Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 210536

National Weather Service Topeka KS
1136 PM CST FRI NOV 20 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 247 PM CST FRI NOV 20 2015

Main focus for the short-term is on the storm system tracking across
the central U.S. today, which will bring light precipitation and
cooler conditions to the area.

As of early this afternoon, the mid-level trough axis was located
across eastern Nebraska into northwest Iowa, where the best forcing
and lift was resulting in snowfall across that area today.  At the
surface, low pressure was advancing eastward into the area with the
cold front stretching into north central KS. With a modest pressure
gradient in place ahead of this boundary across eastern Kansas and
some scattering out of the cloud cover, afternoon temperatures were
able to reach into the 50s across much of the area.  As the mid-
level trough axis continues to shift to the northeast, models show
this cold front tracking eastward across the forecast area late this
afternoon through this evening. Forcing and lift should quickly
increase by mid to late afternoon and into this evening ahead of
this approaching boundary, so short-range models continue to show
some widely scattered precipitation developing primarily along and
ahead of the front across northeast and east central Kansas by late
afternoon/early evening. With surface high pressure advancing into
the area behind this exiting system, expect precipitation to
diminish from west to east this evening with only some lingering
light precipitation possible across extreme eastern Kansas after
midnight.  While much of this precipitation should remain in the
form of rain, we are continuing to monitor the timing in which the
colder air surges into the area and whether or not there is any
light precipitation left to cause a rain/snow mix.  At this time, a
rain/snow mix cannot be ruled out across far northern and far
northeast Kansas this evening as temperatures plunge to near the
freezing mark. However, model soundings show that as temperatures
approach the freezing mark, we start seeing conditions dry out in
the dendritic growth zone aloft. As a result, do not expect any snow
accumulations from this exiting system.

The other concern with this system will be the increasing winds that
are expected this evening through the overnight hours. Models show a
tight pressure gradient developing over the area on the back-side of
the exiting surface low with a modest low and mid-level jet
overhead.  As winds shift to the northwest with the frontal passage,
expect wind speeds to quickly increase by mid to late evening and
persist through much of the overnight hours, with gusts upwards of
35-40mph.  Cloud cover likely won`t fully clear out until after
sunrise, but expect the breezy northwest winds to advect enough cold
air into the area to plunge low temperatures tonight into the mid
20s to low 30s.  These lingering clouds should quickly scatter out
by mid-morning, but with the surface high tracking over the forecast
area during the afternoon, expect cool conditions for Saturday with
highs only reaching into the mid/upper 30s.

.LONG TERM...(Saturday Night through Friday)
Issued at 247 PM CST FRI NOV 20 2015

The period through Tuesday will be dry with a warming trend. The
upper flow pattern will become more zonal early in the week while a
weak vort max is expected to cross KS on Tuesday. This system will
not impact the sensible weather much, but will see increased low
level moisture and warm advection into the area. The low level
moisture will result in increased cloud cover and perhaps some
drizzle developing into the area by early Wednesday as mid/upper
levels will remain dry. The initial wave will also pull a pool of
colder air into the northern Plains, although not as far south as
Kansas through mid week.

Thanksgiving into Friday a large storm system will impact the area.
This will be a very slow moving upper trough with a steady feed of
low/mid/upper level moisture into the central Plains. While still 6
days away, model guidance is consistent in eventually bringing the
frontal zone into the local forecast area, providing a focus for a
band of heavy and persistent precipitation. This will initially
start as rain with elevated instability suggestive of thunderstorm
potential. However, the post-frontal airmass incoming from the
northern Plains is likely to be quite cold, with temperatures
falling near or below freezing shortly after the front passes. At
the same time, there is a strong signal for very warm temperatures
aloft above the strong shallow front. All of this suggests at least
some potential for 1)Heavy rain especially in east central KS,
2)Winter precipitation in the form of freezing rain or snow, and 3)a
generally wet and cloudy Thursday/Friday period.  It is far too
early to say if there will be any accumulating winter precipitation
and this is primarily due to uncertainty in how quickly the upper
levels will dry out and just how cold the initial post-frontal
airmass will be. Regardless, this storm system bears watching...
particularly given the Thurs/Fri time frame.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1133 PM CST FRI NOV 20 2015

Cold front has gone through TAF sites with strong north winds
gusting over 25 knots. Light rain possibly mixed with light snow
immediately following front has ended at MHK and will be ending by
around 07Z at TOP and FOE. MVFR CIGs expected and may go down to
IFR for a few hours before sunrise. Then expect clearing by mid
morning with gradual weakening winds as high pressure builds in.


.TOP Watches/Warnings/Advisories...


SHORT TERM...Hennecke
LONG TERM...Barjenbruch
AVIATION...GDP is the U.S. government's official web portal to all federal, state and local government web resources and services.