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

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FXUS63 KEAX 282330

630 PM CDT Thu Aug 28 2014

Issued at 338 PM CDT THU AUG 28 2014

Pronounced thermal gradient across the CWA this afternoon as
long-impacting frontal boundary continues to lift north in advance
of large scale wave now dropping out of the central Rockies.
Regional radars showing a north-south oriented rain axis across
eastern Kansas this afternoon...with additional isolated activity
noted across north-central Missouri in closer proximity to
aforementioned warm front. This convection has led to a few stronger
cells just east of the EAX CWA which prompted the issuance of a few
severe thunderstorm warnings by our neighbors to the east. Closer to
our neck of the woods...cannot rule out an isolated stronger cell or
two along the boundary...but with large scale forcing for ascent
rather limited at this point...currently think chances are fairly
low. Reference SPC SWOMCD #1629 for more details.

Heading into tonight...main upper trough expected to slowly migrate
east across the central Plains...while the main warm front continues
lifting north. Fcst models again show developing convection during
the early morning hrs as another low-level jet of 30-35 kts develops
over the region. From this stand point...a slightly further eastward
position of main low-level wind max may favor a little more
organization that last night...but current thinking is best thata-e
convergence will likely be found just to our north in southern IA.
Despite this...models in good agreement that region will eventually
reside under the favorable right entrance region of an upper jet
streak located along the eastern periphery of approaching upper
wave...however true impacts from stronger divergence aloft may hold off
until around daybreak. In any event...increasing pressure advection
along the 1.5 PVU surface combined with modest isentropic ascent
along what appears to be a another weak theta-e gradient south of the
main front supports the highest pops across the western zones during
the predawn hrs. For now...have capped pops in the high chc category
across the far northwest with chc mention extending south along and
west of the I-35/Route 71 corridor.

Prospects for area-wide rainfall look to increase tomorrow as main
upper trough axis slides east over the area. Fcst models have been in
excellent agreement with this scenario hence the maintaining of likely
pops through much of the day. Storm movements will likely be
slow...but guidance is actually suggesting lower PWAT values as
the low-level moisture that has been pooled along the front slowly
lifts north of the area. Considering this...not overly concern with
flash flood potential tomorrow but later shifts will definitely have
to monitor the latest model trends to ensure this reasoning remains
in tact. With clouds and rain in the area...have trended towards the
lower end of guidance with highs in lower to middle 80s.

As mentioned above...upper trough to be a very slow mover which will
likely keep the treat for showers and storms going through much of
the Fri ngt/early Sat period. Have maintained likely pops across the
eastern 2/3rds of the CWA with overnight lows largely falling into
the middle to upper 60s. Finally some relief with respect to rainfall
chances set to arrive on Saturday as main trough axis finally slides
east. Have advertised a gradual improving trend through the day with
highs rebounding into the lower to middle 80s.

Towards the end of the weekend...focus will quickly shift to a
northern stream trough tracking east along the U.S./Canadian border.
As this feature ejects east from the northern Rockies...sfc low
pressure is expected to lift northeast from the northern Plains into
the Canadian Prairie provinces. As this occurs...reestablished southerly
flow will force a weak warm front north across our region. This
combined with secondary shortwave energy along the southern periphery
of the main northern U.S. storm system should allow for redeveloping
shwrs/storms Sunday afternoon through Monday.

Beyond this...fcst models begin to show some disagreement as main
synoptic scale front stalls somewhere in the vicinity. With
subtropical ridging expected to flatten thanks to the passing
northern stream system referenced above...very conceivable that the
stalled front will take up residence very close to our area. For
now...the ECMWF and Canadian-CMC show the farthest southward
position...while the GFS is further north and wetter. In any
event...have kept things dry beyond Wednesday as fairly strong sfc high
pressure building into the upper Miss Rvr Vly/western Great Lakes by
midweek should keep the main frontal feature to our south.


.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 624 PM CDT THU AUG 28 2014

VFR conditions will prevail at the terminals over night. Issues at
these sites will likely develop around or after sunrise Friday as an
upper level trough swings through the Plains States. This will spark
some thunderstorm activity across the region, with storms likely at
the terminals late Friday afternoon. Have kept storms in the VFR
range owing to uncertainties in development and timing. Otherwise,
expect surface winds to remain from the south through Friday.




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