Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 181146
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
546 AM CST Thu Dec 18 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 345 AM CST THU DEC 18 2014

Main concern in the short term is the ongoing light to moderate
snowfall across the CWA. Water vapor imagery depicts a few areas of
vorticity maxima within the broad upper trough axis, one rotating
over central KS while the other trailed across western KS. Enhanced
lift in the mid levels coinciding with pockets of instability has
produced heavier bands of snowfall. One snow band in particular
stretched from Ellsworth through Delphos and just south of Concordia
where 3 to 4 inches was reported. Similar reports were observed from
Morris County, northeast to portions of Pottawatomie and Washington
counties. Latest radar images at this hour were showing the back
edge of the heavier snow bands entering portions of north central
Kansas, while additional bands were shifting east towards east
central KS.

The snow is expected to gradually taper with the main
energy lifting north and east by early afternoon. Ice growth is lost
as mid level dry air increases; meanwhile the low levels stay
saturated as forecast soundings show weak lift lingering. Some
uncertainty remains on the extent of this lift, but for now will
leave the mention patchy freezing drizzle through mid afternoon for
much of the area. Overcast stratus and no temp advection to deal
with will hold temperatures to the lower 30s throughout the day.

For this evening, influence from the surface high remains over the
CWA as an upper trough progresses eastward over the northern plains.
Adjusted temps a few degrees down tonight as snow cover drops lows
into the low 20s north central and mid 20s elsewhere. Skies remain
overcast as low level forcing increases slightly below 850 mb. This
varies between guidance, but a slight chance mention for light
freezing drizzle was needed after midnight.

.LONG TERM...(Friday through Wednesday)
Issued at 345 AM CST THU DEC 18 2014

The long term currently appears pretty quiet overall. On Friday, a
trough will cross the Plains states, but locally there will be a
lot of mid-level dry air and no precipitation is expected. The
wild card would be any light shower activity as the enhanced deep
lift perhaps interacts with shallow boundary layer moisture. This
looks unlikely to produce precipitation though.

A wavy zonal flow pattern will exist through the weekend with some
upper ridging on Saturday before the next trough swings into the
Plains states on Sunday. Temperatures will warm a bit this
weekend, but warming could be mitigated by potential cloud cover
and only weak low level warm advection. It appears that this
trough will be well organized and deepening, with a strong incoming
jet streak, but will again lack deep moisture over the local area.
Expect the deep moisture influx to the system to increase by late
Sunday with increasing precipitation, with the question being if
the upper low will advance east of the the local forecast area by
that time. This will depend much on the timing of the jet streak
as the trough is forecast to deepen, stall, and then travel
northeast Monday into Tuesday. If this transition occurs farther
west, then precipitation chances would increase quite a bit for
late Sunday into Monday. For now, have mainly slight chances for
what would likely be rain perhaps changing to snow. Will need to
keep an eye on how this evolves though and changes are possible.

Otherwise, expect nearly normal temperatures for the rest of next
week. The upper flow pattern becomes more zonal in the wake of the
early week storm system, and models are now hinting at what could
be an interesting storm system impacting some portion of the
central Plains by late next week...perhaps including Christmas.

&&

.AVIATION...(For the 12Z TAFs through 12Z Friday Morning)
Issued at 535 AM CST THU DEC 18 2014

Latest radar trends indicate light snow underneath MVFR stratus
will persist through 15Z at KTOP/KFOE. Observations upstream note
IFR stratus pushing eastward while short term guidance hints at
ceilings lowering to just under 1000 feet as the snowfall ends.
These conditions persist through the day with drier air near the
surface attempting to lift cloud deck back to low end MVFR by late
afternoon. Conditions hover near low end MVFR through forecast
period with a low potential for patchy freezing drizzle to impact
terminals overnight.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 9 AM CST this morning FOR
KSZ008>012-020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Bowen
LONG TERM...Barjenbruch
AVIATION...Bowen





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