...January 31, 2008 Winter Storm Summary...


A strong winter storm tracked across portions of the central United States this week, bringing widespread heavy snow to southern locations of the Kansas City/Pleasant Hill forecast area.  This storm initially entered the western portions of the United States on Tuesday bringing widespread precipitation to the Pacific Northwest.  By Wednesday this storm system was expected to dive into the Rocky Mountains and rapidly spin into a major winter storm across portions of Kansas and Missouri.  However, instead of trending further north as was anticipated, this upper level storm system took a slightly southern track providing climatologically heavy snow to portions of northern Oklahoma, south central Kansas, and southern Missouri.  As  you can see on the storm track map below, this storm continued to race northeastward after it made its northern swing and deepened, bringing snows in excess of 8 inches to portions of eastern Missouri, Illinois, Indiana, and Michigan. 


Upper Level Storm Track
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Closer to home, while the heavy snows stayed just to the south of the area, some portions of central Missouri did receive significant snow accumulations. Just after noontime Thursday a strong band of snow developed across portions of the area.  Underneath this very narrow snow band, heavy snow quickly saturated the environment.  Once the atmosphere was primed for heavy snow, visibilities underneath this snow band were reduced under a quarter mile at times.  In addition, heavy snow caused the closure of Highway 13 near the city of Warrensburg with many slide-offs reported on Highway 50.   Locations from  Clinton, to Urich, Warrensburg, Sweet Springs, Marshall and Moberly received at least 4 inches of snow with as much as 6-7 inches of snow reported near the city of Warrensburg.  Found below are images depicting storm total accumulations from the area as well as a satellite image depicting where this band of snow had fallen.

Snowfall Accumulations 
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This small band of snow was created by a process called "Frontogenesis".  Frontogenesis is a very important and common atmospheric process that refers to a change in the magnitude and orientation of a thermal (temperature) gradient at a level or in a layer due to horizontal changes in the total wind (i.e., due to patterns of convergence and divergence). This change (i.e., frontogenetical forcing) alters thermal wind balance, which forces a vertical motion response in the atmosphere which can result in mesoscale bands of enhanced precipitation. 

In our case, warm, moist air continued to stream in from the south while at the same time colder air was beginning to filter in from the northwest.  These two different types of air masses came together across portions of central Missouri, and as they did so, forced air upwards and created the very intense, very narrow snow band.  This band slowly crawled across the southeastern portions of the Pleasant Hill forecast area as the upper level low moved eastward, producing snowfall rates greater than 2 inches/hour and creating whiteout conditions over portions of the area.  A visual aid to understand this complex process as well as a radar image at the height of the snow event can be seen below. Notice the radar reflectivity values greater than 39 dBZ indicative of the heaviest snowfall rates.

Synoptic Setup for Creation of Snow Band
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Here are a summary of a few of the Local Storm Reports from across the area:

...CITY LOCATION...     ....MAGNITUDE....    

7 NE WARRENSBURG, MO       6.0 INCH
WARRENSBURG,MO 5.0 INCH
SWEET SPRINGS, MO 4.5 INCH
MARSHALL, MO 4.5 INCH 
BLAIRSTOWN, MO 4.0 INCH
1 SSE MOBERLY, MO 4.0 INCH
SALISBURY, MO 3.0 INCH
SEDALIA, MO 3.0 INCH
4 E NEW FRANKLIN, MO 3.0 INCH
BOONVILLE, MO 3.0 INCH
MILAN, MO 2.0 INCH
UNIONVILLE, MO 1.9 INCH
4 SW CENTERVILLE,KS 1.8 INCH
LONG BRANCH STATE PARK 1.5 INCH
4 W BUTLER, MO 1.3 INCH
BROOKFIELD, MO 1.0 INCH
KIRKSVILLE, MO 1.0 INCH






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