Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 180422

Area Forecast Discussion
National Weather Service Topeka KS
1122 PM CDT Sun Sep 17 2017

Issued at 1122 PM CDT Sun Sep 17 2017

Models continue to trend slower with the elevated precip spreading
east overnight. Latest water vapor imagery shows a low amplitude
shortwave still over parts of western CO and NM. Meanwhile 850MB
winds remain relatively weak and isentropic surfaces from the NAM
tend to only show disorganized upglide until mid morning once the
shortwave out west begins to impact the region. Therefore have
delayed the higher POPs spread to the east until closer to 12Z.
Skies should remain cloudy for the rest of the night and surface
obs do not indicate any low level cold air advection. With winds
progged to have a more southerly component through the night, do
not expect much more cooling and temps should remain fairly
steady or only cool a degree or so.


.SHORT TERM...(This evening through Monday)
Issued at 334 PM CDT Sun Sep 17 2017

Overnight rainfall followed by a day of cloud cover has helped
keep the cooler airmass in place, with the office just hitting 70
over the past hour. Surface front appears to have pushed southward
into southeastern Kansas, likely aided in that push with earlier
convection over KS and MO. Area is in a bit of a break between
lift for convection, with just a few light showers on approach to
our southern border at this hour. Of note for convection potential
are a weak wave over Western Kansas, with stronger convection
along the high plains east of the Rockies. Appears at this time
like the main player will be the one over the Rockies, moving over
eastern Kansas by tomorrow morning. LLJ is also on the increase
and veers with time ahead of the wave, and some weak jet coupling
noted over our are in the 12-18z timeframe. Have increasing
chances through tomorrow noon then diminishing to the east in the
afternoon. Plenty of CAPE for thunder, with around 1-2K J/kg of
elevated skinny cape available to work with, and area is in a
marginal risk for severe storms with hail the primary hazard. PW
analysis indicating around 150 percent of normal, and may get some
locally heavy rainfall with these storms. Given such dry
antecedent conditions, even after this mornings rainfall, not
overly concerned with flooding but worth noting that higher rates
over the eastern counties could make for problem spots in those

.LONG TERM...(Monday night through Sunday)
Issued at 334 PM CDT Sun Sep 17 2017

Warm air advection continues into early Tuesday morning,
particularly seen on the 310K surface. Weak upper wave exits early
Monday night but with still 1000-2000 J/kg elevated instability,
will likely see some activity persist. Effective wind shear is not
impressive and should keep any organized severe concern in check.
South winds increase through the day Tuesday as the first upper
wave rotates northeast from the mean western trough and with WAA
into the morning, a warm and breezy to windy day is anticipated.
Models begin to diverge with handling of the associated weak cold
front pushing in late Tuesday night into Wednesday but am leaning
toward the farther northwest GFS and ECMWF solutions. Capping in
place from the previous WAA regime keeps convective chances low
but dewpoints may push into the lower 70s ahead of the front. Will
go ahead with a slight PoP in this area Wednesday afternoon and
evening, with this boundary again lifting north for some elevated
convection potential through Wednesday night.

Models continue to struggle with the eastward progression of the
western trough, but do continue to slow its progression for the
most part. Have further backed off on the ramping up of precip
chances with its approach but am still concerned this may not be
enough. Temps again remain above normal, particularly low temps.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday)
Issued at 1122 PM CDT Sun Sep 17 2017

As mentioned above, models are trending slower with the precip
spreading west. Because of this have delayed the lower CIGS and
precip in the TAFS for a few hours. The overall expectation for
degrading conditions overnight and then improvement Monday
afternoon continues. It`s just fine tuning the timing that
remains uncertain.




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