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636
FXUS63 KTOP 210458
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1158 PM CDT Tue Jun 20 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 252 PM CDT Tue Jun 20 2017

Currently, the upper levels of the atmosphere are characterized by
an expansive anticyclone spinning over the Desert Southwest with a
broad ridge in place nosing up into southwestern Canada.  Main belt
of the Westerlies resides just north of the area into the Northern
Central Plains and into the upper Mid-West.  A notable shortwave
impulse is advecting into eastern Wisconsin region.  This feature is
providing energy for a weak surface cold front that is currently
moving through NE and should eventually make its way into
northeastern KS vicinity by this evening.  Afternoon cu field is
developing over western portions of KS.  Further development of this
cu should take place as intense surface heating and deeper moisture
is boosting MLCAPE values into the 4000 J/kg range per SPC Meso
Analysis.

Anticipating the most active weather period in the next 24 to 30 hrs
comes in the near term late this afternoon into the mid evening.  As
storms develop in western and north central KS, it will be possible
that some cells could move into areas generally along the Hwy 81
corridor and perhaps as far east as Manhattan area.  As the weak
boundary sags down through NE, there could also be areas of showers
and storms with a lightning strike or two along the NE/KS border
into very northern counties primarily along the Hwy 36 corridor. As
a weak embedded wave currently over central NE vicinity approaches
the forecast area, it will act to reinforce the low level
convergence in the area.  Along with increasing isentropic ascent on
the 305-310K surface over western and northern portions of the area,
expect that this is the most favored area for showers and storms
through sunset.  If storms do make their way into western portions
of the area, there could be some strong outflow winds with these.
Therefore, a severe thunderstorm watch has been posted for Cloud,
Ottawa, Dickinson and Clay counties until 02Z.

Highs today are hot once again topping out in the low to mid 90s.
Southerly winds increase tomorrow as the lee trough strengthens and
WAA will help push temps a bit higher into the mid to upper 90s.
Heat indicies will probably top out in the upper 90s to around 100
degrees. Have held on any advisory at this point.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 252 PM CDT Tue Jun 20 2017

There still exists the possibility for a few severe storms Wednesday
evening across north central Kansas. Latest guidance is somewhat
waning on the forcing factor from the frontal boundary to our west
in central NE. The GFS remains as the most robust solution while the
NAM remains pretty well capped in north central KS. The ECMWF and
Canadian runs seem more plausible with a few scattered storms being
possible across far north central Kansas by 00Z Thursday. While the
low levels remain fairly well capped, decent mid level lapse rates
and adequate 0-6 km bulk shear should be enough to support rotating
updrafts. Main hazards would be damaging wind gusts and large hail.

Convection is expected to weaken eastward overnight into Thursday
with another round of potential severe weather Thursday evening as
the boundary edges closer to the northern periphery of the CWA.
Optimal mid level lift with an incoming shortwave trough over the
northern plains will reinforce convergence along the front,
resulting in more widespread showers and thunderstorms through the
evening. Combined with decent model consensus, have higher chance
pops for the CWA during this period. A few severe storms are
possible, especially north of Interstate 70 where effective shear is
stronger around 30 kts. The thunderstorms continue overnight into
Friday afternoon with the front tracking through the region. A
reinforcing shot of cooler air accompanied with a shortwave trough
may bring additional thunderstorms in the Saturday to Saturday night
time frame, although both the GFS and ECMWF remain varied on these
solutions. What is looking more probable is the cooler airmass
behind the boundary, beginning Saturday with highs in the 80s to low
70s on Sunday. Overnight lows Sunday morning may fall to the low
50s. Predominant northwest flow pattern aloft heading into the
beginning of next week may keep portions of western and central
Kansas active with thunderstorm activity. These may clip our far
western counties, otherwise dry and seasonable weather returns.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1158 PM CDT Tue Jun 20 2017

VFR conditions are expected throughout the period.  Continued the
mention of LLWS for MHK from 08-12Z although the low-level jet is
centered west of the area. Winds tomorrow will generally persist
out of the south, with gusts up to 25 knots expected in the
afternoon.

&&

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

$$

SHORT TERM...Drake
LONG TERM...Prieto
AVIATION...Heller