Mesoscale Discussion 1001
NWS Storm Prediction Center Norman OK
0605 PM CDT Mon Jun 12 2017
Areas affected...Portions of eastern WY...southwestern SD...western
NE...and northeastern CO
Concerning...Tornado Watch 317...
Valid 122305Z - 130030Z
The severe weather threat for Tornado Watch 317 continues.
SUMMARY...All severe hazards, including strong tornadoes, large to
giant hail, and damaging winds will continue with multiple
supercells across Particularly Dangerous Situation Tornado Watch
317. A downstream watch into western/central NE and southern SD will
be needed within the next several hours.
DISCUSSION...At least 3 supercells are ongoing as of 23Z across far
southeastern WY/northeastern CO into far western NE. With a very
favorable thermodynamic and kinematic environment characterized by
MLCAPE of 2000-3500 J/kg and effective bulk shear of 50-60 kt, these
supercells have produced over a dozen reports of significant hail (2
inch in diameter or greater) over the past few hours, with several
reports of hail greater than 4 inches. At least 2 tornadoes have
also occurred. The airmass downstream of ongoing convection will
easily support continued significant severe hail, along with a risk
for tornadoes and damaging winds through this evening. Strong
tornadoes will continue to be a possibility with any discrete
supercell across far southeastern WY, northeastern CO, and western
NE for the next few hours given a strongly veering and strengthening
wind profile with height. Of note, 0-1 km SRH is around 300 m2/s2
per recent VWP from KCYS, and 0-3 SRH is around 500 m2/s2.
A southerly low-level jet will strengthen to around 40-50 kt across
western/central NE into southern SD this evening/tonight, and all
severe hazards will remain possible into this evening across these
areas. Evolution from discrete supercells into one or more bowing
line segments appears likely to occur at some point later this
evening in tandem with the increasing low-level jet, which would
likely increase the threat for damaging winds with eastward extent.
In addition, large hail and a few tornadoes should continue to be a
threat with any supercell embedded within the line(s). A downstream
watch in western/central NE and southern SD will be needed within
the next several hours.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 40710518 42620583 43380588 43930587 44120395 44060122
43690104 40550104 40500363 40610455 40710518