000
FXUS63 KTOP 260449
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1149 PM CDT Fri Jul 25 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 324 PM CDT FRI JUL 25 2014

Upper high was over New Mexico today with mid and high level
moisture rotating around it into the Central Plains. This moisture
feed met up with a strong mid level thermal gradient from across
Iowa to bring persistent thunderstorms to eastern Missouri today.
Weak pressure rises were occurring behind a trough of low pressure
from eastern Nebraska to western Kansas this afternoon, with south
to southwest winds bringing a very warm and humid airmass into
eastern Kansas. 2 pm heat indices were commonly from 100 to 106
degrees.

Dewpoints not falling much in diurnal mixing, allowing some
weakening of the mid level cap to occur. Convergence along the
trough remains weak and seeing no evidence of cumulus along it under
the scattered high cloud, but will keep small thunderstorm chances
in place into the early evening. Expect the overnight hours to be
benign with weakening winds, but should see an increase in the high
cloud and this will help keep temps on the warm side.

Models are similar with weak warm air advection in the 12-20KFT layer
for much of Saturday and hard to rule out isolated very light precip
reaching the ground, somewhat favoring southern areas where moisture
appears a bit better.  Will again be watching the southeast
progression of another surface feature, this time a cold front as an
upper low pushes southeast into the Northern Plains. Cap strength
again will be rather strong but convergence a bit stronger than
today to keep small PoPs going. Still appears to be a wind threat
with marginal shear, high storm bases, and strong mid-level lapse
rates. The high cloud and overall weaker low level wind fields leads
to some uncertainty on how hot temps will be. 850MB thermal ridge
will still be in place however, but a bit farther south, where the
more cloud concern is, so believe temps will still be around 100F
for central and southern locations. In the north, still looking like
dewpoints should be higher along and behind the boundary to support
higher apparent temps despite cooler temps. Will go ahead with a
Heat Advisory despite somewhat low confidence.

.LONG TERM...(Saturday Night through Friday)
Issued at 324 PM CDT FRI JUL 25 2014

For Saturday night, there remains some uncertainty in how quickly
the front will push south through the forecast area and some models
show it hanging up across the area for much of the night. With
models indicating some modest isentropic upglide along and ahead of
the boundary, have maintained the slight chance POPs through the
night.

By Sunday, drier and cooler air should be advecting in from the
north as a shortwave breaks down the upper level ridge and begins
digging out a longwave trough over the eastern half of the CONUS.
Models keep the longwave trough over the eastern half of the CONUS
through the week and will likely allow temps to remain 5 to 10
degrees below normal for the end of July. Sunday through Tuesday
appears to remain dry. However by Tuesday night, the ECMWF and GFS
show weak shortwaves rounding the upper ridge to the west and
spilling over into the central high plains. This energy may allow
for some showers and thunderstorms to move into parts of eastern
KS Tuesday night through Wednesday night. Instability looks to be
pretty limited with much of the low level moisture pushed south
of the area.

For Thursday through Friday the models continue to generate some
sporadic QPF without an obvious shortwave or lift from a surface
boundary. Based off the GFS BUFKIT soundings, it appears as though
the models lack any inhibition to a surface parcel becoming
positively buoyant due to the cool mid level temps within the upper
trough. With this in mind, think the models may be developing
precip from day time heating. With no surface feature or wave to
denote higher chances for precip, think chances for precip would
be slight at best so have some 20 percent POPs in the daytime for
Thursday and Friday. Confidence in any given location seeing rain
is low, but can`t rule out the isolated storm popping up in the
afternoon.

&&

.AVIATION...(For the 06Z TAFs through 06Z Saturday Night)
Issued at 1145 PM CDT FRI JUL 25 2014

VFR conditions expected through most of the period. There is a
slight chance for isolated thunderstorms after sunset. Coverage
and probability is still uncertain therefore did not add any extra
groups. Any storm that reaches the taf site has the potential of
briefly producing strong wind gusts.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY from 1 PM to 8 PM CDT Saturday FOR KSZ008>012-
020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Sanders