018 
FXUS63 KTOP 122327
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
627 PM CDT Thu Aug 12 2021

...Update to aviation forecast discussion...

.DISCUSSION...
Issued at 256 PM CDT Thu Aug 12 2021

The main focus for this forecast is the chance for storms today
and tonight.

This afternoon, a weakly defined stationary front was located
across northern KS and extended into southeast NE and southern 
IA. The stationary front will remain across northern KS into 
southeast NE through most of the afternoon hours but will begin to
push southward this evening. Thunderstorms continue to develop 
along the front as elevated instability and steep lapse rates
combine with weak convergence along the boundary. The SPC
mesoanalysis page has about 5000 J/Kg CAPE in a nearly uncapped
environment near the boundary. Effective and 0-6 Km shear on the 
other hand appears to be minimal with values of 20 knots or less. 
Therefore, some pulse type storms this afternoon and early 
evening could become severe with damaging wind gusts to 60 mph and
quarter size hail. However, if any updraft becomes more organized
with mesoscale rotation, there may be a larger hail threat with
the very high CAPE values. Models are all over the place when it
comes to the evolution of the front/storms this evening and
tonight. Continued development along the boundary across northern
Kansas this afternoon, followed by a congealing of storms into a 
line segment along the main synoptic front this evening is the 
most likely scenario based on the 12 UTC suite of data 
available. Scattered to numerous showers and thunderstorms could 
continue along and north of the front into Friday morning. There 
may be some brief heavy rainfall within the line of storms 
tonight.

A weak mid-level wave may swing through northeast KS Friday and
Friday night. Off and on showers and thunderstorms are possible
through the day Friday as a result. Shower and thunderstorm
chances should gradually decrease through the overnight hours as
the front, mid-level wave and associated lift exit the area. Northeast
winds, cloud cover and periods of showers and thunderstorms will 
keep temperatures quite a bit cooler Friday with highs in the low
to mid 80s. 

Showers and thunderstorms are possible again Saturday as return
flow kicks in and another mid-level wave swings through the
northwest flow aloft. Cooler temperatures and occasional showers
and thunderstorms will highlight the forecast through mid-week as
we remain under the influence of northwest flow aloft and lee
surface troughing. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 625 PM CDT Thu Aug 12 2021

While showers and storms have generally avoided the main TAF sites 
so far, they should become more widespread again by the late 
evening hours. Ceilings will mostly remain VFR, but visibilities 
in the heavier showers and storms could become MVFR and locally 
worse. Conditions gradually improve by late tonight, with any 
leftover showers or storms exiting by late tomorrow morning. In 
general, winds will be from the northeast around 5 kts behind the 
cold front, but will be widely variable around any stronger 
convection.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for KSZ010>012-022>024-
026-036>040-054>056-058-059.

&&

$$

DISCUSSION...Jones
AVIATION...Reese