River Flood Warning 179, NWS Kansas City, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
621 PM CDT Wed Jun 24 2015

.DISCUSSION...
Issued at 405 PM CDT WED JUN 24 2015

Early morning convection has laid down a pretty obvious outflow
boundary, which has interacted with the synoptic warm front to
produce a rather stationary boundary which is oriented generally NW
to SE from KAFK SEWD toward KVIH in central Missouri. South of this
boundary conditions are rather warm and humid, with temperatures in
the lower 90s, with dew points in the lower to middle 70s, quite a
moist atmosphere. North and east of that boundary surface winds are
backed to the east/southeast, with temps in the lower 80s and dew
points in the upper 60s to lower 70s. Across central Iowa weak,
elevated convection is ongoing, and has laid out a secondary outflow
boundary generally in the KAFK to KLWD area. Given the gusty
southeast winds behind the outflow boundary as well as a veering
with height and increasing speed wind profile, shear through the
deep column is rather high, with effective shear values between 45
and 55 kts across northern Missouri. Given the previously mentioned
juicy atmosphere MLCAPE values are approaching 2500 to 3500 J/kg of
instability and that number could go up in the next couple of hours.
Needless to say the atmosphere has proper parameters for explosive
supercell development across far northern Missouri into southern
Iowa. That being said, the typical caveats apply regarding the
capping inversion over the area. Areas mainly along and south of HWY
36 are generally too warm aloft for any convective activity to form,
however, as you move north along the edge of that capping inversion
storm activity becomes a little more likely, especially as you go
into Iowa. Further helping the chances for convective initiation
farther north is the proximity of a subtle vort max, more evident in
the H7 level than the H5 level. Bottom line is that scattered
thunderstorms are anticipated to form in central and southern Iowa
within the next few hours. As was mentioned early supercellular
conditions are present in this region, and should yield some
significant hail and perhaps a threat for tornadoes, again, mainly
north of HWY 36 and even more likely in southern Iowa. These storms
however could move ESE into far northern Missouri, bringing a threat
for severe weather, with all hazards possible for that area. Hi-Res
convective models aren't doing a great job with consistency, so the
exact scenario of how the next several hours will play out is a bit
uncertain, but confidence is medium to high that after the initial
supercells form the will eventually form a bow echo complex in SE
Iowa and likely dive ESE overnight. This complex could bring a wind
threat, as well as typical lightning concerns, as well as flooding
concerns, with local streams still a bit swollen from recent rains.
Expect this activity to eventually weaken overnight, perhaps keeping
rain around for areas along and north of I-70 through the overnight
hours into Thursday morning.

Thursday will bring a pretty conditional threat for severe weather
through the area. Short term models indicate that the synoptic
boundary will shift southward overnight into Thursday and eventually
set up near I-70. That being said, overnight convection could
influence that boundary location. So the convective threat for
Thursday will be influenced by that interaction between the synoptic
boundary and the outflow. For now the thinking is that there will be
an area of enhanced low level convergence near I-70, which will be
the focus for convective development. While CAPE and shear will be
ample for supercellular development the bigger threat for Thursday
and Thursday night will be flooding and flash flooding. NAM
indicates over 2 inches of PWAT in the vicinity of that boundary,
which will allow for efficient rain rates. Further exacerbating that
threat will be the shear vectors generally parallel to the boundary,
which could cause some training of storms. Wherever these storms set
up could see some localized flooding and flash flooding, but exactly
where that boundary sets up is still a bit TBD. Will pass along
flooding concerns to the overnight shift and allow them to assess
Flood Watch concerns.

Heat is still a concern on Thursday, mainly in the vicinity of the
boundary. Moisture will likely pool right along that boundary,
causing Heat Indices to rise into the upper 90s to lower 100s.

Showers and thunderstorms could persist into Friday morning, but
generally by Friday evening and Friday night the synoptic
front/boundary should be south of the forecast area, allowing for
cooler and drier air to move into the area. Surface ridge sets up
for the weekend keeping things relatively dry and cool. By Monday
the surface ridge moves east allow for southerly surface flow to
bring moisture back into the area. While the mid level pattern
doesn't look overly conducive to good precipitation/severe weather
chances we will remain under relatively good mid level flow, so once
the moisture makes its way back into the area storm chances will be
on the increase, mainly through the early to middle part of next
week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 618 PM CDT WED JUN 24 2015

VFR predominant conditions expected through the period. Primarily a
wind forecast, with direction gradually veering ahead of the next
front over the next 24 hours. Speeds should remain breezy overnight
before relaxing some with the approach of the boundary. Convection
tonight should remain north of terminals, with a trend of increasing
convection near or at terminal tomorrow afternoon.

&&

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

DISCUSSION...Leighton
AVIATION...Blair