|Mesoscale Discussion 682|
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Mesoscale Discussion 0682
NWS Storm Prediction Center Norman OK
0146 PM CDT Sat Jun 09 2018
Areas affected...Far southern MN...North-central/northeast IA
Concerning...Severe potential...Tornado Watch likely
Valid 091846Z - 092045Z
Probability of Watch Issuance...95 percent
SUMMARY...Thunderstorm coverage will likely increase over the next
hour or two. Supercells capable of all hazards are possible and a
watch will be needed.
DISCUSSION...Remnant MCV from the overnight MCS that moved across NE
is currently centered over south-central MN. Attendant surface low
is displaced just east of the mid-level MCV with an effective cold
front/surface trough extending southwestward to south of OMA.
Additionally, a warm frontal zone extends eastward near the MN/IA
and then southeastward through southwest WI.
Discrete storm across Mitchell and Howard counties in northeast IA
has recently shown deviant right motion and persistent storm
strength, suggesting a well-organized updraft. Mesoanalysis
estimates convective inhibition remains over the current downstream
airmass. However, recent RAP soundings modified for current
conditions suggest only minor amounts of convective inhibition
remains in place. Continued filtered heating in the presence of this
very moist and steep lapse rate environment will result in further
destabilization and a moderate to strongly unstable airmass.
As surface convergence continues, thunderstorm coverage is expected
to increase. Favorable vertical shear profiles featuring
southeasterly surface winds beneath moderate westerly/southwesterly
flow aloft will support updraft organization and the development of
supercells capable of large hail and damaging wind gusts.
Additionally, backed surface winds will result in favorable
low-level shear and the potential for a few tornadoes. A watch will
be needed to cover these hazards.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 43209418 43789400 43859237 43379157 42559201 42609306
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