Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 212336
SPC MCD 212336

Mesoscale Discussion 1546
NWS Storm Prediction Center Norman OK
0636 PM CDT Mon Aug 21 2017

Areas affected...Portions of northeastern KS into northern/central

Concerning...Severe potential...Watch possible

Valid 212336Z - 220130Z

Probability of Watch Issuance...40 percent

SUMMARY...An isolated severe threat, with large hail, damaging
winds, and perhaps a tornado or two, may be realized over the next
several hours. While a watch is not immediately imminent, convective
trends will be closely monitored for signs of increasing severe
potential which may increase watch issuance probabilities.

DISCUSSION...23Z surface observations and visible satellite imagery
show an outflow boundary from earlier convection draped generally
east-west across northeastern KS into parts of northern/central MO.
The airmass along and south of this boundary has become strongly
unstable owing to strong diurnal heating and a very moist low-level
airmass, with 23Z RAP Mesoanalysis depicting generally 2000-3000
J/kg of MLCAPE across this region. Although stronger mid-level winds
remain mostly displaced to the north of the surface boundary, there
is enough veering/strengthening of the wind field through 6-7 km AGL
to support 30 to locally 40 kt of effective bulk shear. This should
be sufficient to support multicell to marginal supercell structures,
with an isolated large hail/damaging wind threat. A tornado or two
may also not be out of the question with any supercell given locally
backed 0-1 km AGL winds near the outflow boundary enhancing
effective SRH.

Convective coverage has recently increased in northeastern KS,
probably related to large-scale ascent associated with a weak
impulse moving eastward across central NE/KS. There may be some
potential for one or more small clusters of surface-based
thunderstorms to congeal along the surface boundary and move
east-southeastward this evening as a southwesterly low-level jet
strengthens across this region. While not immediately likely, radar
trends will closely monitored for possible watch issuance.

..Gleason/Goss.. 08/21/2017

...Please see for graphic product...


LAT...LON   39949634 39889480 39289188 38249193 38229340 38289517
            38539634 39219691 39949634 is the U.S. government's official web portal to all federal, state and local government web resources and services.