Alert archive / Wyoming / Mesoscale Discussions in 2018
Mesoscale Discussion 539
The Storm Prediction Center issued this mesoscale discussion at May 27, 2018, 11:36 AM MDT for 10 counties in Wyoming. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 27, 2018, 11:36 AM MDT (17:36 UTC)
- Expired
- May 27, 2018, 2:00 PM MDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 80%
Counties Albany County, WY, Carbon County, WY, Converse County, WY, Fremont County, WY, Hot Springs County, WY, Johnson County, WY, Natrona County, WY, Niobrara County, WY, Platte County, WY, Washakie County, WY
The radar
The Riverton/Lander radar (KRIW), 156 km from the middle of the area, began a volume at 17:39 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
Riverton, WY (KRIW), launched 12:00Z, 5.6 hours before the alert went out and 150 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
- 52 J/kg
- Mixed-layer CIN
- -196 J/kg
- Mixed-layer LCL
- 1809 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 58 m²/s²
- 0-3 km storm-relative helicity
- 145 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
421
ACUS11 KWNS 271736
SWOMCD
SPC MCD 271736
WYZ000-272000-
Mesoscale Discussion 0539
NWS Storm Prediction Center Norman OK
1236 PM CDT Sun May 27 2018
Areas affected...Much of central into eastern Wyoming
Concerning...Severe potential...Watch likely
Valid 271736Z - 272000Z
Probability of Watch Issuance...80 percent
SUMMARY...Storms should increase in coverage and intensity through
the afternoon, with damaging wind and/or hail possible.
DISCUSSION...A moist air mass has spread into central WY due to east
and northeast surface winds, resulting in an unstable air mass.
Heating will persist as well, with MUCAPE in excess of 2000 J/kg
into eastern WY where moisture is most substantial. Meanwhile, lapse
rates are steep through a deep layer courtesy of the upper trough.
Although mid and upper flow is not strong, these southerlies atop
low-level northeasterlies is elongating hodographs and will be
supportive of organized storms over the entire region. Storms are
already forming near the Wind River mountains due to upslope flow,
and these storms will gradually expand southeastward toward a
developing CU field near the south central mountains of WY. Damaging
winds will be possible given the expected elongated/somewhat linear
storm mode, but embedded cells, and/or any isolated cells that may
form will be capable of large hail given the cold air aloft.
..Jewell/Hart.. 05/27/2018
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...RIW...
LAT...LON 42280824 43250919 43690920 44340868 44170629 43950522
43510457 42680432 41610465 41210515 41110566 41300642
41600730 42280824SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 27, 12:05 PM MDT | Severe Thunderstorm Watch | SPC | Albany, Carbon, Converse, Fremont, Goshen, Laramie and 3 more | 9 hr |
| May 27, 2:25 PM MDT | Mesoscale Discussion | SPC | Albany, Carbon, Converse, Fremont, Goshen, Laramie and 2 more | 2 hr |
| May 27, 4:42 PM MDT | Mesoscale Discussion | SPC | Converse, Goshen, Laramie, Natrona, Niobrara, Platte | 93 min |
| May 27, 5:06 PM MDT | Mesoscale Discussion | SPC | Campbell, Crook, Weston | 84 min |
| May 27, 5:27 PM MDT | Severe Thunderstorm Watch | SPC | Campbell, Crook, Weston | 6 hr |
Nearby
Mesoscale Discussions in Wyoming, 2018Every 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.