Severe Thunderstorm Warning 261, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
257 PM CDT Tue Jul 18 2023

...New SYNOPSIS, DISCUSSION...

.SYNOPSIS...
Issued at 250 PM CDT Tue Jul 18 2023

A complex of showers and thunderstorms will affect portions of the
Mid-South mostly across portions of west Tennessee near the
Tennessee River into this evening with a few strong to severe
thunderstorms possible through early evening. Additional showers
and thunderstorms are possible Wednesday and Thursday mainly north
of I-40, then gradually spreading across the remainder of the
Mid-South for Friday into Saturday as a weak cold front moves into
the Lower Mississippi Valley. Very hot and humid conditions will
persist ahead of the approaching cold front with heat index values
ranging between 105 to 115 degrees on Wednesday.

&&

.DISCUSSION...
(This evening through next Monday)
Issued at 250 PM CDT Tue Jul 18 2023

GOES-16 Satellite trends depict a mature Mesoscale Convective
System (MCS) over portions of southeast Missouri and western
Kentucky. KNQA/KPAH WSR-88D radar trends show the leading edge of
convection over portions of the Missouri Bootheel and Northwest
Tennessee gradually propagating east-southeast with time.
Otherwise, a hot and humid airmass is in place across the Mid-
South with surface temperatures mainly in the lower 90s with
surface dewpoints in the 70s to lower 80s as low-level moisture
pools ahead of a quasi-stationary boundary located along the I-70
corridor. Strong to severe thunderstorm and heat concerns remain
the primary focus in this afternoon's forecast issuance.

The aforementioned MCS will continue to propagate east-southeast
into the Tennessee Valley through this evening. Additional showers
and thunderstorms are possible along the southern periphery of
this system for areas mainly north and east of a line from
Blytheville, AR to Jackson and Savannah, TN. Surface-based CAPE
values around 5000 J/kg, moderately-steep 700-500 mb layer mid-
level lapse rates around 6.5 C/km, 0-6 km Bulk Shear values around
40 kts may support a strong to severe thunderstorm threat for the
remainder of the afternoon into perhaps early evening. Damaging
winds will be the primary threat for any thunderstorms that become
severe. QPF values across portions of northwest Tennessee near the
Tennessee River may receive 1 to 2 inches of rain through late
tonight. Confidence is low that these areas will exceed Flash
Flood guidance and subsequently held off on any flood watches for
the time being.

Elsewhere, the Heat Advisory and Excessive Heat Warning for areas
around and southwest of Memphis along the Mississippi River will
continue through early this evening. Lows tonight will remain
quite warm this evening. A very hot and humid airmass is expected
to build across the Mid-South on Wednesday as temperatures rise
into the middle to upper 90s. These very hot temperatures combined
with surface dewpoints pooling across the region will result in
heat index values rising to between 105 to 115 degrees with the
warmest readings occurring mostly along and west of the
Mississippi River. An Excessive Heat Warning was issued for areas
along and west of the Mississippi River and a Heat Advisory for
the remainder of the forecast area from noon through 8 PM
Wednesday. Additional showers and thunderstorms will be possible
Wednesday and Thursday with the

Latest mid to long range model solutions indicate the surface
boundary will begin to move south into the Lower Mississippi
Valley Friday into Saturday as mid-level heights weaken and a
series of shortwaves move through the northwest flow aloft. This
will bring a better chance for showers and thunderstorms for most
of the forecast area. Cooler and slightly drier air will build in
for late weekend into early next week.

CJC

&&

.AVIATION...(18Z TAFS) Issued at 1229 PM CDT Tue Jul 18 2023

Highly uncertain forecast this afternoon and evening as we watch a
thunderstorm complex move east southeast across Missouri.
Confidence is highest that MKL will see on station thunderstorms
and lowest at TUP and JBR. Included a tempo for TSRA at both MEM
and MKL based on HRRR timing. Brief MVFR to IFR conditions due to
heavy rain can be expected with on station thunderstorms along
with gusty wind, most likely from the west to northwest.

Overnight, thunderstorms should diminish in both coverage and
intensity. LLWS is expected after midnight tonight at JBR and MKL
and may last through mid morning especially at JBR. Gradient winds
tomorrow are expected to increase to around 10kts with gusts
around 20kt.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Excessive Heat Warning from noon to 8 PM CDT Wednesday for
     ARZ009-018-026>028-035-036-048-049-058.

     Heat Advisory until 8 PM CDT this evening for ARZ035-036-048.

     Excessive Heat Warning until 8 PM CDT this evening for ARZ049-
     058.

MO...Excessive Heat Warning from noon to 8 PM CDT Wednesday for
     MOZ113-115.

MS...Excessive Heat Warning from noon to 8 PM CDT Wednesday for
     MSZ001-007-008-010>012-020.

     Heat Advisory until 8 PM CDT this evening for MSZ001-002-008-012-
     013-020>022.

     Excessive Heat Warning until 8 PM CDT this evening for MSZ007-
     010-011.

     Heat Advisory from noon to 8 PM CDT Wednesday for MSZ002>006-009-
     013>017-021>024.

TN...Excessive Heat Warning from noon to 8 PM CDT Wednesday for
     TNZ001-019-048-049-088.

     Heat Advisory until 8 PM CDT this evening for TNZ088-089.

     Heat Advisory from noon to 8 PM CDT Wednesday for TNZ002>004-
     020>022-050>055-089>092.

&&

PUBLIC FORECAST...CJC
AVIATION...JDS

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