Expect
overnight lows in the mid 70s during the midweek period.

A strong shortwave trough is progged to move southeast across the
Great Lakes and northern Ohio River Valley on Thursday. This wave
is expected to dig over the eastern CONUS late Thursday into
Friday with a reinforcing shortwave trough following late Friday.
An attendant cold front is forecast to move south across the CWA
Thursday night and Friday, bringing some relief to the heat and
increasing rain chances. The greatest opportunity for showers and
thunderstorms will be Thursday night and Friday, but forecast rain
chances linger into Saturday given some uncertainty in the timing
of the front.

There is good agreement between the GFS and ECMWF and cooler,
drier air will filter into the Mid-South over the weekend. High
temperatures are expected to be in the upper 80s with dewpoints
falling into the 60s. Overnight lows will be in the mid 60s to
lower 70s, resulting in much nicer (and cooler than normal)
weather conditions.

Johnson


&&

.AVIATION...

Fog development is likely overnight, with prevailing MVFR
visibility conditions likely at KMKL with the potential for IFR
conditions by early morning both there and at KTUP. Winds will be
light overnight under mostly clear skies. Winds will become more
from the SSW tomorrow morning as visibility improves back to VFR.
VCTS will be possible at all terminals during the afternoon, with
winds less than 8 kts.

ZDM

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory from 1 PM Tuesday to 8 PM CDT Wednesday for Clay-
     Craighead-Crittenden-Cross-Greene-Lawrence-Lee AR-
     Mississippi-Poinsett-Randolph-St. Francis.

MO...Heat Advisory from 1 PM Tuesday to 8 PM CDT Wednesday for
     Dunklin-Pemiscot.

MS...Heat Advisory from 1 PM Tuesday to 8 PM CDT Wednesday for DeSoto.

TN...Heat Advisory from 1 PM Tuesday to 8 PM CDT Wednesday for
     Lauderdale-Shelby-Tipton.

&&

$$



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