Severe Thunderstorm Warning 223, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
1220 PM CDT Sun Jun 18 2017

.UPDATE...
Updated to include the 18z aviation discussion below.

&&

.PREV DISCUSSION... /issued 1020 AM CDT Sun Jun 18 2017/

DISCUSSION...Surface analysis this morning places a cold front
from Chicago through St. Louis and then through Fayetteville,
Arkansas. Isolated showers and thunderstorms are occurring over
Southeast Missouri and a convective line over portions of
West/Northwest Arkansas. As of 10 AM CDT, temperatures across the
Mid-South range from the upper 70s to lower 80s across many
locations.

Latest mesoanalysis indicates an warm, moist, and unstable
atmosphere across the Mid-South this morning with surface based
CAPE values already in the 2000-2500 J/kg range, LI's of -5 to -6,
and precipitable water values approaching 2 inches. Instability
is expected to increase into this afternoon with conditions
remaining favorable for strong to severe thunderstorms across the
Mid-South this afternoon into perhaps this evening. Damaging winds
will remain the predominant threat for any thunderstorms that
reach severe limits. In addition, high atmospheric moisture
content will be conducive for heavy rainfall. Forecast was already
updated to account for short term trends and to account for
severe thunderstorm watch in effect until 4 pm CDT up to the
Mississippi River thus far.

CJC

PREV DISCUSSION... /issued 426 AM CDT Sun Jun 18 2017/

DISCUSSION...

Currently...Very muggy night underway across the Mid-South with
dewpoints in the mid 70s across much of the Delta. High clouds
have spilled south from upstream convective complexes otherwise it
is quiet weather wise...for the moment.

Today through Monday...A cold front from the Great Lakes to the
southern plains will slowly press south into the region with
multiple rounds of convection possible. A good deal of convection
has already developed across OK/KS/MO along and ahead of the
front. The airmass across the Mid-South is quite unstable at this
hour with SBCAPES above 2000 J/KG across much of the Delta region
and fairly steep mid level lapse rates of 7 C/KM. Latest CAMs show
a line of thunderstorms driven SE by a cold pool across the Mid-
South this morning reaching NE Mississippi early this afternoon.
These storms could produce damaging winds given the instability in
place. As the cold front presses south later this afternoon and
the airmass recharges with additional development that will
continue into the overnight hours. PWs climb to over 2 inches
ahead of the front and given the slow moving nature of the front
training is possible. Considered a Flash Flood watch for this
afternoon into tonight but will defer to the day shift to see how
today's convection evolves. For now will continue to mention
isolated flash flooding in the HWO. Some severe potential will
continue into the overnight hours as well. The long wave trough
over the central states will provide some upper support with a
belt of stronger mid level winds pressing south into the area.
However, a lot will depend on the extent the airmass can
destabilize again after this morning's convection. Rain chances
will slowly taper off from NW to SE later tonight into Monday as
the front gradually exits. A marginal risk for severe weather
continues across NE Mississippi into Monday.

Monday night through Wednesday...High pressure will build over the
area. Some patchy fog is possible Monday night. Tuesday and
Wednesday will be quite pleasant with lower humidities.

Thursday through Saturday...Quite a bit of uncertainty in this
time frame. Low pressure in the Gulf of Mexico may track into
Florida or Texas with large implication to the Mid-South forecast
especially in the Thu-Fri time frame. For now will continue to
introduce low pops with increasing humidity. By Saturday the
medium range models are trending wetter with a cold front
approaching so increased pops a bit.

SJM

&&

.AVIATION...
/18z TAFs/

The primary aviation concern over the next 12 hours is the complex
of storms moving across central AR at this time. These storms are
expected to continue an easterly progression, affecting the Mid-
South forecast terminals throughout the afternoon hours. Gusty
west to northwest winds and tempo IFR conditions are likely with
this line of storms. Additional showers and thunderstorms, and
potentially an area of lingering stratiform rain, are possible
through the afternoon and evening hours with more development
possible overnight as a weak cold front moves across the area.
This will shift winds from the northwest at 5-10 mph for Monday
morning.

Johnson

&&

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

&&

Hazardous Weather Outlook
National Weather Service Memphis TN
435 AM CDT Sun Jun 18 2017

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>022-048>055-088>092-191145-
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-
435 AM CDT Sun Jun 18 2017

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 weather across the Mid-South
today and tonight as a cold front moves through the region.
Multiple rounds of thunderstorms are possible today into tonight.
Damaging winds are the main threat. Large hail is a secondary
threat. The front will move slowly so flash flooding is also
possible.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There is a marginal risk for severe weather across Northeast
Mississippi on Monday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required today through Monday.

SJM

Special Weather Statement
National Weather Service Memphis TN
106 PM CDT SUN JUN 18 2017

ARZ027-181830-
Poinsett AR-
106 PM CDT SUN JUN 18 2017

...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED UNTIL 130 PM CDT
FOR...

Western Poinsett County in eastern Arkansas...

At 106 PM CDT...a strong thunderstorm producing pea size hail or
larger and winds at least 40 mph was located over Weiner, or 9 miles
northwest of Harrisburg, moving east at 15 mph.

Very heavy rain along with continuous cloud to ground lightning are
also possible with this thunderstorm.

People in western Poinsett County should monitor this storm closely.

LAT...LON 3571 9104 3571 9057 3556 9058 3544 9104
TIME...MOT...LOC 1806Z 270DEG 12KT 3562 9087

JOHNSON