Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 231729
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1229 PM CDT Fri Jun 23 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 257 AM CDT Fri Jun 23 2017

Early this morning a positive tilt upper level trough was located
across the upper Midwest and central plains. The upper trough will
amplify as it digs southeast across the mid MS river valley late
this afternoon and absorbs the extra-tropical remnants of Cindy
across the OH river valley.

Showers and thunderstorms have developed across east central KS,
ahead of the surface front early this morning. These thunderstorms
may produce some small hail and gusty winds through 4 AM as they
move southeast across east central KS, generally south of I-70.
Another cluster of storms have developed across Brown county and
these storms may produce small hail as they move east-southeast
across Brown County through 330 AM.

As the upper trough amplifies across the Midwest and eastern plains,
strong low-level CAA will advect cooler and drier air southward
across eastern KS. Dewpoints this morning were in the lower 50s
across northern NE. As the upper trough axis approaches there may be
a slight chance for showers and perhaps an elevated thunderstorms
north of the boundary after 12Z south of I-70. However, as the low-
level CAA increases through the mid and late morning hours these
post frontal showers will dissipate and shift south of the CWA. The
afternoon hours look nice with decreasing cloud cover from north to
south and very comfortable high temperatures in the mid 70s along
the NE border to the lower 80s along and south of I-70.

Tonight, another upper level trough will dig southeast across the
northern plains into the mid MS river valley. Ascent ahead of the H5
trough may cause some cloud cover to move southeast across the
northeast counties of the CWA. There may be a line of afternoon
showers that develop across central NE but these should dissipate
after sunset before reaching the northern counties of the CWA.
Overnight lows will be cooler with mid to upper 50s.

.LONG TERM...(Saturday through Thursday)
Issued at 257 AM CDT Fri Jun 23 2017

Surface high pressure dominates the region this weekend as northwest
flow aloft continues. Therefore temperatures will be below normal
with highs around 80 and lows around 55 through Monday. On Saturday
afternoon a shortwave tracking over the upper Midwest will send a
front towards the forecast area. Isentropic lift increases on the
305 K surface during this time frame, but mainly across northwest KS
and southwest NE. A few showers may reach north central KS as
advertised by the ECMWF, but expect sprinkles are a better
possibility given the dry low levels. That front will stall out
across the forecast area on Sunday as the isentropic lift increases
again on the 300-305 K surfaces especially Sunday night. Chances for
showers and possibly a few embedded storms ramp up as a result.
Soundings show that the instability will be limited with nearly
moist adiabatic mid level lapse rates. During the day Monday return
flow will allow higher dew points to reach the area therefore the
instability increases. Warm advection becomes more established over
a larger area on Monday night so the isentropic lift results in more
chances for showers and storms. Although this development will
depend on the quality of the moisture return in the mid levels. The
warm advection pattern will continue through mid week as a front
hangs up in the high plains and each night brings a chance for
showers and storms that form on that boundary or in the isentropic
lift further east. Late Thursday that front will push into the area
therefore this should be the best chance for more widespread storms.
Temperatures and dew points will decrease again behind this system
before the warm advection tries to quickly reestablish.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1227 PM CDT Fri Jun 23 2017

VFR conditions are expected through the TAF period with isolated
showers dissipating by late afternoon. Northwesterly winds of 10
to 20 kts with higher gusts will also decrease this evening and
remain light into tomorrow.

&&

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

$$

SHORT TERM...Gargan
LONG TERM...Sanders
AVIATION...Skow


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