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Area forecast discussion 
National Weather Service Topeka Kansas
532 am CST Friday Nov 27 2015

..update to aviation forecast discussion...

Short term...(today and tonight)
issued at 329 am CST Friday Nov 27 2015

An extremely complex weather setup remains over the region in the
short term. Winter precipitation took a brief break early this
morning, but the next round was beginning to develop into the
forecast area as of 3 am. A strong temperature gradient, both at the
surface and aloft, also remained in place early this morning and
will remain over the area through the next 24 hours as it waivers
back and forth. At least as of 3 am, the entire area was at or below
freezing at the surface which all but removes rain potential in
favor of freezing rain, sleet, or snow. Through tonight, at times
when precipitation impacts the area, expect the precipitation type
to range from freezing rain in the southeast to sleet and then snow
with northwestward extent. Current indications are that the area
with the best chance to maintain freezing rain as a precip type is
near/southeast of an Emporia to Lawrence line. Sleet or freezing
rain will be predominant near/southeast of a Herington to Holton
line, with a mix of mainly sleet and snow northwest of that line. At
any given time as embedded short waves pass through the flow, those
lines may fluctuate to the southeast or northwest.

In terms of timing and intensity of the precipitation, this is also
a complex topic as it involves persistent vertical motion but with
periods of enhanced vertical motion in advance of embedded short
wave troughs. One rather strong wave will move from SW Kansas across
the area through sunrise while another area of enhanced lift will
follow only a few hours behind the first. In the local area, it
currently appears that the most likely time periods for heavier
precipitation rates will be from 4-7 am, and perhaps again from 9 am
to 1 PM. Within these precip enhancements, freezing rain rates may
briefly approach 0.08-0.10" per hour while sleet could come in at
around 0.25" per hour and some potential for a band of 0.5" per hour

While the specifics of the weather through this period are quite
complex and difficult to nail down, the general impacts are fairly
straight-forward. Travel will be very hazardous at times, especially
now that Road and bridge temperatures have dropped significantly
since yesterday. Otherwise, the main thing to watch will be whether
the freezing rain areas can set up persistently enough to result in
bands of heavier ice accumulation, perhaps enough to cause tree or
power line damage. This is currently a possibility but not a strong
one as there is too much uncertainty regarding the amount of sleet
that will mix in as well as near-freezing surface temperatures
limiting efficiency a bit. Will be closely monitoring the incoming
precip enhancements for any potential need for an Ice Storm Warning.

It does appear that precip will wane a bit after sunset, but the
persistent lift and moist atmosphere along with weak embedded waves
begs the continuance of pops through the night as periods of
additional mixed winter precipitation are likely even if precip is
not as widespread, any additional accumulation along with freezing
drizzle will continue to impact travel. The Winter Storm Warning and
Freezing Rain Advisory have been extended through tonight.

Long term...(saturday through thursday)
issued at 329 am CST Friday Nov 27 2015

The expansive closed upper low will continue to lift waves of
enhanced lift from the southwest, supported by a steady stream of
Gulf moisture into the plains region. Overall, specific tracks of
these waves is varying between guidance on Saturday and Sunday in an
area of qpf lifting across southern and eastern portions of the County Warning Area.
This signal is not particularly strong, but may be enough to cause
additional icing issues. An 750-800mb jet streak warms temps back up
to near 5-7c with any falling precip in the frozen variety. The loss
of moisture in the ice growth layer also begins to diminish through
the weekend, mixing the light freezing rain with freezing drizzle.
Another complicating factor is the shallow sfc cold air advection
that begins to wane allowing temps to rise above freezing (mainly
over east central Kansas where precip chances are highest). Therefore
frozen precip may also switch to rain and/or drizzle temporarily in
the afternoon before falling back to near freezing at the sfc
Saturday evening. This will definitely have implications on the
actual amount of ice we receive Saturday-Sunday night so have gone a
bit on the conservative side with totals as sfc temps hover near
freezing and confidence in precip actually occurring is on the lower
side. So overall amounts are between a thin glaze up to two tenths
of an inch. Will likely need to expand and extend the Winter Weather
Advisory through at least Saturday, but will hold off this forecast
to see if we can get a better handle on areas of greatest icing
impacts. Light freezing drizzle may linger into Sunday morning before
transitioning to drizzle and rain during the day as highs Sunday
recover into the middle 30s. One final push of winter precip occurs
late Sunday evening into Monday as guidance is persistent in a decent
shortwave trough entering the western coast, becoming ingested in
the weakening closed low before lifting northeast. Saturation in the
column may be delayed with a light freezing drizzle for the onset
before the trough axis lifts over northern KS, cooling temps enough
for light snow. Higher chances are emphasized north of Interstate 70
through Monday with a rain/snow mix likely as temps rise in the
upper 30s for highs. Snowfall amounts are still too uncertain at this
point,but something to watch for to start the work week.

Conditions finally quiet Monday evening Onward as the upper low
exits east and upper ridging brings dry and seasonable conditions to
the region.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 528 am CST Friday Nov 27 2015

Ongoing low-end MVFR to IFR cigs will continue in the short term
along with increasing precipitation in the form of freezing rain
and sleet. There will be occasional breaks in precip, but see
enough potential through the entire taf period to keep mention of
fzrapl through the taf. Main uncertainty is if cigs will decrease
to IFR at all sites and then persist at that level, but for now,
MVFR at top/mhk...and periods of IFR and MVFR at foe look to be
the most likely conditions.


Top watches/warnings/advisories...
Winter Storm Warning until 6 am CST Saturday for ksz010>012-

Freezing Rain Advisory until 6 am CST Saturday for ksz026-039-

Winter Weather Advisory until noon CST today for ksz008-009-020-



Short term...barjenbruch
long term...Bowen

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