Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 142324

624 PM CDT Sun Sep 14 2014


.SHORT TERM...(This Evening through Monday)
Issued at 327 PM CDT SUN SEP 14 2014

Kansas is on the south end of stronger northwest flow over the
Northern Plains with a shortwave trough diving southeast out of
southern Saskatchewan early this afternoon. Southerly low-level flow
returning locally with periods of stratus moving through under
still warm mid level air. Isentropic lift over this warm layer
leading to isolated showers over north central Kansas but doubt much
is reaching the ground through the warm/dry mid levels.

Main question through Monday is where elevated convection will be
focused. Isentropic lift persists and increases into the lower
levels tonight as the northern trough quickly rotates southeast into
northern Nebraska. NAM continues to be the more aggressive with
moistening around 6000 feet AGL but even its 18Z run struggles to
generate precipitation this far south, with stronger convergence to
the north. Have backed off on southern extent of higher chances
tonight and for most locations Monday. Front`s passage still occurs
under the warm nose keeping surface/mixed-layers storms in check
here, and also occurs by mid afternoon Monday for little time for
destabilization ahead of it. Any storms that can form tonight into
early Monday will need to be monitored for hail with elevated
instability potentially around 1000 J/kg and decent cloud-bearing
shear. Another round of more fall-like conditions is possible during
Monday with saturation deepening for at least minor drizzle
possibilities and falling afternoon temps but only made minor temp
adjustments at this range.

.LONG TERM...(Monday Night through Sunday)
Issued at 327 PM CDT SUN SEP 14 2014

Precipitation over the far southeast counties moves southeastward
quickly and leaves behind cooler high pressure for Monday night into
Tuesday.  Lows in the 40s should still rise to lower 70s given
mostly sunny skies return for the afternoon. Wednesday and Thursday
the Central Plains remain the transitional area between the upper
ridge over the Rockies and the trough over the east coast, with mid
level warm front parked over the state.  As this boundary slowly
migrates eastward, models consistent in generating very light QPF
through this period. In terms of probability, a slight chance is
warranted given the overall pattern, but confidence remains low on
timing or measurable precipitation.  Highs in the lower to middle
70s rise to 70s and low 80s by Thursday, with lows in the 50s to
lower 60s as slow warming trend continues.

By the late hours on Thursday, EC and GFS differ on how to handle
dissipating hurricane over the west coast and its interaction with
the incoming longwave trough.  GFS is faster and phases some of the
energy, deepening the trough and slowing its eastward progress. It
still takes some of the energy as a lead lobe out into the Plains
states and brings precipitation across eastern Kansas on Saturday.
EC takes a similar path with some of the northern energy, but cuts
off the merging upper trough and hurricane out over the Pacific. Still
with a FROPA on Saturday, sensible weather in either case remains
quite similar. Have kept chance pops for late Friday into Saturday,
diminishing quickly north to south on Saturday night. Might be able
to delay start time of the precip in later forecasts, but will just
have to watch how tropical and extratropical systems interact with
time.  Fridays highs in the low 80s temper a bit into Saturday and
Sunday given precipitation followed by cold front, with highs in the


.AVIATION...(For the 00Z TAFs through 00Z Monday Evening)
Issued at 623 PM CDT SUN SEP 14 2014

Confidence in TS moving into the terminals is to low to put more
than a PROB30 in the forecast for now. Most model guidance keeps
the dynamic forcing from a shortwave moving across the plains to
the northeast over IA while there are suggestions that mid level
moisture may be lacking for mid level frontogenesis to kick start
widespread convection. Nevertheless 700-500MB lapse rates remain
fairly steep so TS continues to be a possibility. Am a little more
confident in MVFR CIGS and VSBY developing behind the FROPA.
Forecast soundings show weak vertical motion within the stratus
deck behind the front, so think there is a chance for some -DZ.
The wild card is whether skies clear out and stratus forms ahead
of the front within the axis of low level moisture advection. With
forecast soundings keeping the moisture return very shallow and
the boundary layer expected to remain mixed, think there may be
some dry air entrainment to make stratus ahead of the front a
little less likely. Will need to monitor trends as the night goes





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