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000
FXUS63 KEAX 182026
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
326 PM CDT Sat May 18 2013

.SHORT TERM...(This Evening through Sunday)
Issued at 326 PM CDT SAT MAY 18 2013

Deepening upper trough over the High Plains is expected to produce
multiple rounds of severe weather across the Plains and Midwest over
the next few days, starting with a severe weather outbreak over
western and central Kansas this evening. Upper shortwave responsible
for this activity, currently near Dodge City, will track into eastern
KS and western MO late tonight. Quite a few questions remain
regarding this feature and if it will be able to spark convection
overnight this far east, especially with a significant capping
inversion in place. Latest aircraft soundings out of MCI depict a
very strong inversion of 16 degrees C around 770 hPa which is quite a
bit stronger than what models had been forecasting. This inversion
is likely to keep our area dry at least through the early evening.
However, a 40-50 kt low-level jet is progged to nose into northwest
MO between 06Z and 09Z. Convergence at the leading edge of this
feature could produce enough lift to weaken and possibly overcome
the cap and spark a complex of thunderstorms over northeast KS and
northwest MO overnight. Models are in very poor agreement with this
potential overnight activity so confidence is not high. However,
should storms develop, elevated instability is forecast to be strong
to extreme, so these storms could produce severe hail and very heavy
rainfall.

Sunday still appears active as the upper trough to the west pushes
into the eastern Plains. Model spread remains rather high with the
middle- and lower-level jet structure and timing of smaller-scale
features, which makes it somewhat difficult to pinpoint exact storm
location, timing and severity. Further complicating matters will be
any overnight convection that lingers into Sunday morning. This could
cut back on instability Sunday afternoon, and is also producing
feedback issues in the model forecasts. It still appears that if
things were to come together correctly, parts of eastern Kansas and
western Missouri could see a line of supercells capable of producing
very large hail (baseball-size or larger), damaging winds and
tornadoes. Exact tornado threat, and any potential for long-lived
strong tornadoes, will depend on the evolution of low-level wind
fields and low-level instability which are difficult to get a feel
for given the model spread. Taking a blend of the faster NAM and
slower GFS would put result in wind fields and thermal profiles
supportive of an enhanced tornado risk along the KS/MO border late
Sunday afternoon and early evening, with an even greater risk further
south toward Tulsa.

Boundary-parallel storm-relative flow is likely to cause any
supercells to gradually congeal into a line over western Missouri
Sunday evening, maintaining the potential for large hail and damaging
winds. This activity could maintain its severity as far east as
central Missouri Sunday night.

.LONG TERM...(Sunday Night through Saturday)
Issued at 326 PM CDT SAT MAY 18 2013

Large question marks remain for the convective forecast on Monday,
given substantial uncertainties on the evolution of thunderstorm
activity Sunday afternoon and night.  As mentioned in previous
discussion, there will likely be some lingering thunderstorm
activity early Monday morning as an embedded shortwave rotates
northeast of the area and the LLJ slowly veers, however it`s
possible that much of the morning and early afternoon hours will be
dry as the area is between shortwaves. Moderate to strong
instability will begin to grow ahead of an elongated surface
boundary over east central Kansas and northwestern Missouri during
the afternoon hours.  By the mid-late afternoon hours a secondary
shortwave and mid-level jet streak will rotate into the area,
reigniting convection over NE OK, SE KS and into areas of west
central MO.   Initially discrete in nature, fairly rapid transition
towards a linear convective mode is anticipated further NE given
unidirectional shear.  Substantial mid-level CAPE values will
support very large hail, with dry air intrusion indicating the
potential for a quick transition to a strong wind producing MCS as
this system moves across the area.

Tuesday-Saturday:

Upper level troughing will swing through the Midwest by Tuesday
bringing cooler temperatures and dry conditions into Thursday.  A
building mid-level ridge will gradually slide eastward by the end of
the week and next weekend.  Moisture will gradually return to the
Western Plains bringing renewed chances for showers and
thunderstorms to portion of Kansas by next weekend.


&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1220 PM CDT SAT MAY 18 2013

Cumulus field is rapidly expanding, and an area of IFR/MVFR ceilings
is lingering west of the area across central Kansas. Southeast flow
is expected to keep those ceilings well to the west of the
MCI/MKC/IXD corridor, and VFR will be the rule through the evening.
While confidence in the latter half of the period is not high, most
models do suggest thunderstorms developing late tonight and early
Sunday across much of the region. Timing this activity is difficult
at this point, but it appears it should hold off until well after
midnight, so pushed back the timing of VCSH until 09Z for areas near
the KS/MO border.


&&

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

$$

SHORT TERM...Hawblitzel
LONG TERM...Dux
AVIATION...Hawblitzel