Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 131855

Area Forecast Discussion
National Weather Service Goodland KS
1155 AM MST Sat Jan 13 2018

.SHORT TERM...(Today through Monday night)
Issued at 354 AM MST Sat Jan 13 2018

Forecast concerns will be the roller coaster of a temperature
forecast through Monday, very cold temperatures/wind chill
temperatures Monday night, chance of snow through tonight, and
then again from Sunday night into Monday. Satellite showing a
progressive flow through the central Pacific before becoming
amplified from the eastern Pacific into the western Atlantic. High
amplitude ridge near the west coast of North America has become
slightly more amplified from yesterday.

Models started out fine at the jet level. Models were doing well at
mid levels with the Ukmet and Ecmwf doing a little better with the
western ridge. Sref looked to do better since it had higher
pressures further west. Models tended to not have the coldest air
far enough west with the Ecwmf and Canadian doing a little better
than the Gfs.

Today/tonight...High resolution guidance, especially the Hrrr, has
been consistent in producing fog in the western portion of the area.
Some clear has occurred in the western portion and the temperature
and dewpoint spreads are all ready very small. So introduced fog in
that area this morning.

Observed 00z soundings along with 850 mb temperature analysis shows
dendritic zone is in the low levels of the air mass. So any kind of
lift will produce flurries which has been happening for much of the
night so far. Left front quadrant of northwest flow jet will move
across the area during the day. A rather strong shortwave trough
moves through the northeast half in the afternoon into this evening.
This LFQ/jet axis waffles/remains over the central and northeast
portion of the area through the night leaving the left front
quadrant affecting the eastern portion of the area late in the night.

As a result of all this, I have inserted flurries this morning, then
a slight chance of light snow in the northeast portion with flurries
to the west of that through the evening hours. Then flurries in the
eastern portion during the overnight hours.

Obviously in this current pattern with the very cold air in place,
the models have been horrible. Based on the snowfield, where the
thickest cloud cover, mainly over the northeast half, and model
performance/recent trends, I lowered maxes, especially the further
north and east you go. The spread in the guidance increases from
along and west of the Colorado border. Kept the warmest temperatures
over eastern Colorado.

Sunday...Jet moves off to the east and north through the day. Models
still showing westerly winds temporarily scouring out the arctic air
mass. So kept the much warmer temperatures the forecast builder gave
me. However, felt confident enough to raise temperatures in the
west. My confidence in the warmup decreases the further east I go
into our area.

Sunday night through Monday night...Depending on which model you
choose, the right rear quadrant of northern jet starts affecting the
northern portion of the area late in the night. That jet shifts
south and west during the day with it moving south and west of the
area during the evening. A secondary jet axis looks to approach the
northern portion of the area late Monday night.

At the same time, a rather baroclinic zone/strong mesoscale forcing
will progress across the area in the same manner. The only not very
favorable are the theta-e lapse rates. However the considering the
strength of the lift through a significant depth, arctic cold front
through at the same as the above, am thinking that there will be a
good chance of light snow across much of the area during this time.

The forecast builder gave me slight chance to medium chance pops.
However, felt confident enough to raise the pops, especially in the
northern sections, to high chance. If current trends continue a
continue raising of the pops will be needed.

With the strong cold air advection, ongoing precipitation, and
extensive cloud cover for most of the day on Monday, high
temperatures should be reached early in the day and then will remain
steady or even slowly fall.

Am getting very concerned about very cold air temperatures and wind
chill temperatures Monday night. Skies should clear out behind
precipitation over most of the area. The western portion of the area
will have the most clouds due to lingering lift and some upslope.
Considering the fresh snow cover, very little cloud cover over the
northeast half, light winds, and a very cold air mass, most of the
area could see temperatures not only below zero but well below zero.
Did lower temperatures from what the builder gave me but that may
not be enough considering the good radiational conditions in place.

Also any kind of wind will create dangerously low wind chills.
Current forecast has wind chill readings from near 15 to near 20
below zero from Monday night into the next period. If current trends
continue, a wind chill highlight will probably be needed.

.LONG TERM...(Tuesday through Friday)
Issued at 220 AM MST Sat Jan 13 2018

There is still some uncertainty during theses periods as models
continue to vary on track of a shortwave moving out of the Pacific
northwest, across the Rockies, and into the Plains. GFS and GEM
shows a weak precip signal with its track in our west and south Wed
night/Thu morning, but ECMWF and GEFS mean is dry. I kept slight
chance PoPs in place, but confidence is low.

Trend will be towards rising heights and moderating temperatures
across our CWA as ridging builds eastward and eventually southwest
flow develops Friday. Cold arctic air mass will likely still be in
place Tuesday with a small moderation in temps aloft. Depending on
clouds we may be running too warm, but it`s far enough out the trend
of sub freezing highs/overnight lows 2-10F should work. Above
normal highs return Thursday and could be quite a bit warmer Friday
depending on how quickly SW flow becomes established. Assuming no
limitations from cloud cover/snow pack we could see locations in the
60s Friday which is warmer than current model consensus. The
current forecast shows a higher trend, so I am comfortable
limiting changes considering the time range. We can fine tune as
we get a better handle on things.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1045 AM MST Sat Jan 13 2018

The colder airmass containing the lower clouds and areas of fog
remains in place across the eastern portions of the central high
plains region this afternoon. The areas of the region outside of
the colder airmass will see VFR conditions and mostly sunny skies
while the areas still in the colder air will start out MVFR with
occasionally IFR conditions possible.

GLD should go quickly to VFR and remain in VFR outside of the
colder airmass as south winds turn southwest this evening and
then west after 06Z.

MCK will start out MVFR in the colder airmass ahead of the surface
trough with light southeast winds continuing through much of the
day. Those winds will become light and variable after 06Z with a
transition to VFR conditions between 00-06Z. There may be some
intermittent low clouds and IFR conditions around sunrise between
11-14Z, but conditions should otherwise stay VFR through the
remainder of the TAF period.




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