SPC MD 1901

MD 1901 CONCERNING HEAVY SNOW FOR NORTHEAST NEB…NORTHWEST AND NORTH CENTRAL IA…EXTREME SOUTHEAST MN

Mesoscale Discussion 1901
NWS Storm Prediction Center Norman OK
0348 AM CST Fri Dec 23 2016

Areas affected...Northeast NEB...northwest and north central
IA...extreme southeast MN

Concerning...Heavy snow 

Valid 230948Z - 231545Z

SUMMARY...A band of snowfall will develop and spread
east-northeastward this morning from eastern NEB across northern IA,
potentially reaching south-central/southeastern MN by midday. 
Snowfall rates should increase to near 1 inch per hour within this
band.

DISCUSSION...A midlevel trough will eject east-northeastward from
the central High Plains this morning to the Middle MS Valley by this
afternoon.  Focused ascent in the left exit region of the mid-upper
jet, combined with low-level warm advection, will support a band of
precipitation that is developing over southern NEB early this
morning and will spread east-northeastward through midday.  Though
surface observations show temperatures a few degrees F above
freezing from NEB into IA, web-bulb temperatures are near 32 F.  As
top-down saturation occurs and precipitation rates increase,
wet-bulb cooling should allow wet snow to become the dominant
precipitation type this morning.  Embedded midlevel convection could
boost snowfall rates to near 1 inch per hour through the morning,
and cold ground from the recent arctic intrusion should still allow
snow accumulations even with surface temperatures slightly above 32
F.

..Thompson.. 12/23/2016

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

ATTN...WFO...ARX...MPX...DMX...FSD...OAX...GID...

LAT...LON   41999374 40709741 40739853 41049873 41989729 43139535
            43789394 43939249 43659187 42989189 41999374 

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