Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 232348

Area Forecast Discussion
National Weather Service Topeka KS
648 PM CDT Sat Sep 23 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Sunday)
Issued at 255 PM CDT Sat Sep 23 2017

19Z water vapor imagery shows the upper trough is still over the
western U.S. with a closed circulation centered over eastern NV.
Upper ridging extended from north TX through the mid MS river valley
and into the Great Lakes. At the surface, high pressure was centered
over the mid MS river valley and a pre-frontal trough stretched from
southwestern KS into eastern NEB. There has been a few storms
develop to the west of the forecast area within the surface trough
where low level moisture convergence has been strongest. A decent
cold front was located from northwest KS through northeast NEB.

For tonight and Sunday, models continue to show a slow progression
to the upper trough and the associated dynamics so that by Sunday
afternoon the pre-frontal trough is across north central KS. The
stronger upper level flow should also be a little closer to the
forecast area by tomorrow afternoon. So the expectation is for
sensible weather to be shifted to the east a little further. With
the surface trough across north central KS, low level convergence
may aid in the development of diurnally driven showers and storms
and have some chance POPs in for the western third of the forecast
area. Until then, there doesn`t look to be any strong dynamics or
isentropic upglide. So showers and thunderstorms should remain to
the west of the forecast area overnight and Sunday morning.
Instability and sheer parameters continue to look marginal for
Sunday afternoon so concerns for severe weather remain low.

Lows tonight should be similar to this mornings with southerly low
level winds persisting. Readings are forecast to be in the upper 60s
and around 70. Models continue to show some slight cooling at 850
MB. With a little more cloud cover anticipated for Sunday, highs are
expected to be a degree or two cooler than today with readings
forecast to be in the in the mid to upper 80s.

.LONG TERM...(Sunday night through Saturday)
Issued at 255 PM CDT Sat Sep 23 2017

By Sunday night, a deep mid-level trough will be stretched across
the Rockies with surface low pressure moving into western KS. Models
show this mid-level trough lifting northeastward into the Northern
Plains into Tuesday.  As a result, surface low pressure will shift
into central KS by Monday morning, with an associated cold front
tracking southeastward across the forecast area through the day and
exiting east central KS Monday evening.  Scattered showers and
isolated thunderstorms will be possible across north central to far
northeast KS Sunday night ahead of the front as a 40kt LLJ sets up
over central KS with a couple of weak embedded waves noted on the
lee-side of the advancing trough. PoPs will increase and become more
widespread across the CWA Monday and Monday night with the frontal
passage, however the potential for any severe weather looks to be
low at this time.  Mid-level lapse rates do not look too impressive
amongst the models at this time, which will keep MUCAPE values less
than 1000 J/kg.  Models show relatively weak 0-6km bulk shear as
well, with values only maxing out at 25 to maybe 30kts.  Post-
frontal precipitation will continue across much of the CWA through
Tuesday with precipitation diminishing from west to east Tuesday
afternoon into Tuesday evening as surface high pressure dives into
the area. The primary hazard with this system will be locally heavy
rainfall as QPF values of 1 to 1.5 inches are possible across much
of the CWA, with some higher amounts closer to 2 inches also
possible. Behind this frontal passage, surface high pressure will
remain anchored across the central U.S., resulting in dry conditions
Wednesday through Saturday.

As for temperatures, a non-diurnal temperature trend is expected on
Monday with the passage of the cold front across the CWA.  As a
result, high temperatures will likely range from the upper 60s to
mid 80s from northwest to southeast over the forecast area.  Cold-
air advection behind the front will bring cooler and more seasonal
conditions to the region, with highs in the 70s and lows in the 50s
and even into the 40s by late week into the weekend.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 643 PM CDT Sat Sep 23 2017

Expect VFR conditions through the next 24 hour at all terminals.
There may be some low level windshear within the lowest 2000 feet
from 3Z through 13Z, as a low-level jet at 1500 feet above the
surface increases to 30 KTS Tonight.




SHORT TERM...Wolters
LONG TERM...Hennecke
AVIATION...Gargan is the U.S. government's official web portal to all federal, state and local government web resources and services.