Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 121743
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1243 PM CDT Fri Sep 12 2014
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 359 AM CDT FRI SEP 12 2014
An amplified positive tilt H5 trough was digging southeast across
the upper Midwest and extended southwest into the central high
plains. A broad area of light rain was moving east across the
northwest of counties of the cwa. The steady light rain extended
back to west across western KS. There was even some light snow
mixing in with the rain across the southern panhandle of NE and
extreme northeast CO.
The H5 trough will move southeast across the central pains and into
the southern plains Today. Ascent ahead of the H5 trough, along with
residual moisture will allow the broad band of scattered to numerous
rain showers to spread from west to east across the CWA this
morning. As the upper trough axis approaches the better ascent will
shift east and southeast of the CWA during the afternoon hours. The
showers will become widely scattered across the CWA during the
afternoon hours before ending from northwest to southeast across the
CWA during the late afternoon hours.
Low-level CAA across the plains combined with cloudy skies and
periods of light rain will keep highs quite cool for this time of
year. Most areas will only see highs in the mid 50s with some upper
50s high temperatures across the southeast counties of the CWA.
Tonight, a broad surface ridge axis will build southeast across the
CWA. North winds will diminish through the night as skies clear from
northwest to southeast across the CWA during the night. A
combination of clear skies, light winds and a cooler and drier
airmass in place will cause overnight lows to drop into the mid 30s
across the northern counties of the CWA, with upper 30s to lower 40s
across the remainder of the CWA. There may be some patchy front
developing across the northern counties of the CWA near sunrise. The
best chance for patchy frost will be north and west of a Delphos, to
Manhattan to Hiawatha line.
.LONG TERM...(Saturday through Thursday)
Issued at 359 AM CDT FRI SEP 12 2014
In the wake of the departing Midwest trough...the surface high
pressure ridge will remain in place across the county warning area
(cwa) on Saturday before sliding off to the east on Sunday. Will
keep patchy frost wording in the northern counties until 8 am
Saturday morning...otherwise a sunny and dry...but unseasonably cool
day weather is in store for the area. Despite the sunshine...the
light winds and weak mixing will limit highs to the 60s...or
generally 15 to 20 degrees below normal for mid September.
As the high pressure center slides eastward on Sunday...the low
level flow will increase from the south through the day and warm air
advection will increase. This will not only translate to warmer lows
Sunday morning in the 40s...but also afternoon highs about 10
degrees warmer generally in the middle 70s. Although moisture will
also be increasing...the stronger combination of moisture...warm air
advection and forcing ahead of an approaching shortwave trough are
evident across the cwa later in the evening and through the
overnight...especially across the northeast counties. The chance for
showers and thunderstorms will persist through Monday before another
front pushes through with drier air into Tuesday. Highs on Tuesday
will not be much cooler than Monday`s with readings generally in the
low to mid 70s.
Warmer air will the spread back to the north and east into Wednesday
and Thursday with highs back into the 80s by Thursday. As this
occurs there will be another chance for showers and thunderstorms
Wednesday and Wednesday night.
.AVIATION...(For the 18Z TAFs through 18Z Saturday Afternoon)
Issued at 1237 PM CDT FRI SEP 12 2014
Isolated light SHRA dissipating towards the east this afternoon.
Scattered low end MVFR gradually improves to VFR at terminals as
drier air migrates southward. Light winds and clear skies aft 09Z may
induce some patchy ground fog at KTOP/KMHK through sunrise.