Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 172331
AFDTOP

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

...AVIATION UPDATE...

.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
areas.

.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 00Z TAFS through 00Z Tuesday)
Issued at 631 PM CDT Sun Sep 17 2017

Complicated forecast with the greatest uncertainty in timing
precip and when CIGS lower again. Obs show the surface front still
over northern OK with low level moisture being lifted north over
the boundary. So the setup is favorable for stratus and restricted
conditions. Although recently CIGS have lifted at TOP and FOE
while an area of drizzle appears to be forming around MHK. Overall
the expectation is for conditions to deteriorate through the night
with showers and storms becoming widespread towards 12Z. A
weakening surface ridge tomorrow should allow the boundary to lift
north or wash out all together with surface winds becoming
southerly and low clouds lifting above 3KFT. Models also show
forcing for precip moving east of the area so precip is expected
to end by early afternoon with VFR conditions developing. Again
timing of the details will likely require amendments through the
night.

&&

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

$$

SHORT TERM...67
LONG TERM...65
AVIATION...Wolters


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