SPC MD 2188

SPC MD 2188


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

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…


LAT…LON 41479476 41619521 41959542 43229547 43549537 43669500
43709321 43529277 42989242 42259233 41749245 41549269
41459308 41479476

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