Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 220445
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1145 PM CDT Fri Jul 21 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 251 PM CDT Fri Jul 21 2017

Another hot afternoon as temperatures rise into the upper 90s and
low to mid 100s across northeast Kansas.  Heat indices between 105
and 110 area wide will continue through into the evening, with
slight relief after sunset.  Even so, low temperatures tonight are
quite warm with temperatures falling only into the mid-70s up into
the low 80s. The persistent upper level ridge shifts slightly
eastward overnight, and finally begins to break down by late
Saturday afternoon.  A surface cold front extending from northern
Illinois into western Kansas will push south, bisecting the area by
late afternoon.  With the later timing of the front, much if not all
of the area will see a warm up similar to that of today.  Highs will
once again be in the 100s and low 90s, with heat indicies from 100-
110.  The Excessive Heat Warning continues through 8pm on Saturday
evening, and this should be the last day of temperatures quite this
hot as the front will make its way through the area. With this
front, there is a chance for some storms to develop in the late
afternoon along the boundary during peak diurnal heating. While deep
layer hear isnt the strongest (with values near the front roughly 20
knots), there looks to be sufficient CAPE so if any storm were to
develop an isolated severe threat is possible with damaging wind
gusts being the main hazard.

.LONG TERM...(Saturday night through Friday)
Issued at 251 PM CDT Fri Jul 21 2017

Still appears the better chances for precipitation this weekend will
come Saturday night into early Sunday as the front sags through.
Forcing remains weak with little support aloft, but could be enough
flow over the boundary for some convection. CAPE values into
Saturday evening should be enough for some stronger updrafts
with continued high LCLs to produce some near-severe wind gusts.
Severe threat should diminish by late evening with boundary layer
stabilizing. This boundary still brings somewhat cooler temps with
it.

Southerly winds return Monday into Tuesday as a weak upper system
approaching northern California midday today passes through. Will
keep decent chances going here too but again too little wind shear
for much concern for severe weather. Upper heights build over the
region in the later periods for warming temps again, though
currently looks like the heat will not be as intense as recent days.
There are suggestions of another stronger wave moving over the
northern Plains dropping a weak cold front south into the central
Plains around Thursday night for another potential break in the heat
and rain chance.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1143 PM CDT Fri Jul 21 2017

Forecast is essentially a wind forecast, with LLWS overnight
followed by a slow moving frontal boundary into Saturday. By late
afternoon/early evening this front may start to produce
thunderstorms near the terminals and have started with VCTS given
confidence in coverage and timing. Bases would be high, and strong
variable wind gusts would be anticipated with any thunderstorms.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM CDT Saturday for KSZ008>012-
020>024-026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Heller
LONG TERM...65
AVIATION...67


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