Area Forecast Discussion
Issued by NWS Topeka, KS

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703
FXUS63 KTOP 231127
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
627 AM CDT MON MAY 23 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 355 AM CDT MON MAY 23 2016

At 3 AM on Monday, a complex of thunderstorms was pushing east
across Nebraska with the southern flank and associated outflow
boundary extending into northern KS. This outflow seems to be pretty
shallow on the southern flank but is intersecting the low level jet
to create rather strong low level convergence. North central KS has
around 1000 J/kg of MUCAPE according to SPC mesoanalysis but RAP
forecast soundings indicate that those MU parcels rooted near or
just above the surface are being suppressed at the moment by a
capping inversion around 6000 feet. However, over the next few
hours, a weak short wave and associated upper cooling/height falls
will influence the region and all expectations are for this cap to
erode with a focus for thunderstorm development in north central KS
between 10Z and 12Z...and gradually shifting east into less unstable
air over eastern KS through the day. Effective shear is quite weak
this morning, and while a few severe storms are not out of the
question this AM, they would probably be limited to areas west of
HWY 77 in the first 1-3 hours of convective development...and see a
better chance for this activity to remain sub-severe with a further
weakening trend with eastward progression.

The morning/early afternoon convective overturning should do a
pretty good job of keeping much of the area stable through the day
and into the afternoon. However, expect at least some recharge into
north central KS by late afternoon where most guidance suggests a
band of 1000-2000 J/kg of MLCAPE to develop with limited inhibition
by late afternoon. Deep layer shear will also improve slightly in
this area with 30-40 kts of 0-6 shear. Do expect thunderstorm
development in this region between 4-7 PM, but unsure at this time
how far east the development will occur and it will depend on the
evolution of early day convection. For now, see at least some
conditional severe potential, again mainly focused west of an
Abilene to Manhattan to Marysville line.

Any diurnally driven afternoon storms will weaken by mid evening,
but see potential for another round of overnight storms probably
after 2 AM as the LLJ intensifies and focuses convergence into
central and northern KS. Unsure just how this will evolve, but given
very steep lapse rates and instability rooted just off the surface,
see a situation for which a forward propagating MCS could develop
with some associated wind and hail potential during the early
morning hours.  Obviously there is plenty of uncertainty throughout
this forecast, with each round of storms and its outflow having an
effect on subsequent storms.

.LONG TERM...(Tuesday through Sunday)
Issued at 355 AM CDT MON MAY 23 2016

The region looks to remain under an active weather pattern this week
and even through next weekend, with chances for showers and
thunderstorms essentially every day.  Models continue to show the
surface and mid-level features remaining fairly persistent through
the entire extended forecast period, noted by steady southwest flow
aloft and southerly surface flow that will contribute to ongoing
warm-air advection and moisture advection into the region. These
advection features will help to support sufficient instability
essentially every day this week.  While model soundings show a cap
developing almost daily, these caps appear to be weak enough to be
easily broken most days, thus supporting the development of surface-
based storms.

On Tuesday, an early morning MCS may be progressing eastward across
the CWA through the morning and cannot rule out a few isolated
strong storms embedded within this morning activity.  Precipitation
may clear out during the afternoon with several models suggesting
the development of additional storms late afternoon/early evening
across north central Kansas in the vicinity of the stationary
boundary. This additional thunderstorm development may also be
enhanced by an embedded mid-level shortwave near this boundary. If
storms are able to develop, they would likely advance into north
central Kansas during the evening hours and continue to spread
eastward overnight.  These storms should be moving out of eastern
Kansas Wednesday morning. Some model soundings suggest that a
slightly stronger cap may build in on Wednesday, however some models
have also been consistently showing a bulge in the dewpoints
possibly extending into central Kansas, which would likely be enough
to help break the cap and thus support strong to severe
thunderstorms once again late Wednesday afternoon and evening.

Thursday is increasingly looking like the best day for potential
severe thunderstorm development across the CWA.  There may not be
much in the way of morning convection, with model soundings showing
the cap quickly weakening through the afternoon hours as the dryline
advances into central Kansas.  Models are in good agreement with the
stationary boundary becoming more southwest-to-northeast oriented,
extending into north central and possibly even northeast Kansas
during the day. Models continue to show sufficient instability in
place, and it`s worth noting that the 0-6km bulk shear values have
increased in the 00z model runs to upwards of 40-50+kts by late
Thursday afternoon/early evening, especially across north central
and far northern Kansas.  With these conditions in place, there is
increasing concern for severe thunderstorms Thursday afternoon and
evening.  The stationary boundary will likely continue to linger
across north central Kansas Friday through the weekend, which will
help to support ongoing thunderstorm chances across the outlook
area.  While some strong to severe thunderstorms may be possible,
shear values look to diminish some into the weekend.

Here`s the bottom line: some strong to severe thunderstorms will be
possible across the outlook area every day this week, with all
severe threats possible: large hail, damaging winds, and possibly a
few tornadoes. Additionally, since several rounds of storms are
possible, there will be an increasing concern for flooding through
the week, especially if storms end up tracking over a particular
location from day to day.  There are still plenty of uncertainties
in the exact details of thunderstorm potential each day due to small
scale features such as potential lingering outflow boundaries.

As for temperatures, conditions will remain fairly steady through
the week and into the weekend with highs ranging from the upper 70s
to upper 80s and low temperatures staying in the 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 621 AM CDT MON MAY 23 2016

Difficult and relatively low confidence TAF through the day today.
Many models are suggesting that MVFR cigs will build into TAF
sites for a prolonged period, but see the best chance for MVFR
cigs to be later this morning into early afternoon as an upper
storm system brings rain and storms across TAF sites. Expect some
mixing as rain ends with cigs likely scattering and lifting a
bit. Another round of storms possible after 06Z but exact timing
remains in question.

&&

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

$$

SHORT TERM...Barjenbruch
LONG TERM...Hennecke
AVIATION...Barjenbruch



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