Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 201723

1223 PM CDT Sat Sep 20 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 252 AM CDT SAT SEP 20 2014

The approaching cold front from the northwest has caused an increase
in the pressure gradient for most of overnight hours. With the
surface ridge stretched across far southwest MO there is a weaker
gradient for areas along and south of interstate 35. The dew point
depressions closer to the ridge are much lower, and any cooling
could allow for a brief period of fog between now and sunrise. Later
this morning the front should enter the northern counties although a
decent cap in place should prevent surface convection until after
18Z. Some of the models are suggesting a few showers and elevated
storms are possible during the morning hours near the NE/KS state
line. The overall forcing with this system is relatively weak so do
not expect coverage to be that widespread. By late afternoon surface
heating and dew points near 70 yield cape around 2000 to 3000 j/kg.
The deep layer shear will be 30 kts at best, which will limit the
severe potential as well as marginal mid level lapse rates. Given
the instability expect pulse type thunderstorms capable of producing
a brief period of marginal hail. Also, an isolated downburst can not
be ruled out during the collapse of a strong storm. A majority of
the models place the front near interstate 70 around 22-02Z.
Convective initiation is most likely to take place during this time
frame near and or just north of interstate 70. As the front
continues southward the chances become more focused south of
interstate 70 during the evening hours. The front should be south of
the forecast area by 06Z with only a slight chance of lingering
precip during the early morning hours in the far southern counties.
Highs today warm into the mid to upper 80s, but cool/dry air quickly
filters behind the front dropping temperatures into the low 60s and
upper 50s by Sunday morning.

.LONG TERM...(Sunday through Friday)
Issued at 252 AM CDT SAT SEP 20 2014

Sunday into Monday bring surface high pressure moving out of the
northern Plains into the Ohio valley, bringing in cooler air with
highs in the 70s and overnight lows around 50 Sunday night with
low to middle 50s on Monday night.

Next chance for rain starts to move into the western counties
early Tuesday, and spreads eastward through the day and into
Wednesday as an upper trof moves out of the northern Rockies into
the northern Plains. While both EC and GFS suggest deeper longwave
upper trof over the Pacific NW by late week, they differ on how to
handle the residual trof over the Plains states and an incoming
system over the southeast eastern seaboard moving northeast with
time. GFS lingers the Tuesday trof into the later week as a cut off
upper low over the Central Plains, while EC shears out the feature
and weakens/retrogrades with time. Pulled out precip chances for
Friday as system continues to weaken in either case. Highs Tuesday
and Wednesday expected to remain in the 70s, with a warming trend
as southerly surface flow returns over the area for the late week
and may bump highs back up near 80.


.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1221 PM CDT SAT SEP 20 2014

Isolated to scattered storms are expected to develop between 20Z and
24Z moving along a frontal boundary pushing SE through the area.
Storms may produce locally heavy rain, gusty winds, and small hail.
Confidence is high on development but lower on timing of initiation and
location of formation.  After sunset, any lingering storms should
weaken and dissipate before skies begin to clear and winds become




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