Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 180452
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1152 PM CDT Mon Apr 17 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday)
Issued at 325 PM CDT Mon Apr 17 2017

Clouds have been clearing across northeast Kansas this afternoon
allowing for temperatures to steadily climb this afternoon.  Have
bumped up high temperatures slightly with highs reaching the lower
to mid 70s.

Tonight, clouds return and the low level jet ramps up in central
Kansas.  Isentropic lift in this area may act to develop showers and
thunderstorms which would move into portions of north central
Kansas.  Winds back through the early mornings hours of Tuesday
coming becoming more southerly.  Low temperatures overnight drop
into the mid and upper 50s.

Tomorrow, a deepening surface low near the Great Lakes region will
bring a trailing front towards the area.  The tail end of this cold
front will move in from the west by Tuesday afternoon.  Rain and
thunderstorms may develop ahead or near this boundary. While CAPE
looks sufficient on the order of 1500-2000 J/kg, afternoon effective
shear looks marginal for any severe weather, near 20 knots in east
central Kansas and 25 by the Kansas-Nebraska boarder. It is possible
that initial storms that develop may be strong enough to produce
marginally severe hail. Southerly winds will pick up Tuesday
afternoon ahead of the front and temperatures will rise into the
upper 70s and low 80s.

.LONG TERM...(Tuesday night through Monday)
Issued at 325 PM CDT Mon Apr 17 2017

Models are in fairly good agreement on the synoptic scale details of
the extended with broad WSW flow aloft for the middle part of the
week followed by an amplification of the pattern for the end of the
week as a seasonably strong PV anomaly dives southeastward across
the High Plains. The GFS/EC/Canadian begin to diverge beyond
Friday as the upper low matures and begins lifting northeast. At
the surface, a decaying cold front will lay out near the NE/KS
border overnight Tuesday/Wednesday. There is some variability
amongst the medium range guidance as to where the boundary will
settle in overnight, but the bulk of the solutions hang the front
north of the border with the GFS being a notable outlier.
Maintained slight to chance POPs over the northern half of the CWA
through the overnight hours with the NAM soundings in particular
depicting over 1000 J/kg of MUCAPE values up through 06Z before
the H850 cap strengthens. Deep shear is low (20-30 kts at best),
so organized convection is unlikely.

A fast-moving, negatively-tilted upper trough will break off a west
coast cyclone Tuesday night and reach the north central Plains by
Wednesday afternoon. Increasing low-level WAA and baroclinicity
ahead of this trough will aid in lifting the aforementioned
surface boundary northward as a warm front with a 1003mb low
pulling off the Front Range and tracking N/NW of the CWA
Wednesday afternoon. Increased winds 5-7 kts for Wednesday closer
to the CONSMOS solution given the tight pressure gradient south
of the low. An attendant cold front will sweep across the CWA
Wednesday afternoon and evening under an 80 kt jet streak. This
front and upper level support will be the focus for thunderstorm
development, some of which may be strong to severe with large hail
and damaging winds the main threat. There remains some
uncertainty in the timing of the boundary and thus the severe
potential, with there being some hints that convective development
may be hindered by the cap until the passage of the front. The
GEM/GFS pose a slower solution (western CWA at peak heating) for
the front while the EC/NAM are faster (eastern CWA). Deep shear of
40-50 kts will be more supportive of organized storms should they
form.

Canadian high pressure moves in for Thursday with highs falling 15-
20 degrees between Wed and Thu. Cool weather will prevail for Friday
and Saturday as our next system passes south of the area. Strong
300K isentropic lift and modest moisture transport north of the
surface low may result in moderate to locally heavy rainfall over
NE Kansas Friday night into Saturday before clearing out late
Saturday and Sunday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1152 PM CDT Mon Apr 17 2017

Have only made small changes to previous forecast. Still have
enough concern to include TEMPO MVFR cigs at all sites around 14Z,
and too little confidence in precip for inclusion.

&&

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

$$

SHORT TERM...Heller
LONG TERM...Skow
AVIATION...65



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