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000
FXUS63 KTOP 292320
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
520 PM CST Thu Jan 29 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Friday)
Issued at 253 PM CST THU JAN 29 2015

The shortwave that moved over the region will continue eastward into
the mid MS valley. In the wake of the departing system high pressure
will build in from the northwest overnight. Meanwhile the cloud
cover in place should gradually erode and trend eastward, which is
evident on the latest satellite loop. Winds will decrease this
evening as the pressure gradient weakens near the high center. Skies
will clear out after sunset allowing decent rational cooling to take
effect as the surface ridge slides across the area. Timing of the
ridge should place it directly bisecting the forecast area during
early morning hours, which should strengthen the nocturnal
inversion. Therefore, have went lower than guidance regarding
temperatures tonight, which drop into the upper 10s and lower 20s.
Due to the limited moisture in the boundary layer and soil do not
expect fog to develop although reduced visibilities or haze will be
possible. The stronger northwest flow aloft gets shunted off to the
east as the ridge builds in ahead of the system over the southwest
US. High pressure retreats allowing for return flow and increase in
mid to high level clouds. Advection is rather weak tomorrow so
expect high temperatures in the 40s like today although with much
less wind.

.LONG TERM...(Friday Night through Thursday)
Issued at 253 PM CST THU JAN 29 2015

By Friday evening, system moving out of the southwest starts to
bring rain into the area from the west. Temperatures remain near
steady in the 30s and are generally near or above freezing for
much of Friday night into Saturday. That being said, considering
that temperatures are below freezing above the surface, expect
that a mix of rain and snow will fall through the overnight hours.
Not expecting much to accumulate, but could bring some slick spots
on roads overnight.

By Saturday around noon, enough warm air is forecast to push back
northward to change precipitation back over to rain, save the
colder counties along the Nebraska border which are more likely
to see a rain/snow mix. Secondary upper wave dropping in from the
northwest starts to push colder temperatures back into eastern
Kansas, and the rain/snow mix shifts slowly southeast through the
evening. Some light accumulations are possible along the Nebraska
border in the afternoon. At this time, around 03z the freezing
mark is forecast to have shifted across the area and will change
precipitation back over to all snow. This could be bit aggressive
with the colder air, and the southeast counties may see a later
start to any falling snow. 06-12z have forecast 1-2 inches across
the northeast and eastern counties. As the colder air drives
southward through the day on Sunday, may see an additional inch or
so across the far east northeast as another weak wave moves across
those areas. Total amounts forecast are highest over Brown/Nemaha
counties with nearly 4 inches, but tapers to 1-2 inches along the I70
corridor. Overall, temperatures are so close to freezing and make
this a challenging forecast, as does the initial warm air
advection followed by the then stronger cold front and secondary
wave, so anticipate some adjustments to amounts as event draws
closer.

Sunday night as cold high pressure moves overhead, lows fall into
the teens. Highs on Monday should rise back into the 30s as
southerly winds and the high plains lee trof return. May make it
back up into the 40s Tuesday before the next cold front comes
through Tuesday night with another reinforcing shot late
Wednesday. Highs overall in the 30s with lows in the upper teens
to 20s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Friday Evening)
Issued at 520 PM CST THU JAN 29 2015

VFR conditions should dominate. Have some concern for light fog
potential around 12Z, but models are similar with 10-15kt north
winds persisting to near this time and cirrus increasing, will
keep this out.

&&

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

$$

SHORT TERM...Sanders
LONG TERM...67
AVIATION...65