Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 282102

302 PM CST Sun Dec 28 2014

.SHORT TERM...(This Evening through Monday)
Issued at 151 PM CST SUN DEC 28 2014

Western US upper trough continued to dig south in the western
CONUS this afternoon. Over the plains...the arctic front was over
the northern plains with a lee trough over Colorado and a weak
high over Missouri. As the western upper trough digs south
tonight...the upper flow becomes nearly zonal over the southern
plains by Monday morning. With a broad upper trough over the
western and central CONUS north on the north side of the zonal
flow over the southern plains...there is nothing holding the
arctic air over the northern plains and southern Canada to slide
south across the plains. The models are fairly similar with the
timing of the arctic boundary. There will not be a sharp frontal
passage, but a gradual backing of the low-level flow as cold
advection increases on Monday. Meanwhile, weak shortwave energy
embedded in the flow aloft produces some synoptic scale forcing at
mid to high levels on Monday. Model soundings showing plenty of
dry air to overcome, but soundings slowly saturate, especially
over our northwest as the cold air deepens. Increased pops over
the northwest counties on Monday for a very low QPF event. Given
the temperature profile, any precipitation that occurs should be
light snow. Temperatures will be tricky and how much we recover on
Monday will depend on timing of the cold air arrival.

.LONG TERM...(Monday Night through Sunday)
Issued at 151 PM CST SUN DEC 28 2014

Monday night through Wednesday...Very cold air continues to slide
southward across the Plains Monday night into Tuesday, with the
center of the high over western Kansas by early Wednesday morning.
Brisk north winds will come with the system into Tuesday, along
with a period of light snow, although anticipate less than an inch
of accumulation and mainly west of Manhattan. The winds and the
dropping temperatures will make for wind chills in the -15 to -20F
range in our northwestern counties. Lift with this system is weak,
and moisture is low, but coupled with ratios of around 18 to 1,
still may get a light dusting out of this as it passes. Winds
diminish into Tuesday daytime, but temperatures continue to fall
into Tuesday night and as a result will have another night of wind
chills in the -15 to -20 range up north, with around -10 farther
south. As westerly flow aloft quickly reestablishes itself over
our area, air mass starts to moderate and brings highs back into
the upper teens to low 20s.

Wednesday night through Thursday night is a break between the
retreating cold air from the early week system and the developing
upper low moving out of the southwest. After another night with
lows in the teens, high temperatures Thursday recover back into
the 30s with lows in the 20s Thursday night. Despite varying
solutions, guidance would suggest Friday still makes it into the
30s before the next system lifts northeast.

Still uncertainty in the speed of the ejecting low, as well as
what kind of temperatures it will have to work with. GFS is
trending warmer as it taps into warm southern temperatures and
cold air to our north has retreated back to the northern plains
states under zonal flow pattern there. Latest EC is on the slower
side and would have more of an opportunity to draw colder air back
on the western side of the low as it lifts out over the Missouri
valley through Sunday. Both would suggest precipitation chances
Friday night through Saturday - and into Saturday night if slower
EC were to verify. Warm southerly track of this storm without a
strong arctic intrusion to ride over makes ice less likely, and
have continued with a rain / snow mix, possibly changing to snow,
before it moves northeastward. Still quite a bit of uncertainty
with this system, stay tuned for updates.


.AVIATION...(For the 18Z TAFs through 18Z Monday Afternoon)
Issued at 1112 AM CST SUN DEC 28 2014

A weak surface ridge over eastern Kansas this morning will move
east this afternoon and tonight while an arctic front moves south
across the plains. Do not expect a rapid wind shift with the
frontal passage. Instead, the boundary will slowly move through
sometime Monday morning and the winds will become northeast. The
models are in decent agreement move through front through. There
should mid/high clouds Monday as upper vertical motion increases
ahead of a mid-level trough. Low-levels will be dry Monday morning
so only VFR cigs.




SHORT TERM...Johnson
AVIATION...Johnson is the U.S. government's official web portal to all federal, state and local government web resources and services.