Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 252304
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
604 PM CDT SAT JUN 25 2016
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Sunday)
Issued at 330 PM CDT SAT JUN 25 2016
Water vapor imagery showing lows over southern Saskatchewan and the
Big Bend of Texas, with tropical moisture plume wrapping north then
northeast into the Central and Northern Plains. Enough isentropic
upglide in this moisture helping keep scattered elevated convection
going for much of the day in western and northern sections of the
local area. 19Z surface obs put cold front from northeastern
Nebraska into west central Kansas. Convective environment ahead of
the front being tempered by the high cloud and scattered precip but
much of the local area is nearly uncapped with 2000-3000 J/kg ML
CAPE. Shear parameters continue to look unimpressive with weak
mid/upper winds and some backing aloft as well.
Models continue to show some variance in precip trends through
Sunday afternoon. Still appears convection should enhance in
coverage and intensity in the next few hours as the front enters the
greater instability. Appears front will enter the area around 7 pm
but could see enhancement of ongoing convection ahead of it with
additional outflow bringing effective front southeast sooner. Have
kept somewhat of a broad brush approach to precip onset times. Hot
prefrontal airmass bringing rather high downdraft CAPE keeping
downburst winds as the more likely severe weather concern.
Front/effective front will likely become more parallel to the upper
flow, with still wet mid/upper levels, but persistent convergence
along the boundary seems unlikely in the weak flow and heavy rain
concerns seem low. Have kept pops a bit higher into Sunday with a
slower exit of the better moisture. Will need to watch how far
front/outflow gets for perhaps more marginally severe storms in
southern area Sunday but feel anything more than isolated coverage
will be low.
.LONG TERM...(Sunday Night through Saturday)
Issued at 330 PM CDT SAT JUN 25 2016
Sunday Night through Tuesday...
For Sunday night, have continued with some chance POPs across east
central KS to account for the front possibly getting hung up across
this region. Models keep a moist and conditionally unstable airmass
south of the boundary and with little to no inhibition to
convection, weak convergence along the boundary could be enough for
scattered showers and thunderstorms to persist. For Monday through
Tuesday, the consensus is for weak surface ridging to build into
northeast KS while northwest flow aloft persist. Although the models
show the better dry and cold air advection occurring more on Tuesday.
Models show varying solutions for precip on Monday and Monday night
and this looks like it will be driven by mesoscale forcing as there
are not a lot of signs for large scale forcing. Since models show
some moisture remaining and the boundary layer only weakly capped,
have retained a slight chance POP for Monday and Monday night. Think
that with the better dry air advection and cooler temps at the
surface increasing inhibition to a surface parcel that the weather
is likely to remain dry for Tuesday.
Temps are expected to trend cooler from Monday to Tuesday as low
level ridging builds south and cold air advection becomes a little
more prominent. Highs on Monday are expected to be around 90 with
the boundary layer mixing to around 825MB. Tuesday`s highs should be
in the mid 80s with the cooler air moving in. Lows Tuesday morning
are forecast to fall into the mid 60s.
Tuesday Night through Saturday...
Northwesterly flow at mid-levels will dominate the extended period.
A subtle shortwave will ride up and over the ridge across the
Western US. This wave will be the focal point for showers and
thunderstorms Wednesday into Thursday. Model guidance has decent
agreement regarding the timing of the wave on Wednesday. Cloud cover
will play a huge role in high temperatures Wednesday and Thursday.
Guidance continues to trend cooler for Wednesday with highs in the
upper 70s to lower 80s. A weak cold front associated with a trough
across the Great Lakes region could spark a few showers or
thunderstorms Thursday night and Friday. At least slight chance
PoPs continue through Saturday as weak embedded waves within the
northwest flow continue moving across the area.
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 558 PM CDT SAT JUN 25 2016
Periods of showers and thunderstorms are expected through midday
on Sunday. A cold front will sweep across the terminals later
this evening into the overnight, shifting winds to the north and
northeast. Current expectation is for any lingering showers to end
at all terminals by 18Z. Redevelopment of thunderstorms should
remain south of the terminals Sunday afternoon.