Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 112048
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
348 PM CDT Tue Aug 11 2020

.SHORT TERM...(This evening through Wednesday)
Issued at 337 PM CDT Tue Aug 11 2020

Currently, the upper air pattern across the CONUS remains with
the main belt of energy across the northern tier of the country.
Semi- permanent ridge continues through the Desert Southwest into
the southern Plains region. This continues to encourage a
southerly flow pattern into the central Plains with a moist and
rich gulf airmass with dewpoints in the 70s. An MCV continues to
slowly track east remaining south of the area. Main impacts to the
forecast area have been in the form of low stratus early and
mainly decreasing mid cloud into the the afternoon.

Mixing continues but a weak cap has been maintained so only a cu
field has resulted mainly across northeastern and into portions of
east central KS.  Highs range in the upper 80s and low 90s across
the area in the mid to upper 90s mainly.

Storms this afternoon remain well southeast of the area as well as
over western NE back into CO and WY with limited forcing aloft
helping the storms over western NE grow upscale.  Therefore, the
clusters in that area that propagate east later tonight should
begin to weaken and die as they move east and lose the better
nocturnal forcing of the LLJ which is also focused west of the
area tonight.

Overnight lows bottom around 70 with a light southeast to southerly
breeze.  Could be some patchy areas of fog in low lying areas that
can decouple but not expecting widespread concerns if fog does
form.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 337 PM CDT Tue Aug 11 2020

Looks like Wednesday night is still one of the focused time frames
for nocturnal storms to move into the area with a good theta-e
advection response along with isentropic ascent and a moderately
strong LLJ remaining from the south much of the late night and early
morning on Thursday.  As a result, storms over western NE should
have enough juice to work with to maintain themselves as they move
into the area.  Heavy rain and damaging winds appear to be the main
threats with these storms.  North central and portions of
northeastern KS look to be the favored areas at this point for the
overall storm track.  But, models tend to not be in the best
agreement with decent spread even from the 12Z suite.  So confidence
in how widespread the impacts will be is still on the lower end.

Thursday afternoon could see some redevelopment along any lingering
outflow boundary into the late afternoon but also remains low
confidence.  Timing with any weak embedded shortwave remains very
hard to discern at this point which could help aid ascent along
any lingering boundary. Bottom line, would expect strong
insolation and high PW airmass to aid in strong updrafts with
destabilization into the afternoon. Likely inverted V type
soundings should provide extra momentum transfer for downdrafts to
cause a damaging wind threat as well as a heavy rain threat. If
the upper wave is strong enough working around the ridge and
shear profiles end up being favorable through the depth of the
unstable layer, then there could be some concern for isolated
supercells which would increase the hail threat as well. Again, at
this time still hard to predict with certainty.

Additional hazards into Thursday and Friday could also be the heat
index values nearing 105 degrees over north central into portions of
east central areas.  Again, dependent on how any outflow boundaries
would set up...especially Thursday.

At least some consistency remains in a nice cool down after a cold
front works through the area sometime on Sunday which appears to be
similar in magnitude from the cool down a couple weeks back.
Dewpoints could drop into the 50s for at least few days.  Question
in how much rain occurs in the process with the cold front.  Right
now, it looks more progressive than last time which brought heavy
rains across much of the area. Not expecting a repeat of that
event at this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1237 PM CDT Tue Aug 11 2020

VFR conditions hold after a few patchy areas of stratus cleared
completely from this morning. No significant weather expected as
showers or storms should remain southeast of the area. Could see
some reduced visibility into early morning with good radiational
cooling effects. But, if the surface winds don`t decouple enough
then this potential would be minimized further. Still expecting
any fog or stratus to remain patchy if it does form.


&&

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

$$

SHORT TERM...Drake
LONG TERM...Drake
AVIATION...Drake



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