Special Weather Statement, NWS Memphis, TN

Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
651 AM CDT Wed Aug 18 2021

.UPDATE...
Updated for 12Z Aviation Forecast Discussion below.

&&

.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...
12Z TAFs

Deep subtropical moisture feed will extend across the Midsouth
today, downstream of an upper level trof over TX, and coupled with
rich low level moisture. Difficult to rule out any time of the
day for TSRA, given how convectively unstable the atmosphere will
become with daytime heating. For the 12Z TAFs, have focused TEMPOs
near maximum heating, which appears will be about the time an
early morning shortwave near TXK arrives in the Midsouth.

Expect a lull in activity during the evening, or at least a
reduction in TSRA coverage. For the overnight, additional clusters
of SHRA/TSRA are expected, associated with a subtle wave lifting
out of the Arklamiss.

PWB

&&

.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
1044 AM CDT Wed Aug 18 2021

MSZ013-021-022-181615-
Lafayette MS-Calhoun MS-Yalobusha MS-
1044 AM CDT Wed Aug 18 2021

...A strong thunderstorm will impact portions of southeastern
Lafayette, northeastern Yalobusha and northwestern Calhoun Counties
through 1115 AM CDT...

At 1043 AM CDT, Doppler radar was tracking a strong thunderstorm near
Water Valley, moving northeast at 20 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...
Oxford, Water Valley, Springdale, Tula, Denmark, Paris, Taylor,
Altus, Pine Valley, Delay and Yocona.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3418 8968 3443 8943 3425 8925 3421 8925
      3404 8954
TIME...MOT...LOC 1543Z 228DEG 18KT 3417 8955

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

SWB