Severe Thunderstorm Warning 284, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
1234 PM CDT Sun Jul 15 2018

.UPDATE...
Updated for 18Z TAF issuance.

&&

.DISCUSSION...

Convection continues to hold off from entering the Midsouth this
morning from Missouri and Kentucky. So reduced chance PoPs to just
within 30 miles of the border through 1pm. CAM's indicate storms
quickly ramping up in the 20-21z time frame across northwest
Tennessee...supported by the current MCV southwest of St. Louis.
These cells could quickly become severe as they track southeast
towards the Tennessee River. Not sure if these storms will quickly
back build into eastern Arkansas this afternoon or whether new
cells will form hours later early this evening from lingering
outflow boundaries. DCAPE of 1000-1300 j/kg are anticipated off
forecast skew-T's across West Tennessee suggesting water
loading/wet microburst potential. In addition...cell training
coupled with rainfall amounts of up to 3 inches per hour could
lead to localized flash flooding.

All other forecast parameters are currently on track with current
heat indices already breaching 100F in a few locations.

JAB

&&

.PREV DISCUSSION... /issued 655 AM CDT Sun Jul 15 2018/

UPDATE...

Updated to include 12Z aviation discussion below.

PREV DISCUSSION... /issued 411 AM CDT Sun Jul 15 2018/

DISCUSSION...

At 3:00 AM heat indices are still in the upper 80s to even low 90
across the Midsouth. Jackson, TN is still reading a Heat index of 93
degrees with 91 at Jonesboro, AR.  Temperatures are mostly in the
upper 70s although Jonesboro is 82 degrees, even warmer than last
night when the low was only 79 degrees. Its possible that Jonesboro
doesn't fall below 80 this morning. Most of the Midsouth should cool
into the middle to upper 70s. The coolest temperatures across the
region will be near the Tennessee River where we may see some low
70s. A few showers are developing near the Missouri Bootheel and
Northeast Arkansas. Short term guidance continues to develop and
strengthen this precipitation as a positively tilted trough
approaches the Mississippi River.

Another Heat Advisory is in effect today for the entire MidSouth.
Heat indices may approach 110 degrees at the warmest locations.
Surface high pressure and a ridge aloft is slowly shifting off the
the East. The intense heat should easily overwhelm the cap this
afternoon resulting in scattered to numerous thunderstorms. Storms
could produce locally heavy rainfall and gusty strong wind, but
are not expected to be severe.

A ridge will build to our West early next week resulting in Northwest
flow across the Midsouth. This pattern will keep at least a slight
chance of rain across the area through midweek before the ridge
shifts to the East later in the work week. Thursday and Friday look
mostly dry. Slightly cooler, but only near normal temperatures are
expected Monday with slightly below normal temperatures Tuesday
through Thursday. Guidance is now a bit more bullish in bringing in a
deep trough across the Eastern US after midweek.  Will keep
temperatures near to slightly below normal for now...but there is the
potential for well below normal temperatures along with enhanced rain
chances.

30

&&

.AVIATION...
/18z TAFs/

Forecast challenge today is timing and extent of SHRA/TSRA affecting
TAF sites. Scattered SHRA/TSRA already developing across the area.
Will include afternoon VCTS at all sites. A weak upper system should
bring another round of SHRA/TSRA in the 03-06Z period. Considered
TEMPO groups for the evening round, but given uncertainty in
timing/details, will hold off for now and continue VCTS at TAF sites
into late evening/overnight hours. Will amend and ramp up if
guidance/observed trends converge better. Otherwise, mostly VFR with
light W to S winds and possible spotty BR before daybreak Monday.

GW

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory until 9 PM CDT this evening for Clay-Craighead-
     Crittenden-Cross-Greene-Lawrence-Lee AR-Mississippi-
     Phillips-Poinsett-Randolph-St. Francis.

MO...Heat Advisory until 9 PM CDT this evening for Dunklin-Pemiscot.

MS...Heat Advisory until 9 PM CDT this evening for Alcorn-Benton MS-
     Calhoun-Chickasaw-Coahoma-DeSoto-Itawamba-Lafayette-Lee MS-
     Marshall-Monroe-Panola-Pontotoc-Prentiss-Quitman-
     Tallahatchie-Tate-Tippah-Tishomingo-Tunica-Union-Yalobusha.

TN...Heat Advisory until 9 PM CDT this evening for Benton TN-Carroll-
     Chester-Crockett-Decatur-Dyer-Fayette-Gibson-Hardeman-
     Hardin-Haywood-Henderson-Henry-Lake-Lauderdale-Madison-
     McNairy-Obion-Shelby-Tipton-Weakley.

&&

Hazardous Weather Outlook
National Weather Service Memphis TN
811 AM CDT Sun Jul 15 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>092-161515-
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-
811 AM CDT Sun Jul 15 2018

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

.DAY ONE...Today and Tonight

Heat index values are expected to exceed 105 degrees across the
Midsouth today.

There is a Marginal Risk for severe thunderstorms north of a
Forrest City Arkansas to a Savannah Tennessee line this afternoon
and evening. Damaging winds and localized heavy rainfall will be
the main threats.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

A few strong thunderstorms with gusty winds will be possible,
Monday afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed across the northern two thirds of
the Midsouth this afternoon and evening.

JAB

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Special Weather Statement
National Weather Service Memphis TN
1222 PM CDT SUN JUL 15 2018

TNZ002>004-151815-
Weakley TN-Obion TN-Henry TN-
1222 PM CDT SUN JUL 15 2018

...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED UNTIL 115 PM CDT
FOR...

Northern Weakley County in northwestern Tennessee...
Northeastern Obion County in northwestern Tennessee...
Northwestern Henry County in northwestern Tennessee...

At 1222 PM CDT...a strong thunderstorm producing ${allThreat}over
Palmersville, or 15 miles northwest of Paris, moving east at 10 mph.

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

People in northern Weakley...northeastern Obion and northwestern
Henry Counties should monitor this storm closely.

LAT...LON 3633 8822 3634 8908 3650 8907 3650 8816
TIME...MOT...LOC 1722Z 257DEG 10KT 3642 8853