Area Forecast Discussion
Issued by NWS Memphis, TN

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FXUS64 KMEG 200850

Area Forecast Discussion
National Weather Service Memphis TN
350 AM CDT Sun Aug 20 2017

The subtropical ridge continues to build over the southern CONUS
this morning with a broad ridge axis extending from west to east
from the Southern Plains to the western Atlantic. There is a
weakness in this ridge over the central Gulf of Mexico where a
well-defined upper-level cyclone continues to meander in a general
westerly direction. The flow aloft on the poleward side of the
ridge is quasi-zonal with several shortwave troughs embedded
within the flow. An MCS is noted over the Midwest but it should
have no impact for us other than some cirrus blowoff during the
day. Otherwise, the synoptic pattern is rather benign for our neck
of the woods.

As the ridge continues to build today, mid-level temperatures will
warm slightly. This will be reflected by afternoon highs in the
low/mid 90s. Low-level moisture is progged to mix out over much
of west TN and northeast MS but will remain in place along and
west of the Mississippi River. The combination of this heat and
humidity will yield heat indices at or just above 105 degrees
from Jonesboro south to Clarksdale, extending as far east as
Memphis and Batesville. A Heat Advisory is in effect from 11A-7P
today to account for these conditions. Isolated diurnal convection
is expected today but the anticipated coverage doesn`t warrant
PoPs above 20%. Once we lose surface heating, any ongoing
convection should quickly dissipate.

Hot and humid conditions will continue Monday and Tuesday but low-
level moisture is expected to trend down slightly, keeping
forecast heat indices between 100-105 degrees both days. Will
continue to monitor the dewpoint trends for the heat advisory
potential in the coming days. Otherwise, expect highs in the
low/mid 90s each afternoon.

Monday`s sky cover forecast continues to be the big-ticket item
for those wishing to view the solar eclipse. Diurnal cumulus
clouds expected to develop by midday, eventually growing into a
typical Cu field during the afternoon. Given the eclipse timing
between 1-2 PM, this Cu field will likely be in place but
shouldn`t be too significant. That said, there may be some areas
where viewing conditions are less than optimal. However,
forecasting these exact locations will be difficult until Monday
morning. A few diurnal showers and thunderstorms will be possible
on Monday, mainly over the western half of the CWA. By Tuesday,
rain chances begin to increase as a shortwave trough moves into
the Ohio Valley and weakens the ridge aloft.

This trough will push a cold front into the Mid-South Tuesday
night into Wednesday. Showers and thunderstorms are likely with
this cold front with PoPs peaking Wednesday morning. Rain chances
will quickly taper off Thursday evening with cooler and drier
conditions anticipated for Thursday and Friday. Afternoon highs
are progged to be in the low/mid 80s for the end of the work week.
Low temperatures will be in the low/mid 60s for much of the CWA
with some areas expected to dip into the upper 50s Friday morning.

The synoptic pattern looks to remain somewhat progressive late in
the forecast period with the next trough progged to affect the
Mid-South over the weekend. PoPs of 20-30% were included across
portions of the CWA during this period with temperatures remaining
several degrees below climatology.



/06z TAFs/

VFR conditions will prevail through much of the period with the
exception of vsby reductions in fog late tonight. A weak low level
boundary remains positioned across northern Arkansas and has been
a focus for continued evening convection as a weak shortwave
traverses the top of the upper ridge. This convection should
remain west of our region, but blow off mid and high level cloud
cover may continue to impact the TAF sites overnight.

Isolated convection should again develop west of the Mississippi
River on Sunday afternoon during peak heating. This activity may
get close to KJBR and VCTS has been maintained.

Winds should remain light and below any critical thresholds
through the forecast period at all terminals.



AR...Heat Advisory from 11 AM this morning to 7 PM CDT this evening
     for Craighead-Crittenden-Cross-Lee AR-Phillips-Poinsett-St.

MS...Heat Advisory from 11 AM this morning to 7 PM CDT this evening
     for Coahoma-DeSoto-Panola-Quitman-Tallahatchie-Tate-Tunica-

TN...Heat Advisory from 11 AM this morning to 7 PM CDT this evening
     for Shelby.


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