Special Weather Statement, NWS Memphis, TN

Area Forecast Discussion
National Weather Service Memphis TN
633 AM CDT Mon Jun 21 2021

.UPDATE...
Updated to include 12Z Aviation Discussion.

&&

.PREV DISCUSSION... /issued 339 AM CDT Mon Jun 21 2021/

DISCUSSION...
A strong shortwave trough will rotate around the Hudson Bay vortex
today, driving a cold front through the Mid-South late today and
tonight. This front is currently located from a surface low in
southern WI, across central MO, and arcing back into northern OK.
A few storms are ongoing in southeast MO to near the OH River
ahead of this front but the scope is quiet across the Mid-South at
this time. The western ridge has retreated into the southwest
CONUS, with the ridge axis extending northwest into the PacNW with
a weakening jet streak on its western flank. Another jet streak
is beginning to intensify downstream of the trough axis is will
provide additional upper-level support today.

Large scale forcing for ascent will continue to erode the cap that
held throughout the day yesterday, resulting in a moist, unstable
air mass across the region today. Scattered showers and
thunderstorms are expected to initiate along a pre-frontal trough
by mid-morning, increasing in coverage throughout the day. Forcing
along this trough will be enhanced by divergence aloft associated
with the right entrance region of the intensifying jet streak.
While storms will be most organized along the surface boundary,
scattered cells are expected to develop in the open warm sector as
well within a broad area of warm advection.

Ample surface-based instability is expected ahead of the cold
front this afternoon and evening with SBCAPE likely exceeding
3000 J/kg. This will certainly support some strong updrafts. The
question the past few days as been the quality of the deep-layer
shear. Vertical shear remains somewhat marginal with 0-6 km bulk
wind difference near 30 kts. This should still be sufficient to
support scattered multicell clusters capable of damaging winds. In
addition to the wind threat, the potential for locally heavy
rainfall will exist area wide. QPF amounts have decreased
slightly, but many areas should pick up close to an inch, with
locally higher totals. Convection intensity is expected to wane
after sunset, gradually shifting south overnight.

The cold front will continue south through Tuesday with any
lingering rain ending across north MS during the morning hours.
Cooler and much drier air will settle over the Mid-South with
Tuesday afternoon highs in the upper 70s to near 80F. This air
mass will be quite dry with precipitable water progged to fall to
around 0.6" (lowest 3% of climatology for late June). The dry
air, light winds, and clear skies will set the stage for potential
record low temperatures at a few sites Wednesday morning with
overnight lows in the mid/upper 50s in many locations. We'll
maintain pleasant weather conditions, albeit a bit warmer on
Wednesday. Temperatures forecast to rebound into the mid 80s.

Medium range guidance continues to indicate the subtropical ridge
attempting to build back into the region by midweek, but another
strong trough digs into the central CONUS and pushes the ridge
back to the west over the weekend. The resultant flow is highly
amplified which should keep temperatures at or below climatology
this weekend. Rain chances could return as early as Thursday with
isolated, diurnal air mass convection possible. In addition, the
global deterministic models show a strong shortwave trough
ejecting out of the Central Plains Thursday evening. This could
drive an MCS south into the area during the overnight period.
Confidence is low, but it's worthy of slight chance PoPs.
Additional scattered thunderstorms are expected on Friday as
moisture deepens across the region.

Rain chances become a bit more focused over the weekend as a cold
front approaches. The global deterministic models have some
significant disparity in the timing of the trough, but the
ensembles keep the trough axis to the west of the CWA through the
day Sunday. Thus, will go with likely PoPs in most areas Saturday
and Sunday.

MJ

&&

.AVIATION...
12Z TAFs

Low stratus developed in the past few hours over North Mississippi
producing MVFR conditions. This stratus has the potential to
spread into MEM for a few hours this morning. Otherwise, VFR
conditions should prevail during the day outside of thunderstorms
ahead of the cold front. Thereafter, MVFR conditions are expected
to develop towards this evening. Showers and thunderstorms will
begin to develop late this morning at JBR, then spreading to
MKL/MEM after 17Z, then at TUP this afternoon. Gusty SW/WSW winds
will veer NW/N with frontal passage.

CJC

&&

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

Hazardous Weather Outlook
National Weather Service Memphis TN
402 AM CDT Mon Jun 21 2021

ARZ009-018-026>028-035-036-048-049-058-MOZ113-115-MSZ001>017-
020>024-TNZ001>004-019>022-048>055-088>092-221100-
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-
402 AM CDT Mon Jun 21 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 thunderstorms will be possible across the
Mid-South, mainly this afternoon and evening. Damaging winds and
locally heavy rainfall will be the primary hazards.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.

MJ

Special Weather Statement
National Weather Service Memphis TN
952 AM CDT Mon Jun 21 2021

ARZ018-026-211515-
Greene AR-Craighead AR-
952 AM CDT Mon Jun 21 2021

...A SIGNIFICANT WEATHER ADVISORY HAS BEEN ISSUED UNTIL 1015 AM CDT
FOR...

Southwestern Greene County in eastern Arkansas...
Northwestern Craighead County in eastern Arkansas...

At 951 AM CDT...a strong thunderstorm producing pea size hail or
larger and winds at least 40 mph was located near Minturn, or near
Hoxie, moving east at 35 mph.

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

People in southwestern Greene and northwestern Craighead Counties
should monitor this storm closely.

LAT...LON 3588 9087 3592 9087 3593 9086 3596 9086
      3598 9084 3599 9086 3602 9084 3604 9084
      3605 9083 3608 9082 3609 9080 3612 9077
      3618 9060 3593 9049 3583 9101 3588 9103
TIME...MOT...LOC 1451Z 251DEG 30KT 3595 9096