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

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FXUS63 KEAX 211747

National Weather Service Kansas City/Pleasant Hill MO
1247 PM CDT Sat Oct 21 2017

Issued at 337 AM CDT SAT OCT 21 2017

Southerly winds gusting to around 30 mph this morning across
the area, as a surface low continues to deepen over the High
Plains. This southerly wind is keeping a steady flow of warm/moist
air into the area, in advance of a potent mid level trough, which
is poised to move through the area later this afternoon. In the
meantime, warm air advection, elevated showers and thunderstorms
have popped up over far northern Kansas and NW Missouri, into
southern Iowa. A very stiff low level jet, characterized by H85
winds in the 50 to 70 kt range is currently located over Kansas
and Nebraska, with eastern Kansas and western Missouri located on
its eastern periphery. This low level jet may be enhancing some
low level lift, but lack of convergence and fairly neutral
isentropic ascent is keeping higher activity at bay for now. The
showers and thunderstorms that are currently ongoing across parts
of eastern Kansas, northern Missouri, and southern Iowa appear to
be more influenced by a shortwave trough, which is gliding over
the area early this morning. Deeper moisture and relatively low
mid level ascent associated with this early morning shortwave is
keeping this morning activity somewhat minimal. Expect broken
stratocu through a good portion of the day, with perhaps some
periods of breaks in the clouds, yielding partially sunny skies
through the day on Saturday.

As the more potent trough pushes into the area later this
afternoon it will bring with it better ascent to get some isolated
to scattered thunderstorms during the late afternoon and early
evening. The wider coverage of thunderstorms will likely come once
the surface cold front drives into the area from the northwest.
Expect widespread thunderstorm activity - starting in far NW
Missouri and NE Kansas - in the later part of the evening, likely
in the 5 pm to 7 pm time frame. While there could be a few post
frontal strong storms capable of producing some large hail, in the
quarter to golf ball range, the storms will quickly congeal into
an advancing squall line, which will move into the KC Metro area
in the 6 pm to 9 pm time frame. While the prefrontal more discrete
storms could bring the hail threat, the line of storms along or
just ahead of the cold front will bring almost predominantly a
wind threat, with perhaps some gusts approaching 60 to 70 mph.
Stiff southerly winds ahead of the line, along with a low level
jet in the 40 to 50 kt range out of the southwest will yield a
good turning in the low levels, which will bring a non-zero
tornado/meso-vortex concern within the line of storms. ML CAPE
values around 1500 J/kg and deep layer shear in the 30 to 40 kt
range will help this complex of storms to maintain some
organization as it goes through the KC metro area around sunset
and into central Missouri through the early overnight hours.
Expect the low level jet to wane a bit through the late evening,
which will help take away some of the loop in the hodograph and
CAPE will gradually wane with diurnal cooling. So, as the complex
continues eastward into central Missouri the concern for
widespread severe weather will gradually wane. PWAT values in the
1.25" to 1.6" range will make rain rates pretty efficient with
these storms, so despite the relatively progressive nature of the
complex rain amounts could still reach over an inch in most
places, with perhaps a few isolated heavier down pours or
favorable storm orientation resulting in amounts in the 2-3 inch
range in some locations. This will bring a marginal concern for
flooding across the area, perhaps more relegated to flood prone
areas and sensitive streams. This complex of storms will push
eastward into central Missouri and out of the forecast area by
sunrise Sunday morning.

A benign pattern then emerges for Sunday through the remainder of
the work week. A series of surface ridges move through the area,
which will keep a steady diet of fair weather and alternating
warmer and cooler conditions on tap through next weekend. The only
real notable portion of next week`s forecast comes late in the
week with a progressive shortwave trough, which will bring a
transient chance for some light precipitation. However, perhaps
more notable is the potent surface ridge that moves into the area
in its wake, likely bringing the coldest temperatures of the
season thus far, as overnight lows on Friday night into Saturday
morning could drop as low as the lower to middle 30s across a
large portion of the area. While that time period remains 6-7 days
out, it might be a time period worth watching for the first
widespread sub-freezing temperatures across the region.


.Aviation...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1247 PM CDT SAT OCT 21 2017

MVFR clouds currently prevail ahead of a cold front that will
sweep across the terminals this evening, roughly between 6 and 8
PM. Winds ahead of the front will be rather strong and gusty, but
anticipate a quick wind shift and strong gusty winds with a line
of storms moving through. Winds behind the front should remain
rather strong till much later tonight when the gradient relaxes.
Clouds are also expected to start clearing and/or lifting early
Sunday morning as the dry air moves in.




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