Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 232343

543 PM CST Tue Dec 23 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Wednesday)
Issued at 211 PM CST TUE DEC 23 2014

This afternoon temperatures have warmed into the mid to upper 30s
across the CWA. The light snow across north central KS has changed
to rain as the boundary layer temperatures have warmed into the mid

The upper low across the upper Midwest has now phased with a more
amplified upper trough digging southeast across western and central

Weak mid-level frontogenetical forcing was causing a band of rain
across north central KS. The rain was mixed with snow or all snow
west of the CWA. The area of light rain will expand southeast across
the CWA during the late afternoon and evening hours. The light rain
will mix with snow and then change to snow across north central KS
during the mid and late evening hours as low-level CAA brings a
slightly colder and drier airmass southeast from western NE. As
dewpoints drop into the lower 30s and upper 20s, wet-bulb cooling
with the low-level boundary layer will cause a gradual transition to
light snow across northeast and east central KS after midnight. The
better frontogenetical forcing will also shift eastward across
northeast and east central KS after midnight. The snow will
gradually end across the western half of the CWA after Midnight.
Temperatures will gradually cool to around freezing by day break
across the eastern counties of the CWA. Any moisture on the roadways
may freeze in some areas, especially side streets and elevated road
ways. I suppose some areas may see a dusting of snow on grassy
surfaces. The northern counties of the CWA may see a half inch with
some isolated areas receiving up to 1 inch.

On Wednesday, The upper trough across central TX will lift northeast
into the mid MS river valley. Any light snow in the morning across
the eastern counties will shift northeast into MO. Skies will
gradually clear from west to east across the CWA during the late
morning and afternoon hours. Low-level CAA will keep highs cool on
Wednesday with only mid to upper 30s expected. Northwest winds will
be 15 to 25 MPH with gusts to 30 MPH. Thus, windchills will be in
the 20s.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 211 PM CST TUE DEC 23 2014

Tomorrow night the main upper trough departs to the east leading to
slight ridging aloft between the next system over the western
Rockies. Highs on Thursday reach the upper 40s although southerly
winds will gust up to 25-30 mph during the day. On Friday the next
system begins to move into the plains. There is model differences on
how to handle the energy coming out of the western trough. The GFS
brings out a stronger lead wave and a mid level dry slot over the
area. The EC keeps this energy out within the western trough, and
then progresses the positively tilted wave over the plains Friday
night and Saturday. This brings the chance for light precip most
likely in the form of snow. Surface temps are below freezing and
there is no melting layer over the area. But just to our southeast
temps are slightly warming and a slight shift in the track or temps
could result in a mixture. The bulk of the precip remains along and
south of the KS turnpike. Into next week the eastern longwave trough
and west coast ridge amplify, which may allow colder air to spill
southward. The GFS is showing a wave in the northwest flow bringing
light snow on Tues of next week.


.AVIATION...(For the 00Z TAFs through 00Z Wednesday Evening)
Issued at 543 PM CST TUE DEC 23 2014

MVFR cigs are expected to continue through 03Z then transition the
IFR. Light precipitation in the form of rain should begin to mix
with snow after 02Z at MHK with mvfr vsbys with -SN through 10Z.
TOP and FOE should see mainly -RASN and could briefly change over
to SN before ending by 12Z. Expect improvement to MVFR cigs by 17Z
and then VFR in the 21Z-24Z period.




LONG TERM...Sanders
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