Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 221738

1238 PM CDT Mon Sep 22 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 253 AM CDT MON SEP 22 2014

Mid level ridge is currently building over the central plains,
while a surface high pressure slides across the region. Dry air
has overtaken the forecast area with dew points reaching the mid
to upper 40s. With the surface high axis directly across northeast
KS winds are light and skies mostly clear. The only exception are
some mid level clouds over western and central KS due to moisture
advection ahead of the next system. Not sure how much these clouds
will limit radiational cooling, but they are expected to stay out
of most of the forecast area. Dew point depressions continue to
decrease and are only a few degrees in some locations. With
lighter winds tonight expect that favorable areas near valleys,
lakes, and rivers could experience ground fog around sunrise.
Overnight lows will drop towards the current dew points in the mid
40s to low 50s.

The rest of today will be comprised of an increase in mid level
clouds as the trough crashes the ridge over the Rockies. High
temperatures reach the mid 70s across the entire area. There is
decent agreement that the mid/upper level trough passes over NE/SD
tomorrow. With an increase in mid level moisture and frontogenesis
it appears showers with isolated thunder will develop over western
KS in the evening and track eastward. The timing is slightly off
between the models with the NAM bringing precip into north central
KS by 06Z, while the GFS hold off until after 12Z. The ECMWF and GEM
agree better with the timing of the NAM therefore have kept the
slight pops between 06-12Z in far north central KS. Instability into
tomorrow morning remains under 500 j/kg, and deep layer shear barely
reaches 25-30 kts hence only isolated thunder possible. An increase
in the pressure gradient as the surface high retreats eastward, and
cloud cover should keep lows tonight in the low to mid 50s.

.LONG TERM...(Tuesday through Sunday)
Issued at 253 AM CDT MON SEP 22 2014

Tuesday and Wednesday the upper trof moves out of the Rockies and
into the Central Plains. While there is enough CAPE aloft for
thunder, and some directional shear is present, both are modest
and still expect the system to bring generally showers with
embedded thunder as it passes. Coverage and intensity should also
diminish through Wednesday, and kept just a lingering isolated PoP
out west for Thursday as trof weakens and retreats westward with
time. Highs Tuesday and Wednesday expected in the 70s, slowly
warming back toward 80 for the late week and into the weekend as
large upper ridge dominates into the northern Plains and Great
Lakes states by late in the period.


.AVIATION...(For the 18Z TAFs through 18Z Tuesday Afternoon)
Issued at 1232 PM CDT MON SEP 22 2014

Very dry air remains across the terminals and will be slow
to saturate. Will maintain a VFR forecast and dry fcst at all
terminals with only a gradual increase in mid and high
clouds...mainly after 00z/23. Winds will remain generally
southeast at speeds under 10 kts...although a strengthening
gradient aft 15z/23 will allow for winds to veer more southerly
and slowly increase.




SHORT TERM...Sanders
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