SPC MD 1579


MD 1579 Image

Mesoscale Discussion 1579
NWS Storm Prediction Center Norman OK
0702 PM CDT Sat Oct 13 2018

Areas affected...Portions of southeastern WY...the western NE
Panhandle...and far northern CO

Concerning...Heavy snow 

Valid 140002Z - 140600Z

SUMMARY...Heavy snow, with rates in excess of 1 inch per hour, will
likely develop through 06Z (midnight CDT).

DISCUSSION...A strong cold front over far southern WY, northeastern
CO, and NE will continue moving southward tonight. Large-scale
forcing for ascent will increase over southeastern WY, northern CO,
and the western NE Panhandle as the right entrance region of a
90-100+ kt upper-level jet overspreads this region. Low-level cold
air advection will rapidly cool the surface to 700 mb layer, and a
rapid transition from rain to snow will occur behind the front. This
transition has already been noted at Torrington, WY, where the
surface air temperature dropped 6 degrees in one hour. Correlation
coefficient dual-pol data from the KCYS radar shows the melting
layer less than 500 ft AGL in the vicinity of Cheyenne as of 00Z,
and snowfall will likely begin within the next hour or two across
much of southeastern WY and vicinity.

A saturated profile is forecast through the dendritic growth zone,
which will support efficient snowfall production. Heavy snow will
likely develop in a narrow band along and just behind the surface
front in southeastern WY, the western NE Panhandle, and parts of
northern CO, with rates of 1 to locally 2 inches per hour becoming
common for at least a few hours. Most recent high-resolution
guidance is in general agreement with this scenario.  Low-level
post-frontal northeasterly winds may aide in upslope enhancement to
snowfall rates in the lee of the Laramie Mountains in southeastern
WY and the Front Range in northern CO. Eventually, the continued
southward progression of the surface front and northeastward
displacement of large-scale ascent will lead to a gradual lessening
of snowfall rates overnight across this region, mainly after 06Z
(midnight MDT).

..Gleason.. 10/14/2018

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


LAT...LON   41810540 42070465 42190400 42190344 42000307 41450300
            40940332 40690404 40610469 40590523 41110544 41470547

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