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094
FXUS63 KEAX 181702
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1202 PM CDT Tue Jul 18 2017

.Discussion...
Issued at 341 AM CDT TUE JUL 18 2017

The main story line for the next week will be excessive heat and
humidity that will build into the area starting Wednesday. Currently
the upper level ridge and high pressure are located over the central
plains with the surface high over SE Missouri. A weak LLJ over
northern Kansas will help elevated convection over southern Nebraska
continue to redevelop and slowly slide to the east into NW Missouri
just after sunset dissipated by mid morning. Winds will start to
pick up on the backside of this surface high pressure providing some
relief to the muggy conditions we have seen the last few days.  The
850mb axis of higher temperatures will stay over Kansas today but
dewpoints will start to increase along a band of southerly winds
from the Gulf of Mexico up into our area late Tuesday increasing the
heat index closer to 100 degrees this afternoon.

As the upper level ridge and surface high pressure start to advect E-
SE the low level axis of warm air advection will move over northern
MO Wednesday setting off a string of high temperatures in the upper
90s to near 100 degrees through Saturday. The placement of this axis
will be the driving factor for high temperatures during this period
as it slowly shifts south each day.  This will cause the higher
temperatures to start out north of Missouri River and then shift
along and south of the river Friday and Saturday brining the best
chance for 100 degrees in KC with it. The steady stream of moisture
from the gulf will keep dewpoints in the lower 70s each day creating
heat index values between 105 and 110 each day for most of the
region which has lead to an excessive heat warning for all counties
except the northern most counties along the IA/MO border. There will
be two periods of potential convection and cloud coverage that may
inhibit the current forecasted temperatures with that being Tuesday
night into Wednesday morning and Saturday morning into the
afternoon.  The guidance does show a MCS like feature forming over
central Iowa along the northern edge of the LLJ that will move
towards northern Missouri as it dissipates near sunrise with clouds
clearing out by mid morning. The added cloud cover may keep these
northern counties from reaching the 105 heat index thresholds for an
advisory and will need to be watched for any upgrade to the current
excessive heat watch in place. Saturday morning the ridge will have
moved far enough east to allow a weak shortwave to move across Iowa
creating a weak backdoor like frontal boundary that will move into
the MO/IA border in the morning.  This boundary and associated cloud
coverage may cause issues with the northern counties reaching
current forecast temperatures, but currently it looks to mainly
effect the border counties the most. The slightly cooler
temperatures aloft on the backside of this ridge may actually allow
for convection Saturday afternoon if convective temperature (98-
100F) is reached mainly north of the Missouri River, but a lot of
uncertainly will keep only Chance PoPs in the forecast. With almost
no shear these storms would rise and dissipate rather quickly with
downdraft winds being a potential threat due to the inverted V type
soundings over the area.

This boundary is expected to push south Sunday brining much needed
cooler and drier temperatures along with some scattered showers and
thunderstorms into the area with highs only reaching into the lower
90s. Monday a shortwave looks to enhance this stalled boundary and
provide an even greater chance of precipitation and cooler temps in
the upper 80s over the area.

&&

.Aviation...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1159 AM CDT TUE JUL 18 2017

Quiet weather overall - VFR. Winds will remain below 12 kts with
little change in direction. Some signal for potential convection
over NE KS, SE NE overnight into tomorrow morning, but activity
should reside north/west of terminals tomorrow morning, dissipating
prior to reaching terminal space.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...Excessive Heat Warning from noon Wednesday to 8 PM CDT Saturday
     for KSZ025-057-060-102>105.

MO...Excessive Heat Warning from noon Wednesday to 8 PM CDT Saturday
     for MOZ011>015-020>025-028>033-037>040-043>046-053-054.

     Excessive Heat Watch from Wednesday afternoon through Saturday
     evening for MOZ001>008-016-017.

&&

$$

Discussion...Barham
Aviation...Blair