ACUS11 KWNS 140542
SWOMCD
SPC MCD 140541=20
IAZ000-MOZ000-140945-

Mesoscale Discussion 2266
NWS Storm Prediction Center Norman OK
1141 PM CST Fri Dec 13 2024

Areas affected...parts of north central Missouri into southeastern
Iowa

Concerning...Freezing rain=20

Valid 140541Z - 140945Z

SUMMARY...Rain and embedded thunderstorms forming across western
Missouri during the next few hours appear likely to continue
developing northeastward and eastward overnight, supporting moderate
freezing rain with potential for appreciable icing north-northwest
of Kirksville MO through the Ottumwa IA vicinity by 2-4 AM CST.

DISCUSSION...Downstream of a notable short wave trough progressing
across the central Great Plains, moisture return within a developing
area of large-scale ascent, rooted within lower/mid-tropospheric
warm advection, is contributing to an ongoing gradual increase in
precipitation northeast of the middle/lower Missouri Valley into
eastern Oklahoma. From east of the Sioux Falls area into
southeastern Iowa, this appears focused along a 700 mb baroclinic
zone which is forecast to slowly develop northward toward the upper
Mississippi Valley overnight. Southward across western Missouri
into eastern Oklahoma, this appears generally aligned with better
lower-level moisture return along one branch of a strong low-level
jet (40-50 kt around 850 mb), which is forecast to slowly shift
eastward toward the middle Mississippi Valley through 08-10Z.

Models indicate that substantive further warming and moistening
along the low-level jet will contribute to sufficient steepening of
mid-level lapse rates to support weak CAPE above a slowly modifying,
but still cold and stable near surface environment across much of
Missouri into Iowa. Based on the latest NAM/Rapid Refresh, among
other output, it appears that this may be accompanied by a
blossoming band of convection and perhaps embedded weak thunderstorm
activity north of Springfield MO through and north of Kirksville by
07-08Z, before continuing to spread northeastward and eastward.

North/northwest of Kirksville, northeastward across the Ottumwa
vicinity of southeastern Iowa, forecast soundings indicate that a
pronounced warm nose will continue to develop above sub-freezing
boundary-layer air, which may be maintained (aided initially by
evaporative cooling of precipitation) as far south as portions of
north central Missouri at least into the 10-11Z time frame. This
may allow for appreciable ice accrual as developing convection
supports a sustained period of moderate freezing rain, including
rates occasionally on the order of 1/4+ inch per hour.

..Kerr.. 12/14/2024

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7gXGV_ns6bQGZvny5fabjuC9DeP9cNlPpGgvPJLYrjaQqfnafCfnGYrtqh2UWlXRI2nSdyiXW= c50_TS-y3XAliC1Yew$ for graphic product...

ATTN...WFO...LSX...DVN...DMX...EAX...

LAT...LON 40239343 41359317 41749235 41399167 40719191 40289234
40069292 40239343=20


=3D =3D =3D
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