Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 282337
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
637 PM CDT Thu Aug 28 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 249 PM CDT THU AUG 28 2014

19Z water vapor shows the upper trough over eastern CO while the
surface trough axis was located from near DDC through central NEB.
There appears to be a lobe of vorticity within the base of the upper
trough that may be starting to lift out into southwest KS and there
has been some renewed convection over the TX panhandle. Think that
weak isentropic assent near the surface trough axis has allowed for
the light shower activity to persist through the day across central
KS.

For tonight and Friday, the upper trough should continue to slowly
propagate east across the state with modest forcing overspreading
the area. Therefore will maintain some decent chances for precip
through the day Friday. Models continue to show fairly deep moisture
over the area so locally heavy rainfall remains something to watch
out for. However the overall intensity of any thunderstorm may
remain rather modest due to shallow lapse rates above 700MB and
marginal deep layer shear around 20 KTS. Lows tonight could be
affected by several factors including rainfall. However there does
not appear to be much if any cold air advection overnight while
models prog dewpoints to remain in the mid and upper 60s. Because of
this have continued with lows in the upper 60s to around 70. Think
the cloud cover and precip may have a bigger impact on highs for
Friday by limiting insolation. If the rain is continuous, we may not
see highs reach the 80s. However it looks like there should be some
breaks in the precip through the day with the chance for some
sunshine, so have highs in the lower to mid 80s.

.LONG TERM...(Friday Night through Thursday)
Issued at 249 PM CDT THU AUG 28 2014

Vorticity maximum associated with the upper trough axis is centered
over east central KS by Friday evening. Ongoing showers and
thunderstorms are most prominent over east central areas of the CWA
during the evening hours...gradually diminishing eastward Saturday
morning as heights quickly rise behind the departing wave. Temporary
ridging should spell for a mostly sunny Saturday afternoon with
highs in the middle to upper 80s. A weak frontal boundary meanders
through the CWA...positioning over south central KS during the late
afternoon. Surface heating along with some weak convergence along
the boundary may trigger late afternoon thunderstorms over far east
central areas.

Surface trough deepens over eastern CO Saturday evening as a weak
approaching upper trough develops scattered thunderstorms over
Nebraska. Timing is still uncertain between model guidance with
latest runs of the GFS remaining faster than all other guidance.
Have carried low end chance pops over far north central KS thinking
the better chances will exist as the upper trough nears the area
late Sunday afternoon into the overnight period. For being 4-5 days
out, models are in very decent agreement on the track and timing of
the potent shortwave trough. Southwesterly flow increases in advance
of an approaching cold front, advecting h8 temps to the low 20C
range as surface moisture nears 70 degrees. Highs for Sunday were
increased a few degrees into the lower 90s. Strong mixing of the
boundary layer through late afternoon weakens the capping inversion
and develops scattered thunderstorms near the front in northern
Kansas. Severe storms are possible with ample surface based
instability and enhanced wind shear through 6 KM from 30 kts
initially, to 45 kts as the LLJ picks up near sunset. During the
overnight period, precip chances increase CWA wide as an MCS
develops over NE and tracks southeast. Wind appears to be the main
threat overnight.

The cold front becomes stationary over the CWA Monday and Tuesday as
weak embedded waves within the upper zonal flow bring possible
thunderstorm chances periodically through the period. Pattern
becomes more uncertain thereafter as the GFS and ECMWF differ on
placement of frontal boundaries with no apparent troughs to trigger
thunderstorms. Opted for a dry forecast at this time. Temporary cool
down for Monday and Tuesday with highs in the low to middle 80s,
followed by 90s to round out the period.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 634 PM CDT THU AUG 28 2014

An area of thunderstorms across southwest and west central KS may
move into the TAF sites between 4Z and 10Z FRI. Isolated to
scattered thunderstorms will be possible throughout the day
Friday. Most of the time expect VFR conditions, though during
thunderstorms there maybe MVFR conditions.

&&

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

$$

SHORT TERM...Wolters
LONG TERM...Bowen
AVIATION...Gargan






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