Mesoscale Discussion 1279
NWS Storm Prediction Center Norman OK
0508 PM CDT Mon Jul 10 2017
Areas affected...Portions of eastern WY...far southeastern
MT...southwestern ND...and western SD/NE
Concerning...Severe potential...Watch unlikely
Valid 102208Z - 110015Z
Probability of Watch Issuance...20 percent
SUMMARY...An isolated strong/damaging wind and large hail threat
should persist through this evening. Watch issuance is unlikely.
DISCUSSION...Scattered thunderstorms have developed this afternoon
across parts of the northern High Plains along a lee surface trough.
A minor perturbation noted in water vapor satellite imagery across
central/eastern WY may also be aiding convective development.
Although mid-level winds are not overly strong (around 25-30 kt at
500 mb), they do veer veer from southeasterly at the surface to
westerly at mid levels. Resultant 35-40 kt of effective bulk shear
will aid updraft organization and support some supercell structures
with an associated large hail threat. The boundary layer along and
east of the surface trough has become very well mixed late this
afternoon, and temperature-dewpoint spreads around 30-40 F are now
common outside of higher terrain and ongoing convection. Downdrafts
may accelerate and reach severe levels at the surface owing to this
well mixed boundary layer and related strong DCAPE. Current
expectations are for the overall severe threat to remain isolated
through this evening, and a narrow north-south corridor of weak
instability along the surface trough should tend to limit the
eastward extent of this threat. Therefore, watch issuance appears
unlikely.
..Gleason/Thompson.. 07/10/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BIS...LBF...UNR...CYS...BYZ...GGW...
LAT...LON 43710492 45660462 46760447 47310374 47390305 46900235
45270197 43300187 41070205 41030324 41060472 41390503
43710492
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