Mesoscale Discussion 1063
NWS Storm Prediction Center Norman OK
0656 PM CDT Fri Jun 16 2017
Areas affected...Portions of the upper Mississippi Valley
Concerning...Severe Thunderstorm Watch 340...
Valid 162356Z - 170100Z
The severe weather threat for Severe Thunderstorm Watch 340
SUMMARY...A few strong/severe storms may advance outside the
northern bounds of Watch 340 this evening. Currently, downstream
watch issuance does not appear imminent, but convective trends will
be monitored for an uptick in intensity near southern/eastern
portions of the watch this evening.
DISCUSSION...A pair of left-moving cells are advancing towards the
northern edge of Watch 340 this evening. Forecast sounding and
regional VWP data indicate relatively straight mid-level hodographs,
suggesting some maintenance of these cells and a persisting threat
of strong/gusty winds and near-severe hail. However, over time,
decreasing buoyancy with northward extent should result in a
downward intensity trend. Farther southwest, a large precipitation
shield has overspread much of northern Iowa, casting some doubt upon
convective intensification/re-development here. Nonetheless, a warm
and moist boundary layer exists to the south of a trailing outflow
boundary stretching across northern Iowa. Within this corridor,
high-res guidance indicates strong/severe convection may develop
later this evening, with an attendant threat of damaging winds and
large hail. While new watch issuance does not appear imminent, one
could be necessary later this evening.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 42479557 42949471 43149294 43249281 43599192 44349148
44709117 44739026 44418946 43018945 41988940 41649053
41869321 41879488 42209563 42479557