Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 062329
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
529 PM CST Tue Dec 6 2016

...AVIATION UPDATE...

.SHORT TERM...(This evening through Wednesday)
Issued at 233 PM CST Tue Dec 6 2016

A cold day has been seen even with clear skies after high pressure
has pushed into the area throughout the day.  Northwest winds have
aided in cold air advection keeping high temperatures today mainly
limited to the upper 30s and low 40s.  Tonight, cloud cover is
expected to move in from the southwest and overspread the area with
temperatures dipping into the low and mid 20s.

The main feature of the period will be a progressive system moving
through the area tomorrow bringing the possibility of snowfall to
northeast Kansas.  Models continue to bring in precipitation chances
in north central Kansas by early tomorrow morning, with these
chances increasing from west to east through the morning, shifting
south in the afternoon.  With very cold temperatures holding through
the day, all precipitation is expected to fall as snow.  The cold
temperatures also allow for a higher than average snow to liquid
ratio which will lead to a lighter and fluffier snow.  Models still
vary on QPF with some models almost even dry over the area, although
most keep QPF under a tenth of an inch. The main inhibitor will be
dry air in the lower levels that will need to be overcome before
snow can make it to the ground and accumulate. The best forcing
starts in the morning into early afternoon, decreasing through the
afternoon, with snow chances mainly southeast of the area by sunset.
Overall, most of the area is expected to see up to an inch, with
north central Kansas possibly up to two inches.

There is the potential for some snow banding which would offer up
locally heavier amounts wherever this band set up.  A band of
frontogenesis is noted near 650mb in east central Kansas in the late
morning/early afternoon timeframe, along with elevated CSI which
could result in locally higher amounts near this area.  If a band
does set up through the event, it is more likely areas north of this
band would see little snowfall at all.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 233 PM CST Tue Dec 6 2016

Forcing will be shifting southeast quickly by sunset Weds night so
will end snow chcs for all but extreme southeast by 00z.  Thereafter
Strong arctic high pressure will build into the region through
Thursday with very cold temperatures and wind chills.  The coldest
wind chills should occur Thursday morning with readings of 0 to 10
below expected.  The coldest air temperatures should occur Thurs
night into early Fri when most areas should fall to between 5 and 10
above.

WAA will develop later Friday into Sat with some light rain or snow
expected to develop Sat night into early Sunday. Amounts should be
light and confidence is low on both type and timing given how far
out and progressive the wave appears at this point.

CAA should return to the area by Sunday in wake of the wave but that
doesn`t appear to last long with a fast northwest flow expected to
allow southwest winds to develop by early next week before what
appears to be another cold arctic cold front by either Tues/Weds of
next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday)
Issued at 529 PM CST Tue Dec 6 2016

Models are in agreement that frontogenesis will pass across the
forecast area through the day Wednesday. The question is whether
low levels will saturate enough for snow to reach the ground.
There are signs of weak instability as the forcing moves through,
so think there are enough signals for some -SN with MVFR
conditions for a few hours. Given the low level dry air, only have
confidence to include a tempo for CIGS between 2 and 3 KFT with
VSBY remaining at 6SM. Will be watching later model runs for clues
to how low level moisture will evolve.

&&

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

$$

SHORT TERM...Heller
LONG TERM...Omitt
AVIATION...Wolters


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