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000
FXUS63 KTOP 042342
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
542 PM CST Wed Dec 4 2013

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Thursday)
Issued at 251 PM CST WED DEC 4 2013

Much colder air invaded the region overnight, with falling
temperatures across much of the area through the day on Wednesday.
It would appear that temperatures will not rise above freezing in
the coming week. A fast moving short wave trough, over southern Utah
this afternoon, will track across southern Nebraska by tomorrow
morning. As it passes, a re-enforcing surge of cold air will impact
the area. This system will also bring a period of enhanced lift this
evening into the early morning hours, with a band of frontogenesis
expected from north central into northeast Kansas. While cold and
dry advection will be ongoing in the low levels, almost all model
guidance is suggesting that the magnitude of lift will be sufficient
to overcome the dry air...with short term high-res guidance a bit
more aggressive in setting up the snow band. The time frame for snow
will be short-lived however, as the short wave trough is very fast
moving and dry advection should diminish snowfall quickly as the
forcing for ascent wanes. In the end, it appears that areas north of
a Herington to Topeka line could see between a dusting and an inch
of snow tonight. Winds will be gusty as the snow falls, and could
result in brief periods of reduced visibility.

The area of frontogenesis is forecast to persist, although weaker,
through Thursday as it shifts south across the area. At this time,
the expectation is that the lift will not be sufficient and the dry
air too dry to produce more than virga and flurries across the area
on Thursday. Meanwhile, widespread cloud cover and cold advection
will only allow highs in the lower to middle 20s with the warmest
wind chill of the day expected to range from 5 to 15 above zero.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 251 PM CST WED DEC 4 2013

By Thursday afternoon a mid level shortwave will lift NE into the
southern plains. Ahead of the trough an area of moisture and lift
will work into far southeast KS overnight Thursday. The best chances
for snow during this period will be along and south of interstate
35. The snow will most likely be relatively light and only amount to
around 1 inch in those areas. The models have been trending south
with the track of the track of the shortwave so would not be
surprised if this continues and those areas receive flurries at
best. Cold temperatures definitely certain during this period which
really take over the entire area Thursday night. On Friday morning
the combination of the temps and wind result in wind chills
approaching -0s to -10s especially across the northern areas. Clouds
try to clear out of the region during the day Friday but do not
expect the sun to have much of an influence on this air mass with
high temperatures struggling to reach the 20s, and wind chill values
remaining in the 0s.

On Saturday that mid level shortwave progresses eastward and
surface high pressure slides through the northern plains and upper
Midwest. High temperatures on Saturday will be in the low 20s with
wind chills in the 10s and clouds building into the region. On
Saturday night the main longwave trough and associated energy lift
NE into the central plains. Ahead of the passing wave isentropic
lift develops over most of eastern KS. Low level moisture works back
into the area from the Gulf while Pacific moisture spreads across
the region in the mid levels. The shortwave supplies the large scale
lift which will result in widespread light snow. Snow develops early
Sunday morning and persists through most of the day. The snow will
generally be light due to a relatively thin dendritic growth layer
and no banded precipitation expected. The models agree that liquid
QPF amounts will be around 0.20 inches...with "snow to liquid"
ratios around 13-15 to 1...giving the entire area 2 to 4 inches of
snow by Sunday evening. The highest amounts appear to fall in
southwest and central KS but that is subject to change depending on
the shortwave evolution. If the system tracks further north
southern portions of the area could experience a change over to
freezing drizzle as a mid level dry punch moves over. After 00z
Mon the better lift moves east of the area and isentropic
downglide develops in the mid levels although flurries or drizzle,
depending on the dry punch, may linger through the evening hours.

Monday and Tuesday will remain cold with high temperatures in the
20s and low temperatures in the 0s. Surface high pressure builds
into the plains on Monday night and low temperatures drop into the
low to mid 0s. Wind chills approach the mid -10s Tuesday morning
which is close to advisory criteria and bears watching. Would not be
completely surprised to see several places drop below 0 especially
with clearing skies and possible widespread snow cover. By Wednesday
high temperatures could warm to near freezing for most areas with
low temperatures in the mid 10s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Thursday Evening)
Issued at 542 PM CST WED DEC 4 2013

MVFR ceilings are slowly working out of terminals, and attempted
clearing timing based on upstream trends and short-range models.
Cannot rule out MVFR visibilities and possibly ceilings in -SN,
mainly at KMHK in the 05Z-11Z window, but chances seem rather low
at this point.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Barjenbruch
LONG TERM...Sanders
AVIATION...65