A potent late winter storm is taking shape for the local area today. A strong area of low pressure is currently located over N. Central OK and S. Central KS and is expected to take a classic snow storm track for the local area. This track is across southern MO and northern AR, south of the I-44 corridor and northeast south of St. Louis.
Copious amounts of gulf moisture are being drawn into the system which will potentially lead to significant snow accumulations over the local area. Here is a look at this mornings water vapor imagery, current surface analysis and short term forecast (18Z Sunday) analysis:
One fly in the ointment is the time of year the storm is occurring in. Late winter storms have the tendency to have decent warm air advection occur ahead of the storm, before colder Canadian air can be wrapped into it on the back side. This warm air advection brings in warmer air a few thousand feet above the surface (850mb level) and melts the snow crystals as it falls…the precip falls as rain and with surface temps below freezing it freezes on contact. We are seeing this in areas from KC south and east along I-70 as freezing rain has been the dominant precipitation type. Some locales from KC south and east could see .25 to .50 inches of ice accretion. It appears the warm air advection will not move much further north during this storm, but it is something to watch as the storm progresses. We should be all snow through the duration of the event! Here is a look at the NAM 850mb temps for this afternoon:
Snowfall will continue through the day today, possibly heavy at times, with total snowfall accumulations in the 5” to 8” range with locally higher amounts. The higher amounts will occur within convective bands of the snow. The convective banding is hard to determine with prognostic models and will need to be nowcasted based on radar trends. Snow ratios appear to be in the 10:1 category where 1” of liquid precip equals 10” of snow. This will be a heavy, wet snow and any blowing and drifting will be minimized, but some may occur. Here is a look at the HPC snowfall / ice accumulation probability composite maps:
Cold Canadian air will be brought in behind the system to usher in the new work week. Highs in the local are are forecasted to be in the mid 20's with gusty northwest winds with wind chills in the single digits. Here are the forecasted high temperatures for Monday:
The National Weather Service has continued the Winter Storm Warning through midnight tonight for snow. Here is the map of the current watches and warnings valid for Sunday afternoon:
~ CS ~
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