Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 3
The Storm Prediction Center issued this mesoscale discussion at Dec 31, 2020, 9:31 PM CST for 16 counties in Mississippi. It was in force for 119 min.
The area
The outline as issued.
The facts
- Issued
- Dec 31, 2020, 9:31 PM CST (03:31 UTC)
- Expired
- Dec 31, 2020, 11:30 PM CST
- In force
- 119 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Copiah County, MS, Covington County, MS, Forrest County, MS, Greene County, MS, Hinds County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Marion County, MS, Perry County, MS, Rankin County, MS, Simpson County, MS, Smith County, MS, Wayne County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 53 km from the middle of the area, began a volume at 03:32 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, 3.5 hours before the alert went out and 62 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.
- 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
The text
As transmitted.
972
ACUS11 KWNS 010332
SWOMCD
SPC MCD 010331
ALZ000-MSZ000-010530-
Mesoscale Discussion 0003
NWS Storm Prediction Center Norman OK
0931 PM CST Thu Dec 31 2020
Areas affected...Central/Southeast Mississippi...Southwest Alabama
Concerning...Severe potential...Watch possible
Valid 010331Z - 010530Z
Probability of Watch Issuance...40 percent
SUMMARY...Some risk for tornadoes will focus along the warm front
over the next several hours. Even so, it's not clear a tornado watch
is warranted.
DISCUSSION...Surface warm front has lifted into central MS, arcing
southeast into southwest AL. Warm sector is characterized by
mid-upper 60s dew points but lapse rates are marginal and this is
limiting buoyancy across this region. 00z sounding from LIX supports
this with deep-layer lapse rates on the order of 5.5 C/km, though
strongly sheared with more than enough flow for sustaining
supercells. Convection has struggled to organize across the lower MS
Valley into the central Gulf coast region, partly due to the lack of
stronger forcing which is currently ejecting northeast across TX.
Additionally, substantial mid-level drying has overspread the warm
sector and this may be inhibiting more substantial updrafts,
especially given the weak low-level convergence. For these reasons,
if sustained supercells materialize they will likely focus along the
warm front where low-level convergence is greater. Given the dearth
of robust convection at this time it's not clear a new tornado watch
will be warranted.
..Darrow/Bunting.. 01/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MOB...JAN...
LAT...LON 32619059 32318917 31618813 30878863 31098970 32029097
32619059SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 1, 1:04 AM CST | Mesoscale Discussion | SPC | Attala, Holmes, Humphreys, Jasper, Leake, Madison and 7 more | 116 min |
Nearby
Mesoscale Discussions in Mississippi, 2021Every 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.