MD 1563 CONCERNING SEVERE THUNDERSTORM WATCH 489… FOR PORTIONS OF SOUTHERN MN…NORTHERN IA AND SOUTHWEST WI
Mesoscale Discussion 1563
NWS Storm Prediction Center Norman OK
1043 AM CDT Sat Jul 23 2022
Areas affected...portions of southern MN...northern IA and southwest
WI
Concerning...Severe Thunderstorm Watch 489...
Valid 231543Z - 231715Z
The severe weather threat for Severe Thunderstorm Watch 489
continues.
SUMMARY...Damaging gusts and large hail will continue to be possible
across WW 489. The severe threat will develop south and east of WW
489 over the next couple of hours and a new downstream watch is
likely.
DISCUSSION...Severe thunderstorms are ongoing across
southern/central MN this morning, with strong gusts and hail up to 2
inches noted with this activity over the past 30-60 minutes.
Additional thunderstorms are now developing south of persistent
morning convection across south-central MN, and additional storms
are expected to increase into northern IA over the next 1-2 hours.
This activity is developing along a quasi-stationary/warm front
extending across southern MN into southern WI. A very moist airmass
with 70s dewpoints and steep midlevel lapse rates will maintain
strong instability gradient along the surface boundary. The KFSD VWP
is sampling a westerly 40-50 kt jet around 1-2 km, while the KABR
VWP is sampling 45-60 kt westerly flow around 4-6 km. This is
resulting in elongated hodographs above modestly curved low-levels.
This favorable instability/shear parameter space will continue to
foster organized supercells developing into one or more bowing
clusters with east/southeast extent through the afternoon. Damaging
gusts and hail will be the main concern with initial semi-discrete
supercells in the short term. With time, as convection develops
upscale, the damaging wind threat should increase downstream from WW
489. Enhanced low-level shear within the frontal zone and favorably
curved low-level hodographs will support mesovortex formation as
well, and a couple or tornadoes also may accompany this activity as
low-level instability increases this afternoon. A downstream watch
will likely be needed within the next hour or so across parts of
southeast MN, northern IA and southwest WI.
..Leitman.. 07/23/2022
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...DVN...ARX...MPX...DMX...FSD...
LAT...LON 45039495 45089406 44989314 44889279 44649146 44329048
43968992 43598981 43328982 42909002 42679037 42489093
42429139 42489223 42619363 42879517 43229559 43579565
44869535 45039495
