Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 232353
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
553 PM CST Fri Feb 23 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 241 PM CST Fri Feb 23 2018

Clouds have persisted across most of the forecast area today, save
the far northwestern counties in north central Kansas.  This has
held high temperatures down a few degrees from forecast, and will
likely have a residual influence on where the freezing line ends up
overnight.  Temperatures have risen to the middle 30s in NC KS and
down along the I70 corridor, with a few degrees lower to the south
in the thicker cloud deck.  Broad area of precipitation in Oklahoma
is lifting to the north and east, associated with an impulse lifting
northeast in the broader southwesterly flow aloft.

For tonight, the devil is in the details with the location of the
freezing mark at the surface.  Overall pattern is for the western
trof to continue to approach the area, generating warm advection and
isentropic lift ahead of it, with the leading edge of the trof axis
into the western counties by Saturday evening.   This will bring a
warmer trend to the eastern counties, but favors keeping the
northern and western counties below freezing through the tonight and
tomorrow timeframe.  The line between drizzle and freezing drizzle
will be what we are watching tonight, and will make adjustments as
necessary as this will impact the frozen/not frozen aspect of the
forecast.

Considering another night with cold air at the surface, good
agreement between models for no ice in the cloud, and broad
isentropic lift bringing precipitation into the cold dome, have
initiated a winter weather advisory for freezing drizzle across the
northwest half of the forecast area - generally north of I-70. Its
fair to say this is about a row of counties farther south that
initially anticipated, given the persistent clouds and cooler
temperatures left behind today.  Also worth noting that as warm
advection continues in the east, it will likely bring the far
eastern counties in the advisory above freezing somewhere near the
noon to early afternoon hours.  Given the uncertainty of where the
line begins, wasn`t ready to start trimming off counties based on
time this early out.  Overall think the advisory best highlights the
areas most likely to see a light accumulation of ice which will
create slick spots on roads and elevated surfaces and have an
impact on travel through Saturday morning. Areas in east central
Kansas will likely stay in the rain and drizzle through the
overnight period, with a rumble of thunder possible in the far
southeast. Except for northern portions of our northern counties,
does seem that most areas will rise above freezing on Saturday by
the late afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 241 PM CST Fri Feb 23 2018

Some dry weather finally in store from Sunday through Tuesday as
surface high pressure behind the weekend`s departing system holds in
place.  Highs gradually increase from the 40s and 50s Sunday to the
upper 50s and mid-60s by Tuesday.  A low forming on the lee side of
the Rockies in Colorado strengthens Tuesday night ahead of a mid-
level wave that was sweep across the central Plains Wednesday night.
 There are some decent precipitation chances with this system, but
temperatures will be warm enough that the dominant precipitation
type should be rain.  It is not out of the question for some wintery
mix or snow to fall as temperatures fall overnight on Wednesday,
however.  Also for Wednesday afternoon, have continued with the
thunder chances as the GFS and ECMWF indicate sufficient instability
for some elevated storms.  Dry conditions return after this system
with models indicating mid-level ridging over the central CONUS
Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 540 PM CST Fri Feb 23 2018

Minor adjustments for the 00Z TAF forecast. Thinking a slight
earlier onset for -FZDZ potential at the terminals as isentropic
lift increases steadily after the 03Z time frame. Expect overnight
temps to be cold enough that freezing precip is more likely.
Changing to -DZ as temps begin to warm overall enough for liquid
transition to take place. Low CIG/VIS likely overnight and
carrying through into the day tomorrow with very slow progress to
lift into the afternoon as it stands now. Expected as low as LIFR
conditions to set up. Overall confidence is medium to high in
conditions happening but timing is medium confidence.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM to 3 PM CST Saturday for
KSZ008>012-020>024-034>036.

&&

$$

SHORT TERM...67
LONG TERM...Heller
AVIATION...Drake



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