Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 241136
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
636 AM CDT TUE MAY 24 2016

...Update to near-term and aviation forecast discussions...

.UPDATE...
Issued at 625 AM CDT TUE MAY 24 2016

The low level jet continues to veer and weaken a bit this morning
as it rides over an outflow boundary that has now pushed into the
Wichita area and east northeast toward Garnett. Thunderstorms
continue to be fueled by 1000-1500 J/kg of MUCAPE but effective
shear has weakened in recent hours and lifted parcel levels have
increased as well so cold pool driven convection is becoming
increasingly more difficult to sustain. With all of these factors
in mind, along with the region just being pretty well worked over
by convective overturning, believe that the severe weather
potential for the rest of the morning is minimal and have
cancelled the severe thunderstorm watch.

&&

.SHORT TERM...(Today and Tonight)
Issued at 300 AM CDT TUE MAY 24 2016

A large complex of thunderstorms was oriented in a west-to-east band
across northern KS early Tuesday morning. These storms have shown
organization at times, and are now showing signs of individual
segments accelerating to the east. One such segment will enter Cloud
and Ottawa counties around 3 AM, and has at least some potential to
produce damaging winds. The good news is that instability decreases
with eastward extent and we have already seen decreasing intensity
trends with other cells as they progress farther east into the
forecast area. However, there is also persistent advection of
moisture and warmth into the southern flank of this storm so it may
be able to persist for a while as it moves east. The main question
is whether it will be severe while it progresses east. Forward
propagating Corfidi vectors are toward the east at only 20-25 kts so
cold pool forward motion will not help in wind gust production much
and will likely rely on rear inflow jet and precip-loading induced
wind fields for any sort of severe wind production. Severe hail
potential seems to decrease with eastward extent as well given the
limited instability, but effective shear of 30-40 kts suggests we
can not completely rule out some severe hail. Hi-res model guidance
suggests that this first wave will push east of the area by around
sunrise but attention turns farther upstream as another complex
associated with a short wave trough will follow across northern KS
and has at least some chance to be strong, although it will enter an
airmass that has had plenty of convective overturning in north
central KS and this should limit overall strength of any incoming
MCS.  Even still, expect thunderstorms to progress east across the
area through mid morning with a drying trend beyond that time.

The main question for later Tuesday will be the quality of airmass
recovery through the day. Expect an outflow boundary to be laid out
well south of the area for much of the day but should then see it
wash out and lift back north later in the day. This may provide a
focus for thunderstorms as it lifts north by afternoon, and
especially as a weak short wave trough approaches central KS by mid
to late afternoon. Effective wind shear should be in the 35-45 kt
range with a 2000-3000 MLCAPE near this boundary...wherever it may
be. Thus, the devil is in the mesoscale details this afternoon and
evening as any storms that develop stand a good chance of becoming
supercells and severe. Tornado potential would be non-zero but yet
not particularly impressive unless a steady-state supercell can
develop near a boundary and ingest some rich helicity air.  But
again, this will depend on near-real-time storm-scale features.
Thunderstorms are likely to continue in one or more clusters/rounds
through the night as a series of short wave troughs cross the
region. Of course, flooding will again be a concern especially
overnight and especially in the areas that received training storms
and a shot of heavy rain early today.

.LONG TERM...(Wednesday through Monday)
Issued at 300 AM CDT TUE MAY 24 2016

Overnight convection gradually clears eastward by the afternoon as
temporary subsidence aloft tempers thunderstorm redevelopment on
Wednesday afternoon. No major changes seen with current guidance and
previous runs with the exception of the dryline location by 00Z
Thursday. The GFS and SREF are further within the CWA while the NAM
and ECMWF maintain the furthest progression over north central
Kansas. Regardless, decent capping inversion will limit overall
storm potential. However, if a storm develops on the dryline over
north central KS, it will likely be severe with large hail, damaging
winds, and perhaps a tornado. This threat is fairly isolated and
have maintained the highest chances Wednesday evening across these
areas.

Atmosphere becomes capped once again Thursday afternoon as the main
upper trough approaches Colorado and New Mexico. Stronger forcing is
present by late afternoon with weak vorticity lobes noted lifting
out ahead of the main forcing. In addition, sfc low/dryline edges
towards central Kansas once again with a very warm and moist airmass
over our CWA. Focus for convection is somewhat muddled from
guidance, but it appears the sfc warm front near the KS and NE
border and the dryline to our west may be the focus areas for severe
storms late Thursday afternoon and evening. Given the decent speed
and directional shear profiles and ample CAPE present, all severe
hazards would be possible including the risk for flash flooding.
Assuming overnight convection clears out by Friday morning, could
see another round of strong to severe storms Friday afternoon and
evening as the main upper trough axis lifts overhead. The dryline is
fairly similar between the GFS and ECMWF across central KS with main
question being any mesoscale influences and the strength of the
inversion layer to inhibit sfc based storms initially. Overall,
while details still remain somewhat uncertain it still appears
severe storms are likely at some point between Thursday and Friday.
Flash flooding may play a more widespread hazardous threat given the
excessive rainfall the area has received in the recent past.

The weekend onward is still showing signs of remaining unsettled
with southwesterly flow persisting over a warm and moist airmass.
Low end chances for thunderstorms seemed reasonable given the
various uncertainties on timing and coverage. Relief from the rain
may finally come to an end later next week as the upper air pattern
finally begins to shift.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 625 AM CDT TUE MAY 24 2016

TAF will again be driven by convection with a relatively low level
of confidence in the forecast. This morning, expect mainly VFR
cig/vis conditions, although with periods of thunderstorms with
heavy rain at all TAF sites from 12Z through 15 or 16Z. Much of
the afternoon should be VFR with no precipitation, although a
stray storm is possible just about any time today. Increasing
thunderstorm chances return by 06Z to 12Z period.

&&

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

$$

UPDATE...Barjenbruch
SHORT TERM...Barjenbruch
LONG TERM...Prieto
AVIATION...Barjenbruch



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