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000
FXUS63 KSGF 122220
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
520 PM CDT Sat Apr 12 2014

.SHORT TERM...(This evening through Sunday night)
Issued at 120 PM CDT SAT APR 12 2014

The main concern will be severe weather potential Sunday
afternoon/night.

The 12z KSGF raob shows the establishment of a cap/elevated mixed
layer (eml). Upstream raob sites would indicate some further
strengthening of the cap over the next 24 hours. Can`t rule out
some modest measurable rain chances/pops over the northern and
western cwfa as some elevated warm advection convection occurs
late tonight and Sunday morning, but the better chances for precip
will be near a sfc warm front north of the area where weaker
capping is present.

A shortwave now over far southern CA and northern Baja will move
quickly northeast into southeast KS and eastern OK by early Sunday
evening while a long wave upper trough axis (and much colder sfc
air) shifts south and east into northern/central Plains. Guidance
trends have slowed the progress of the approaching shortwave
slightly, and this in effect has delayed the progged timing of
the eroding of the cap just a bit Sunday afternoon (GFS is a bit
faster weakening the cap versus the NAM).

In general we should see convection intensify/blossom in two
areas toward mid and/or late afternoon Sunday: 1) Along the main
cold front from nw MO into eastern KS and ne OK, and 2) As the cap
weakens breaks over the four states KS/MO/OK/AR area. By this time,
progged instability/mlcape over far southeast KS is fcst to be
around 1000-1200 J/kg. Discrete updrafts that can initiate ahead
of the front will have chance to become supercells.

Convection should quickly go linear given the parallel
orientation of the front relative to the mid level flow and as the
sharp initially shallow front undercuts convection. Wind/hail
should be the main storm risks. But a brief tornado risk will also
exist in the afternoon and early evening over the far west and
southwest cwfa while stronger instability exists where (and if)
initial discrete storm development can occur where sfc winds are
somewhat more backed farther out ahead of the sfc front.

While a brief period of heavy rain is likely with localized brief
flooding possible, most likely Sunday evening/overnight with the
frontal passage, the progressive nature of the front should keep
the overall threat for flooding low. Actually, many areas could
use the rain.

.LONG TERM...(Monday through Saturday)
Issued at 120 PM CDT SAT APR 12 2014

Unseasonably cold air comes rushing in behind the front. The NAM
and GFS raw guidance has definitely trended colder for Monday. If
and when there is enough moisture depth, wet snow will be possible
during the day Monday. Went with a blend of mos and raw
temperature guidance which will keep temperatures in the 30s for
much of the day for a large portion of the cwfa. Cloudy, dank,
blustery, and cold sums it up for Monday.

A frost/hard freeze is definitely possible Monday night and
Tuesday morning with guidance trending colder with GFS mos
guidance temperatures falling into the mid 20s.

Given the dry/chilly air mass, some additional frost will be
possible for many areas Tuesday night as well.

A warming trend to more seasonable temperatures is expected by
Thu and Fri. Another system may affect the area by Friday. The GFS is
bullish with the progged rain amounts Friday, and in general question
how fast it is bringing back moisture from the Gulf. The 00z
ECMWF is slower in bringing in the system and slower with moisture
return which seems reasonable. Will disregard or at least tone down
the very high pops of the GFS for now and use a modified version
of a model blend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 517 PM CDT SAT APR 12 2014

Winds will be the primary aviation hazard for much of the 00z TAF
with the approaching storm system. Will have gusts through the
period in the 25 to 32kt range and will likely have low level wind
shear tonight at 40 to 50 kts. As the front moves closer to the
area on Sunday, thunderstorms are expected to develop by late
afternoon and will include a tempo group for this at JLN and
prob30 for SGF/BBG in the last few hours of the TAFS. Should start
to see ceilings lower tonight into the MVFR category as low level
moisture increases in advance of the shortwave.

&&

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

$$

SHORT TERM...DSA
LONG TERM...DSA
AVIATION...Lindenberg