SPC MD 648


MD 0648 Image

Mesoscale Discussion 0648
NWS Storm Prediction Center Norman OK
0114 PM CDT Fri May 17 2019

Areas affected...Parts of northeast Colorado...southeast
Wyoming...southwest Nebraska

Concerning...Severe potential...Watch possible 

Valid 171814Z - 172015Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorm development is expected to increase near the
Cheyenne Ridge vicinity through 1-3 PM MDT.  This will be
accompanied by at least some increase in severe weather potential. 
The need for a watch is not yet certain, but trends are being
monitored for this possibility.

DISCUSSION...Insolation within a relatively moist post-frontal
boundary layer near the Cheyenne Ridge appears to have contributed
to a corridor of weak to modest CAPE of 500-1000 J/kg.  This
destabilization has contributed to the initiation of thunderstorm
activity along the Front Range, to the south-southwest of Cheyenne,
aided by orography and forcing for ascent associated with at least
one initial short wave perturbation pivoting northeastward into the
high Plains.

In general, the leading edge of stronger mid-level height falls and
lower/mid-tropospheric cooling are forecast to continue gradually
spreading eastward across the high Plains through mid to late
afternoon.  As this occurs, vigorous thunderstorm activity is
expected to spread off the higher terrain, along the Cheyenne Ridge.
Some upscale growth is possible, preceded by additional discrete
thunderstorm development.

Given pronounced veering of wind fields with height beneath 50+ kt
southwesterly 500 mb flow, vertical shear is strong and supportive
of organizing convection, including supercells.  This may be
accompanied by primarily a risk for severe hail, but a relatively
short-lived tornado or two is possible, along with perhaps some
increase in potential for strong surface gusts by late afternoon.

..Kerr/Hart.. 05/17/2019

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


LAT...LON   42070505 41960384 41330259 41020255 40540287 40370410
            40240520 40740528 42070505 

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