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

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FXUS63 KEAX 162350
AFDEAX

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
650 PM CDT Tue May 16 2017

.Discussion...
Issued at 338 PM CDT TUE MAY 16 2017

Very active weather pattern shaping up from the Lower Missouri
Valley in the coming days as upstream satellite trends show two
potent upper-level disturbances across the Western U.S. this
afternoon. The first of these features currently spinning across
the Desert Southwest will continue tracking east overnight before
ejecting into the Central Plains Wednesday morning. Out ahead of
this however, increased synoptic scale lift resulting from several
lead shortwave impulses along with sufficient boundary layer
moisture and steep lapse rates will support robust convective
development upstream along the dryline in western Kansas and
Oklahoma this afternoon. With time, this activity is expected to
organize into a MCS, before tracking northeast into our area,
primarily after the 03z time frame. Latest high-res model guidance
continues to show a bowing appearance in the simulated
reflectivity fields, which combined with the forward propagation,
suggest strong winds in excess of 50 kts will be the primary
threats across far northeast Kansas and northwest Missouri. This
initial round should exit into southern Iowa shortly after 06z,
with NAM and NAMNest solutions strongly suggesting a secondary
round moving east from central Kansas during the predawn hours.
Latest high res guidance suggests this activity will be weakening
as it approaches, however cannot rule out some isolated severe
potential further south than the initial round during the predawn
hours. Again the bowing appearance suggests strong winds as being
the primary concern if this predawn activity achieves severe
limits.

Moving forward to the daylight hours on Wednesday, latest
deterministic guidance continues to highlight a strong synoptic
signal for severe storm development along the eastward moving
dryline/Pacific cold front by Wednesday afternoon. Fcst soundings
from the Metro and points east are nothing short of impressive
from a severe wx perspective, with large looping hodographs seen
on both BUFKIT and AWIPS forecast profiles. A few details:

1) Aforementioned upper trough will take on a strong negative-
tilt by late morning/early afternoon directly off to our west,
suggesting max DPVA and synoptic-scale lift will be centered
directly over our region by afternoon.

2) Latest models suggest plenty of instability will be present,
with both NAM and GFS suggest MLCAPE levels on the order of
1000-1500 J/kg.

3) Very strong wind fields will exist aloft, as a midlevel speed
max of close to 100 kts rotates into the region along the
underbelly of the previously mentioned, negatively-tilted trough.

All told, the synoptic scale is more than supportive for supercell
(possibly low-topped w/ELs around 30 kft) Wednesday afternoon
with shear profiles off the charts. Quick look at CIPS historical
analogs reveals several high-end tornado days for the top returned
cases, which adds concern to tomorrow`s convective potential. At
this point, the main caveat remains whether overnight convection
contaminates the environment for tomorrow, however little airmass
modification is expected after both rounds of convection later
tonight and early Wednesday morning. Regardless, its rare to see
such a strong signal synoptically speaking, with further support
provided from past historical guidance.

Tomorrow`s activity should translate east by early evening with
mainly dry conditions expected on the backside of the initial wave
Wednesday night into Thursday. Precip chances start to increase
Thursday night and Friday as the wave currently seen over the
Pacific Northwest this afternoon gradually starts to work east
from the Central Rockies by week`s end. Again, severe chances look
to return with this activity, but those details will be looked at
more closely as the event timing nears. Rain chances continue
right into the weekend as the wave slowly meanders its way across
the area with dry weather returning Saturday night and Sunday.

&&

.Aviation...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 648 PM CDT TUE MAY 16 2017

Expecting winds to persist through the night in the 20 to 30 kt
range with isolated stronger gusts. Winds will pick up through the
day and remain rather gusty through the rest of the forecast
period. A couple rounds of thunderstorms will be possible, but the
better chances will likely remain north and east of the terminals,
with KSTJ having the best chance for seeing a few thunderstorms.

&&

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

$$

Discussion...32
Aviation...Leighton



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