Alert archive / Mississippi / Mesoscale Discussions in 2018

Mesoscale Discussion 1621

November 5, 20184 states

The Storm Prediction Center issued this mesoscale discussion at Nov 5, 2018, 3:38 PM CST for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Nov 5, 2018, 3:38 PM CST (21:38 UTC)
Expired: Nov 5, 2018, 5:45 PM CST
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 57 counties

Arkansas County, AR, Ashley County, AR, Bradley County, AR, Chicot County, AR, Crittenden County, AR, Desha County, AR, Drew County, AR, Lee County, AR, Lincoln County, AR, Phillips County, AR, Union County, AR, Bienville Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, East Carroll Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Richland Parish, LA, Union Parish, LA, West Carroll Parish, LA, Alcorn County, MS, Benton County, MS, Bolivar County, MS, Calhoun County, MS, Carroll County, MS, Chickasaw County, MS, Coahoma County, MS, DeSoto County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Lafayette County, MS, Lee County, MS, Leflore County, MS, Marshall County, MS, Montgomery County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tunica County, MS, Union County, MS, Washington County, MS, Webster County, MS, Yalobusha County, MS, Fayette County, TN, Hardeman County, TN, Shelby County, TN

The radar

The Jackson/Brandon,MS radar (KDGX), 170 km from the middle of the area, began a volume at 21:41 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 9.6 hours before the alert went out and 161 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 679 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 158 m²/s²
0-3 km storm-relative helicity: 223 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

500 
ACUS11 KWNS 052139
SWOMCD
SPC MCD 052138 
MSZ000-TNZ000-ARZ000-LAZ000-052345-

Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0338 PM CST Mon Nov 05 2018

Areas affected...northern Louisiana...eastern Arkansas...northern
Mississippi and western Tennessee

Concerning...Severe potential...Watch likely 

Valid 052138Z - 052345Z

Probability of Watch Issuance...80 percent

SUMMARY...Storms are expected to increase in coverage mainly after
23-00Z across northern Louisiana and eastern Arkansas, and will gain
strength as they develop eastward into northern Mississippi and
Tennessee during the evening. Damaging winds and tornadoes will be
possible.

DISCUSSION...The air mass across east TX and the lower MS Valley
continues to destabilize via both low-level theta-e advection
associated with a warm front, and mixing of the boundary layer aided
by pockets of heating. As of 21Z, the most unstable air was located
over southeast TX, where 70s F dewpoints and strong heating exist.

18Z soundings indicate a substantial midlevel inversion which is
limiting instability. This inversion will weaken somewhat this
evening as a strong jet max noses into AR, northern MS and western
TN, providing cooling aloft.

Currently, scattered convective showers exist near the instability
axis over east TX and northwest LA, but they are shallow with no
lightning due to the warm midlevel temperatures. However, they are
already rotating. Farther north, a band of ascent was evident on
radar from the ArkLaTex into central AR, with gradually warming
temperatures south of that area. 

Over the next several hours, both these areas will likely
consolidate into thunderstorms across northern LA and southern AR,
and may mature into northern MS and western TN this evening. Shear
profiles will continue to increase as the low-level jet intensifies
to over 50 kt. Hodographs will strongly favor supercells,
potentially tornadic, but storms may eventually transition to a
QLCS. Therefore, both damaging winds and tornadoes will be possible.
The greatest threat is likely to exist east of the MS river and
after 03Z, when lift, shear, and low-level moisture are maximized.

..Jewell/Thompson.. 11/05/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MEG...JAN...LZK...SHV...

LAT...LON   32719056 32259196 31919297 31779346 31789375 32059397
            32339384 34239146 34999072 35349027 35538956 35448887
            35128851 34618835 34378839 33368946 32719056

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 5, 4:06 PM CST	Tornado Watch	SPC	Ashley, Chicot, Union	7 hr
Nov 5, 5:05 PM CST	Mesoscale Discussion	SPC	Bienville, Caldwell, Franklin, Jackson, Madison, Natchitoches and 4 more	55 min

Nearby

Mesoscale Discussions in Mississippi, 2018 Mesoscale Discussions in Louisiana, 2018 Mesoscale Discussions in Arkansas, 2018 Every mesoscale discussion in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.