MD 2188 CONCERNING SEVERE THUNDERSTORM WATCH 691… FOR IOWA
Mesoscale Discussion 2188
NWS Storm Prediction Center Norman OK
0623 PM CDT Sat Sep 23 2023
Areas affected…Iowa
Concerning…Severe Thunderstorm Watch 691…
Valid 232323Z – 240130Z
The severe weather threat for Severe Thunderstorm Watch 691
continues.
SUMMARY…The environment across central to northern Iowa remains
conditionally favorable for organized convection; however, it is
unclear how much re-development will occur in the coming hours.
DISCUSSION…Latest surface analysis shows a well-established cold
pool lingering over central to northern IA. Although mid-level
drying is overspreading the region, a stout low-level stratus deck
is muting late-day diurnal heating with temperatures largely
remaining in the 70s (and even falling in a few locations). Latest
RAP mesoanalysis estimates and forecast soundings show diminishing
MLCAPE with meager buoyancy profiles due to the stable low-level
conditions. Despite the thermodynamic challenges, strong low aloft
is maintaining elongated hodographs with effective bulk shear values
on the order of 40-45 knots. Overall, this environment remains
conditionally supportive for organized (likely elevated) convection
given residual MUCAPE on the order of 1000 J/kg. But confidence in
redevelopment is low: GOES IR and low-level water-vapor imagery
depicts slow deepening of convective cells within a weak warm
advection regime over the warm front/cold pool, and convective
development along the cold front in eastern NE is similarly
sluggish. Areas across northern to northeast IA may see the best
near-term severe threat where ongoing convection is showing some
signs of gradual intensification, but the severe threat becomes less
clear with southwestward extent.
..Moore.. 09/23/2023
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…ARX…MPX…DMX…FSD…OAX…
LAT…LON 41479476 41619521 41959542 43229547 43549537 43669500
43709321 43529277 42989242 42259233 41749245 41549269
41459308 41479476
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