SPC AC 231945
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 PM CST Thu Feb 23 2017
Valid 232000Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER NORTHEAST
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
KANSAS THROUGH SOUTHEAST NEBRASKA...NORTHERN MISSOURI INTO IOWA...
Thunderstorms may produce isolated severe hail across portions of
northern Kansas and far southern Nebraska into Iowa and northern
Missouri this evening and overnight.
Previous forecast appears on track, and only minor adjustments have
been made. Elevated thunderstorms should develop from north central
to northeast KS, moving into southeast NE and southern IA this
evening where a progressive shortwave trough and strengthening
low-level jet will augment isentropic ascent and destabilization
north of a warm front currently located across southern KS. While
updrafts will be elevated, effective shear will be sufficient for a
few storms to develop mid-level rotation which, in addition to steep
mid-level lapse rates and 500 J/kg MUCAPE, will promote a modest
threat for mainly large hail.
.PREV DISCUSSION... /ISSUED 1029 AM CST Thu Feb 23 2017/
...Central Plains and middle Missouri Valley/Midwest...
Limited moisture observed across the central and southern Plains
(per surface observed and 12Z upper-air data/soundings) casts some
uncertainty regarding the timing/extent of convective development,
while otherwise likely limiting the overall potential for severe
storms later today.
This limited moisture and the existence of an appreciable elevated
mixed layer is expected to preclude surface-based development
through the afternoon, although an increase in elevated thunderstorm
development may begin to occur around and after sunset (as early as
23Z-00Z time frame). Aided by DPVA and increasing isentropic ascent,
this development should mainly be focused across north-central
Kansas just to the north of an eastward-developing surface low and
north of a sharpening warm front. While moisture/overall buoyancy
will be meager, very steep mid-level lapse rates and long
straight-line hodographs within the cloud-bearing layer could yield
some hail/locally gusty winds, with latest forecast soundings
generally suggesting that storms should generally be rooted near or
above 850 mb. Any such threat should be semi-focused across
north-central/northeast Kansas this evening, but other
strong/locally severe thunderstorms could occur across far southern
Nebraska into Iowa and northern Missouri through the overnight.
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