000
FXUS63 KEAX 172316
AFDEAX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
616 PM CDT Fri May 17 2013

.SHORT TERM...(This Evening through Monday Night)
Issued at 331 PM CDT FRI MAY 17 2013

Weak upper low over the Mississippi Valley will push east this
evening, leaving the area under the influence of a building ridge
across the Plains. May see some low clouds redevelop late tonight across
eastern KS into central MO on the back edge of the retreating low.
Any such clouds should lift and scatter through Saturday afternoon as
the ridge builds in overhead. This will allow 850 temps to rise to
near 20C, which with ample sun should bring surface temps into the
middle and upper 80s. This will cause the atmosphere to become
strongly unstable by afternoon, and with models slowing down the
onset of a strong capping inversion, it`s conceivable that CIN could
be weak enough for a few storms to pop up over eastern KS or western
MO later in the day. Best timing for this should be near or after 00Z
when a weak impulse will track overhead and a developing LLJ noses
into eastern KS. Any such storms would be primarily instability
driven since mid-level flow will be weak, and any threat for strong
storms should be short-lived and limited mainly to marginally severe
hail or winds.

Sunday still appears active with the potential for a widespread
severe weather event across the central and southern Plains into Iowa
and Missouri. There are still some subtle differences in the model
mass and wind fields, which while minor, could have significant
impacts on the location and type of severe weather. GFS and GEM
depict an alignment of the lower and upper-level jets that would
favor organized storms across eastern KS and western MO Sunday
afternoon and evening, potentially in the form of long-lived
supercells. ECMWF and NAM are slower with the upper-level jet and
more boundary-parallel with the mid-level flow. This would keep the
highest severe weather threat over southern KS and OK, though still
keeping some threat for severe storms this far north likely in the
form of a disorganized convective system. In addition, instability
could be in question if convection develops early Sunday morning and
produces lingering clouds and light precip like the NAM suggests.
Therefore the exact details of Sunday`s severe event are still to be
determined, but if all factors come together, the potential exists
for supercells with very large hail (2"+) as well as a few tornadoes,
potentially congealing into a convective system with large hail and
damaging winds Sunday night.

Monday could see another potentially active severe weather day across
the area, but uncertainty is even greater due to model differences
with the lingering frontal boundary and weak impulses rounding the
base of the Northern Plains upper trough. Mid- and upper-level flow
will likely be stronger on Monday which could set the stage for
additional severe storms depending on how convection from
Sunday/Sunday night affects destabilization on Monday and the
location of the front. The better chance for widespread storms may
come after dark Monday when the low-level jet will intensify and
interact with the boundary somewhere over eastern KS and
western/central MO. Current indications are that the focus for this
activity may be just south of the forecast area across the MO Ozarks.

.LONG TERM...(Tuesday through Friday)
Issued at 331 PM CDT FRI MAY 17 2013

Tuesday through Friday...

In the wake of Monday`s convection, most of the extended will be
under the influence of a slow moving upper low which will take its
sweet time exiting the region. With this upper low nearby it will
keep temperatures pleasantly near average. That upper low may also
enable some isolated, generally weak, convection through much of the
extended...though by the end as the ridge builds in those chances
should subside.

Bailey

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 612 PM CDT FRI MAY 17 2013

GFS lamp guidance has backed off on IFR cigs for tomorrow morning,
couple that with models/MOS guidance being too moist in the boundary layer
lately and have opted to remove IFR group from going TAF. Models do
continue to hint at MVFR cigs tomorrow morning however so kept that
in the TAF from 10Z- 15Z with a little light fog reducing vsbys to 5SM.
MVFR cigs should scatter out tomorrow morning before cu builds in
tomorrow afternoon around 5kft. Winds will be out of the southeast
through the period between 7-13kts.

&&

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

$$

SHORT TERM...Hawblitzel
LONG TERM...Bailey
AVIATION...73