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000
FXUS63 KTOP 171751
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1251 PM CDT Thu Apr 17 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 338 AM CDT THU APR 17 2014

Water vapor imagery this morning shows the shortwave trough axis
from New Mexico through southeast Colorado into western Kansas.
Enhanced lift ahead of the wave has resulted in light rain and
drizzle over western and central Kansas. Across northeast Kansas,
the surface trough that carried gusty north winds through the
evening continues to push east as high pressure and drier air settles
southward, weakening winds below 10 mph. Temperatures remain mild in
the upper 30s due to high clouds and a mixed surface layer.

As the main upper trough slides southeast into Oklahoma today, a
weaker secondary shortwave trough brings an enhanced area of forcing
over northeast Kansas. Very dry air below 800 mb will be difficult
to overcome for most of the area. However, weak 800-700 MB
frontogenetical forcing seen on cross sections over east central
areas, combined with just enough moisture for light showers to
develop. Mid term guidance is maintaining its previous trends with
showers, and perhaps drizzle, reaching as far north as Interstate 70
by 18Z while the NAM/RAP/HRRR/SREF maintain measurable precip over
far east central Kansas. Have sided closer to short term high res
models and adjusted rain chances to slight near Interstate 70 while
placing highest confidence of measurable rainfall south of the KS
Turnpike. Unfortunately, the lack of deep moisture will only result
in a few hundredths QPF at best.

Temperatures vary on location today as the subsidence brings
sunshine to north central Kansas during the early afternoon. They
are the warmest with highs in the upper 50s. Denser cloud cover and
light showers will cool highs to the low 50s over northeast and east
central areas. Highs may be even cooler dependent on the
precipitation/cloud coverage.

Chilly and mostly clear tonight with light and variable winds
underneath the ridge. With the high pressure centered just to our east
in MO, have opted to cool overnight lows a few degrees into the
lower 30s (just above the freezing mark).

.LONG TERM...(Friday through Wednesday)
Issued at 338 AM CDT THU APR 17 2014

Friday into Saturday will be a warming period as south winds and
warm advection return to the area quickly on the heels of today`s
trough. Friday afternoon could be another period of hazardous fire
weather in north central KS as winds once again increase before
moisture advection can get into full swing. It will also depend upon
the quality of mixing in the area and the overall airmass should not
be quite as dry as some recent dry days...but still worth paying
close attention. Saturday will be warmer and windier yet, but expect
dewpoints to increase markedly into the 50s, easing fire weather
hazards.

By late Saturday, a cold front will likely extend from northwest KS
into eastern NE, and should become nearly stalled overnight. A broad
upper trough will also be moving across the southern Rockies, and
will begin to see height falls across the area by late Saturday
associated with this feature. Low level convergence along the front
will be quite strong with a weakening cap and 1000 J/kg or so of
MLCAPE in north central KS. Expect convection to initiate along the
frontal zone by early evening. The primary uncertainty with this
forecast is in the location of the frontal zone by late Saturday as
areas near the front are likely to have precipitation while most
others will not. The best chances now appear to be northwest of
Concordia, although could see some changes. While modest CAPE will
be present, wind shear is forecast to be weak, and severe weather
seems unlikely at this point. After midnight, weak elevated
instability develops amidst low level isentropic ascent across much
of the forecast area, and may be sufficient for scattered showers or
thunderstorms to develop, although there is not a great focusing
mechanism outside of the frontal boundary which should still be in
north central KS.

The broad southern trough gradually moves across the Plains through
Monday, providing a prolonged period of modest precip chances across
much of the area through early Monday. Instability is forecast to
develop on Sunday afternoon but again with minimal shear so
thunderstorms appear possible but severe weather quite unlikely.
Despite a long period of POPs, precip amounts are not expected to be
particularly impressive as forcing with this trough is rather weak.
The exception would be if thunderstorms could develop with slow
motion given light mid level winds.

Will see another warming trend through Wednesday as upper ridging
builds in advance of the next storm system. Models are consistent in
bringing a deep trough onto the west coast by late Tuesday with a
prolonged period of moisture advection across the Plains states in
advance of the system. Currently see discrepancies in trough timing
as it enters the Plains, but it currently appears that ingredients
may come together somewhere across the central Plains for a severe
weather event...possibly locally. There are also some potential
limiting factors evident that keep this rather uncertain,
particularly the likelihood of a strong EML/Cap that could limit
convective development entirely. For now, have thunderstorm chances
in the forecast by Wednesday and will need to keep an eye on the
Wed/Thur time frame.

&&

.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1244 PM CDT THU APR 17 2014

MVFR ceilings have shifted to the southeast of the TAF sites.
Expect VFR conditions for the next 24 hours. Skies will become
clear tonight as winds become light and variable. Winds will
become southeast and south after sunrise Friday and increase to 6
to 10 KTS.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Barjenbruch
AVIATION...Gargan