Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 170849

Area Forecast Discussion
National Weather Service Topeka KS
349 AM CDT Sun Sep 17 2017

.SHORT TERM...(Today and tonight)
Issued at 348 AM CDT Sun Sep 17 2017

Latest surface analysis at 08Z showed the cold front generally along
Interstate 35 with surface high pressure in southwest South Dakota.
Showers and thunderstorms continued to develop along the cold front
and move northeast into Missouri. Additional showers and storms were
occurring over northeast Kansas ahead of the 850 mb front. Short
term high resolution models linger the convection across east
central Kansas through the morning hours. Additional thunderstorms
over southwest Kansas may move northeast and reach north central
Kansas this morning. The frontal boundary is forecast to stall over
far southeast Kansas and southwest Missouri this afternoon. Small
chances of showers and thunderstorms are possible again this
afternoon as perturbations move northeast in the southwesterly mid
level flow across the area. Forecast soundings Clouds and cold
advection with northerly winds will keep temperatures much cooler
than yesterday with highs in the lower to mid 70s expected.

Tonight the front begins to lift north during the evening and
overnight as a warm front. Isentropic lift over the frontal boundary
occurs tonight with elevated showers and thunderstorms becoming
widespread after midnight. Additional shortwave energy in the mid
levels is forecast to move northeast across the area later tonight.
Also upper level difluence associated with the exit region of the
southern stream jet and the entrance region of the northern stream
jet max will enhance the upward vertical motion across north central
and northeast Kansas later tonight. Therefore have increased
precipitation chances along with forecast QPF. Could see some
locations receive close to an inch of rain in northern Kansas after
midnight. Lows tonight will range from the lower to mid 60s.

.LONG TERM...(Monday through Saturday)
Issued at 348 AM CDT Sun Sep 17 2017

On Monday morning it appears there is some spread among the models
as to how much precipitation will linger in portions of eastern KS.
The ECMWF and GFS are much wetter than the NAM, which could likely
be contributed to the speed and location of the shortwave activity.
Most of the models show a decent low level jet that continues
through a good portion of the day, which keeps moisture and lift in
place. The is some weak lift indicated on the 310-315 K theta
surfaces that persists into the afternoon and is reflected in the
model QPF. A closer examination into that afternoon shows that if
the clouds break up it will allow surface heating therefore cape
values could approach 3,000 j/kg in some spots. The deep layer shear
is forecasted to be 30 kt across the entire area. Weak cin on during
the afternoon could lead to storm development. A lack of obvious
focus for lift especially at the surface makes it difficult to pin
point any specific locations, and there might not be much
organization to the convection due to the lack of forcing.

On Monday night another shortwave trough could track over the
central plains causing additional lift and a strengthening low level
jet. It is difficult to determine if the waves indicated by the
models are convectively driven or actual waves in the southwest flow
aloft. If so another round of showers and storms could occur late
Monday evening and Tuesday morning. The operational GFS seems to be
most aggressive with this overnight precipitation, while the other
deterministic models are indicating much less QPF. Only half of the
GEFS members indicate any accumulation over eastern KS during that
time frame. Things should quiet down until late this week and next
weekend. A longwave trough deepens over the western US with several
stronger embedded shortwaves. A frontal boundary will begin moving
across the central US as a result. Depending on the duration of
longwave trough over the western US that front may be slow to move
eastward so it could make for a prolonged period of rainfall. Too
many uncertainties at this point, but something to watch.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1147 PM CDT Sat Sep 16 2017

Scattered to widespread showers and thunderstorms will persist
through the night with pockets of MVFR to IFR conditions in the
heaviest of rain. A cold front having just passed through TOP will
continue SE, with winds veering to the north behind the boundary.
MVFR stratus looks to persist through much of the day on Sunday.




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