Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 101140
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
540 AM CST Wed Jan 10 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today through Thursday)
Issued at 345 AM CST Wed Jan 10 2018

Complicated weather pattern through Thursday as a closed mid-level
low moves towards the Central Plains through the day, expected to
transition to an open wave as it moves across northeastern Kansas
Wednesday night through Thursday.  For today, southerly winds pick
up ahead of the aforementioned system as a tightening pressure
gradient forms over eastern Kansas aiding in another day of warmer
temperatures.  Expect highs today to top out in the low 60s in
central Kansas and upper to mid 50s elsewhere.

The main concern of the period comes Wednesday night as the open,
negatively-tilted wave traverses the area bringing chances for rain,
mixed precipitation, and snow.  Most of the area remains in the warm
sector of this system by Wednesday night with temperatures in the
40s and upper 30s by midnight.  This will lead to rain (and possibly
some drizzle) to begin Wednesday night, transitioning over to snow
by the early morning hours of Thursday as the cold front moves
across the area.  Overall, this change over looks to be fairly rapid
with cold air rushing into northeast Kansas behind the front.  With
this said, there still is a potential for some freezing drizzle or
rain in the morning hours, especially across the eastern portion of
the area where soundings indicate a stronger warm nose. As for snow
amounts, general consensus is the highest amounts will be seen in
north central Kansas with just upwards of two inches expected, and
tapering off further south and east.  Most the area is expected to
see a trace to two inches. There are still many uncertainties with
this system, the most prevalent being if and where a mesoscale band
of heavier snow develops. Frontogenetical forcing at 850mb indicates
the strongest ascent would be near north central Kansas, aligning
with where the highest forecast amounts look to be.  If this does
occur, expect possibly an inch or two more in this area.  Although
snow ratios are not too high, with strong winds behind the front and
gusts up to 35 mph, some blowing snow is expected to occur through
the afternoon hours before winds begin to die down as the system
moves east of the area.  Another factor that looks concerning is the
small time frame in which colder air moves into the area. With wet
conditions ahead of this front, re-freezing on roadways and elevated
surfaces may cause slick conditions on top of falling snow.  For
now, a Winter Weather Advisory has only been issued in north central
Kansas where the highest snowfall amounts are expected. Some
expansion to the Advisory area may become necessary in later
forecast updates.

.LONG TERM...(Thursday night through Tuesday)
Issued at 345 AM CST Wed Jan 10 2018

Cold advection will continue into Thursday evening as a surface
ridge builds over the central CONUS, with wind chill readings
falling to the single digits below zero. Thereafter, mean midlevel
troughing will become established over much of the eastern two-
thirds of the CONUS, as multiple disturbances advance through the
broadly-cyclonic-flow belt surrounding the trough. This pattern
will support another long duration of cold temperatures/wind
chills into the weekend and next week, with periodic chances for
snow accompanying the aforementioned disturbances. The
frontogenetic circulation accompanying a migratory speed maximum
will support a chance for light snow Friday evening and night,
while a band of frontal ascent encourages light snow potential
late in the weekend into Monday. These disturbances may tend to
be somewhat sheared and fast moving, and present indications are
that moisture influxes should be inadequate for substantial
precipitation amounts. Regardless, snow-to-liquid ratios will be
relatively high amid the cold air mass -- conditionally supporting
the potential for some -- albeit modest -- snow accumulations.
Otherwise, reinforcing Arctic air masses will be associated with
periods of sub-0F wind chills.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 539 AM CST Wed Jan 10 2018

IFR to MVFR ceilings associated with stratus will persist through
this morning, before low stratus partially erodes. Marginal LLWS
may affect the TAF sites early this morning, but should be too
marginal/brief for inclusion in the TAFs. Generally VFR conditions
are expected through this afternoon as gusty southerly winds
affect the area. MVFR to LIFR ceilings/visibilities will become
established tonight, with rain developing during the night. The
rain will change to snow from northwest to southeast through early
Thursday morning, as a cold front moves across the region -- with
KMHK experiencing the greatest chance for snow to occur prior to
12Z Thursday. Winds will abruptly shift to the northwest to north
following frontal passage, becoming strong and gusty yielding
areas of blowing snow.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 AM to noon CST Thursday for
KSZ008>010-020-021-034.

&&

$$

SHORT TERM...Heller
LONG TERM...Cohen
AVIATION...Cohen



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