Area Forecast Discussion
Issued by NWS Topeka, KS

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211
FXUS63 KTOP 230450
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1150 PM CDT THU SEP 22 2016

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 322 PM CDT Thu Sep 22 2016

Water vapor imagery showing tropical feed of moisture aloft
weakening in the continued southwest flow with deep upper low
moving into Nevada. Frontal boundary remains nearly in place over
the last day or so from far northwest Kansas to east central
Nebraska. Dewpoints are not quite what they have been but heat
index values were still in the mid 90s in most areas.

Troposphere to continue to dry tonight into Friday with a more
southerly low level flow developing as the upper flow amplifies.
This also brings slightly cooler air with highs in the upper 80s
more common with mainly clear skies both tonight and Friday.

.LONG TERM...(Friday night through Thursday)
Issued at 322 PM CDT Thu Sep 22 2016

A shift in the weather pattern is expected this weekend into next
week, with increasing precipitation chances and much cooler
temperatures.

By Friday night, the deep mid-level trough over the Rockies will be
advancing eastward into the Northern and Central Plains, which will
help to push a cold front into the area. This front will move into
western KS late Friday night, shifting into central KS by Saturday
morning. Decent southerly flow ahead of the front will support
decent warm-air and moisture advection into the area. The frontal
passage will provide enough lift to support the development of
widespread showers and thunderstorms through the day. With the slow
progression of the frontal passage on Saturday, much of the CWA
should remain predominantly under southerly flow. However, with the
increasing cloud cover, afternoon high temperatures will be cooler
in the low/mid 80s.  Model soundings show the cap eroding away
during the early afternoon hours, resulting in surface-based storms
developing. With 1500-2500 J/kg of CAPE in place along with 0-6km
bulk shear values near 30 kts, there is the concern for some
marginally strong to severe storms to develop along the front. The
primary concerns with these storms will be strong winds and heavy
rain. The slow-moving nature of this frontal passage along with PWAT
values of 1.5 to 2.0 inches will result in the potential for some
locally heavy rainfall Saturday into Sunday. The front will finally
shift east of the CWA Sunday morning with post-frontal showers and
isolated storms diminishing in coverage from west to east.  Winds
will finally shift around to the north overnight into Sunday, so
these northerly winds combined with cloud cover and lingering
precipitation will result in much cooler conditions by Sunday with
highs only reaching into the low 70s. The GFS/ECMWF move
precipitation out of the CWA by Sunday night into Monday with dry
conditions through mid-week. The Canadian model is the outlier with
keeping precipitation chances across eastern KS through mid-week due
to it`s placement of a closed mid-level low southwest of the area.
Have discounted this model and have gone with a dry forecast Monday
night through Thursday as the GFS/ECMWF both show a large ridge
moving into the central U.S.  Cooler than normal conditions will be
present through the first half of next week with highs in the upper
60s to low 70s, and lows in the upper 40s to low 50s.  Conditions
will gradually moderate by mid-week with seasonal conditions
expected by Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1145 PM CDT Thu Sep 22 2016

VFR conditions are expected through the TAF period. 30-35 kt winds
at 1000 feet will persist through around 12Z but will remain
slightly less than LLWS criteria.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...65
LONG TERM...Hennecke
AVIATION...Barjenbruch



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