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

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FXUS63 KEAX 271737

1237 PM CDT THU AUG 27 2015

Issued at 332 AM CDT THU AUG 27 2015

There are a couple of chance for showers and storms over the next
couple of days as a shortwave trough moves over the top of the
longwave ridge over the western half of the country. The first chance
will be over eastern Kansas and western Missouri this morning. An
area of strong isentropic ascent should lift east over eastern
Kansas/western Missouri through late morning. Deeper, richer
moisture, in association with the strong lift may lead to the
development of showers and storms. Convection allowing models are
very robust/aggressive with this development, while the coarser scale
NAM and GFS aren`t, even though some precipitation is generated.
Observationally, this mid-level moisture and lift seems to be
manifesting itself in a layer of clouds forming over eastern Kansas
and western Missouri. Given that this area matches the area of lift
depicted, have maintained chance POPs along the western portion of
the forecast area. This activity is expected to diminish by noon as
warm air aloft spreads into the area, capping the atmosphere. This
should result in a warmer, but still seasonal, day as low level
moisture increases.

The next good chance for precipitation will then arrive late
tonight, and even then, mainly across northern Missouri, as the
upper shortwave trough and associated surface low track from the
Central High Plains into the Mid-Missouri Valley. Models are in good
agreement tracking the surface low north of the forecast area and
focusing the LLJ to the north of Missouri. This implies that the best
precipitation chances and highest rainfall amounts will be north of
the forecast area, and quite possibly north of I-80. None- the-less,
precipitable water values climb to over 2" in northern and as the
front pushes into and through the area, any showers or storms that do
develop in the area could produce localized very heavy rainfall. The
threat of severe storms during the day friday looks low at this time.
But instability may be very high, if the NAM verifies, so there may
be some initially robust updrafts. However sheer looks week as the
strong dynamics are departing to the northeast with the upper
shortwave. The GFS is much weaker with the instability with a similar
scenario regarding the sheer. So there remains some uncertainty still
with the degree of destabilization and resulting intensity of any
convection. Scattered showers and storms may persist overnight as the
front moves east, but conditions look to dry out for Saturday.

The air mass moving into the region isn`t dramatically different from
the one it`s replacing. As a result, a slight downward trend in
temperatures and dewpoints is expected. So highs in the low to mid
80s look reasonable at this point. For the rest of the extended, dry
conditions will prevail as the upper ridge moves east. There looks
to be some weakness in the ridge over the Ohio and Mississippi
Valleys and this seems to blunt some of our warming up potential.
But given increasing thickness values, warming temperatures aloft and
southerly flow, highs should climb back into the upper 80s to the
lower 90s.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1235 PM CDT THU AUG 27 2015

Convection should be out of the area by 18z-19z, although it might
hold on until 19-20z considering the light upstream echoes to the
west. Otherwise, timing of the precip for tomorrow is tricky. Since
the better precip looks to take place later in the day, went ahead
and backed off on the timing a little bit. So, with the better
chances being in the 18-00z time frame tomorrow evening went ahead
and shaded the timing more toward that time frame. Added the 14z
grouping for winds picking up during the day.




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