Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 260015
SPC MCD 260014

Mesoscale Discussion 0554
NWS Storm Prediction Center Norman OK
0714 PM CDT Tue Apr 25 2017

Areas affected...Portions of central/northeastern
Oklahoma...southeastern Kansas...and far western Missouri

Concerning...Severe Thunderstorm Watch 159...

Valid 260014Z - 260145Z

The severe weather threat for Severe Thunderstorm Watch 159

SUMMARY...Severe thunderstorms will continue to develop across
western portions of Watch 159 this evening, with activity gradually
spreading east. Large hail and damaging winds will be the primary
threats, but a tornado or two will also be possible across primarily
southeastern portions of the watch.

DISCUSSION...More vigorous convection has developed this evening
from Chautauqua Co, KS south/southwestward to northern portions of
the OKC Metro, in response to low-level convergence along a cold
front. Despite considerable residual dry air near the LFC (noted in
the 00Z OUN sounding), low-level ascent has been strong enough to
sustain a few strong/severe thunderstorms. In conjunction with
MLCAPE values around 1500-2500 J/kg, ample effective shear (noted in
KTLX VWP data) will continue to support mid-level updraft rotation,
enhancing hail growth as these cells spread northeast.

In addition to these storms, cells are expected to develop farther
south along/west of the boundary. Visible satellite and radar data
depict mid-level precipitation to the west/southwest of OKC,
suggesting improved large-scale ascent associated with an
approaching impulse. This ascent will further reduce convective
inhibition across southern portions of the watch this evening. In
turn, sustained surface-based updrafts are expected to develop over
the next hour or so. As these cells encounter richer moisture to the
east (e.g., surface dew points in the mid 60s), they will likely
intensify, with an attendant threat for large hail and damaging
winds. The damaging wind threat may be bolstered if cells congeal
into small bowing segments that propagate into the instability axis
over eastern Oklahoma. Additionally, as low-level moisture continues
to stream north, a strengthening low-level jet (and resultant uptick
in low-level shear) may support a tornado or two across
southern/southeastern portions of the watch over the next several

..Picca.. 04/26/2017

...Please see for graphic product...


LAT...LON   35119810 36509718 37849630 38119525 37979442 36599431
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