Alert archive / Oklahoma / Mesoscale Discussions in 2020
Mesoscale Discussion 1721
The Storm Prediction Center issued this mesoscale discussion at Sep 27, 2020, 5:57 PM CDT for 19 counties in Oklahoma. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 27, 2020, 5:57 PM CDT (22:57 UTC)
- Expired
- Sep 27, 2020, 8:00 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
Counties Atoka County, OK, Bryan County, OK, Carter County, OK, Coal County, OK, Garvin County, OK, Haskell County, OK, Hughes County, OK, Johnston County, OK, Latimer County, OK, Love County, OK, Marshall County, OK, McClain County, OK, McIntosh County, OK, Murray County, OK, Pittsburg County, OK, Pontotoc County, OK, Pottawatomie County, OK, Pushmataha County, OK, Seminole County, OK
The radar
The Norman radar (KTLX), 83 km from the middle of the area, began a volume at 22:59 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
Norman, OK (KOUN), launched 12:00Z, 11.0 hours before the alert went out and 88 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
- 520 J/kg
- Mixed-layer CIN
- -528 J/kg
- Mixed-layer LCL
- 1047 m above ground
- 0-6 km bulk shear
- 24 kt
- 0-1 km storm-relative helicity
- 201 m²/s²
- 0-3 km storm-relative helicity
- 198 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
212
ACUS11 KWNS 272257
SWOMCD
SPC MCD 272257
OKZ000-TXZ000-280100-
Mesoscale Discussion 1721
NWS Storm Prediction Center Norman OK
0557 PM CDT Sun Sep 27 2020
Areas affected...Parts of south central Oklahoma
Concerning...Severe potential...Watch possible
Valid 272257Z - 280100Z
Probability of Watch Issuance...40 percent
SUMMARY...A few strong storms are possible across parts of southern
and eastern Oklahoma into early this evening. This may include
potential for a supercell or two, mainly near/east of the Interstate
35 corridor south-southeast of Oklahoma City. It is not yet certain
that a severe weather watch will be needed, but trends are being
monitored for this possibility.
DISCUSSION...The surface cold front continues to surge southward
into the southern Great Plains, generally well south/ahead of the
stronger mid-level cooling and large-scale forcing for ascent. The
shallow leading edge of the cold air may already be undercutting a
zone of strengthening lift associated with lower/mid tropospheric
warm advection. Both sources of lift appear to be contributing to
increasing precipitation and embedded convective development, which
seems likely to become mostly focused to the cool side of the
surface frontal with further southward progression this evening.
While the moist pre-frontal boundary layer appears characterized by
moderately large CAPE, potential for sustained boundary-layer based
storm development seem confined to a relatively narrow corridor near
the intersection of the front and the pre-frontal dryline, roughly
near the Interstate 35 corridor south-southeast of Oklahoma City.
Even here, this may be limited in duration, but deep-layer shear
appears sufficient for an isolated supercell or two.
..Kerr/Hart.. 09/27/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SHV...TSA...FWD...OUN...
LAT...LON 35319707 35509613 35579507 34159501 33819725 34969787
35319707Nearby
Mesoscale Discussions in Oklahoma, 2020Every mesoscale discussion in 2020
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.