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

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206
FXUS63 KEAX 281143
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
643 AM CDT Wed Jun 28 2017

.Discussion...
Issued at 404 AM CDT WED JUN 28 2017

The well advertised active weather pattern has begun as the first of
many shortwave troughs moves overhead. This in conjunction with a
low level jet and surface low centered over the Northern Plains has
resulted in the development of an MCS. The MCS is currently moving
across northwest MO producing gusty winds. They should stay below
severe weather thresholds though. The MCS is projected to weaken
as the morning continues drying our area out by late morning.

The MCS will likely leave an outflow boundary somewhere near the
IA/MO border, which will be the focus for the late afternoon/evening
storm potential. Models suggest storm initiation will be in IA,
eventually pushing southeast into far northern MO as a line,
around 7 PM CDT. Severe weather will be possible along this line.
Dew points will be in the low 70s, 0-6 km shear will be about
40-50 kts, with instability around 2500 J/kg. Large hail and
damaging winds will be the main concerns but we can`t rule out the
tornado threat. The main threat area for this part of the day is
far northern MO. It is important to note though a lot of this
relies on how long this morning`s MCS sticks around. If the clouds
take their time clearing out, we may not see much in the way of
storm development this evening.

As we continue on into the night tonight, the low level jet will
ramp up transitioning the line into elevated convection. The NAM
and GFS have the MCS more focused over eastern IA and northeastern
MO and western IL and dissipating over our area, while the
NAMnest and ECMWF have the MCS further west, mainly in our
northern area and weakening as it moves south. The NAM has been
very consistent though, so current thinking is our area will be
dry for most of the night. Wherever this MCS does set up though,
severe weather will continue to be a concern with damaging winds
becoming the main threat with hail also being a possibility. This
MCS should weaken during the morning hours.

On Thursday morning, another shortwave will move over the area,
while another surface low is developing in southeastern CO. This
will bring an MCS across northern KS/MO that formed in central KS
overnight. There is a marginal chance hail and damaging winds
will accompany this system. As the day continues, a warm front
associated with the surface low will move north becoming
stationary across northern MO. This front will be the focus for
the potential Thursday afternoon/evening storms. Plenty of
instability (~3000 J/kg), 0-6 km shear (50 kts), and moisture
(dew points in low 70s) will be present, making severe weather
possible again. Large hail and damaging winds will be the primary
concerns, but can`t rule out the tornado potential along the warm
front. In addition, storms may be training as storm tracks seem to
be parallel to the warm front. This results in flooding being a
big concern, not only because of training storms but also because
at this point, multiple rounds of storms will have moved through
northern MO. Again, the afternoon/evening storm potential will all
be somewhat contingent on the morning MCS and how quickly it
dissipates/exits the area. The hail, damaging wind, and especially
flooding threat will continue into Thursday night through Friday
morning as the main upper level trough and surface low finally
move through. A low level jet will also ramp up aiding in the
development of another MCS. The MCS and cold front should be
through by Friday afternoon. When all is said and done, areas
across northern MO could see 2-4 inches of rain with locally
heavier amounts, areas south of I-70 may only see about 0.5 inch,
with areas in between seeing 1-2 inches of rain. So again, flash
flooding and river flooding could be a big concern, especially
Thursday night into Friday, especially along and north of HWY 36.

We will dry out for Saturday and part of Sunday as a surface high
settles in over the area. However, Friday`s cold front is expected
to stall out near the MO/AR border and retreat north bringing
storms back to the area Sunday afternoon through Monday and
possibly the 4th of July.

&&

.Aviation...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 642 AM CDT WED JUN 28 2017

A cluster of storms is moving northeast through northwest MO and
northeast KS right now but they are weakening as they do so. This
cluster should dissipate/move out of the area within the next few
hours. VFR conditions are expected for the forecast period but
obs are already showing a windy day is in store. South-
southwesterly winds are expected to be sustained around 18 kts
gusting up to around 30 kts. Winds will weaken some after sunset
but it won`t be until closer to midnight that winds decrease below
12 kts. This evening through the end of period, storm chances
return, but there is uncertainty about coverage and timing. This
evening, a line of storms look to move in near the IA/MO border
around 00Z. This is somewhat contingent on this mornings activity
and whether or not clouds move out quick enough. If they do move
out quickly, this line shouldn`t have much of an issue forming.
As the night goes on, the low level jet will ramp up and the line
will become elevated and move southeast. The NAM consistently
(and to a certain extent the GFS) has had this elevated line
forming over IA and moving southeast into northeastern MO and
western IL. Whereas, the NAMnest and ECMWF have this line further
west, moving south-southeast across central MO. If the NAMnest
and ECMWF verifies, STJ, MCI and MKC could see some scattered
storms; otherwise, they should remain dry. It looks like another
cluster of storms will develop in central KS late tonight, and
move east into our area tomorrow morning. This system shouldn`t
enter the area until after 12Z Thursday but it is possible it
arrives a little early.

&&

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

$$

Discussion...Grana
Aviation...Grana



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