Subj : MESO: Mesoscale Discussion 2054
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Dec 21 2022 16:33:40

ACUS11 KWNS 211633
SWOMCD
SPC MCD 211633=20
WIZ000-MNZ000-IAZ000-SDZ000-212030-

Mesoscale Discussion 2054
NWS Storm Prediction Center Norman OK
1033 AM CST Wed Dec 21 2022

Areas affected...Southeast South Dakota...far northwest
Iowa...southern Minnesota into far northwest Wisconsin

Concerning...Heavy snow=20

Valid 211633Z - 212030Z

SUMMARY...The potential for heavy snowfall rates between 1-2 inches
per hour is expected to increase through the late morning and early
afternoon from the mid Missouri River Valley to the upper
Mississippi River Valley.

DISCUSSION...Regional radar mosaics from the past 1-3 hours show an
elongated zone of increasing reflectivity values from eastern SD to
southern MN. This is likely in response to strengthening isentropic
ascent in the 925-700 mb layer within a broad warm frontal zone
draped across the region. This mesoscale ascent is augmenting more
broad, synoptic lift ahead of an approaching shortwave trough over
the northern Plains, and is supporting an increase in coverage of
moderate, to at times heavy, snowfall rates per latest surface
observations and regional web cams. Latest guidance suggests that
this trend should continue through at least early afternoon as the
synoptic low continues east/southeast and saturation of the lowest
1-2 km continues. Forecast soundings indicate that much of the
low/mid-level ascent coincides with a ~100 mb deep dendritic growth
zone, which will favor efficient snow production and the potential
for heavy snowfall rates around 1 inch per hour.=20

The current warm advection regime over eastern SD/southern MN will
likely support periods of broken snow bands through the early
afternoon (which appears probable based on latest reflectivity
trends), and this may yield localized higher snowfall rates between
1-2 inches/hour. The approach of the mid-level cold front later this
afternoon may maintain the potential for localized banding via
frontogenetical processes.

...Moore.. 12/21/2022

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!7woIEW352ifqrMvcUK_isLyWjS4LdDWu0fUkpWZNXdtLYC_hZVdNthxBUJgO8BfzCmFR6zP08=
A3e1sXYQ-dRUOVXRiQ$  for graphic product...

ATTN...WFO...DLH...ARX...MPX...DMX...FSD...ABR...

LAT...LON   45649472 45919387 45959300 45809240 45299199 44759199
            44179265 43729372 43059523 42879587 42899669 43129722
            43519746 44169712 44959611 45649472=20


=3D =3D =3D
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