Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 030438
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1138 PM CDT WED SEP 2 2015

...Update to aviation forecast discussion...

.SHORT TERM...(THIS EVENING THROUGH Thursday)
ISSUED AT 307 PM CDT WED SEP 2 2015

19z sfc map shows low pressure across the northern plains with a
trough extending south into western KS with most of eastern Kansas
now mixed out into the warm sector as remnants of elevated
convection wane. Water vapor loop shows a wave across Nebraska
moving E along the northern periphery of the upper ridge axis.

For tonight, the wave will track into northern MO overnight and may
help to enhance the LLJ which will contribute to modest WAA around
850mb. There is some additional WAA fcst to occur around the 700mb
level as well. Interesting that both the RAP and HRRR and GFS are
showing some small areas of QPF across central KS overnight despite
the 850mb thetae ridge remaining north of the CWA overnight. This
appears to be due to modest lift and saturation around 700-650mb
where even the NAM soundings show saturation after 6z. Fcst
soundings suggest modest elevated CAPE of 100j/kg or less. Other
convective models do not show this weak lift resulting in saturation
or convection so for now will keep the pops below 15 and keep the
fcst dry but something to watch for overnight.

We should see another day much like today on Thursday with 1000-
850mb thickness and temps nearly identical to today so will go with
persistence for temps. Pressure gradient is also similar so look for
another breezy day as well.

.LONG TERM...(Thursday NIGHT THROUGH Wednesday)
ISSUED AT 307 PM CDT WED SEP 2 2015

Thursday night through Saturday...Deep, moist southerly low-level
flow will continue through the period. With stronger south-
southwest flow aloft off to our west and northwest, no
recognizable dynamic feature is depicted in the short range
guidance to focus showers and thunderstorms in eastern KS. Only
possibility would be the remnants of some High Plains convective
cluster that might migrate into north central KS/south central/NE
before dissipating. Would expect any system like that to die out
before affecting our northwestern forecast area.

Saturday night through Wednesday...Strong upper trough over the
Rockies on Saturday evening will move northeast into southern
Manitoba and become an occluded system by Monday morning. While
strong dynamics are well to the north, southern extent of system
is a cold front that moves into central/eastern KS and then
becomes nearly stationary. This will be the focus for thunderstorm
chances late in the weekend into early next week. Medium range
models have some differences in the location of this boundary
already by Monday, but all depict it in the area with periodic
chances of thunderstorms into Tuesday night/Wednesday morning.
Then another strong trough moves across the central U.S. with the
result that the front pushes south of the area by late Wednesday.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z Thursday NIGHT)
ISSUED AT 1138 PM CDT WED SEP 2 2015

For the 06z TAFs, VFR conditions are expected through the period.
There is a slight chance for a few isolated showers to develop early
Thursday morning, however confidence is not high enough on the
probability of these showers developing (let alone where they would
develop) to include in the TAFs at this time, but will continue to
monitor this potential.  Otherwise, southerly winds will become
more gusty Thursday afternoon.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Omitt
LONG TERM...GDP
AVIATION...Hennecke


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