Mesoscale Discussion 1736
NWS Storm Prediction Center Norman OK
0254 PM CDT Wed Aug 14 2019
Areas affected...Portions of southeastern WY...western NE...and
Concerning...Severe potential...Watch possible
Valid 141954Z - 142200Z
Probability of Watch Issuance...60 percent
SUMMARY...A gradual increase in an isolated severe risk should occur
this afternoon. Large hail, damaging winds, and perhaps a couple
tornadoes will all be possible. Watch issuance may be needed by 22Z
(4 PM MDT).
DISCUSSION...Cumulus is slowly building across the Laramie Mountains
of southeastern WY and the Front Range in northern/central CO.
Current expectations are for convective inhibition to gradually
erode through the remainder of the afternoon across eastern CO,
southeastern WY, and parts of western NE. 19Z surface analysis shows
a weak surface low over southeastern WY, with a front extending
southeastward from this low across the central High Plains. Surface
dewpoints across this region are several degrees lower than
yesterday, generally in the mid to upper 50s, but up to the lower
60s along and just north of the surface boundary. Still, steep
mid-level lapse rates emanating from the Rockies have overspread
this area, which coupled with strong diurnal heating will likely
support 1500-2500 J/kg of MLCAPE through peak heating.
With modestly enhanced northwesterly flow persisting aloft,
large-scale forcing for ascent will remain nebulous across the
central High Plains this afternoon. This lends some uncertainty
regarding overall storm coverage. Isolated storms should eventually
form over the higher terrain and slowly move east-southeastward.
Additional convective development may occur with weak low-level
convergence along the surface boundary extending into parts of
western NE. Rather weak low-level flow is expected to persist
through the early evening, but northwesterly flow does increase
above 3 km, which is promoting around 35-45 kt of effective bulk
shear. The presence of steep mid-level lapse rates, moderate
instability, and enough shear to support supercells suggests
isolated large hail should be the primary threat initially. Very
large hail, potentially in excess of 2 inches in diameter, could
occur with the strongest storms. A couple of tornadoes may also be
possible along and immediately to the cool side of the front where
low-level flow is backed to southeasterly, locally augmenting
effective SRH. Depending on observational trends, a watch may be
needed for some part of this area by 22Z.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 41040470 41460487 42320535 42540521 42660469 42640404
42080273 41170177 40200142 39510138 38960163 38490213
38350319 38420426 38710465 41040470