Alert archive / Iowa / Mesoscale Discussions in 2017
Mesoscale Discussion 718
The Storm Prediction Center issued this mesoscale discussion at May 15, 2017, 3:48 PM CDT for 22 counties in Iowa. It was in force for 87 min.
The area
The outline as issued.
The facts
- Issued
- May 15, 2017, 3:48 PM CDT (20:48 UTC)
- Expired
- May 15, 2017, 5:15 PM CDT
- In force
- 87 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 22 counties
Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Crawford County, IA, Floyd County, IA, Franklin County, IA, Hamilton County, IA, Hancock County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Mitchell County, IA, Pocahontas County, IA, Sac County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA
The radar
The Des Moines radar (KDMX), 114 km from the middle of the area, began a volume at 20:50 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
Minneapolis, MN (KMPX), launched 12:00Z, 8.8 hours before the alert went out and 241 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
- 4 J/kg
- Mixed-layer CIN
- -548 J/kg
- Mixed-layer LCL
- 1538 m above ground
- 0-6 km bulk shear
- 26 kt
- 0-1 km storm-relative helicity
- 136 m²/s²
- 0-3 km storm-relative helicity
- 125 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.1
The text
As transmitted.
658
ACUS11 KWNS 152049
SWOMCD
SPC MCD 152048
IAZ000-MNZ000-152215-
Mesoscale Discussion 0718
NWS Storm Prediction Center Norman OK
0348 PM CDT Mon May 15 2017
Areas affected...northern ia
Concerning...Severe potential...Watch possible
Valid 152048Z - 152215Z
Probability of Watch Issuance...60 percent
SUMMARY...Isolated strong thunderstorms may develop across northern
Iowa late this afternoon into the evening hours. Large hail and
damaging winds are the primary threats. WW may be required by 23z.
DISCUSSION...Early-day MCS that moved across SD has progressed into
WI aided in part by weak low-level warm advection. Short-range
model guidance has struggled with this activity, likely due to weak
forcing, with multiple disjointed surface boundaries possibly being
influential later this evening for renewed development.
Latest satellite imagery suggests a mid-level vort max may be
approaching the Missouri River northwest of OMA. Ahead of this
feature, mid-level convection is gradually thickening and isolated
elevated thunderstorms are now evident ahead of the vort stretching
into northern IA. While boundary-layer cu is focused along the
southern-most outflow across central IA, there appears to be
sufficient CINH across this region such that deep convection may
struggle. Current thinking is deep convection will focus north of
the southern-most outflow with a gradual upward trend possible into
the evening hours. Hail and wind are the primary threats with this
slowly evolving activity.
..Darrow/Kerr.. 05/15/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ARX...MPX...DMX...FSD...OAX...
LAT...LON 42319595 43429405 43569240 43059198 42619300 41749537
42319595SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 15, 9:15 AM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Clay, Dickinson, Emmet, Lyon and 7 more | 90 min |
| May 15, 5:11 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Black Hawk, Bremer, Buchanan, Butler, Calhoun and 24 more | 9 hr |
Nearby
Mesoscale Discussions in Iowa, 2017Every mesoscale discussion in 2017
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.