Area Forecast Discussion
Issued by NWS Springfield, MO

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000
FXUS63 KSGF 211750
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1250 PM CDT Tue Apr 21 2015

...Scattered Storms this Afternoon into Tonight...

.MESOSCALE DISCUSSION...
Issued at 1245 AM CDT TUE APR 21 2015

Gusty southwesterly winds continue across the area early this
afternoon with gusts around 30 mph at times. These gusty winds
are ushering in increased low level moisture as dewpoints in the
40s are spread over the area. The increase in low level moisture
along with day time heating are allowing weak instability to start
developing across the area this afternoon.

An upper level low is located across the great lakes region this
afternoon and energy from the low will rotate through the area
into this evening. Isolated to scattered storms will develop this
afternoon across west central and central MO and then spread
southeast into this evening as lift from the low interacts with
the weak instability that is developing. A few updrafts are
currently trying to develop early this afternoon, but are still
struggling. As low level moisture advection and day time heating
continues enough instability should develop for the isolated to
scattered storms to develop in the next hour or two.

Temperatures in the mid levels are on the cool side with the upper
level low located north of the area. Therefore, it will not take
much of an updraft to get small hail this afternoon and evening.
The severe risk is limited given weak instability and will not be
widespread in nature, but a few of the strong storms may be
capable of hail to the size of quarters and wind gusts over 50
mph.

The scattered storms will push southeast out of south central MO
later this evening. Then overnight a weak cold front will sag
south through the area. Additional isolated to scattered storms
will occur along the front. Instability will still be on the weak
sides but there will still be a risk for small hail with any
storms that develop.

&&

.SHORT TERM...(Today and Tonight)
Issued at 338 AM CDT TUE 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 TUE 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
impossible.

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 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1245 PM CDT TUE APR 21 2015

For the KSGF, KJLN, and KBBG TAFS: Gusty southwesterly winds will
continue to occur this afternoon relaxing later this evening.
Scattered thunderstorms will develop across west central and
central Missouri early this afternoon and spread southeast. This
activity may clip the KSGF TAF site later this after but is expected
to remain east and north of the KJLN and KBBG TAF sites at times.

Low level wind shear will be possible this evening into the
overnight but should start to decrease after a cold frontal
passage later tonight.

Additional scattered thunderstorms will be possible along the front
as is slowly sags south through the area overnight. Winds will
swing around to the north behind the frontal passage.

VFR conditions will occur through much of the TAF period, with
flight conditions being reduce briefly in any thunderstorms that
are able to affect a TAF site.

&&

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

$$

MESOSCALE...Wise
SHORT TERM...Schaumann
LONG TERM...Schaumann
AVIATION...Wise





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