Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 141132
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
532 AM CST Tue Nov 14 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 309 AM CST Tue Nov 14 2017

Isentropic lift has caused areas of drizzle to form across most of
eastern Kansas associated with the broad low level jet.  Reduced
ceilings and visibility are also seen early this morning due to the
drizzle and possibly some patchy fog.  Unfortunately, these
persistent cloudy skies and drizzly conditions look to continue
through the day today as the boundary remains saturated through the
period.  Cloud cover will only allow temperatures to rise slightly
into the mid-upper 50s across the area.

Tonight, mid-level ridging begins to break down as shortwave trough
moves eastward across Canada.  At the surface, a front is expected
to move across the area late tonight into the overnight hours.
Soundings indicate an increase in low level lift with this front
which will allow for any drizzle to become rain showers.  Did
include the mention of some thunder mainly across east central
Kansas where meager elevated instability looks to be best.  With very
limited CAPE across the area ahead of this front, no severe weather
is expected even with the robust 0=6km bulk shear values noted.
Skies finally start to clear from northwest to southeast as the
front moves through overnight.  With this, cooler temperatures in
the low 40s will be seen in north central Kansas tonight, with lows
near 50 in east central Kansas.

.LONG TERM...(Wednesday through Monday)
Issued at 309 AM CST Tue Nov 14 2017

Wednesday through Thursday, an upper level trough will be
moving east from the mid and upper MS river valley eastward
to the Atlantic coast. A more amplified upper trough will be
moving on shore across the Pacific northwest. A low-amplitude
upper ridge will move east across the plains on Thursday.
A weak front will push southeast of the CWA by 12Z WED brining
an end to any showers. Skies will clear across east central KS
during the morning hours. A weak surface ridge of high pressure
will move east across the CWA on Wednesday, then shift east across
the mid and lower MS river valley on Thursday. A lee surface
trough will amplify across the central and southern high plains on
Thursday. Southerly low-level winds will begin to advect residual
moisture northward across the southern and central plains
resulting in an increase in low stratus clouds Thursday afternoon.
Highs on Wednesday may be a bit warmer to do insolation with
highs reaching the mid to upper 50s. The cloud cover Thursday
afternoon may keep highs in the mid 50s.

Thursday night through Friday, The upper trough moving east across
the western conus will have a positive tilt orientation as it
moves east across the central Rockies. Our better chance of rain
and drizzle will be Thursday night into Friday morning as more
southerly low-level flow continues to advect modified gulf
moisture northward across eastern KS. The resulting Isentropic
lift should provide for a chance for drizzle and/or light rain. As
the 850mb winds veer to the southwest through the day Friday, the
deeper moisture transport will be across eastern TX northeast to
MO. Skies may even clear a bit Friday afternoon. Highs wil reach
the mid to upper 60s due to the WAA and if we see more insolation
during the afternoon hours we may reach the lower 70s.

Friday night through Saturday, the positive tilt upper level trough
will move east across the upper midwest and southern plains.
Stronger low-level CAA across the northern and central high plains
will cause a cold front push southeast across the CWA late Friday
night into Saturday morning. The deeper moisture will be located
well to our east ahead of the H5 trough, but there may be enough
ascent ahead of the H5 trough for a chance for light rain showers
Friday night into Saturday morning. However, due to the lack of
low-level moisture we may only see trace precip amounts. The
positive tilt upper trough will quickly pass east of the CWA and
isentropic downglide on the west side of the trough axis will
clear skies Saturday morning. Highs will be cooler Saturday, with
lower 50s expected.

Saturday night through Tuesday, The extended range model solutions
begin to diverge. The ECMWF remains progressive and moves the H5
trough east of the plains, eastward off the Atlantic coast by
Sunday night. The pattern transitions into a high over low block
as an upper trough in the southern stream of the jet amplifies as
it moves east onto the southern CA coast, then east-northeast into
the four corners region on Tuesday. While a broad downstream
upper ridge develops over the central Rockies within the polar jet
as a longer wave-length trough amplifies across the eastern
Pacific Ocean/Gulf of Alaska region. The ECMWF solution would
provide the CWA with dry conditions with highs in the mid to upper
50s and lows in the upper 20s to lower 30s. The GFS has a more
amplified solution, developing a longer wave-length trough across
the eastern US and an upper ridge across the western US. This
pattern will keep the plains states under northwestelry flow at
mid and upper levels of the atmosphere. The GFS digs a minor upper
through southeast across the central plains Monday night into
Tuesday brining a chance for light rain showers which may mix with
and change to snow showers early Tuesday morning. Highs will be
in the lower to mid 50s with overnight lows in the upper 20s to
lower 30s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 532 AM CST Tue Nov 14 2017

Reduced visibilities and ceilings are expected for the entire
period. IFR to LIFR conditions are seen this morning with patchy
drizzle and BR expected to continue most of the day. A front moves
through this evening bringing -SHRA to sites between 02-04Z.
Southerly winds will shift from the north behind this front. Exact
timing of the front will need to continue to be monitored, as well
how low ceilings will stay today as some models show a brief
period of improvement this afternoon.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Heller
LONG TERM...Gargan
AVIATION...Heller



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