Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 162205
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
505 PM CDT Thu Apr 16 2015

...Mesoscale discussion regarding short term thunderstorm
potential...

.MESOSCALE DISCUSSION...
Issued at 450 PM CDT THU APR 16 2015

Storms ongoing from Mcpherson southwest toward Kingman are of
interest to parts of the local forecast area over the next several
hours. The atmosphere in areas generally west of Emporia to
Manhattan to Marysville is moderately unstable with MLCAPE in
excess of 1500 J/kg, but deep layer wind shear is rather weak in
these areas and unlikely to sustain storm organization for long.
Over the past hour, the cells developing on the eastern flank of
the ongoing activity have had a tendency to feed on the rather
unstable air and sustain updrafts strong enough to produce
marginally severe hail. While the individual storms have tended to
move NNE, the new updraft development has been toward the ENE, and
there have also been signs of weak cold pool development west of
Wichita where a multicell appearance and weak inhibition have
allowed the cold pool to propagate toward the east into the
instability. While inhibition is minimal, the key to additional
storm development may be in localized areas of boundary layer
convergence, of which there seems to be weak convergence from
Mcpherson toward Emporia at the present time.

To summarize thoughts on storms through 7 PM, there is some
potential for storms to develop into the Abilene, Minneapolis, and
Council Grove areas, with potential for marginally severe hail and
wind gusts into the 50 mph range with any collapsing updrafts.
While instability weakens a bit into the evening, inhibition
remains very weak well into the evening and some thunderstorm
activity may sustain through the evening.

&&

.SHORT TERM...(This Evening through Friday)
Issued at 341 PM CDT THU APR 16 2015

Upper low continues to spin around the Four Corners this afternoon.
Latest 300 mb analysis shows upper level divergence over western
Kansas into parts of central Kansas. Speed max moving across AZ into
NM and another in southwest Kansas increasing upward vertical motion
and sustaining scattered thunderstorms in western and central
Kansas. Isentropic lift and 850 mb convergence are forecast by
models to focus across central and western Kansas tonight. Low and
mid level moisture transport into central and western Kansas will
continue this evening and increase overnight as the low level jet
strengthens. Expect scattered showers and thunderstorms to continue
through the evening and overnight with the highest confidence mainly
west of a Marysville to Manhattan to Council Grove line where shear
and instability will be favorable for strong to a few severe storms.
Lows tonight will be mild with lows in the mid 50s.

On Friday, the upper low will pivot east northeast from the four
corners into southern Colorado. This will increase lift across
western and central Kansas with diffluent flow shifting east as well
into north central and northeast Kansas. Models are in agreement
with the moisture axis across central and eastern Kansas and
focusing more across the western half of the forecast area in the
afternoon hours. MUCAPE around 1000-2000 J/kg will vary across the
cwa while the more favorable shear will be confined to western into
north central Kansas in the afternoon hours along with steepening
mid level lapse rates. Some storms may be strong to severe mainly
west of a Herington to Clay Center to Washington line. Large hail
and winds will be the main hazards.

.LONG TERM...(Friday Night through Thursday)
Issued at 341 PM CDT THU APR 16 2015

Expect periods of precip through much of the next several periods as
the upper low makes initially slow east progress from eastern
Colorado into western Kansas Friday night into Sunday morning then
accelerates east out of the state by late Sunday. Still appears the
stronger convection late Friday afternoon will form well to the west
and continue north with the mean flow and not impact the local area,
but increasing large-scale forcing and deepening moisture profiles
should support waves of convection Friday night into midday
Saturday. Models are fairly consistent with a mid/upper dry slot
advecting into central Kansas in the afternoon with varying degrees
of destabilization taking place as mid-level lapse rates fall to
around 7.5 C/km. Fairly weak wind fields remain to be anticipated
and keep storm organization limited, and the CAPE profiles are of
the "skinny" variety, but at least pulse severe storms seem possible
in the afternoon and evening hours where clearing can occur. The
skinny CAPE, well above-normal precipitable water levels, storm
motions on the slow side, and even some training potential at least
suggests some heavy rain possibilities Friday night into Saturday
night. Sunday afternoon presents another small opportunity for
stronger convection, with the cold front preceding the upper trough
and some destabilization likely in mainly east central Kansas, with
shear somewhat increased though instability will likely be weaker.
Upper trough`s passage brings and end to precip by early Sunday
evening.

Dry and cooler northwest flow behind the northern stream wave
prevails for at least the early week periods, with the main concern
being how cold and calm conditions can get in the night/early
morning hours. At this point frost/freeze potential looks low but
will need to be monitored. Details in the pattern bring differing
solutions for the mid week, though at least some measure of return
flow brings increasing moisture and small precip potential.

&&

.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1236 PM CDT THU APR 16 2015

Skies continue to dissipate throughout the afternoon keeping
conditions VFR.  Storm coverage for tonight is still uncertain,
although most models are indicating scattered thunderstorms will be
predominantly in the western half of our CWA overnight.  For this
reason, have kept VCTS at MHK from 03-12Z.  Thunderstorms are still
expected tomorrow, but the focus may be later than this TAF package.


&&

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

$$

MESOSCALE...Barjenbruch
SHORT TERM...53
LONG TERM...65
AVIATION...Heller





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