Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 231722

1222 PM CDT Wed Apr 23 2014

Issued at 327 AM CDT WED APR 23 2014

Showers and an occasional brief thunderstorm have developed over
portions of southern Nebraska and north central Kansas as of early
this morning. It appears much of this activity is tied to a weak
upper disturbance, inferred from both water vapor imagery and model
depiction, in addition to warm air/moisture advection. Coverage is
expected to gradually increase some during the next few hours based
on high-resolution model guidance and this solution seems
reasonable. Forecast maximum instability through the vertical column
is very meager to none over the area through midday, and do not
expect much in the way of thunderstorm activity at this time, but
rather shallow, high-based convection in the form of scattered
showers. The highest probability of rainfall will remain over the
northwestern half of the CWA through the daylight hours. Temperatures
will be dependent on cloud cover, with the northeastern sections of
the forecast area cooler in the middle/upper 60s to the upper 70s in
more cloud-free southwestern areas.

A progressive trough, gradually becoming negatively-tilted, will
move through the central CONUS tonight. Robust convection is
expected to initially develop late this afternoon well to the west
of the CWA in the proximity of a cold front in central Nebraska and
a dryline over the High Plains. The front will quickly overtake much
of the dryline during the evening hours over Kansas, leading to
additional convective development. Models are in decent agreement in
bringing a complex of showers and thunderstorms across the forecast
area late tonight into Thursday morning. While severe weather is
expected well to the west of the area, conditions will become less
supportive for severe weather with eastward extent. As thunderstorms
approach the forecast area, a decrease in intensity is expected as
weak instability will be present (MUCAPE < 500 J/kg, SBCAPE < 50
J/kg), yet sufficient to support thunderstorms. Deep layer shear will
remain strong, so we will have to continue to monitor convective
evolution to the west later this evening. Many areas may receive up
to one-half inch of precipitation, with locally higher amounts in
areas with thunderstorms. Rainfall should quickly come to an end
during Thursday afternoon from west to east as a cold front moves
through the area.

Temperatures will remain warm as little cold air advection will be
present upon the departing upper system. Another highly-amplified
upper trough will move into the western US on Friday, and emerge
into the Plains during the weekend. Models are in decent agreement
through much of the weekend with regards to the synoptic placement
of key features, but diverge by early next week. The theme continues
for an active weather pattern Saturday through Monday. Initial
chances for thunderstorms are possible on Saturday, as a warm front
lifts into the area and warm air advection increases. As the trough
moves into the Plains on Sunday, strong upper ascent and an
approaching pacific cold front will lead to increasing chances of
thunderstorms. While specifics cannot be accurately resolved this
far in advance, several signals suggest strong or severe weather
possible for portions of the forecast area on Sunday. As the upper
trough becomes nearly cut off over the mid Missouri Valley on
Monday, cooler and rainy conditions are expected. Exactly how cold
temperatures fall remains highly uncertain due to model differences
handling the upper pattern and subsequent cold air advection.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1213 PM CDT WED APR 23 2014

Ongoing scattered light showers are expected to taper off this
afternoon and should not have an adverse impact to CIGS and VIS. The
story for this afternoon and evening will be breezy southeast winds
gusting in the middle to upper 20 kts range. But otherwise VFR CIGS
and VIS are expected. Late overnight tonight a line of thunderstorms
are expected to impact the terminals. Have timed this to begin by 08Z
but that may be off an hour or so either side of 08Z. Surface winds
will shift near 12Z with the passage of a cold front along with
periods of SHRA through the morning. The activity should clear out
just beyond the end of the TAF period.




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