000
FXUS63 KTOP 172314
AFDTOP

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

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 348 PM CDT THU APR 17 2014

An upper level trough was moving east-southeast across the southern
plains this afternoon. The more intense PV anomaly if progged to
move southeast across northern and eastern OK this afternoon and
evening. Also, the deeper moisture was located across central and
northern TX...south of a stationary front along the Red River
Valley. An area of light rain was located along and south of I-35
this afternoon. A combination of weak ascent and residual moisture
will provide a chance for very light rain across the southeast
counties of the CWA through 600 PM.

Tonight...a surface ridge of high pressure will build southeast
across the CWA. Calm winds and clear skies will allow for
radiational cooling...allowing overnight lows across the eastern
counties of the CWA to dip down into the lower to middle 30s.
Dewpoint temperatures may only be 1 to 3 degrees cooler then the
ambient temperatures...thus scattered front may develop after 200
AM across the central and eastern counties of the CWA. Temperatures
will warm into the upper 30s about an hours after sunrise. Southerly
winds will increase to 5 to 10 MPH across the western counties of
the CWA during the early morning hours of Friday...thus frost should
not form in the western one third of the CWA. Due to the potential
for scattered frost formation and for some low-lying areas to dip
down to 32 degrees, I will issue a frost advisory for the eastern
third of the CWA...generally along and east of a Herington...to
Abilene...to Clay Center...to Washington line.

Friday...An upper level ridge across the western US will move east
over the plains. A lee surface trough will deepen and the surface
winds will become southerly and increase through the afternoon
hours. Southerly winds will increase to 20 to 30 MPH across the
western counties with gusts up to 40 MPH by afternoon...with 15 to
20 MPH southerly winds across the eastern counties. Highs will reach
the upper 60s to lower 70s with good WAA. We may see enough
sfc/850mb moisture advection to prevent surface dewpoints from
mixing out into the 30s during the afternoon hours. Given the
stronger southerly winds and RH`s in the upper 20 to lower 30
percent range, there will be a very high rangeland fire danger
across much of the CWA Friday afternoon.

.LONG TERM...(Friday Night through Thursday)
Issued at 348 PM CDT THU APR 17 2014

Friday night through Monday...

Good mixing is still expected to persist through Friday night and
should help to maintain warmer temperatures...especially in the
northwest half of the county warning area (cwa) where readings in
the low to mid 50s are expected.

Precipitation chances continue low and limited to after 4 pm over
mainly the far northwest counties in north central Kansas.  With the
system fcst to slow from previous runs and the drier air remaining
in place across the eastern cwa beyond midnight...have slowed the
eastward progression of any convection into the eastern counties
until after midnight and lowered to slight chance. Will however
maintain likely pops across the north central through the night
as moisture/instability and lift will be slow to spread eastward
across the cwa. Models continue in good agreement that moisture and
some instability for showers and thunderstorms will gradually
increase eastward on Sunday as the upper trough advances out into
the central plains through the day before starting to exit the cwa
early Monday. Will therefore maintain high end chance pops through
Sunday night before decreasing northwest to southeast across the cwa
on Monday as the trough exits to the southeast. Will maintain highs
in the lower 70s for both Sunday and Monday. Clouds will be more
extensive on Sunday than the afternoon hours on Monday but the
offsetting factor will be the north winds behind the front for
Monday.

Tuesday: a broad longwave trough makes its exit out of our CWA. Some
leftover showers could linger into early Tuesday, particularly in our
southeastern most counties. However, things should clear out by the
afternoon as high pressure builds into the area. The remainder of
Tuesday should be dry.

Wednesday and Thursday: the ECMWF and GFS models are both progging a
strong mid-latitude cyclone to develop over Montana. An associated warm
front should bring very warm temps to the region, with highs
reaching into the lower 80s. These warm temperatures, coupled with
abundant moisture from southerly winds should be conducive of
showers and even thunderstorms. The ECMWF is progging CAPE values ~1400
J/kg along the western edge of the CWA, indicating sufficient
instability for convection. Convective initiation timing and location
are still uncertain ATTM due to model discrepancy. As the
mid-latitude cyclone translates closer to the region, a cold front
is progged to develop, which could concentrate CI along the boundary.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 612 PM CDT THU APR 17 2014

VFR conditions expected through the period. Winds light overnight
and pick up a southeasterly component with time. Slowly increase
above 12kts for MHK in the afternoon but will not add to taf line
this far out.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY from 3 AM to 8 AM CDT Friday FOR KSZ010>012-
022>024-026-036>040-054>056-058-059.

&&

$$

SHORT TERM...Gargan
LONG TERM...63
AVIATION...67