Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 301018
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
518 AM CDT Fri Jul 30 2021

...Update to aviation forecast discussion...

.DISCUSSION...
Issued at 257 AM CDT Fri Jul 30 2021

Upper level high pressure was centered over Kansas early this
morning with some cirrus managing to ooze west into eastern Kansas
from thunderstorms in central Missouri. Some more isolated activity
has formed as far west as northwest Missouri behind a weak frontal
boundary laying near I-70 from central Missouri into central Kansas.
Very moist air behind the front has pushed dewpoints into the middle
to upper 70s in northern Kansas.

The front looks to refocus in northeast Kansas this afternoon as lee
cyclogenesis takes place. Low-level thermal trends suggest a
slightly cooler day for air temps though some differences linger on
dewpoint values, with quite high levels possible near the front.
Area-wide heat index values of 103+ should be the rule for mid to
late afternoon. Thunderstorms may develop along and just behind the
front this afternoon into tonight with little afternoon and evening
CIN (especially if the higher dewpoints are realized) and MLCAPE
around 2000 J/kg. Post-frontal deep shear nears 30 knots, dropping
off along it, but with DCAPE near 1500 J/kg some strong winds may
occur. The front looks to align near the mid/upper flow and some
locations could see repeat storms for locally heavy rain with PW
values near 2 inches. A decent nocturnal low-level jet and
convective debris could keep lows from falling too far past 80
degrees.

The front slides south tonight through Saturday evening as weak
waves traverse the upper flow and carve out modest upper troughing.
Unless outflows are rather stout, the front`s pace is trending
slower and the southern few/several counties could remain in the
warm sector into peak heating. Have raised temps and apparent temps
a bit but until the details of the front are better known am
hesitant to extend the Heat Warning. Similar CAPE, shear, and
moisture values bring the potential for more strong to severe
downbursts and locally heavy rains Saturday afternoon and evening as
DCAPE values rise to near 2000 J/kg.

The remainder of the weekend brings north to northeast winds for
cooler temps under clearing skies as the upper ridge is shunted
southwest. Dry conditions should persist through at least Tuesday
though some breaking down of the ridge in the mid week may allow for
some chances for showers and storms Wednesday and Thursday though
highs should remain near to slightly below normal levels.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 518 AM CDT Fri Jul 30 2021

VFR conditions expected. Appears any chance for diurnal BR/FG has
passed with some cirrus overhead and richer moisture to the north.
Winds should be light for the bulk of the forecast. Will need to
keep an eye on low-level wind shear potential late in the
forecast.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 9 PM CDT this evening for
KSZ008>012-020>024-026-034>040-054>056-058-059.

&&

$$

DISCUSSION...65
AVIATION...65


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