Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 291946
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
246 PM CDT MON AUG 29 2016

.SHORT TERM...(This Evening through Tuesday)
Issued at 157 PM CDT MON AUG 29 2016

Mid level trough over the four corner region will continue to send
several shortwave over the central plains the next few days. Ahead
of this trough the tropical air mass remains in place with pwat
values around 1.90 in across most of the area. A weak cap has
allowed diurnally driven storms to develop which should continue
through the evening. Resulting storms will produce outflows which
will force additional development and control movement of these
storm clusters. Plenty of moisture along with the potential for slow
moving storms will allow for heavy rainfall. Some areas have already
received substantial amounts of rain so the potential for localized
flooding will be possible. The MLcape is around 1500 j/kg, which is
less than yesterday and the shear is minimal. Expect there is an
outside chance for isolated small hail and gusty winds through this
afternoon. Model guidance is showing lift will increase close to the
wave track over southern NE and near strong 850 mb convergence. The
low level jet will also increase out of the south tonight and
gradually veer adding another focus for lift over any established
cold pools. High res model QPF show that rainfall amounts could
range from 1 to 3 in at some locations mainly northwest of a line
from Herington to Holton. Most of this rain is expected to fall
later this evening through tomorrow morning. There are difference as
to where exactly this lift will maximize through the period. A few
of the models clip north central KS while others shift the axis
further southeast. Therefore given the potential for diurnally
driven storms this afternoon with another round expected tonight
have gone with a flash flood watch across portions of the forecast
area. As the trough tracks eastward and low level jet veers chance
will spread into eastern KS. Another wave may track over northwest
KS and southern NE later tomorrow, which may support yet another
round of rainfall to redevelop over the same locations in central
KS, and portions of east central KS. The potential for flash
flooding will continue through tomorrow if multiple rounds of
rainfall occur so the watch may be to be re-evaluated.

.LONG TERM...(Tuesday Night through Monday)
Issued at 157 PM CDT MON AUG 29 2016

The unsettled weather pattern will continue into Wednesday evening
as weak short wave energy continues to provide vertical motion on
a broad scale while a back door cool front sinks into the forecast
area from the northeast. Instability will be a bit lower Tuesday
night into Wednesday and will decrease with time, but there will
be instability present in conjunction with precipitable water
values of 1.9-2.2 inches. Also expect to see periods over which
the focus for convective development is nearly stationary along
the front and slow moving embedded vorticity maxima. Thus will
probably see another round or rounds of thunderstorms with heavy
rainfall potentially exceeding flash flood guidance. The main
question in this setup may end up being the magnitude of
instability available for heavy rain production, and with this in
mind have not extended the flash flood watch into Wednesday at
this point but will want to consider in future forecast updates.

A much drier and somewhat cooler airmass will build into the
region by Wednesday night and Thursday. Expect to see some low
temperatures in the 50s with highs only around 80 through at least
Friday. Could see some fog develop mainly Thursday morning,
depending mainly on the timing of clearing and associated impact
on temperatures and dewpoints.

Return flow in the low levels and a resumption of southwesterly
flow aloft by next weekend will bring thunderstorm chances back to
the area for late Saturday and Sunday. Then have indications that
a front will stall in the general Kansas area and could provide
another setup for heavy rain into early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1235 PM CDT MON AUG 29 2016

VFR conditions are expected throughout the period, although MVFR
may be needed in later outlooks as exact timing and location of
thunderstorm activity becomes more apparent. Isolated to
scattered thunderstorms are expected to continue developing this
afternoon into the early evening hours. More widespread
thunderstorm activity is expected to begin at MHK after 06Z and
slowly spread eastward to the Topeka terminals after 08Z. These
thunderstorms may produce brief heavy rainfall that could limit
visibility. Thunderstorm chances look to continue through the end
of the TAF period.


&&

.TOP Watches/Warnings/Advisories...
Flash Flood Watch from 5 PM CDT this afternoon through Tuesday
evening for KSZ008>011-020>023-034.

&&

$$

SHORT TERM...Sanders
LONG TERM...Barjenbruch
AVIATION...Baerg



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