Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 292353

653 PM CDT Fri Aug 29 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 316 PM CDT FRI AUG 29 2014

Satellite imagery shows a vort max near CNK slowly lifting towards
southeast NEB. Dry air and some weak subsidence has allowed some
sunshine to break out across much of the forecast area. This has
helps temps warm into the mid 80s and a CU field to develop. There
is still a chance for some scattered showers and thunderstorms as
long as the trough axis continues to pass overhead. Therefore will
maintain some chance POPs through the evening. 700-500MB lapse rates
remain rather modest and deep layer shear unimpressive within the
trough axis. So while there could be some pop up storms, organized
severe weather appears unlikely.

By the late evening, the models have the mid level trough axis
propagating east of the forecast area. With the loss of day time
heating and any forcing from the vort max lifting northeast, precip
chances should come to an end. There may be some localized ground
fog over areas that have received higher amounts of rain this
morning. However there is some uncertainty in the chances for
widespread fog. Models indicate a weak shortwave, that shows up on
water vapor over eastern WY now, moving across northeast KS around
day break. While the deep lay moisture is expected to be pushed off
to the east and models prog no real vertical motion with this
feature, think it may keep some high clouds passing aloft through
the morning which could inhibit radiational cooling and fog
formation. There is also some signs of dry air advection from the
northwest, albeit weak. Because of this have opted to leave out any
mention of fog for now. Lows are expected to be in the lower and
middle 60s.

Saturday looks to be dry with no real forcing seen from the model
progs and relatively high pressure at the surface. Mostly sunny
skies are anticipated with shortwave ridging developing by the
afternoon. With mixing to around 825MB, this should help warm temps
from the mid 80s across far northeast KS to around 90 in central KS.

.LONG TERM...(Saturday Night through Friday)
Issued at 316 PM CDT FRI AUG 29 2014

Central Plains to be on the southern end of fairly quick and
mainly zonal upper flow into the middle of next week. Initial
upper trough, approaching the Pacific Northwest today, comes just
south of east into the Central and Northern Plains late Sunday into
Sunday night with an attendant Pacific cold front. Increasing upper
forcing coincides with fairly thick high clouds for trace-type
elevated precip potential for the late morning and early afternoon.
Still looks like the front will hold off locally until the evening
hours but fairly strong surface pressure gradient ahead of it should
keep mixing up and the boundary layer fairly well mixed into the
early evening hours. Deep layer shear and instability should remain
in moderate levels and support severe weather potential of mainly
hail and wind through the evening hours. At this point flooding
concerns remain low with the quicker upper flow keeping storm
motions up, but as the upper trough translates more north of east
with time, storm motions should become more parallel to the synoptic
front overnight into early Labor Day for a higher potential for
training. This would most likely occur in southern areas where
recent rainfall has been sparse and light further minimizing
flooding concern.

The zonal flow should keep the synoptic front nearby into at least
Monday night, though models are handling the boundary`s definition
differently and have little doubt outflow boundaries will play a role
in where convection will focus. Have increased chances somewhat into
Tuesday night. Severe weather potential will again need to be
watched for these periods with at least some potential for modest
shear and CAPE. The next upper trough passing west-to-east
across the Northern Rockies should allow the front to mix back north
for Wednesday and Thursday, but the front with this trough could
reach northern areas around Friday.

As for other sensible weather, wind speeds ahead of the front Sunday
pick up through the day but look to stay slightly below advisory levels.
Good warm air advection will also boost temps and heat index levels
could near triple digits. Somewhat cooler temps anticipated behind
and near the front and associated convection Labor Day and Tuesday,
though apparent temps in far southern areas should be well into the
90s. Highs through the remainder of the forecast under the broad
upper ridging expected to return to the lower to middle 90s.


.AVIATION...(For the 00Z TAFs through 00Z Saturday Evening)
Issued at 651 PM CDT FRI AUG 29 2014

Latest satellite imagery shows a longwave trough axis just West of KTOP.
A line of general TSRA will remain in the area for the next couple hours
which is mainly diurnally driven and will subside as the heat is lost and
the trough moves through.  Outside of that, expect mostly VFR conditions to
be the main feature.  Fog could be a very small factor early in the morning
but is not currently in the TAF due to uncertainty as dry air will advect in
behind the trough axis.  Additionally the amount of previous moisture has been
somewhat limited.  The afternoon late in the TAF period will see winds start to
show a southerly influence due to the high surface feature quickly moving East
of the TAF locations.




SHORT TERM...Wolters
AVIATION...Drake is the U.S. government's official web portal to all federal, state and local government web resources and services.