Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 141114
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
514 AM CST Sun Jan 14 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 314 AM CST Sun Jan 14 2018

Early this morning, light snow was seen across all of northeast
Kansas with the heaviest returns in north central Kansas co-located
with the main wave of this system.  Visibilities have varied from
nine miles down to a mile with the falling snow, with limited
visibilities expected through the morning hours before precipitation
moves east and out of the area.  With temperatures this morning in
the teens, snow ratios have been on the order of 12:1 to 15:1.  By
late this morning, expect most areas to have received anywhere from
a half inch to just over two inches.  Precipition will end by noon
across the area today.

For this afternoon, southerly to southwesterly flow across the area
will help bump temperatures into the mid 30s.  Cloudy skies may
briefly break up this afternoon before stratus moves in ahead of an
Arctic front.  The aforementioned front is forecast to move through
the area tonight into early tomorrow morning and bring another
chance for precipitation to the area.  Precipition will be generated
by a strong band of frontogenesis associated with the front moving
southeast across the area.  With temperatures near or slightly above
freezing as precipitation begins, areas of rain/freezing rain/sleet
may be seen briefly before the cold Arctic air moves in changing
everything over to snow.  Snowfall totals look to be slightly less
than this morning, generally due to the progressive nature of the
band along with low snow ratios at the onset of precipitation.
Accumulations of a half inch up to an inch and a half are expected.
Behind this front, cold air rushes into the area and temperatures
drop to the teens with wind chills in the single digits.

.LONG TERM...(Monday through Saturday)
Issued at 314 AM CST Sun Jan 14 2018

With models trending faster with the front Monday morning, think
snowfall should be coming to an end across east central KS a
little sooner than earlier forecast as dry air move in from the
north. The main concern turns to the very cold temperatures.
Models show good cold air advection through the day with
thicknesses and 925MB temps falling throughout the day. So it is
unlikely there will be a diurnal change in temps during the day
Monday. The bitterly cold temps look to stick around into
Wednesday as the arctic high pressure system moves across the
central plains. Highs Tuesday may struggle to reach the teens as
the center of the high builds into the area. Frostbite and
hypothermia may pose a problem Monday night and Tuesday. With sub
zero temps and a 5 to 10 MPH wind through the night, wind chill
values are likely to range from -15 to
-25. Will probably end up needing at least an advisory for the cold
temps Monday night into Tuesday morning, but will wait for now and
let the advisory for the snow play out.

There remains a signal for a wave to potentially impact the central
plains Wednesday night and Thursday. However run to run consistency
remains poor, especially with the ECMWF this morning. Now in stead
of taking the wave across north TX, the ECMWF passes a closed low to
the north of the forecast area. Needless to say there is still some
spread in model solutions with this potential wave. However
available moisture looks to be limited for any precip as the arctic
high pressure system is progged to still be over the lower MS river
valley and nosing into east TX. Given this any significant moisture
return ahead of the upper wave is questionable.

An upper trough looks to move out of the southern Rockies and into
the plains on Saturday. While there appears to be some difference in
how deep this trough may be, the overall trend with the track is to
lift the bulk of the energy to the northwest of the forecast area or
have it progress slower lifting it over the forecast area Saturday
night and into Sunday. In either scenario, it appears the dry slot
could limit precip chances. So the forecast remains dry through the
day Saturday.

Once the surface high begins to move out of the area Wednesday,
temps should moderate for the last half of the week. Southerly low
level flow is progged to develop by Thursday in advance of the upper
wave moving into the southern Rockies. Highs on Friday and Saturday
are forecast to be in the 40s to around 50 and this may end up being
a little on the cool side.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 514 AM CST Sun Jan 14 2018

IFR to MVFR conditions are ongoing at sites due to snowfall early
this morning. Conditions are expected to improve this afternoon
with light snow ending between 13-14Z at sites. Ceilings may break
up this afternoon briefly before stratus moves back in ahead of
the next system. For now, have included the best timing for snow
tonight which is between 03-04Z. IFR visibilities have been added
with the -SN using a persistence forecast from this mornings
snowfall.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM CST this morning for
KSZ008>012-020>024-026-036>040-054>056-058-059.

&&

$$

SHORT TERM...Heller
LONG TERM...Wolters
AVIATION...Heller



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