Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 170454
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1154 PM CDT Thu Apr 16 2015

...Update to aviation forecast discussion...

.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 06Z TAFs through 06Z Friday Night)
Issued at 1151 PM CDT THU APR 16 2015

VFR conditions appear likely through 18Z, although there is some
small potential for visibility to reduce between 08Z and 13Z with
the best chance for this at MHK. Thunderstorms become more likely
and widespread from around 20Z through the end of the TAF period.
Conditions will worsen with individual thunderstorms, but
confidence in specific timing of these features is low so have
used a VCTS group to highlight the general timing.

&&

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

$$

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





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