Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 212015
SWOMCD
SPC MCD 212015
OHZ000-KYZ000-INZ000-212115-

Mesoscale Discussion 0482
NWS Storm Prediction Center Norman OK
0315 PM CDT Mon May 21 2018

Areas affected...Parts of the mid Ohio Valley

Concerning...Severe potential...Watch possible

Valid 212015Z - 212115Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorms will continue to develop across
southern/central Indiana this afternoon, before moving into western
Ohio this evening. A few could become severe, with a primary threat
of damaging winds. Trends will be monitored for possible watch
issuance.

DISCUSSION...Aided by broad/modest forcing for ascent along the
southeastern fringe of stronger southwesterly mid/upper flow, a
corridor of more vigorous convection has organized from western
Kentucky to southern Indiana late this afternoon. These cells appear
to be focused by differential heating on the edge of a mid/upper
cloud canopy associated with a warm-advection corridor ahead of the
primary cyclone. Regardless, cells over Kentucky are likely too far
south for sufficient organization (owing to weaker flow aloft) to
pose a sustained severe threat. Visible satellite data are
consistent with this conclusion, in that they show rather circular
anvil evolution, which would suggest weak mid/upper storm-relative
flow.

Farther north, although mixed-layer buoyancy is not as robust, weak
southerly warm/moist advection and adequate insolation are yielding
upwards of 500-1000 J/kg at present. Mid-level flow is slightly
stronger than points farther south as well, and recent KIND VWP data
sampled bulk 0-6km shear of 30-35 kt. Therefore, the strongest cells
may organize into occasional multicell or weak supercell structures
(especially as they reach greater boundary-layer moisture near the
IN/OH border) through early evening. Thereafter, an evolution into
localized bowing segments is possible, given relatively straight
hodographs. Such evolution would promote a few damaging gusts as the
primary threat, and convective trends will be monitored for possible
watch issuance.

..Picca/Weiss.. 05/21/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CLE...ILN...LMK...IWX...IND...PAH...

LAT...LON   38338762 39218703 40408564 40948467 40988386 40818339
            40528325 40138320 39518344 38878438 38328525 37938645
            37848726 37918771 38338762




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