Special Weather Statement, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
1230 PM CDT Wed Aug 18 2021

.UPDATE...

Updated for the 18Z Aviation Discussion

&&

.PREV DISCUSSION... /issued 341 AM CDT Wed Aug 18 2021/

DISCUSSION...
The Bermuda High remains anchored off the East Coast with the
remnants of Fred tracking north across the Upper OH Valley. A deep
trough continues to dig over the Pacific Northwest with a messy
pattern over the central CONUS. An upper-level trough axis
extending from the great Lakes through the Southern Plains is
blocked by the Bermuda High but will begin to gradually shift by
late week as the ridge weakens. In the meantime, persistent, deep
southwesterly flow throughout the column will continue to
provide a feed of tropical moisture into the region. Satellite
derived Blended Total Precipitable Water indicates widespread
PWATs of 2.0-2.3 inches across the Arklatex into the MS Delta.
This moisture, along with a tall, skinny CAPE profile, will
provide the fuel for efficient rainfall producing thunderstorms
over the next couple of days.

One shortwave trough is moving east across the Mid MS Valley but
its effects will likely remain too far north. A stronger wave is
approaching the Arklatex, with large-scale forcing for ascent
noted on the water vapor loop. Strong lift across the area today
will yield numerous showers and thunderstorms across the Mid-
South. Deep-layer shear may be just sufficient to support a few
strong/severe multicellular storms this afternoon capable of
damaging wind, but localized heavy rainfall may be the greater
threat. Showers and thunderstorms will develop this morning and
move into the eastern reaches of the CWA by late afternoon. HREF
6-hr PMM fields indicate a fairly widespread potential for 1-2"
with localized higher amounts today. We should see a lull this
evening, but warm advection processes should result in some
redevelopment overnight.

Heavy rainfall doesn't look to be as widespread on Thursday. The
strongest forcing does look to move east early in the day with
shortwave ridging building in during the afternoon and evening.
That said, we'll maintain a moist, unstable air mass capable of
diurnal convection, but the loss of large scale ascent should
result in less coverage. The shortwave ridge will remain in place
Friday, but a strong shortwave trough is progged to dive south
across the OH Valley, enhancing support for further rainfall
Friday. Temperatures through Friday will remain below climatology
with highs generally in the mid/upper 80s and lows in the lower
70s.

The subtropical ridge begins to build over the South Plains and
Lower MS Valley this weekend. NAEFS/EPS progs continue to suggest
a 594+ dam ridge (> 90th percentile) by Sunday, signaling a return
to hot/humid conditions this weekend through at least the middle
of next week. We'll also see rain chances diminish each day as
large scale subsidence eats away at instability. PoPs were limited
to chance category Saturday, decreasing further Sunday-Tuesday.
Temperatures are expected to warm into the low/mid 90s during this
time with afternoon heat indices again approaching 105F. The good
news is this ridge is likely to retrograde to the west by
Wednesday or Thursday and this may help alleviate heat concerns.

MJ

&&

.AVIATION...
18Z TAF cycle

Showers and thunderstorms will continue to move across the Mid-
South this afternoon from southwest to northeast. VFR conditions
will be found most of the time but there will be periods of lower
ceilings and visibilities. Most of this activity will end early
this evening with another round of showers and thunderstorms
starting Thursday morning. Winds will be mainly from the south at
around 5 knots for much of the forecast period.

ARS

&&

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

Hazardous Weather Outlook
National Weather Service Memphis TN
435 AM CDT Wed Aug 18 2021

ARZ009-018-026>028-035-036-048-049-058-MOZ113-115-MSZ001>017-
020>024-TNZ001>004-019>022-048>055-088>092-191100-
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-Lee AR-Lee MS-
Madison-Marshall-McNairy-Mississippi-Monroe-Obion-Panola-Pemiscot-
Phillips-Poinsett-Pontotoc-Prentiss-Quitman-Shelby-St. Francis-
Tallahatchie-Tate-Tippah-Tipton-Tishomingo-Tunica-Union-Weakley-
Yalobusha-
435 AM CDT Wed Aug 18 2021

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

.DAY ONE...Today and Tonight

A few strong to severe storms are possible across the Mid-South
this afternoon. The strongest storms may be capable of producing
damaging winds. Locally heavy rainfall may lead to flash flooding.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Numerous showers and thunderstorms will continue to pose a threat
for locally heavy rainfall Thursday and Friday.

Hot and humid conditions will return this weekend into early next
week with heat indices approaching 105 degrees.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.

MJ

Special Weather Statement
National Weather Service Memphis TN
1246 PM CDT Wed Aug 18 2021

MSZ007-010-011-181815-
Tunica MS-Coahoma MS-Quitman MS-
1246 PM CDT Wed Aug 18 2021

...A strong thunderstorm will impact portions of east central
Coahoma, south central Tunica and central Quitman Counties through
115 PM CDT...

At 1246 PM CDT, Doppler radar was tracking a strong thunderstorm near
Kings, or near Clarksdale, moving northeast at 25 mph.

HAZARD...Winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Marks, Jonestown, Belen, Darling, Kings, Coahoma, Lyon, Falcon, West
Marks, Rudyard, Riverview, Tibbs, Hinchcliff, Clover Hill, Roseacres,
Matagorda, Rich and Essex.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3432 9063 3451 9030 3431 9019 3430 9019
      3429 9018 3427 9017 3422 9055
TIME...MOT...LOC 1746Z 245DEG 20KT 3429 9053

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

SWB

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Special Weather Statement
National Weather Service Memphis TN
248 PM CDT Wed Aug 18 2021

MSZ015-022-023-182015-
Pontotoc MS-Calhoun MS-Chickasaw MS-
248 PM CDT Wed Aug 18 2021

...A strong thunderstorm will impact portions of northwestern
Chickasaw, southeastern Calhoun and southwestern Pontotoc Counties
through 315 PM CDT...

At 248 PM CDT, Doppler radar was tracking a strong thunderstorm over
Calhoun City, or 17 miles west of Houston, moving northeast at 25
mph.

HAZARD...Winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Houston, Bruce, Calhoun City, Vardaman, Derma, Pittsboro, Pyland,
Houlka, New Houlka, Robbs, Thorn, Parkersburg, Reid, Loyd, Pannell,
Thelma and Matthews.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3378 8933 3390 8945 3420 8914 3394 8886
TIME...MOT...LOC 1948Z 235DEG 22KT 3389 8932

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

SWB