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ACUS11 KWNS 201022
SPC MCD 201022

Mesoscale Discussion 0156
NWS Storm Prediction Center Norman OK
0522 AM CDT Tue Mar 20 2018

Areas affected...Southwest to central OH and north-central KY

Concerning...Freezing rain

Valid 201022Z - 201515Z

SUMMARY...Freezing rain producing 0.05-0.10 inch per 3-hour will
continue to develop prior to daybreak across southwest into central
Ohio and adjacent parts of north-central KY, and persist through
late morning (10 AM to 12 PM EDT). Some locations may experience
sleet as the initial precipitation type before becoming mainly
freezing rain.

DISCUSSION...Satellite imagery showed a west-southwest to
east-northeast oriented deformation zone extending from southwest OH
and adjacent north-central KY across central to eastern OH,
generally north of the track of a midlevel cyclone shifting east
from KY this morning.  Forcing for ascent within this zone and
low-level warm advection per objective analyses will continue to
support the development of precipitation across the middle to upper
Ohio Valley.  Trends in surface observations showed light to
moderate precipitation had developed in central into southwest OH to
north-central KY, as the antecedent dry lower troposphere per 00Z
ILN sounding has moistened overnight.  Meanwhile, surface wet-bulb
temperatures extending along and north of a line from Boone County
KY to Muskingum County OH were below freezing.  Northeasterly
surface winds across OH will maintain cooler temperatures this
morning into the discussion area, while some locations will undergo
further evaporative-cooling processes with surface temperatures
remaining below 32 F.

Although Monday`s high temperatures were around 60 F across this
region, objects such as vehicles and metal, and elevated surfaces
including trees that have attained a temperature at or below 32 F
could accumulate freezing rain.  The last several runs of the HRRR
and 00Z HREF precipitation guidance each suggest the freezing rain
should continue to develop and persist until 14-16Z. This timing
appears reasonable, as the forcing for ascent will shift east of the
discussion area with the weakening and departing midlevel cyclone.

..Peters.. 03/20/2018

...Please see for graphic product...


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