Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 230542
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1142 PM CST Mon Dec 22 2014
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Tuesday)
Issued at 257 PM CST MON DEC 22 2014
This afternoon, an upper low was located across northeast NE. One
shorter wave length upper level trough was moving east across
southeast NE, eastern KS into eastern OK this afternoon. Once this
H5 trough axis shifts east of the CWA we should see a break in the
rain showers through most of the night. A weak cold front extended
from OMA, south-southwest to west of TOP, southward to east of EMP.
Temperatures behind the front were only a degree or two cooler.
Tonight, much of the area will remain dry as the first H5 trough
lifts northeast across MO into the Great Lakes States. A second H5
trough was located across WY and UT and will dig southeast into the
TX PNHDL and phase with the upper low in extreme southwestern IA.
Overnight lows will only drop into the lower 30s.
Tuesday, the phased positive tilt H5 trough that extends from the
upper low in IA, southwest to a deeper H5 trough in west TX will
move east across the KS. A stronger band of frontogenetical forcing
at mid levels will develop across central NE and western KS Tuesday
morning. However the frontogenetical forcing will weaken as the H5
trough deepens across north TX. Low-level CAA should allow for the
precipitation across north central KS to be in the form of light
snow. As the snow band shifts southeast through the day, boundary
layer temperatures across the eastern half the CWA will warm to near
40, thus the snow may become mixed with or change to rain during the
afternoon hours across the eastern counties of the CWA. Wet bulb
cooling across north central KS should keep highs in the mid 30s, so
north central KS may keep light snow through the morning and into
the afternoon hours of Tuesday. The snow will be light plus some
melting will occur at the surface as highs across north central KS
will reach the mid 30s. Some areas of north central KS may see up to
an inch of snow during the day Tuesday. Once temperatures warm above
freezing then road surface should remain wet to slushy.
.LONG TERM...(Tuesday Night through Monday)
Issued at 257 PM CST MON DEC 22 2014
Tomorrow night energy rotating around the main mid level low closed
off over IA will bring a chance for light precip through Wed
morning. This energy will begin to phase with southern energy
lifting from the base of the main trough axis. Soundings show weak
lift across the area, which may be enough for a few hundredths of
liquid precip. Due to the lack of frontogenesis and upper level
forcing this seems reasonable. The better chances appear to be far
northeast KS during the early morning hours. Temperatures at the
surface appear to be a few degrees above or right at freezing during
the lift. Also, most of the profile is below freezing leading to a
very thin possible melting layer right at the surface, and surface
wet bulb temperatures are also near zero as well. This all appears
to support mainly snow as a precip type, although there is a chance
of a lack of ice in the cloud that could result in drizzle.
Especially after mid level dry air intrudes behind the mid level
energy. Do not expect much snow accumulation...possibly a dusting
for most areas with borderline temperature in place and weak lift.
By noon Wed the lift should focus east into MO leading to a
lingering cloud cover during the evening hours. On Friday a
shortwave tracks north of the area, but far enough now most
locations stay dry. Several waves then pass south of the forecast
area as depicted by the ECMWF. This brings a very slight chance for
rain or snow to east central KS. Otherwise mainly dry through the
extended period with temperatures near normal.
.AVIATION...(For the 06Z TAFs through 06Z Tuesday Night)
Issued at 1142 PM CST MON DEC 22 2014
Could see brief very light precip at the terminals over the next
few hours from mid cloud. Reductions from low cloud still expected
for much of the period from 15Z through the end of the forecast,
likely MVFR. There is enough potential for precip development for
an inclusion, but will keep MVFR going with still some doubts on
intensity and duration.