Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 031958
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1258 PM MST Sat Dec 3 2016

.SHORT TERM...(This evening through Sunday)
Issued at 1252 PM MST Sat Dec 3 2016

Light rain and snow will gradually end this afternoon as upper
shortwave moves away from the area. Area webcams show only light
accumulations on grassy surfaces, so not expecting any impacts
from the snow. Cloud shield will lag a bit behind the
precipitation but should be clearing the local forecast area by
around 06z tonight.

A dry zonal flow will develop aloft on Sunday, resulting in mostly
sunny skies, light winds and temperatures near seasonal normals.

.LONG TERM...(Sunday through Friday)
Issued at 319 AM MST Sat Dec 3 2016

Main concerns will be chance/amounts of snow from Tuesday into
Wednesday and how cold do the temperatures get during this time.
Satellite continuing to show an active and amplified flow from the
Pacific into North America.

Sunday through Monday will be dry as the trough axis that was west
of the Tri-State Area shifts east.  Dry northwest flow will
transition to zonal flow by Sunday night.  Highs on Monday will be
above normal ahead of an arctic cold front to move through Monday
night.

Monday night an upper level trough will drop south out of Canada.
Accompanying this trough will be an arctic front.  Behind the front
northwest winds gusting around 35 MPH are expected.  Am anticipating
strong cold air advection to occur behind the front causing
temperatures to quickly fall once the front moves through.

Models differ by about 3 hours or so regarding when the front will
move through.  Have higher confidence that the front will begin to
move through during the early evening as apposed to the late
afternoon.  If the front moves through during the late afternoon,
the winds may be stronger, gusting around 40 MPH, and highs may be
cooler.

Snowfall will move in behind the front as well.  There may be a
brief window of rain during the early evening before temperatures
cool enough to change the precipitation to snow.  Based on the
strength of this front, am thinking the initial precipitation may
start as rain then rapidly change to snow.  Models show the snowfall
being a short duration event, lasting two or three hours over a
location before ending.  There may be some blowing snow due to winds
gusting 35 MPH.  The snowfall will end before sunrise Tuesday.

Wind chills behind the front will fall into the single digits after
midnight.  Some locations may fall to zero for wind chill around
sunrise on Tuesday.  This will be a drastic change from highs in the
low 50s the previous day.

Tuesday through Friday...
Models coming into better agreement on this time period.
Main/strongest portion of the upper trough lies well to the north.
However in the northwest flow behind the main upper system, a
significant shortwave trough will rotate through late Tuesday
afternoon into Wednesday morning. Frontogenesis is rather strong
but the theta-e lapse rates are not very favorable to get a good
response from the lift.

Considering the amount of cold air advection and how strong the
shortwave trough is, believe that the probability of snow will end
up being rather high but the amounts will not be very high due to
the fast nature of the system and the unfavorable lapse rates. As a
result I did not change what the forecast blend gave me for pops and
amounts but would not be surprised if the chances get nudged up the
closer we get to the event.

What appears and has appeared fairly certain is the large amount of
rather significant cold air that will accompany this upper system.
The Canadian, Ecmwf, and Gfs disagree a little on how cold this air
mass will be with the Canadian being the coldest while the Gfs is in
the middle but only a little colder than the Ecmwf. The Gefs 850 mb
temperature ensemble mean tends to fit in the middle of the
deterministic output.

As a result I felt confident enough to lower the forecast blend
maxes from Tuesday into Thursday. The maxes look to be too warm
especially on Tuesday. I did not make huge changes but did start to
trend those maxes down, and if the ensemble/deterministic output
continues to be close, additional adjustments will need to be made.
The mins may not be too bad considering there may be some cloud
cover around, and made little to no adjustments to them. Of course
all these temperatures could change if we end up getting more snow
than currently expected.

Something else to be watching. The combination of the winds and
these cold temperatures will produce wind chill temperatures well
below zero. Depending on how the details work out, wind chill
highlights may be needed during this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1012 AM MST Sat Dec 3 2016

Low cloud deck has crept northward to KGLD and may continue to
cause occasional MVFR cigs through this afternoon. KGLD will be
right on the edge so a tough call. Meanwhile, KMCK seems to have
settled around 5kft though cant totally rule out a reduction to
MVFR there either this afternoon with the lower ceilings just to
the south. After 00z, both terminals will see ceilings lift as
the upper system moves out of the area leaving only scattered high
clouds.

&&

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

$$

SHORT TERM...024
LONG TERM...BULLER/JTL
AVIATION...024


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