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ACUS11 KWNS 111537
SPC MCD 111536

Mesoscale Discussion 0017
NWS Storm Prediction Center Norman OK
0936 AM CST Thu Jan 11 2018

Areas affected...Portions of northern Missouri and southern/eastern

Concerning...Winter mixed precipitation

Valid 111536Z - 111930Z

SUMMARY...Freezing rain, mixing with and changing to sleet and/or
snow, will continue spreading northeast through mid-day across
northern Missouri and eastern Iowa. Pockets of freezing rain rates
up to 0.05 inches per hour will be possible.

DISCUSSION...A compact shortwave impulse, with a fairly impressive
water-vapor presentation, is lifting northeast across the mid
Missouri Valley this morning. In association with this impulse,
isentropic ascent ahead of it, as well as subtle convective
enhancement within a mid-level dry slot, is aiding mixed
precipitation from northeast Kansas to southern Iowa currently. As a
cold front continues to accelerate east, rapidly falling low-level
temperatures will continue to aid a transition from rain to freezing
rain and sleet across the region.

Larger depressions in KDMX CC data (suggesting incomplete melting
aloft with larger hydrometeors) likely signal that the thermal
profile is favoring ice pellets along the I-35 corridor in far
southern Iowa. Farther east (directly behind the front), more
complete melting aloft and warmer low-level temperatures are
favoring a narrow band of light/moderate freezing rain. As the
shortwave trough lifts northeast, this precipitation will also
advance northeast, and rain should then quickly switch to freezing
rain, eventually mixing with/changing to sleet, over eastern Iowa.
Minor convective enhancement may yield brief heavier precipitation,
but microphysical processes and cooling low levels will probably
favor sleet/wet snow in any such elements.

..Picca.. 01/11/2018

...Please see for graphic product...


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