Valid 161200Z – 171200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN
KANSAS INTO WESTERN MISSOURI…
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY…
…SUMMARY…
Severe storms are possible from the central High Plains, across
Kansas and Missouri and into southern Illinois Friday with large
hail and damaging wind the main threats. Other isolated strong to
severe storms with large hail and damaging wind may occur over the
central High Plains region.
…Synopsis…
A series of shortwave troughs will move through the Plains within a
broad fetch of modest westerlies. At the surface a convectively
reinforced warm front extends from a weak surface low in central KS
through southwestern MO. A stationary front extends southwest from
the low into southwestern KS and southeast CO. The warm front should
move northeast during the afternoon, with the effective front likely
extending from north-central MO west southwest through central and
southwestern KS.
…Central Plains through the middle Mississippi Valley region…
By the start of the period, a convectively reinforced front should
extend from southern MO northwest to a weak surface low in central
KS, with a stationary front extending from the low through southwest
KS. Thunderstorms should still be in progress from far eastern KS
into central and southern MO, but are expected to gradually diminish
as the nocturnal southwesterly low-level jet weakens. The reinforced
front should begin to move northeast as a warm front and become
situated across northeast KS into northern MO by early evening with
trailing stationary front remaining across central through southwest
KS. The warm sector south of these boundaries will be very moist,
with low 70s F dewpoints beneath steep lapse rates associated with a
warm EML supporting 2500-3500 J/kg MLCAPE. Shortwave trough now
moving through WY will continue through NE north of the warm sector.
A capping inversion, associated with the warm EML, and only weak
forcing, suggests surface-based thunderstorm initiation should
remain limited during the day, except possibly near the convergence
boundary over south-central or southwest KS where deeper mixing is
possible. Isolated downburst winds and hail will be possible with
this activity. Assuming morning storms diminish as anticipated,
more substantial severe threat is expected to evolve from a portion
of eastern KS into MO when storms should redevelop mainly along and
north of the warm front within zone of increasing isentropic ascent
on nose of a strengthening low-level jet. This region will reside
within belt of moderate westerlies supporting 40-45 kt effective
bulk shear. Low-level hodographs will also be augmented in vicinity
of the boundary. All severe threats are possible including
supercells with very large hail and possibly a couple tornadoes,
with primary threat eventually transitioning to damaging wind as
storms grow upscale later in the evening.
…Central High Plains region…
An easterly upslope component will persist over the central High
Plains where moderate instability and 40-45 kt effective shear will
reside during the afternoon. While forcing aloft will remain weak,
at least isolated storms are expected to develop over the higher
terrain and spread east into the corridor of moderate instability. A
few supercells and bowing with large hail and downburst winds will
be the main threats. Additional storms may develop over northern KS
within zone of isentropic ascent north of the stationary front
overnight with a threat for mainly isolated hail.
…Northeast States…
A progressive shortwave trough will interact with a modest
thermodynamic environment during the afternoon, contributing to a
few thunderstorms developing along a convergent trough axis. A few
of these storms could produce isolated strong wind gusts before
diminishing during the evening.
..Dial/Nauslar.. 08/16/2019
$$