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

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FXUS63 KEAX 252339
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
639 PM CDT Thu May 25 2017

.Discussion...
Issued at 350 PM CDT THU MAY 25 2017

The main concerns this forecast period will be: 1) the potential for
an isolated severe storm tomorrow capable of large hail and damaging
winds 2) the potential for a widespread severe weather event with
all modes of severe storms possible on Saturday.

This afternoon a perfect late Spring day is playing out with highs
topping out in the mid to upper 70s. However, tonight models are
forecasting a MCS is expected to develop across southwestern
Nebraska and northwestern Kansas. This MCS is progged to progress
eastward overnight but is expected to diminish as it approaches the
area. It may hold together long enough to bring a few showers or
thunderstorms across northern Missouri tomorrow morning. It will
however force a frontal boundary into the area which will come into
play for the first half of the holiday weekend. Tomorrow afternoon
temperatures will warm into the upper 70s and lower 80s. This will
lead to extreme instability across the area with MUCAPE values
between 2500-3500J/Kg along and south of the frontal boundary.
Severe weather tomorrow afternoon and evening will be conditional on
the cap breaking. The 12Z NAM keeps the area capped throughout the
day tomorrow while the GFS weakens the cap by late afternoon (which
is exactly opposite from the 06Z runs). This leads to low confidence
however, if storms do develop they should quickly become severe with
the instability in place. The main threats would be for large hail
and damaging winds.

Models are consistent in developing another MCS over northeastern
Colorado Friday evening that will again progress across northern
Kansas/southern Nebraska overnight. The MCS will maintain itself
into Saturday moving into northwestern Missouri during he morning.
As this MCS moves into the area, a warm front will be lifting
northward through the CWA with warm air advection showers. During
the afternoon, an upper level shortwave will move into the area an
act as the trigger for convective development along the front. As
the surface, there may be additional convergence as the MCS
interacts with the warm front. Instability along and south of the
warm front will be extreme between 2500 to over 4000 J/Kg of MUCAPE
with extremely steep lapse rates. 0-6km bulk shear values are on the
order 50kts. This will lead to the potential for damaging winds and
hail and with the frontal boundary and any outflow boundaries left
over from the MCS also in play, tornadoes can not be ruled out. The
front does quickly push off to the south and east with storms coming
to an end by Saturday night.

The second half of the holiday weekend looks much more quiet and
pleasant with dry conditions and highs in the mid to upper 70s. The
next chance for organized precipitation does not reach the area
until Tuesday night into Wednesday as model advertise a series of
shortwaves moving through the area on northwest flow. Temperatures
will remain in the low to middle 70s through the middle of next week.

&&

.Aviation...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 638 PM CDT THU MAY 25 2017

VFR conditions are expected to prevail for the forecast period.
Overnight, models are hinting at the MCS in western KS moving to
the northeast across areas along/north of I-70. It should get to
the KS/MO border around 07Z and exit the Kirksville area by 12Z.
Have only put VCSH in the forecast though due to the question of
whether or not rain will actually reach the ground. Soundings show
some dry air in the lower-levels right now, so will continue to
monitor to see if this changes. Late tomorrow morning, a broken
cumulus field is forecast to develop between 3-4 kft and last
through the evening. Some could grow into storms during the
afternoon but there is still uncertainty about whether or not the
cap will break. Finally, a cold front will sweep through the area
tomorrow, veering winds to the northwest by the afternoon hours.
Wind speeds should remain light.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...73
Aviation...Grana


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