Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 221138

Area Forecast Discussion
National Weather Service Topeka KS
638 AM CDT Wed Mar 22 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 249 AM CDT Wed Mar 22 2017

A longwave upper level ridge axis centered over the western High
Plains will translate eastward into the Central Plains by Thursday
morning. An embedded H300 shortwave over western Kansas will
likewise move eastward this morning. Elevated radar returns
associated with this wave have been expanding southward from
western Nebraska into western Kansas, though based on surface
observations, little precipitation is reaching the ground. Did
increase POPs slightly ahead of this feature, but kept only
sprinkle wording for the NW counties for a few hours this morning
around 12Z.

As a large area of high pressure currently over far SW Ontario moves
into the Great Lakes today and tonight, shortwave ridging over the
region will likewise pull eastward and allow H850 return flow to set
in throughout the day. Despite modest H850 theta-e advection, there
is little in the way of an attendant precip signal in either the
synoptic or high-res guidance with a decently dry sub-cloud layer
below H800. Given this trend plus the fact that guidance over the
last 24 hours has overestimated the lower tropospheric moisture
profiles, removed POPs in the south for today.

Continued H850 moisture and temperature advection will result in a
deepening of the stratus shield over Kansas after 00Z with ceilings
in the NAM bufr profiles falling to 500 ft or lower. Deep and broad
lift through the BL and stratus deck may lead to areas of drizzle
after 06Z across NE Kansas. Given the strength of the inversion
above the stratus, removed the mention of thunder from the forecast.

.LONG TERM...(Thursday through Tuesday)
Issued at 249 AM CDT Wed Mar 22 2017

Lingering drizzle or showers anticipated on Thursday morning lift
to the north of the forecast area by the noon hour, and leave
Thursday afternoon breezy and warm with highs once again in the
70s. The larger scale upper trof is on approach for Friday, and
bring some slight chances west of Manhattan in the overnight
hours, before the better push of moisture and broad scale lift
move over the forecast area. ALthough all models remain dynamic
with the upper low moving over the state along with speed shear,
they vary on the position of the surface low - which would impact
directional shear and moisture return, along with the position of
the triple point. They all struggle at bringing enough instability
this far northward before the system pushes eastward, but still
see enough to continue to mention potential for strong to severe
storms on Friday afternoon and possibly the evening hours across
the eastern counties. Kept mention of thunder behind the low
overnight Friday night into Saturday morning with some remaining
lapse rates aloft still bringing a chance for thunder. Despite
incoming cloud cover and rain chances, still anticipate highs near
70 on Friday in the warm advection ahead of the system, and highs
on Saturday in the 50s north to low 60s east as the cooler air
wraps southeastward into the state behind the system.

A short break is possible between systems on Sunday before the
next low moves out of the southwest toward the state. The GFS
shunts much of the rain chances southward with a faster, less
defined low, while the EC keeps a similar solution to previous
days with a more developed low bringing more chances for rain and
thunder over the state. The progressive tracked EC brings the next
shortwave out of the southwestern trof over Kansas on Tuesday,
while the GFS holds the leading energy to the south and
strengthens the low over the desert southwest. Result is a wet
forecast for Tuesday versus a dry one, and current PoPs are
a probabilistic blend.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 632 AM CDT Wed Mar 22 2017

VFR stratus/stratocumulus will persist through portions of the day
with easterly winds veering to the southeast by this afternoon.
MVFR stratus will push northward after 00Z tonight with CIGs
falling to IFR or even LIFR overnight under light drizzle.




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