Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 251746

National Weather Service Topeka KS
1246 PM CDT Tue Oct 25 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 319 AM CDT Tue Oct 25 2016

A lead upper level trough ahead of a nearly stationary longer wave
length upper trough off the western coast of the US will lift
northeast across the plains Tonight. A lee surface low across
western KS will deepen through the day and move northeast into south
central NE by 00Z WED. A surface cold front will move from eastern
CO, eastward across west central KS through the afternoon hours and
into the western counties of the CWA by 02Z WED.

Point forecast soundings from the 00Z NAM and WRF models show an EML
at around 735MB overspreading the warm sector during the afternoon
hours and through the evening hours as well. There may be enough
ascent ahead of the weak upper trough and lift along the surface
front for scattered thunderstorms to develop southwest along the
surface front from southern NE across the central counties of the
CWA after 3Z. The only model that shows deep moist convection
developing after 00Z is the 00Z GFS model. The WRF solutions keep
the CAP strong enough that only isolated storms develop after 9Z
along the surface front along and southeast of the KS turnpike.

The most favorable environment for strong to severe thunderstorms
would be during the late afternoon and early evening hours where
MLCAPES will increase to 1500-2000 J/KG with 0-6KM shear increasing
to 25 to 30 KTS. However the cap may prevent storms from developing
along the front. If surface based storms manage to break the cap,
they may become severe with the potential for large hail and
damaging wind gusts across north central KS. If the NAM, WRF and RAP
solutions end up verifying then thunderstorms may not develop until
near midnight across the eastern and southern half of the CWA. The
MUCAPE will decrease to 1000-1500 J/KG but the 0-6KM shear will
increase slightly to 30 to 40 KTS. Thus a strong or severe
thunderstorms will still be possible. If deep moist convection does
not develop until around 6Z the primary hazard with any strong to
severe storm would be large hail, since the boundary layer may
decouple enough to prevent severe wind gusts. Rainfall will depend
on thunderstorm coverage and intensity. If storms develop along the
front around 6z and last through the early morning hours, then some
locations across east central KS may pick up a quarter to a half
inch of rainfall.

Highs this afternoon will reach the mid to upper 70s this afternoon
as WAA at 850mb increases 850mb temperatures between 14 and 18
degree C. The boundary layer should mix to around 850mb and any
stratus this morning should mix out during the late morning and
early afternoon hours. South winds will increase to 15 to 25 MPH
with higher gusts from the late morning hours through the afternoon
and into the evening hours.

.LONG TERM...(Wednesday through Monday)
Issued at 319 AM CDT Tue Oct 25 2016

The mid range and extended forecast will be dominated by an upper
ridge over the southern US resulting in mainly zonal flow over
the region. A series of dry cold fronts will cause up and down
temperatures. The first front passes through the area Friday
night, therefore Friday appears to be the warmest day. High
temperatures are forecasted to reach around 80, but only cool into
the low to mid 70s over the weekend. Another front approaches the
area on Monday so highs slightly increase only to drop into the
60s by Tuesday. A deepening trough over the western US will allow
more shortwaves to track over the central plains, which will bring
chances for showers and storms through mid week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1246 PM CDT Tue Oct 25 2016

Only minor changes to the forecast. Uncertainty on timing of
precipitation remains somewhat high however with a wide range of
possibilities from guidance. Visibilities could reach IFR in the
stronger storms however.




LONG TERM...Sanders
AVIATION...65 is the U.S. government's official web portal to all federal, state and local government web resources and services.