Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 091739

Area Forecast Discussion
National Weather Service Topeka KS
1139 AM CST Mon Dec 9 2019

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 400 AM CST Mon Dec 9 2019

A cold front sweeps through the forecast area early this morning,
with strong winds and falling temperatures in its wake today.

Ahead of the aforementioned boundary, warm-sector stratus and fog
have become established overnight, mainly along and east of a
Manhattan to Marysville line as depicted by surface obs and
GOES-16 nighttime microphysics RGB imagery. Visibilities within
the fog had fallen to one quarter of a mile in some locations,
necessitating the issuance of a dense fog advisory through 6:00am
this morning. By this time, increasing northwesterly winds with
the approaching cold front should scour out the fog and clouds
quite quickly.

As of 3:00am, the leading edge of the cold front had punched into
north-central Kansas and is progged to race southeastward through
the morning. Winds in the wake of the boundary have gusted over
40 to 50 kts in many locations in central Nebraska since midnight.
Even though the pressure gradient should lessen as the boundary
sweeps through, 5-7 mb/3hr pressure rises and a strong corridor of
negative theta-e advection will support mixing of higher winds at
H925 to the surface. RAP forecast soundings are the most
aggressive but also the closest to reality upstream of the
forecast area, thus have leveraged this solution for winds today.
The strongest winds will be towards central and north-central
Kansas, where a wind advisory has been issued through 10:00am
today. Further east, the weakening pressure field will reduce wind
speeds slightly, but it will still be a blustery day with gusts
of 30 to 35 mph.

A narrow region of mid-level frontogenetical forcing tied with
the elevated boundary has developed over central Nebraska as
previously forecast. This corridor of light rain/snow should track
across the region before noon, though with a substantial wedge of
H800-H600 dry air in place as noted in the 00Z TOP RAOB,
precipitation/snow amounts should be quite light and the
"heaviest" amounts should remain confined north of the Nebraska

High temperatures for today should be reached before sunrise,
with falling readings through the day. Current temperatures of 43
to 45 degrees in eastern Kansas will fall into the low 30s by
sunset. Skies clear in the wake of the morning rain/snow band and
winds become light as a 1020 mb high builds southeastward. With
mostly clear to clear skies expected, leaned towards the MOS-
weighted guidance for lows tonight--dropping most locations into
the upper teens to around 20 degrees. Most of the warmer raw
guidance appears to be over-weighting the return flow setting in
after 06Z, which will likely not be realized at the surface until
the commencement of daytime mixing Tuesday morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 400 AM CST Mon Dec 9 2019

Relatively quiet weather is forecast into next weekend with
minimal chances of precipitation.

Split upper level flow or longwave ridging will dominate the
weather pattern over Kansas for the bulk of the week, keeping dry
weather in place. A series of high pressure cells reinforce a pool
of continental arctic air over the Northern Plains through
Thursday, but with each high pressure cell tracking further
eastward, Kansas will find itself increasingly in the WAA regime
on the western flank of the pattern. By Thursday and Friday, highs
should once again be sitting in the lower 50s. A meridional H300
wave approaching the region on Thursday and Friday may bring
increasing clouds and a very slight chance for light precipitation
for Friday. Confidence in the details of the longwave pattern
decreases over the weekend, but there is an increasing signal for
a potentially strong storm to affect the central U.S. early next
week. It is too early to pin down the details of the storm`s track
and impacts given that temperatures will be flirting with the
freezing mark.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1134 AM CST Mon Dec 9 2019

Gusty winds to between 30 and 35 kts will continue to be possible
at times until around 23/00Z. Light winds with a shift to the
southwest will occur tonight, before directions shift back to the
north tomorrow morning. Otherwise, clear skies are expected
through much of the period, so VFR conditions are forecast.




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