Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 241954
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
254 PM CDT SUN APR 24 2016

.SHORT TERM...(This Evening through Monday)
Issued at 213 PM CDT SUN APR 24 2016

An upper level trough will lift east-northeast across eastern KS
Sunday night. Thunderstorms will continue along and east of the
dryline due to surface convergence ahead of the dryline and larger
scale ascent ahead of the H5 trough. MLCAPES will range between1500
and 2500 J/KG across the central counties of the of the CWA. The
0-6 KM effective shear will increase across the northern counties
to 40 to 55 KTS through the early evening hours. The combination
of CAPE and vertical windshear will create a favorable environment
for severe thunderstorms. Most numerical models show a line of
storms developing across the northeast and central counties of the
CWA. There may continue to be embedded supercell thunderstorms
within the line of storms but areas north of I-70 may see more of
a widespread damaging wind event during the evening hours. From
abilene to east of MHK may see more discrete supercells extending
southwest to east of ICT. These storms will be capable of
producing large hail and localized damaging wind gusts. By 3Z MON
the 18Z NAM model backs the surface winds across the eastern half
of the CWA. This increased the 0-1 KM SRH to 200 to 300 J/KG and
would make the environment more favorable for any discrete
supercell to produce isolated tornadoes. However, as the boundary
layer cools during the evening hours, the tendency will be for
discrete supercells to be come more elevated. But there may be a
window from 7 PM to 9 PM where discrete supercells may have the
best environment to produce isolated tornadoes.

After 6Z MON the stronger ascent ahead of the H5 trough will shift
northeast of the CWA and the thunderstorms will diminish in
intensity across the CWA and shift northeast of the CWA. During the
early morning hours of Monday a weak cold front will over take the
dryline and shift southeast across the CWA. There could be enough
surface convergence for an isolated shower or thunderstorm ahead of
the cold front.

Monday through Monday night. Most models show the surface cold front
pushing southeast across the extreme southeast counties of the CWA.
Frontolysis will occur along the front and the front will become
very weak diffuse across southeast KS. A down stream upper ridge
will amplify across the plains as an intense upper low digs
southeast into the four corners area. I don`t expect much in the way
of any isolated showers or thunderstorms Monday and through most of
Monday night. I kept a slight chance for showers and thunderstorms
in late Monday night as deeper moisture will begin to return
northward across central KS. So, there could be some weak isentropic
lift for an isolated shower or elevated thunderstorm. Highs Monday
will be slightly cooler with mid to upper 70s.

Tuesday, this could be an interesting day across the plains by
afternoon. The ECMWF looks to be too robust with its QPF forecast
for the morning hours as subsidence will continue under the
downstream H5 ridge across the plains during the morning hours.

The 18Z NAM models is the slowest lifting the upper low across the
four corners region into the central high plains. The NAM models
shows an EML over spreading the CWA with a strong CAP across much of
the CWA through 00Z WED. The NAM does punch the dryline east into
south central and central KS by 00Z WED, but has no surface based
convection during the day. The surface warm front will lift
northward to the NE border by the late afternoon hours. The main
upper trough will be lifting northeast into CO and norther NM which
will keep the stronger ascent across western KS. The H5 jet max of
50-55 KTS will lift northeast across west central KS and much of the
CWA will be on the subsidence east side of the H5 jet. However, if
temperatures get close to 80 degrees along the dryline there may be
enough convergence for an isolated supercell thunderstorm to develop
and move northeast off the dryline towards Ottawa and Cloud Counties
during the late afternoon hours. The NAM had over 4,000 J/KG of
MLCAPE and stronger vertical windshear forecasted across the western
counties of the CWA. Thus if a storm were to develop it would quickly
develop into a supercell that would produce large hail, local
damaging wind gusts and tornadoes.

 The GFS model does not show as stout of an EML over spreading the
area, which would cause a weaker CAP to develop during the afternoon
hours. The GFS moves the dryline east of I-135/US 81 by late
afternoon with the warm front along I-70. The GFS develops QPF along
and south of the warm front across much of east central KS during
the afternoon hours. If the GFS were to verify there would be a much
better chance for surface based storms to develop during the mid and
late afternoon hours. The MLCAPE is progged to be in the 2500-4000
J/KG range across the CWA. Given the high CAPE and stronger
vertical windshear, initial supercell thunderstorms will produce
large hail, damaging winds and tornadoes. The storms may become more
widespread towards 00Z WED, which may cause line segments of storms
to develop. The main threat from any line segment of severe
thunderstorms would be widespread wind damage and the potential
for meso vortice tornadoes within the line of storms.

At this time based on the slightly slower progression of the upper
level trough I`m leaning more towards the 18Z NAM solution. But
severe storms will develop during the evening hours as the stronger
ascent ahead of the H5 trough spreads east across the CWA. Everyone
should pay attention to the latest forecast on Tuesday afternoon and
evening since the combination of high CAPE and stronger vertical
windshear may cause some of the supercells late Tuesday afternoon
and evening to produce stronger tornadoes in or near the CWA.

.LONG TERM...(Monday Night through Sunday)
Issued at 213 PM CDT SUN APR 24 2016

High impact severe weather outbreak still looks possible Tuesday
evening.

Elevated convection could develop after 06Z Tues as strong Thetae
advection takes place in advance of the upper wave with some
decrease in coverage expected by mid morning as a strong capping
inversion holds until later in the afternoon.

Both EMCWF and GFS show next upper wave taking on a negative tilt
by 00Z Weds with main mid-lvl wave expected to move across the
TX/OK panhandle by 00Z. The sfc low should deepen across western
KS with a warm front extending ENE through some part of the CWA by
00Z Weds as well. CAPE/Shear parameters supporting supercells as
well as tornadoes will be in place so will continue to highlight
that message during the evening hours.

The dry slot will work across the area after midnight into early
Weds with the upper system fcst to drift across the area with some
lingering chcs for precip.

The active and potentially high impact pattern will continue with
the next upper wave forecast to induce low pressure across the
TX/OK panhandle Thurs night with widespread elevated convection
possible north of the warm front into Friday. The timing and track
of this 3rd upper system remain uncertain but another round of
severe weather looks possible as does the potential for heavy
rains somewhere across the CWA. Hopefully we`ll get a break after
this system with hints of a pattern change for the first week of
May.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1238 PM CDT SUN APR 24 2016

For the 18Z TAFs, have focused VCTS on highest likely time frames
for TS development over the terminals. Still not highly confident
on coverage for any storms, so have not added prevailing line for
TS. However, the expectation is storms will move as a line once
formed and will be able to be tracked with more certainty at that
time. Winds continue out of the south this afternoon and veer
slightly into after storms pass. Then MVFR CIGS likely as the cold
front becomes stationary over the region into the early morning
time frames.


&&

.TOP Watches/Warnings/Advisories...
Wind Advisory until 7 PM CDT this evening for KSZ037-038-054-055-
058.  Tornado watch until 11 PM CDT this evening.

&&

$$

SHORT TERM...Gargan
LONG TERM...Omitt
AVIATION...Drake



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