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000
FXUS63 KTOP 192340
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
640 PM CDT Tue Sep 19 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 350 PM CDT Tue Sep 19 2017

Currently, an upper level trough is becoming negatively tilted over
the Northern Rockies into the Northern Plains as the associated
trough axis pivots into the region.  This is reinforcing frontal
features at the surface with a warm front analyzed from the Dakotas
into Iowa.  A cold front is marching into western Nebraska and a
dryline feature is extending from western KS into the TX panhandle.
With southwestern flow over the Rockies, a surface pressure gradient
has tightened up over the forecast area.  This along with deep
mixing above the H85 level has allowed winds to increase this
afternoon to above 30mph across much of the area and temps to rise
into the upper 80s and even mid 90s around Manhattan and points
west. Have kept wind advisory in place until 00Z tonight as winds
will stay strong through the afternoon. Forcing for ascent is not
very strong over the area, but a LLJ will be in place tonight with
speed maximums possible up to 50kts. With moisture quality aloft
lacking though, not expecting storms overnight.  Thus, going with a
dry forecast at this time. The weak cold boundary will eventually
push into the area by morning and stall out over eastern portions of
the forecast area leaving the surface trough spread over the region.
Expecting winds to remain light tomorrow due to this type of set up.
Boundary layer should remain capped though aloft, so at least
tomorrow during the day, have again gone with a dry forecast.  Temps
also should be cooler over much of the area in the low to mid 80s.
It is possible on the warmer side of the boundary that some of the
counties in east central KS could reach into the upper 80s and
around 90.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 350 PM CDT Tue Sep 19 2017

Expect to see a few storms fire across East Central Kansas in the
unstable airmass ahead of weak front Wednesday evening. Weak shear
across the area will limit overall severe potential.

12Z GFS/ECMWF are in good agreement in slowly progressing the long
wave trough over the western US eastward into the plains through the
period.  Newer runs continue to slow the onset of precipitation
across eastern KS with timing now delayed into Sunday/Sunday Night.
Ahead of the trough, strong southerly flow will push temperatures
well above seasonal normals into the upper 80s to mid 90s with
apparent temperatures in the middle to upper 90s.

Slow movement of the upper trough along with high precipitable water
values will bring the threat for heavy rains Monday and Tuesday.
Persistent cloud cover on Monday and Tuesday will restrict
temperatures to the 70s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 634 PM CDT Tue Sep 19 2017

VFR prevails at terminals with strong southerly winds gradually
veering with the frontal passage progged in the 12-14Z range for
KMHK and 17-19Z for KTOP/KFOE. Dry conditions are anticipated with
the frontal passage with perhaps diurnal cumulus around 4 kft
developing aft 18Z. There is a slight chance for post frontal TSRA
towards the end of the forecast period, with better chances just
east of terminals. LLWS is also of concern aft 03Z as a strong
LLJ increases up to 60 kts near 2 kft.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM CDT this evening for KSZ008-009-020>022-
034>038.

&&

$$

SHORT TERM...Drake
LONG TERM...BW
AVIATION...Prieto