Severe Thunderstorm Warning 209, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
600 AM CDT Fri Jun 22 2018

.DISCUSSION... /issued 453 AM CDT Fri Jun 22 2018/

An unusually deep upper low for late June was evident on GOES
East water vapor imagery near St. Louis. This feature will lift
east into central Indiana by early evening. Latest short range
convection-allowing models depict additional thunderstorms
developing later this morning over north MS, with return flow and
surface heating destabilizing the boundary layer that was modified
by storms late Thursday evening. Storms will remain more limited
over the remainder of the Midsouth, given weak instability and
shallow lapse rates north of the midlevel dry slot.

Fast zonal flow aloft will prevail behind the departed upper low
tonight. Storms will likely form over the southern high plains
this afternoon, eventually forming an MCS that will track from OK
into AR overnight. The MCS will likely weaken by the time it reaches
eastern AR toward sunrise Saturday, as it encounters a diurnally-
weakening low level jet. Additional storms will be possible over
the Midsouth later in the day Saturday, rooted in the boundary
layer and perhaps focused along old outflow boundaries.

Upper level heights gradually build through the day on Sunday,
portending upper ridge amplification on Monday. There will one
last shot of nocturnal storms over northwest TN Sunday night,
before the upper ridge builds firmly in on Monday and Tuesday.

Rain chances under the upper ridge will not completely disappear,
as afternoon heat and humidity provide the opportunity to break
the convective capping layer aloft. Most areas away from the TN
River valley will see rain chances less than 15 percent, below
mentionable levels in most cases. Where storms do manage to form,
weak shear should limit organization and persistence beyond the
afternoon hours. The aforementioned heat and humidity will likely
drive heat indices near advisory levels over the MS River delta by
Tuesday.

Rain chances may edge up a bit by midweek, as the upper ridge
axis lifts east and an upper trof axis moves into the middle MS
River valley.

PWB

&&

.AVIATION...

12Z TAF Set

LIFR CIGS are skirting KTUP this morning. CIGS should gradually
lift as a new round of convection that has developed along an old
outflow boundary across Southern Arkansas will push east towards
KTUP by 14-15Z. Expect scattered convection to be near KTUP
for the remainder of the day. Thus have a mention VCTS wording
between 14-01Z. Elsewhere, can't rule out an isolated SHRA/TSRA
from popping up, but not enough to mention in the TAFS. VFR
conditions are expected. SW winds will increase to around 11-12
KTS with higher gusts through 01Z. Speeds will diminish during the
overnight hours. Another round of convection may be pushing into
Eastern Arkansas between 9-15Z Saturday based on several of the
CAM models. For now have left mention of vicinity wording out of
TAFS until there is some better timing agreement.

KRM

&&

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

Hazardous Weather Outlook...UPDATED
National Weather Service Memphis TN
324 AM CDT Fri Jun 22 2018

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>022-048>055-088>092-231030-
Alcorn-Benton MS-Benton TN-Calhoun-Carroll-Chester-Chickasaw-Clay-
Coahoma-Craighead-Crittenden-Crockett-Cross-DeSoto-Decatur-
Dunklin-Dyer-Fayette-Gibson-Greene-Hardeman-Hardin-Haywood-
Henderson-Henry-Itawamba-Lafayette-Lake-Lauderdale-Lawrence-
Lee AR-Lee MS-Madison-Marshall-McNairy-Mississippi-Monroe-Obion-
Panola-Pemiscot-Phillips-Poinsett-Pontotoc-Prentiss-Quitman-
Randolph-Shelby-St. Francis-Tallahatchie-Tate-Tippah-Tipton-
Tishomingo-Tunica-Union-Weakley-Yalobusha-
324 AM CDT Fri Jun 22 2018

This hazardous weather outlook is for portions of East Arkansas...
the Missouri Bootheel...North Mississippi...and West Tennessee.

.DAY ONE...Today and Tonight

There is a Slight Risk of severe thunderstorms south of a
Clarksdale to Oxford to Corinth Mississippi line through this
afternoon. There is a Marginal Risk of severe thunderstorms to
north of the Slight Risk area, along and south of Interstate 40.
Damaging winds and locally heavy rainfall will be possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

There is a Marginal Risk of severe thunderstorms over most of the
Midsouth on Saturday. Damaging winds and locally heavy rainfall
will be possible.

Heat indices will likely exceed 100 degrees next week and may
exceed 105 degrees over the Mississippi River delta.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed over north Mississippi through
this afternoon.

PWB