Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 020526
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1126 PM CST Thu Dec 1 2016

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 208 PM CST Thu Dec 1 2016

A quiet weather pattern will persist through tonight and tomorrow
with generally zonal H300 flow in place tonight, transitioning to
more southwesterly flow tomorrow as a broad longwave trough moves
into the western CONUS. Trended towards the ADJ/MOS guidance for
lows tonight given the minimal changes in the air mass and last
night`s lows. There is some uncertainty with regards to low temps
in the south with both the NAM and RAP developing a patch of
altostratus over SE KS that barely skirts the CWA. Weak northerly
surface flow should keep highs tomrrow similar to today with
increasing clouds late ahead of our weekend storm system.

.LONG TERM...(Friday night through Thursday) Issued at 208 PM CST
Thu Dec 1 2016

For the long term, we are continuing to deal with the evolution of
the long wave upper trough over the central US, timing and impact
of shortwave energy and the eventual first intrusion of arctic air
into Kansas early next week.

All operational models continue to spread moisture north across
the southern plains northeast of an upper low over northern
Mexico and breaking out precipitation by Friday afternoon south of
Kansas. The moisture, weak lift and mainly light precipitation
continues spreading north across eastern Kansas on Saturday.
Meanwhile, a shortwave in the northern stream is forecast to cross
the central plains Saturday night and Sunday morning shifting the
moisture and precipition east of the area. The models have been
somewhat consistent with this weak system over the past couple of
days. Much of the precipitation should be rain, but there is a
risk of a wintery mix especially early Saturday and Sunday
mornings, but winter weather impacts are not expected.

The models are in fair to poor agreement with the movement the
northern Mexico upper low and the eventual arrival of the arctic
air in northeast Kansas. We are confident that the upper low will
be kicked out by shortwave energy moving south on the western side
of the large upper trough early next week. As the upper low
approaches, light rain is forecast to develop and it should
remain liquid until the arrival of deep cold air behind the front.
With respect to the arctic air, the models have been very
inconsistent with the passage of the front. The 12Z GFS is now the
most aggressive with the cold air which is totally different than
yesterday. The new GFS has the cold air being drawn down behind
the exiting upper low over the Missouri Valley Monday night while
the old ECMWF and Canadian are much slower with boundary not
drawing the cold air into the exiting upper low. The end result is
low confidence with the timing of arrival of the cold air, but
there is high confidence that it will arrive between Monday night
and early Wednesday. After the deeper cold air moves in, the
precipitation type should be snow. Given the high degree of
uncertainty, will forecast low to moderate pops for light
snow/rain in the extended from late Monday night through early
Wednesday. At this point, there is no clear indication that the
snow would be impactful or not given the low confidence in the
various model solutions.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1125 PM CST Thu Dec 1 2016

VFR conditions and light winds will persist through the TAF
period.

&&

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

$$

SHORT TERM...Skow
LONG TERM...Johnson
AVIATION...Barjenbruch



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