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Area forecast discussion 
National Weather Service Springfield MO
638 am CDT Tue Apr 21 2015

..12z aviation update...

Short term...(today and tonight)
issued at 338 am CDT Tuesday Apr 21 2015

The next 24 hours or so will be interesting and challenging from a
forecasting perspective. The synoptic scale pattern will feature
a northwesterly flow aloft with multiple embedded short wave
troughs and jet speed maxes passing through the flow. These types
of setups can often overachieve when it comes to precipitation and
convective potential given both the amount of synoptic scale lift
and cold temperatures in the mid-levels of the atmosphere
(resulting in instability). One item really going against
precipitation potential is the very dry state of the lower and
middle troposphere. This is evident when looking at 00 UTC
regional raobs.

It looks like we have three distinct features that will provide US
with precipitation potential through tonight. The first feature
is a short wave trough currently moving southeast across western
Kansas. Regional radar and satellite trends are indicating weak
convective development rooted in the mid-levels of the atmosphere
across southern Kansas and Oklahoma. This activity will slide east
early this morning as isentropic upglide ahead of that short wave
trough punches into western Missouri. At this time, we believe
that sprinkles/very light rain showers will be the main weather
phenomenon with this activity this morning.

As we head into this afternoon, this first wave will continue the
threat of showers...mainly across the central and Eastern
Ozarks. Short range models then indicate another approaching short
wave trough dropping southeast into eastern Kansas this afternoon.
Model cross-sections indicate a weak confluent flow initially
developing from eastern Kansas into central Missouri ahead of this
feature. This should be enough to kick off additional showers and
even a few thunderstorms. This activity should then shift south
towards Highway 60 late this afternoon and early this evening.

Setups like this can also overachieve when it comes to the
potential for "stronger" convection. Instability today will be
rather marginal and largely due to very cold mid-levels of the
atmosphere. MLCAPE values will be in the 400-800 j/kg range during
peak heating (highs in the mid 60s to around 70 degrees). Deep
layer shear will certainly be formidable with 0-6 magnitudes in
the 40-50 knot range. These types of setups can often result in
cellular showers/thunderstorms developing...many of which produce
small hail (even the showers). Some of the stronger updrafts will
be capable of putting down slightly larger hail...perhaps around
the size of quarters. If the lower levels of the atmosphere are
able to remain fairly dry, higher bases with the convection may
also result in good evaporative cooling and gusty wind potential.

Not to be forgotten, we may then see a third round of convective
precipitation later this evening and tonight as a stronger short
wave trough dives southeast across the corn belt. This wave will
drive a cold front south into the Ozarks with this front providing
another potential focus for this convection.

Long term...(wednesday through monday)
issued at 338 am CDT Tuesday Apr 21 2015

That cold front will then settle south towards the Red River
valley from Wednesday into Wednesday night. The 850 mb front will
tend to hang up from eastern Kansas into northeast Oklahoma and
western Arkansas. This may keep the door open for precipitation
chances across extreme southeastern Kansas and southwestern
Missouri... especially Wednesday night if any sort of isentropic
upglide develops. This will be largely dependent on any sort of
approaching short wave energy (which models are not really
indicating at this point).

Upper level ridging will then overspread the area on Thursday.
Besides any leftover precipitation from Wednesday night across
southwestern Missouri, Thursday should generally be dry. That
ridge axis will then slide to our east starting Thursday night as
a strong short wave trough begins to eject out of the baja of
California and towards the Southern Plains. This should lead to
increasing chances for showers and thunderstorms later Thursday
night as large scale ascent begins to increase across the region.

That upper level energy will then track right towards the Missouri
Ozarks on Friday with surface low pressure developing across the
Texas/Oklahoma Panhandle region. This will likely lead to
continued showers and thunderstorms Friday and Friday night.
Showers and perhaps some thunderstorms will then linger into
Saturday as that low pressure system tracks through Missouri and
towards the Ohio Valley.

We will then slip back into a northwest flow aloft early next week
with global models indicating another ripple or two of energy
traversing the region. We kept pops in the 10-30% range early next
week for now given that timing such features out that far is

Temperatures from later this week into early next week will
generally remain slightly below normal. The coolest days will
likely be Wednesday and Thursday with highs from the upper 50s to
middle 60s. While we will see a few nights with lows well down
into the 40s, there does not appear to be any frost threats at
this point.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 623 am CDT Tuesday Apr 21 2015

Showers and perhaps a few thunderstorms are expected to develop
this afternoon, lingering into the evening hours as a frontal
boundary slips into the area. Coverage isn't expected to be all
that widespread, and have utilized a pro30 group for now to
account for the scattered nature to the showers/thunderstorms.
While a brief dip to MVFR or even IFR isn't out of the question
should a storm directly impact a terminal, right now it appears
that VFR should prevail most of the day today into tonight.

Otherwise, expect gusty southwest winds during the day today ahead
of the front.

Precipitation chances should decrease later tonight as the front
starts to move through the area, with winds starting to become
northerly behind the front late tonight.


Sgf watches/warnings/advisories...


Short term...schaumann
long term...schaumann

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