Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 210547

1147 PM CST Sat Dec 20 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Sunday)
Issued at 325 PM CST SAT DEC 20 2014

A weak upper level trough moving eastward across the central Rockies
this afternoon will move east into the plains on Sunday. Ahead of
the upper level trough residual moisture across TX and OK will
advect northward later tonight into Sunday. The resulting
WAA/isentropic lift will cause low stratus to form and move north
across the area during the evening hours. Areas of fog and patchy
drizzle will develop after midnight from south to north across the
CWA. Temperatures across the CWA should be in the mid to upper 30s
by the time the drizzle develops towards sunrise.

Sunday will be mostly cloudy with areas of fog and patchy drizzle
through the morning hours. The drizzle may continue on and off
through the day as weak lift continues ahead of the H5 trough. The
low-level WAA advection should warm temperatures into the lower to
mid 40s despite the cloud cover.

.LONG TERM...(Sunday Night through Saturday)
Issued at 325 PM CST SAT DEC 20 2014

A shortwave trough will move eastward across the Plains Sunday night
while another trough/upper low moves southeast out of Canada.
Increasing large scale forcing ahead of each trough will bring a
chance of light rain to the area. The better forcing, mid level
frontogenesis and convergence of Q vectors will be across eastern
Nebraska into northeast Kansas and northwest Missouri where highest
probabilities are expected. A cold front will move through during
the day with bulk of cool advection in the late afternoon and
evening. Highs Monday will top out in the upper 40s to lower 50s in
warm advection pattern despite cloud cover. Conversely highs Tuesday
will be some 10 to 15 degrees cooler with highs mainly in the upper

Energy rotating around the upper centered over northeast Nebraska
will be focused further north and no loner expect any precipitation
in the far northern counties on Tuesday.

Upper flow transitions from northwest to a more west to southwest
upper flow on Christmas Day with both the ECMWF and the GFS coming
into more agreement in the overall pattern. Each is still developing
a lee side low over southeast Colorado with it moving northeast
across Kansas Thursday night and into northeast Missouri or
southeast Iowa by 12Z Friday. 12Z runs of both the ECMWF and the GFS
are focusing precipitation further north in Nebraska than previous
runs and ensembles. Will continue to keep a slight chance of snow
for Thursday night and Friday. Will need to monitor later runs, but
for now will continue in a low confidence forecast. Thickness
profiles suggest that whatever falls will primarily be light snow.


.AVIATION...(For the 06Z TAFs through 06Z Sunday Night)
Issued at 1142 PM CST SAT DEC 20 2014

MVFR cigs have moved into MHK and are expected to move into
TOP/FOE in the next few hours. Could see a few breaks but think
these cigs will prevail through the day on Sunday. Did not add
drizzle to terminals as lift is weak and may remain in obs as BR.
Second system approaches right behind first to keep clouds and
possibly light precipitation going into the next overnight period.




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