Subj : MESO: Mesoscale Discussion 1998
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Dec 09 2022 05:37:23

ACUS11 KWNS 090537
SWOMCD
SPC MCD 090536=20
IAZ000-MNZ000-SDZ000-090930-

Mesoscale Discussion 1998
NWS Storm Prediction Center Norman OK
1136 PM CST Thu Dec 08 2022

Areas affected...northern Iowa...adjacent southern Minnesota and
southeastern South Dakota

Concerning...Heavy snow=20

Valid 090536Z - 090930Z

SUMMARY...Heavy snow rates on the order of 1-2 inches per hour, with
occasional heavier convective bursts accompanied by lightning, may
continue to develop through 1-4 AM CST.

DISCUSSION...Strong differential cyclonic vorticity advection
associated with a short wave impulse migrating east-northeastward
across the middle Missouri Valley is beginning to contribute to
intensifying mid-level lift and cooling in a corridor across
northern Iowa, roughly from north-northeast of Sioux City toward the
Mason City area.  This is supporting increasing precipitation and
embedded convection, in the wake of an initial northeastward
advancing convective band.  Although temperatures in a layer around
850 mb are still near and above freezing across northwestern into
north central Iowa, models suggest that this will change with
further dynamic and latent cooling during the next few hours.=20=20

Through 07-10Z, Rapid Refresh forecast soundings indicate that lift
will become maximized within the 700-500 mb layer, where
temperatures will become favorably cold for large dendritic ice
crystal growth.  This may contribute to a consolidating band of
heavy snow rates on the order of 1-2 inches per hour, in the
presence of precipitable water on the order of .6-.7 inches.  With
steepening mid-level lapse rates also contributing to sufficient
destabilization for weak CAPE (and convection capable of producing
lightning), even higher rates are possible in occasional convective
bursts.

...Kerr.. 12/09/2022

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!5l6TklQvkkwbv5oLW5HdK6XcRgS_-C-QWdwfG9BWMgCu-36-hsgMbbZCRcCzl9LCh8vk-YOsV=
evr7LSP5JpH7MkxPeY$  for graphic product...

ATTN...WFO...ARX...MPX...DMX...FSD...

LAT...LON   42819652 43859626 43429235 42539305 42449382 42819652=20


=3D =3D =3D
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