Area Forecast Discussion
Issued by NWS Topeka, KS

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624
FXUS63 KTOP 201119
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
619 AM CDT Wed Sep 20 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 244 AM CDT Wed Sep 20 2017

Both radar and IR imagery early this morning clearly show a surface
front entering north central Kansas near 07Z.  This boundary is
expected to bisect the CWA by mid-morning oriented from the
northeast to southwest, before stalling out through the afternoon
hours.  Not too much in the way of temperature change with this
front with highs in the 80s throughout northeast Kansas this
afternoon.  Dewpoints, on the other hand, will be significantly
drier west of this boundary by the afternoon leading to much more
pleasant conditions in this area than yesterday.  East of the front,
dewpoints once again reach into the low 70s leading to another hot
and muggy day. Soundings show a fairly stout cap over the area this
afternoon and into the evening which would prevent any storms from
forming along this boundary in the afternoon.  Some models do erode
this cap in the early evening, especially in east central Kansas
which may allow for a few scattered storms to develop across this
area during this timeframe. Sufficient CAPE is seen in this corridor
for storms to form, although 0-6 km bulk shear does look a bit weak
between 20-30 kts which will limit the overall widespread severe
potential. If anything were to form, marginally severe hail and wind
look to be the main threats.  Low temperatures range from the mid-
60s in north central Kansas to the low 70s in east central Kansas.

.LONG TERM...(Thursday through Tuesday)
Issued at 244 AM CDT Wed Sep 20 2017

Return flow quickly establishes on Thursday behind the front so
temperatures will be warm once again with highs in the low to mid
90s. Dew points will also be relatively high so afternoon heat
indices will be in the mid to upper 90s. Southerly winds remain
breezy with gusts approaching 30 to 35 mph Thursday and Friday. This
is all in response to a deepening longwave trough over the western
US. One of the associated shortwave troughs over Canada will get
absorbed by the westerlies and push a cold front into the central
and northern plains. It appears that this front will stay west of
the forecast area through a majority of the weekend. The main mid
level low pressure should be centered over the northern Rockies
during this time. By late weekend it appears that this low will
gradually get sheared out and begin to interact with a shortwave
trough digging through the southern extent of the longwave. That
energy will give it the final push causing the trough to lift out
over the plains therefore driving the front eastward. By sunday
night and Monday several rounds of widespread precipitation is
expected. There is no obvious sign of severe storms a this point,
but it can`t be completely ruled out on Monday given the right
timing. Plenty of time to watch that scenario play out though. It
could end up that extensive cloud cover inhibits the instability.
The precipitation should linger into Tuesday with the slow frontal
progression. By Wednesday the boundary pushes south of the area and
brings back more seasonal temperatures.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 619 AM CDT Wed Sep 20 2017

LLWS will end at 13Z for TOP/FOE and VFR conditions are expected
through the period. A front in the area will cause winds to shift
from the northeast by 00Z, and eventually continue turning from
the east then southeast near the end of the TAF period. Have added
VCTS for TOP/FOE at 01Z when scattered storms may develop along
the boundary.

&&

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

$$

SHORT TERM...Heller
LONG TERM...Sanders
AVIATION...Heller



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