Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 020455
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1155 PM CDT Mon Sep 1 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Tuesday)
Issued at 319 PM CDT MON SEP 1 2014

Quick cyclonic upper flow remains in place with the core of last
night`s wave already in the Great Lakes and another weaker wave
coming into the High Plains per recent water vapor imagery. The cold
front`s location is hard to nail down behind outflow from the
overnight convection and weak pressure fields, but appears to be
bisecting the local area from southwest to northeast. Lower cloud
under a modest inversion has been rather prevalent today, keeping
temps in the 70s.

Modest convergence persists in east central Kansas this afternoon.
With still some CIN remaining per RAP analysis, confirmed by recent
visible satellite imagery, and the western upper wave staying well
north, storm chances don`t look great, but will maintain some
mention ahead of the front in east central Kansas, diminishing with
time as weak high pressure continues to move across northern sections
of the state. There are some breaks in the clouds to the south, and
some increase in instability is anticipated for the next few hours.
Deep layer is not very high in the weak low level wind fields, but
hard to completely rule out with mixed layer CAPE likely rising to
near 1500 J/kg. As the surface high builds in, winds should be
rather light, and depending on cloud trends particularly with
convection, a fairly good setup for radiational fog will be in place
with cloudy skies and limited mixing today and low cloud scouring
out following the recent heavy rain. Will go ahead with some patchy
fog mention at this point and let later shifts watch trends. Storm
chances continue to look like Tuesday but with the boundary again
possibly not far south, will keep a small chance near it. Better
mixing and insolation should yield highs back into the 80s.

.LONG TERM...(Tuesday Night through Monday)
Issued at 319 PM CDT MON SEP 1 2014

Models continue to show the potential for elevated thunderstorms
and large hail Tuesday night. The one wrinkle is the NAM appears to
be quite a bit stronger in magnitude for both the elevated
instability and effective shear. There is still good theta-e
advection along the nose of the low level jet as well as
isentropic upglide, so I think there should be some storms over
eastern KS. The question is whether they will be strong enough to
produce severe hail. Have continued with a chance POP through the
night and think the potential still exists for some severe storms.
It just may be more marginal than the NAM would suggest.

With the exception of some elevated precip possibly lingering
through the morning Wednesday, the forecast should quiet down as
the models keep the jet stream and synoptic scale energy north of
the forecast through Thursday morning. By Thursday night, a frontal
system is projected to begin moving into the area. There is some
uncertainty in the timing of the frontal system as most solutions
have trended faster with the front, the NAM being the fastest. For
now I`ve not made many changes from the previous forecast thinking
the front would move through mainly Friday and Friday evening with
the higher chances for precip in these periods. However if the
faster trend continues, the POPs may need to be pushed up in the
forecast as well. Have continued to trend POPs down for Saturday
and kept a dry forecast for Sunday with models showing surface
ridging and relatively dryer air over KS. By Monday, there is some
disagreement with the GFS and ECMWF in the amplification of an
upper trough across the west. Because the GFS is the more
amplified solution, it is quick to set up return flow with the
potential for shortwaves within southwesterly flow aloft to pass
near the area. Have taken a conservative approach with the
forecast at this time and have introduced only a slight chance for
precip on Monday until there is a little more agreement in
solutions.

Temps will remain quite warm Wednesday and Thursday as the models
show the thermal ridge over portions of the state. Because of this
have continued with highs in the 90s and lows from around 70 to
the mid 70s. Cold air advection is expected to increase Thursday
night as the front moves through the area. This should bring a
cool down for the weekend with highs in the 70s and lows in the
50s to around 60.

&&

.AVIATION...(For the 06Z TAFs through 06Z Tuesday Night)
Issued at 1149 PM CDT MON SEP 1 2014

Elevated thunderstorms have moved well south and east of the taf
sites. Mid and high level clouds have blanketed the area from the
convection in southern KS, but they are slowly progressing
eastward. Once the clouds clear out there maybe brief periods of
patchy especially during calm winds in the predawn hours. Although the
forecast winds just above the surface may inhibit fog development.
Therefore did not add any tempo for dense fog at this time.

&&

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

$$

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





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