000
FXUS63 KTOP 090538
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1138 PM CST Sat Mar 8 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Sunday)
Issued at 256 PM CST SAT MAR 8 2014

Longwave trough from Great Lakes southwest into the Southern Rockies
becoming increasingly sheared out per recent water vapor imagery
with a stronger wave pushing out of the trough across southern
Kansas today bringing precipitation to southeastern portions of the
state today. Weak continental surface high was into western and
central portions of the state at 20Z.

With the southwest portion of the upper wave continuing to dive
south and the northeastern portion continuing east, rising heights
and modest anticyclonic flow will develop overhead, with skies
clearing this evening. Late evening and early morning winds should
be rather light with southwest winds taking hold overnight as lee
troughing takes place. Warm air advection increases through the day
Sunday and just how warm surface temps get are a challenge. Going
forecast seemed pretty good, though forecast mixing depths appear a
bit lower and shaved a degree or so off most locations.

.LONG TERM...(Sunday Night through Saturday)
Issued at 256 PM CST SAT MAR 8 2014

Highs for Monday continue to look warm as models advect warmer air
in from the west and southwest. Mixing 925MB winds adiabatically
to the surface would suggest highs in the upper 60s to lower 70s.
Therefore have not made many changes to the prev forecast highs.
Models seem to keep the weak backdoor front mainly to the north of
the forecast area, so about the only concern that could prevent
highs from reaching the 70s would be limited mixing due to the
boundary slipping into the area.

Models seem to be converging on a frontal timing for Tuesday. With
the front moving through Tuesday afternoon and an open shortwave
passing overhead Tuesday night, it looks like the better chances
for precip will be Tuesday night. The biggest differences continue
to be the quality of moisture with this system as the ECMWF seems
to be the only solution able to saturate the atmosphere. The GFS
and GEM show more dry air to overcome and generate little if any
precip. With this in mind have kept a 30 to 40 percent chance for
rain and snow Tuesday night. If the ECMWF pans out, 1000-500MB
thicknesses and cold air advection suggest temps could be cold
enough for all snow. However the ECMWF forecast soundings do not
have the vertical resolution to show whether there is a warm nose
or not, and the GFS doesn`t saturate the column so its hard to
decipher precip type from it`s soundings. All the forcing and
moisture appears to be east of the forecast area by 12Z Wednesday
so have removed the slight chance pops from Wednesday morning.

For Thursday and Friday, southwesterly low level flow redevelops
allowing temps to trend warmer for the end of the week. By the end
of the week and for the weekend, models are showing northwest flow
strengthening with the chance for embedded shortwaves to affect
the central plains. Continuity with these weak waves has been poor
so confidence in the forecast diminishes towards Saturday. Have
kept the forecast dry as there is no obvious signal for precip
from the GFS and ECMWF. Also kept temps relatively mild into
Saturday, but there are mixed signals from the models in whether
there will be warm southerly flow or cool northerly winds during
the day Saturday.

&&

.AVIATION...(For the 06Z TAFs through 06Z Monday Night)
Issued at 1134 PM CST SAT MAR 8 2014

VFR conditions are expected at the taf sites with the exception
of TOP, which may develop haze causing MVFR visibilities. Not too
confident in this happening therefore did mention 6sm visibility
for now.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Sanders