Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 250451 AAA

1151 PM CDT Sun Aug 24 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 301 PM CDT SUN AUG 24 2014

On Sunday afternoon, a nearly stationary front extended from just
south of Dodge City to just south of Concordia to near Beatrice NE.
While winds south of the front were oriented mainly parallel to the
front, there was some broad low-level convergence along the
boundary, particularly in the zone from near Salina NNE to Beatrice
where persistent but shallow convective clouds have been developing
since noon. Adjusting model soundings for current conditions suggest
around 1000-1500 J/kg of MLCAPE with cloud bases around 10K feet and
40 degree F dewpoint depressions on the hot side of the front. Wind
shear is weak, and the main question in forecasting thunderstorms is
whether a somewhat dry mid-level airmass will inhibit deep updrafts.
A weak short wave, barely evident in 700 hPa wind profiles over SC
Kansas may be enough of a forcing mechanism to initiate scattered
storms, and the HRRR/RAP guidance has been persistent in doing so. A
bit hesitant to put too much faith in this guidance due to the
over-mixing of the boundary layer but it does seem to be a
reasonable solution. If storms are able to develop, the best
coverage would likely be between 4 PM and 7 PM, and the strongest
updrafts would have a good chance to produce localized damaging
downbursts...especially with any downdrafts falling into the very
hot airmass. If storms develop, would also expect this activity to
mainly be confined to areas east of Concordia and west of Topeka.

The weather pattern is essentially stagnant locally, and expect
similar conditions tonight into Monday as what occurred Sat night
into today. A low level jet overnight will focus most of its lift
north of the area but may support a few non-severe storms in
northern KS after midnight through around sunrise. There is a small
chance that this activity could persist into the day on Monday, but
expect a gradual decrease in coverage during the morning (assuming
storms are ongoing at sunrise). The front will then remain located
in the vicinity of far northern Kansas and may provide another weak
focus for late afternoon storms on Monday. Temperatures south of the
front will be similar to today, although perhaps a degree cooler
while dewpoints may hold in the mid-60s east to upper 50s in central
KS. The heat advisory will continue through Tuesday for the 8th
consecutive day (for much of the area) with heat index values
greater than 100.

.LONG TERM...(Monday Night through Sunday)
Issued at 301 PM CDT SUN AUG 24 2014

By Monday night the front will bisect north central and northeast KS
as the strong upper low lifts through southern Canada. Thunderstorms
are possible along and north of that front during the overnight
hours especially in NE. This front will lift north during the day
Tuesday, although progress could be complicated by any outflow
boundary moving south into the area. Additional thunderstorms are
possible along any potential outflows as well as the front trying to
lift northward. Cape during the day could reach 2000 j/kg, and this
combined with a deep mixed layer may lead to gusty thunderstorm
winds. Organized severe convection will be limited due to the lack
of deep layer shear, which remains north of the area. On Tuesday
night with the front somewhere near the NE/KS state line elevated
storms will develop north of the front overnight on the nose of the
low level jet. On Wednesday the upper level trough over the central
Rockies slowly progresses eastward while the front stalls out
across the northern forecast area. On Wednesday night as the
trough ejects the Rockies a decent low level jet develops again
focusing another round of nocturnal thunderstorms north of the
front. The models now disagree on the exact track of the cut off
low as the GFS moves it over the southern plains. The ECMWF is
further north tracking the low over the forecast area, therefore
leading to a difference in front timing. As opposed to yesterdays
thinking the chances for precip could linger into the weekend.
Temperatures again are forecast to be hot on Tuesday although this
could be complicated by possible convection. The slower frontal
passage could mean the southern portion of the forecast area could
remain hot on Wednesday. After that the temperatures go back to
near normal especially with the possible widespread rain as the
upper low tracks nearby.


.AVIATION...(For the 06Z TAFs through 06Z Monday Night)
Issued at 1147 PM CDT SUN AUG 24 2014

Confidence remains too low to insert vcts or a tempo group into the
TAFS beyond will continue with a dry VFR forecast...although
will need to monitor for any convective trend changes.
Otherwise...outflow boundary near KTOP/KFOE may back winds more
southeast...then southerly beyond 14z as main sfc boundary and
better chances for convection remain to the north of the terminals.


HEAT ADVISORY until 8 PM CDT Monday FOR KSZ010>012-021>024-026-



SHORT TERM...Barjenbruch
LONG TERM...Sanders
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