Alert archive / Mississippi / Mesoscale Discussions in 2021

Mesoscale Discussion 4

January 1, 202113 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Jan 1, 2021, 1:04 AM CST for 13 counties in Mississippi. It was in force for 116 min.

The area

The outline as issued.

The facts

Issued: Jan 1, 2021, 1:04 AM CST (07:04 UTC)
Expired: Jan 1, 2021, 3:00 AM CST
In force: 116 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

Counties Attala County, MS, Holmes County, MS, Humphreys County, MS, Jasper County, MS, Leake County, MS, Madison County, MS, Neshoba County, MS, Newton County, MS, Rankin County, MS, Scott County, MS, Simpson County, MS, Smith County, MS, Yazoo County, MS

The radar

The Jackson/Brandon,MS radar (KDGX), 31 km from the middle of the area, began a volume at 07:08 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 nearest sounding before it

Jackson, MS (KJAN), launched 00:00Z, 7.1 hours before the alert went out and 33 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: 90 J/kg
Mixed-layer CIN: -82 J/kg
Mixed-layer LCL: 802 m above ground
0-6 km bulk shear: 76 kt
0-1 km storm-relative helicity: 255 m²/s²
0-3 km storm-relative helicity: 305 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

673 
ACUS11 KWNS 010705
SWOMCD
SPC MCD 010704 
MSZ000-010900-

Mesoscale Discussion 0004
NWS Storm Prediction Center Norman OK
0104 AM CST Fri Jan 01 2021

Areas affected...central MS

Concerning...Severe potential...Watch unlikely 

Valid 010704Z - 010900Z

Probability of Watch Issuance...20 percent

SUMMARY...A strong gust or brief tornado is possible across central
MS the next couple of hours. However, the overall threat is expected
to remain limited in magnitude.

DISCUSSION...A line of convection extending from Humphreys to
Jefferson Davis Counties has increased in intensity over the last
hour. This is likely due to a slight increase in low level
instability as dewpoints have increased 2-4 degrees over the past
2-3 hours. Additionally, stronger pressure falls have been noted
along the west-east oriented warm front draped across northern MS,
acting to increase low level convergence across central MS. This
increase in instability and low level convergence coincides with
favorable vertical shear and 0-1km SRH values around 200-300 m2/s2,
supporting briefly organized cells embedded in the line of
convection. Some broad, transient rotation has been noted recently
across Madison County, indicating the modestly favorable
environment. 

A strong gust or brief tornado could accompany this activity given
modest low level instability and favorable shear environment.
However, stronger mid/upper forcing will continue remain well to the
west and north of the region. Furthermore, midlevel subsidence is
still evident in water vapor imagery and 05z RAP forecast soundings.
This will likely inhibit stronger, better organized updrafts, and as
such, the overall severe threat is expected to remain limited
through the overnight hours.

..Leitman/Edwards.. 01/01/2021

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

ATTN...WFO...JAN...

LAT...LON   32739065 33119061 33289029 33338997 33298975 33238947
            32818899 32368872 31988881 31798912 31678965 31688987
            31769002 32209032 32609054 32739065

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 31, 9:31 PM CST	Mesoscale Discussion	SPC	Copiah, Covington, Forrest, Greene, Hinds, Jasper and 10 more	119 min

Nearby

Mesoscale Discussions in Mississippi, 2021 Every mesoscale discussion in 2021

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.