Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 131758
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1258 PM CDT Fri Oct 13 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 323 AM CDT Fri Oct 13 2017

Surface low continues to slowly move eastward out of eastern
Colorado into southwest Kansas over the past several hours. Warm
front extends to the northeast of the low, generally from Hays
toward St. Joseph MO.  This low essentially moves along the
orientation of the warm front through the morning hours, with the
western side making more southern progress through the evening
hours. Boundary then becomes washed out this evening and retreats
back northward overnight in the low level jet regime.  Initial
impacts are on temperatures for the day, with areas to the north
remaining in the 60s and clouding up, while locations southward make
it into the 70s and 80s this afternoon.  Front also provides a focus
for convection later this afternoon as instability develops over
northeast Kansas. Impulse lifting out of the southwest into eastern
Kansas overnight also aides in providing lift as well as moisture
return and increases instability overnight, where we could see a few
strong storms. Some model differences on how far northward these
storms develop depending on how far north the front retreats, so do
have chances across the forecast area, with northern counties more
favored.  Lows north in the 50s with lows in the 60s in the
southeast.

.LONG TERM...(Saturday through Thursday)
Issued at 323 AM CDT Fri Oct 13 2017

On Saturday morning a positively tilted mid level trough lifts
northeastward over the northern plains. A surface cold front will
begin to deepen across north central KS in response to the
shortwave. Elevated convection north of the front will likely be
ongoing in the morning due to isentropic ascent and elevated
instability. The front will progress southeastward through forecast
area during the day Saturday. Models are indicating the warm sector
may be entrenched in low level stratus. As the winds in the lowest
levels veer to the southwest ahead of the front warmer air will try
to erode the stratus. The main concern will be how quickly the
stratus clears out to allow surface based convection as the front
pushes eastward in the afternoon and evening. Forcing along the
front should support convective initiation, which will likely become
linear as the vertical shear profile becomes quasi-parallel to the
boundary. With dew points in the mid 60s and marginal mid level
lapse rates there should be enough instability for a threat of
severe wind gusts and possibly some hail. This will especially be
true if the warm sector can clear out, which is more likely east of
a line from Holton to Council Grove. The SRH will be limited with
the veered flow, but low level speed shear could certainly support
mesovorticies along the leading edge of the cold pool. This will
likely be associated with any bowing segments that become more
perpendicular to the low level shear vector, which will generally be
out of the southwest. Although given the fast nature of this
advancing front updrafts may have trouble persisting. Most the
convection and post frontal precipitation should exit the forecast
area by midnight.

Gusty winds up to 35 mph are possible behind the front due to a
tight pressure gradient. Highs on Sunday struggle to reach 60 so
this along with lingering wind gusts will make for a balmy day.
Behind this system an expansive high pressure builds across the
plains. Northwest flow aloft will continue to support this high
pressure thus keeping the weather fairly quiet. Temperatures will
also moderate to more seasonable with highs in the 70s and lows in
the 40s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1258 PM CDT Fri Oct 13 2017

A front will move southeastward through this evening before
stalling, with MVFR ceilings overspreading portions of north-
central and northeast KS through tonight. A period of IFR ceilings
should affect MHK Saturday morning. The front will advance
northward on Saturday, with southerly winds and increasing
ceiling heights south of the front. Showers and thunderstorms will
increase tonight into Saturday, though confidence in
thunderstorms affecting any TAF site is too low for mention in the
TAFs at this time.

&&

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

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...Cohen



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