Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 231723
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1223 PM CDT FRI SEP 23 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 253 AM CDT Fri Sep 23 2016

Another warm and relatively humid night across the forecast area.
Upper low centered over Utah and Nevada making slow progress toward
the east.  Area starts to see some mid level cooling as the trof
approaches, which should shave a few degrees off high temperatures
for today with highs in the upper 80s.  Southerly surface winds pick
up a little speed by the afternoon hours, with north central Kansas
in the 15-20mph range with 10-15 east, which may also make it feel
just a bit cooler.  Did keep the overnight slight rain chance
generally west of Manhattan, but think the rain will overall hold
off until after sunrise into Saturday.  Lows Friday night once again
forecast in the upper 60s to near 70s with front still not through
the area by morning.

.LONG TERM...(Saturday through Thursday)
Issued at 253 AM CDT Fri Sep 23 2016

On Saturday morning a strong mid/upper level trough will lift out
over the northern plains, which will push a front into western KS.
Ahead of that system moisture advection will increase in the low to
mid levels. Due to the meridional flow in the column and a tropical
air mass in place the mid level lapse rates will be modest. This
should yield mlcape on the order of 1500 to 2000 j/kg across the
area by Saturday afternoon. As mentioned the shear will be rather
directional and the higher wind speeds will be confined over
western KS closer to the closed system. Therefore the deep layer
shear will also be modest, but possibly approach 30 kt in north
central KS. The cold front will stay out in western KS most of the
day, but warm sector development is expected as surface heating
and large scale lift increases. Scattered to widespread showers
and thunderstorms are expected during this timeframe. A few of
these storms may be capable of producing large hail and damaging
winds especially given the instability and some shear. Heavy
rainfall might be more of an issue with plenty of moisture
spreading northward and pwat values around 1.75 in. Going into
Saturday night the coverage will likely increase as the cold front
pushes through the area. The front will become more zonal and
decent frontogenesis will provide additional lift as the mid level
low pressure moves over ND.

Heavy rainfall threat will continue through the Saturday night with
the possibility of training storms. As of now the high rainfall
totals appear to be confined to east central KS with lesser
amounts westward. These totals could be as high as 2 in at some
locations. The front will clear the area Sunday morning. Although
there are some model differences on how to handle the energy that
will get cut off over the southwest US. The ECMWF and GEM keep the
northern and southern energy more phased therefore have more post
frontal precip that lingers into Sunday. The GFS and NAM dry
things out much quicker so have leaned more towards this solution
given the ensembles agree with this scenario. A Canadian air mass
will move in behind the front causing highs to barely reach the
70s and lows in the upper 40s and lower 50s through mid week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1223 PM CDT Fri Sep 23 2016

VFR conditions will continue through the majority of this
forecast. Some increase in cloud not far above MVFR levels should
occur after 0Z with chances for convection increasing after 12Z.
MHK could see some scattered activity by the end of the period.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...65



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