Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 1217
The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2021, 5:40 PM CDT for 21 counties in Iowa. It was in force for 95 min.
The area
The outline as issued.
The facts
- Issued
- Jul 9, 2021, 5:40 PM CDT (22:40 UTC)
- Expired
- Jul 9, 2021, 7:15 PM CDT
- In force
- 95 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 21 counties
Benton County, IA, Black Hawk County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cedar County, IA, Delaware County, IA, Fayette County, IA, Grundy County, IA, Henry County, IA, Iowa County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Linn County, IA, Louisa County, IA, Muscatine County, IA, Poweshiek County, IA, Tama County, IA, Washington County, IA
The radar
The Quad Cities radar (KDVN), 119 km from the middle of the area, began a volume at 22:43 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
Davenport, (KDVN), launched 12:00Z, 10.7 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1131 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 100 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
525
ACUS11 KWNS 092241
SWOMCD
SPC MCD 092240
ILZ000-IAZ000-100015-
Mesoscale Discussion 1217
NWS Storm Prediction Center Norman OK
0540 PM CDT Fri Jul 09 2021
Areas affected...portions of eastern Iowa
Concerning...Severe potential...Watch possible
Valid 092240Z - 100015Z
Probability of Watch Issuance...40 percent
SUMMARY...Some severe hail may accompany the stronger, elevated
updrafts over the next few hours. How widespread the severe hail
threat will be is uncertain given lack of stronger, deep-layer lift.
Conditions will continue to be monitored for the need of a WW
issuance should more robust updrafts become relatively widespread.
DISCUSSION...Multicellular thunderstorms, rooted at/above 850 mb
(per latest RAP forecast soundings) have been intensifying along an
elevated moist-frontal boundary in the 850-700 mb layer given the
passage of a small, embedded impulse at 700 mb. Latest mesoanalysis
suggests that 1000-2000 J/kg MUCAPE parcels are advecting into this
region, supporting updraft intensification and subsequent severe
hail potential. While 40+ kts of effective bulk shear suggest that
some storm organization is possible over the next few hours, the
storms will likely quickly propagate into a relatively more stable
elevated airmass, suggesting that the severe hail threat may also be
short-lived. Given the potentially limited spatial/temporal coverage
of the severe hail threat, the need for a WW issuance is uncertain.
Nonetheless, conditions will continue to be monitored should more
widespread, robust updraft development becomes more prevalent.
..Squitieri/Thompson.. 07/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DVN...ARX...DMX...
LAT...LON 41049208 41719261 42259315 42679333 42929299 43049229
42979184 42669144 42159100 41679087 41259089 40979108
40759161 41049208SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 8, 9:33 PM CDT | Severe Thunderstorm Watch | SPC | Buena Vista, Cherokee, Clay, Ida, Lyon, O'Brien and 3 more | 5 hr |
| Jul 9, 2:41 AM CDT | Mesoscale Discussion | SPC | Buena Vista, Cherokee, Clay, Crawford, Ida, Lyon and 6 more | 34 min |
| Jul 9, 1:28 PM CDT | Mesoscale Discussion | SPC | Boone, Dallas, Lucas, Polk, Warren | 2 hr |
Nearby
Mesoscale Discussions in Iowa, 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.