Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 121155
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
455 AM MST Fri Jan 12 2018

.SHORT TERM...(Today through Sunday night)
Issued at 316 AM MST Fri Jan 12 2018

Forecast concerns will be chance/amount of snow today, next chance
of snow at the end of the weekend, and temperatures through the
period. Satellite showing a progressive flow through most of the
Pacific. This transitions to a more amplified flow from along the
west coast of North America into the western Atlantic. Flow over the
eastern Pacific and western North America has become more amplified
over the last 24 hours. Very cold air mass entrenched across the
center portion of the country.

Models started out fine at mid and upper levels. However, models do
not have the cold air far enough south and west over our area. Even
though it was too warm the Gfs was doing the best.

Today/tonight...Models continue to bring a fast moving but
moderately strong shortwave trough through the northern half to two
thirds of the area from mid morning into the afternoon. As yesterday
theta-e lapse rates are not negative but are low positive. Not the
best but adequate. Mesoscale forcing is not the most organized or
strong as well. Also the main jet is well south and west of the area
so will not get any help from it.

Models consistent in producing light qpf in the northeast half and
this matches up with the best lift and moisture profile as well. So
will keep slight chance to high chance pops in this area. Lift and
instability are to the east of the area by late in the afternoon.
Amounts remain less than an inch.

As shown yesterday, will have plenty of cloud cover at multiple
levels, especially the northeast half through the day. Rather big
spread, especially the further west you go in our area in the model
forecast temperatures. Based on yesterday, previous model
performance in similar scenarios earlier this season, and latest
data which shows another reinforcing shot of cold air moving in
during the day, reduced the high temperatures. The Canadian surface
temperature looks to have the best handle on the temperatures.

There will be some linger cloud cover through the night with light
winds in place. Any kind of breaks and the temperatures will have no
problem plummeting. Lowered the lows with the coldest lows in the
eastern portion.

Saturday/Saturday night... Left front quadrant of upper jet moves
across during the day. Another jet remains near or over the during
the night. Should see a decent amount of cloud cover around through
the day but since low layers are dry expect dry conditions to occur
during this period.

The big question for the day is how far east does the cold air move.
Models commonly push the cold air too far east. Considering the flow
aloft and the resulting surface pressure/wind field, expect the cold
air to remain over most of the area east of the Colorado border. So
tried and put a west to east gradient in that problematic
temperature forecast. Tended to use the cooler guidance to the east
of the Colorado border.

Later in the night models bring westerly winds and warmer air into
the area.

Sunday/Sunday night...Models continue the trend from Saturday night
and bring westerly winds and warmer air across the entire area by
early in the day. As a result the models and forecast blend warm up
high temperatures considerably from the previous two days. At
this time that looks reasonable. One thing will have to watch is
if mid and upper level cloud cover will hinder the warming.

During the night another rather strong jet moves in from the north.
Decent mid level forcing/baroclinic zone moves in at the same time.
Instability/theta-e lapse rates are not the greatest. The slight
chance to low chance pops the builder gives look acceptable at this
time. If the lapse rates get better I would get more excited about
this.

.LONG TERM...(Monday through Thursday)
Issued at 234 AM MST Fri Jan 12 2018

Monday-Monday night: Shortwave trough axis will transition south
of our CWA, with post frontal elevated frontogenesis axis lingering
through 18Z monday. There are also negative saturated THETA-E
lapse rates in the upper part of this layer of saturation/lift.
This could support possibly more intense banding than currently
indicated. Due to the progressive nature of favorable
lift/moisture advection, any total snow amounts should generally
be light. Amounts could vary from dusting to one inch based on
current model QPF of choice and elevated snow-liquid ratios. More
intense banding could support isolated higher amounts,
particularly in our west (stronger forcing/instability signal).

Regarding temperatures Monday/Monday night: ECMWF/GEM have
handled past arctic surges over our CWA better, and they currently
support stronger CAA than GFS Monday/Monday night. I trended
highs and lows downward, but could still see lowering temps
another 3-5F to be more in line with colder guidance. I could see
wind chill values approaching advisory criteria (-15F) Monday
night, but winds may not be strong enough even if coldest
solutions are realized. This will need to be monitored.

Tuesday-Thursday: There is increasing spread in these periods, with
low run-run consistency lowering confidence significantly. A
upper level shortwave is shown to move from the Pacific NW along
the Rockies, over the Central High Plains, or over the Northern
Plains and deepen/close off. There has been at lot of variance on
this.

There are two consistent impacts on the sensible weather based on
current tracks: low precip potential across the majority of our CWA
and moderating temperatures. We should see a slow upward trend in
temperatures through these periods, and when this shortwave finally
does move east of the Rockies all solutions show a moderated air
mass (just varying reasons and magnitude of moderation).
Precipitation potential and wind magnitude could change depending on
track/evolution, so this still deserves monitoring.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 445 AM MST Fri Jan 12 2018

An upper level storm system followed by another arctic front will
bring snow and subvfr conditions to the region. For Kgld, until
18z vfr conditions are expected as south winds continue near 12
knots. Around 18z, very light snow will be near the site until 21z
as the south winds continue. Around 21z the winds will begin to
shift to the north northeast at near 15 knots with gusts to near
24 knots. Around sunset those winds will decrease and quickly
become light and variable. Mvfr conditions will develop around 00z
and continue for the rest of the period.

For Kmck, until 17z vfr conditions and southeast winds near 8
knots are expected. From 17z to 00z, mvfr conditions and light
snow will develop as the winds shift to the east. At 00z the snow
will have ended with mvfr conditions and light and variable winds
continuing until the end of the period.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...BULLER
LONG TERM...DR
AVIATION...BULLER



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