Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 091733
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1133 AM CST Tue Jan 9 2018

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 235 AM CST Tue Jan 9 2018

08Z water vapor imagery shows an closed upper low off the southern
CA coast that appears to be phased with an upper shortwave moving
towards the Pacific Northwest. Downstream across the plains is a
broad ridge with a weaker shortwave moving out from the central
Rockies. This has been responsible for higher clouds moving across
the area. At the surface, a trough of low pressure has been
gradually deepening along the lee of the central Rockies with
surface high pressure remained over the lower and middle MS river
valley. This has kept a southerly wind over the area through the
night.

There is still the possibility for some fog across east central KS
through mid morning before the boundary layer begins to mix out and
winds pick up. Recent satellite imagery shows the dense fog across
MO gradually spreading west. Although most guidance keeps the dense
fog from getting into the area. There could still be enough breaks
in the high clouds for some patchy radiational fog to develop.
Otherwise the forecast for today and tonight calls for the lee
trough to continue to deepen causing southerly winds to become gusty
today. This should also allow for some warmer air to advect in from
the south. Relatively dry air in mid levels is expected to preclude
any precip chances from the weak forcing provided by the wave moving
out from the Rockies today. Highs this afternoon are forecast to be
in the 50s with warmer readings likely over the western half of the
forecast area where there is expected to be better insolation by the
afternoon. The NAM and GFS are suggesting a stratus deck will
develop this evening as moisture advects north within the low level
warm air advection pattern. Forecast soundings maintain some mixing
of the boundary layer through the night suggesting stratus is more
likely than fog. So have increased sky cover for the late evening
and overnight hours. This cloud cover along with persistent south
winds should help keep lows in the mid and upper 30s.

.LONG TERM...(Wednesday through Monday)
Issued at 235 AM CST Tue Jan 9 2018

Main feature of the extended period will be the digging, negatively-
tilted mid-level trough that makes its way across the Central Plains
overnight Wednesday night into Thursday.  With this system comes a
potential for accumulating snowfall followed by much colder
temperatures continuing through the beginning of next week.
Wednesday continues to look warm as gusty southerly winds aid in
warming temperatures into the 50s, and even low 60s in central
Kansas during the afternoon hours.  The surface low begins to move
towards central Kansas late Wednesday evening, with the exact
position of this low still a but uncertain with models, with the
ECMWF further south than the NAM/GFS.  This leads to some
differences in precipitation location, through all models look to
bring the associated cold front passage through the area by early
Thursday morning.  With temperatures falling quickly behind the
front, a change over from rain to snow is expected to take place
quickly with only a small window for mixed precipitation to occur.
Did opt to include some mention of blowing snow due to the strong
winds behind the front, at least through the morning while winds are
at their strongest with gusts up to 35-40 mph.  Accumulations right
now look to be near anywhere from a trace up to a little more than
an inch.

After this system, cold temperatures take hold once again with highs
on Thursday and Friday in the 20s, and lows in the single digits.
Wind chills this morning may approach -15 degrees Saturday morning.
High pressure moves over the area Sunday morning bringing lows to
the low single digits.  From here, the cold weather continues with
highs in the 20s and low 30s through Tuesday.

There are some small chances for more snow Friday afternoon and
night with a shortwave that quickly moves through.  Accumulations
look to be light with any snow during this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1133 AM CST Tue Jan 9 2018

VFR cigs are expected through 05Z with a transition to MVFR cigs
that should continue through the end of the period. Some IFR cigs
may be possible at TOP and FOE but confidence is not high enough
to add at this time. VFR to MVFR vsbys with HZ and BR are expected
through the period. Winds south around 10 to 14 kts are expected
with higher gusts to near 25 kts at times.

&&

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

$$

SHORT TERM...Wolters
LONG TERM...Heller
AVIATION...53



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