Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 131956

National Weather Service Kansas City/Pleasant Hill MO
256 PM CDT Fri Oct 13 2017

Issued at 256 PM CDT FRI OCT 13 2017

Main concern continues to be potential for severe thunderstorms
Saturday afternoon and evening. A strong but neutral to slightly
positively tilted trough will move across the center of the
country Saturday. This will help push the quasi stationary front
through the area as a strong cold front. Strong forcing along the
front and large scale ascent associated with the upper trough should
be more than enough to get storms going. There are several
important variables that will aid or diminish the overall severe
threat. 1) How much cloud cover will erode within the warm sector
to build instability? 2) How veered will surface winds be to
detract from the amount of helicity? Higher resolution models
show clouds decreasing and the warm sector becoming moderately
unstable by the afternoon with 1000 to 2000 J/KG CAPE. This is
rather robust instability for this time of year. Surface winds
also are veered to the south-southwest. This is, thankfully,
limiting the amount of helicity in the pre-storm environment.
However, hodographs in our southeastern zones, ahead of the
convection, still show strong curvature and 0-1km helicity values
may be in the 150 to 250 m^2/s^2 range. This is still very high
and when put in context of a 30 kt west-to-east 0-3 km shear
vector, the near storm environment will need to be watched closely
tomorrow afternoon. While initial storms may be supercellular,
they`re expected to quickly become linear in nature. If updrafts
orient orthogonal to the 0-3km shear vectors it would greatly
enhance the environment for mesovortices and a few tornadoes,
given the higher helicity values. Regardless of the tornado
potential, the strong winds aloft suggest a good potential for
damaging winds at the surface. Folks who are outside tomorrow
afternoon need to be very weather aware as storm motions will be
very fast and any potential tornadoes could quickly spin up from
within the fast-moving line of storms.

Behind the front, much cooler air will settle over the region. Highs
on Sunday will struggle to reach 60 degrees. This will set us up for
a chilly night with temperatures falling into the middle to upper
30s. It`s possible these could be lower, depending on where the
surface high settles overnight. So the potential for frost will
exist and folks with sensitive vegetation may need to take
measures to protect their plants.

The rest of the forecast looks quiet and dry, with temperatures
getting back normal Monday, and then a bit above normal through
the end of next week.


.Aviation...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1236 PM CDT FRI OCT 13 2017

The frontal boundary is nearly stationary from northwestern MO
into south central KS. North of the front MVFR to IFR ceilings are
present. South of the front, scattered cumulus may develop this
afternoon. As the front slowly moves south this evening, there may
be trend to fill this cloud deck and then potentially lower
ceilings to MVFR. Confidence in this is highest at STJ and MCI,
where the front is more likely to encroach upon this evening and
tonight. The front should lift back north late in the morning and
with ceilings raising. The best chances for precipitation will
come after this forecast. But it`s possible some drizzle or light
showers may work into the STJ or even as far south as MCI terminal
this evening.




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