000
FXUS63 KTOP 221137
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
637 AM CDT Tue Jul 22 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 411 AM CDT TUE JUL 22 2014

Water vapor imagery this morning showed a broad mid-level ridge
stretched across the Southern Rockies and the Southern and Central
Plains, with a modest embedded shortwave skimming eastward along the
Canadian/U.S. border toward the Great Lakes region. An area of
surface low pressure was associated with this shortwave, with a cold
front across Minnesota extending southwest into far northern
Nebraska this morning. With the region wedged between this
approaching surface trough and surface high pressure over the
southeastern U.S., southerly winds prevailed overnight with high
clouds streaming over the southern two-thirds of the forecast area.
As a result, overnight temperatures remained mild in the mid/upper
70s. A very weak embedded shortwave was noted across southeast
Nebraska/southwest Iowa, which helped to develop a few spotty
showers and isolated thunderstorms early this morning just north of
the forecast area.

Another very warm day is expected today as we will be starting the
day already with mild conditions and model soundings show deep
mixing occurring through this afternoon. The strong shortwave to the
north will strengthen into a more well-defined mid-level trough over
the Great Lakes region today. This deepening trough combined with
advancing surface high pressure behind the shortwave over the
Northern Plains will help to push the cold front southward toward
the area. Models are in pretty good agreement in having the front
situated near the Nebraska/Kansas border between 16z-18z. The front
should slowly sink southward, bisecting the forecast area from west
to east by early this evening and advancing south of the area early
Wednesday morning. Winds look to be a bit slow in veering to the
north behind the front this afternoon across far northern Kansas, so
expect high temperatures to reach into the mid 90s to low 100s
across the entire forecast area. While much of the region should see
dewpoints in the low/mid 70s, the models are in good agreement in
low-level moisture mixing out strongly today across portions of
north central and central Kansas by this afternoon. However, feel
that the models may be a bit too aggressive in dropping dewpoints
into the low/mid 60s, so only trended with dewpoints dropping into
the mid/upper 60s across the far southwest corner of the forecast
area. Also expect increased low-level moisture across far northern
Kansas behind the frontal passage this afternoon, so should see
rising dewpoints over this area. Will need to monitor these
conditions closely today as they will have an impact on heat
indices. At this time, expect heat indices to rise into the 105 to
110 degree range this afternoon, so the existing Heat Advisory will
remain unchanged for today.

The next area of focus is the potential for scattered showers and
thunderstorms to develop along and behind the cold front late this
afternoon through tonight. Models continue to vary greatly in
whether or not they think storms will even be able to develop. Model
soundings show that any storms that develop will likely be
high-based. The environment will need to be able to overcome the
modest CIN in place across the region and be able to lift parcels
through the deep mixing layer to tap into the 3000-4000+ J/kg of
CAPE aloft. In general, 0-6km bulk shear values are fairly weak but
may reach upwards of 25-35kts. With the notable inverted-V
soundings, damaging winds will be the primary threat with any storms
that develop and cannot rule out some marginally-large hail. The
models that are picking up on this potential for post-frontal storms
have scattered activity developing across far northern Kansas by
early evening and advancing southeastward. Additional scattered
showers and storms will be possible overnight as an embedded
shortwave approaches the area from the northwest.

.LONG TERM...(Wednesday through Monday)
Issued at 411 AM CDT TUE JUL 22 2014

Wednesday morning the cold front should be across southern Kansas
with some post frontal precipitation as far north as east central
Kansas. Have left small chances of precipitation in the morning then
dry for the afternoon hours. Cooler temperatures are also expected
on Wednesday, generally near our normal around 90 for late July.

Temperatures expected to be a couple of degrees cooler on Thursday
with warmest temperatures toward central Kansas in the nose of the
thermal axis.

Next chance of showers and thunderstorms comes Thursday night along
and east of a warm front moving across central and eastern portions
of Nebraska and Kansas. Elevated thunderstorms will be possible in
the waa regime/isentropic lift along with some upper support from a
weak shortwave. The precipitation may linger in the far east Friday
morning.

For the weekend a cold front is expected to move through the area
slowly keeping a small chance of showers and thunderstorms in the
forecast through Sunday evening. Models show the upper ridge moving
southwest as an upper trough deepens over the Great Lakes and into
the eastern states with northwest flow aloft redeveloping across the
Central Plains. There is some uncertainty with the timing of the
upper level forcing and have kept precipitation chances low. Cooler
temperatures are expected for Monday as high pressure builds into
eastern Kansas from the north as the upper trough deepens in the
eastern CONUS and upper ridge builds over the Rockies and west.

&&

.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 637 AM CDT TUE JUL 22 2014

For the 12z TAFs, VFR conditions are expected through the period.
Southwesterly winds will veer to the north tonight as a cold front
tracks southward over the region. There is the potential for a few
scattered showers and thunderstorms to develop behind this front
late this afternoon through this evening, however there is still a
great deal of uncertainty in the timing and location of any of these
storms. At this time, have just included a mention at KTOP/KFOE and
will adjust as needed with future updates.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY from Noon today to 9 PM CDT this evening FOR
KSZ008>012-020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Hennecke
LONG TERM...53
AVIATION...Hennecke