Mesoscale Discussion 1281
NWS Storm Prediction Center Norman OK
0140 PM CDT Wed Jul 14 2021
Areas affected...much of Iowa...far eastern Nebraska
Concerning...Severe potential...Watch likely=20
Valid 141840Z - 142045Z
Probability of Watch Issuance...95 percent
SUMMARY...Storms are expected to develop by 21Z from the
Nebraska/Iowa border across northwest Iowa, with supercell potential
spreading east/northeast across Iowa and perhaps extreme southern
Minnesota this evening. A few tornadoes will be possible, along with
damaging gusts and hail.
DISCUSSION...A diffuse warm front currently extends from northeast
NE across central IA, with outflow-cooled air from northeast IA into
southwest WI. The outflow farther west across north-central IA has
modified somewhat with dewpoints holding near 70 F along with backed
Southerly winds are currently gusting to over 20 kt across the MO
Valley, with area of heating across western IA and NE. Continued destabilization is therefore likely across these areas, and this is
also where surface convergence is focused along the low pressure
trough. Farther to the northwest, a secondary from extends from
southwest MN into northern NE, and low-topped convection has been
noted over far northwest IA.
Lift will continue to consolidate over western IA over the next few
hours, where instability and shear parameters will also maximize. A
downstream zone of supercell potential will exist in association
with the warm front/outflow with enhanced low-level shear and low
LCLs. A few tornadoes will be possible, as well as large hail.
Damaging wind potential may increase should more of a linear storm
mode materialize a few hours after initiation.
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