Storm Prediction Center Mesoscale Discussion 2266

   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 

   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 www.spc.noaa.gov for graphic product...

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

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