Alert archive / Colorado / Mesoscale Discussions in 2021
Mesoscale Discussion 1270
The Storm Prediction Center issued this mesoscale discussion at Jul 13, 2021, 1:38 PM MDT for 9 counties in Colorado; 6 counties in Nebraska; Laramie County, Wyoming. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 13, 2021, 1:38 PM MDT (19:38 UTC)
- Expired
- Jul 13, 2021, 3:45 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Adams County, CO, Larimer County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Weld County, CO, Yuma County, CO, Banner County, NE, Chase County, NE, Cheyenne County, NE, Deuel County, NE, Dundy County, NE, Kimball County, NE, Laramie County, WY
The radar
The Cheyenne radar (KCYS), 84 km from the middle of the area, began a volume at 19:40 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
Denver, CO (KDNR), launched 12:00Z, 7.6 hours before the alert went out and 125 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
- 41 J/kg
- Mixed-layer CIN
- -357 J/kg
- Mixed-layer LCL
- 2811 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 23 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
247
ACUS11 KWNS 131938
SWOMCD
SPC MCD 131938
NEZ000-KSZ000-COZ000-WYZ000-132145-
Mesoscale Discussion 1270
NWS Storm Prediction Center Norman OK
0238 PM CDT Tue Jul 13 2021
Areas affected...Southeast WY...Northeast CO...Southern NE
Panhandle...Far Southwest Nebraska
Concerning...Severe potential...Watch unlikely
Valid 131938Z - 132145Z
Probability of Watch Issuance...20 percent
SUMMARY...A few strong thunderstorms are possible this afternoon,
with a threat of isolated hail and damaging wind gusts.
DISCUSSION...At 1930Z, scattered thunderstorms are moving eastward
off of the higher terrain of far southeast WY/north-central CO.
Downstream, strong heating is occurring across the lower elevations,
though some MLCIN remains per recent mesoanalyses. As heating and
destabilization continue this afternoon, ongoing convection may
intensify into northeast CO and the NE Panhandle, or else redevelop
later this afternoon as MLCIN continues to erode. MLCAPE increasing
into the 1000-1500 J/kg range combined with effective shear of 30-40
kt will support the potential for a loosely organized cluster or
perhaps a supercell or two, with an attendant risk of large hail and
locally severe wind gusts. At this time, coverage of the severe
threat is expected to remain too isolated for watch issuance.
..Dean/Dial.. 07/13/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...GLD...BOU...CYS...
LAT...LON 41560592 41870479 41780377 41560234 41280180 40430148
40040168 39330289 39910472 40430534 40830575 41560592SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 13, 2:21 PM MDT | Mesoscale Discussion | SPC | Box Butte, Dawes, Sheridan, Sioux | 84 min |
| Jul 13, 4:25 PM MDT | Severe Thunderstorm Watch | SPC | Banner, Box Butte, Dawes, Morrill, Scotts Bluff, Sioux | 8 hr |
Nearby
Mesoscale Discussions in Colorado, 2021Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Wyoming, 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.