Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 102056
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
156 PM MST Sat Dec 10 2016

.UPDATE...
Issued at 1133 AM MST Sat Dec 10 2016

Based on latest data cooled temperatures a few degrees
along/behind the warm front. Latest near-term data indicates
cooler highs, and has been trending cooler since early this
morning. This seems reasonable given the mostly cloudy to overcast
sky that is expected to linger. Current forecast could be too
optimistic for some parts of the Tri-State Area along the warm
front where temperatures are currently around 30 degrees.

&&

.SHORT TERM...(Today through Monday night)
Issued at 200 AM MST Sat Dec 10 2016

Today-tonight...may have some patchy freezing fog generally along
and a row of counties east of the CO/KS border where saturated
boundary layer moisture is forecast. For the rest of the day should
only have some mid and high cloudiness. Forecast challenge will be
afternoon high temperatures. Warm front generally extends along and
perhaps a row of counties east of the CO/KS border during the day
with high temperatures in the mid 40s to mid 50s west of it and only
mid 30s to near 40 east of it. Pinpointing the exact position always
difficult. Throwing in some lingering snow cover to the frontal
position only makes it more difficult. For tonight warmer air aloft
mixes down from west to east as winds veer to the west and
northwest. Coldest temperatures will be across the east where low
20s expected while to the west mid and upper 20s expected. May see
some light snow in Yuma, Dundy, Cheyenne KS counties toward sunrise
as some mid level moisture moves in from the north. Lack of moisture
below should limit pops to slight chance.

Sunday-Sunday night...a weather disturbance quickly moves across the
area during the morning and early afternoon hours from west to east.
Should see decreasing cloudiness from west to east following its
track. Some moisture in the 850-500mb layer moves across the area
during the night and for right now looks to not produce any
precipitation. High temperatures generally in the mid 30s north to
the low 40s far south. Low temperatures in the mid teens to low 20s.

Monday-Monday night...should see quite a bit of sunshine with an
increase in cloudiness during the night as mid and high clouds move
in from the west-northwest. High temperatures in the low 40s
northwest to around 50 from Norton and Hill City to Tribune. Dry
weather expected Monday night with lows ranging from near 10 to the
mid teens.

.LONG TERM...(Sunday night through Saturday)
Issued at 153 PM MST Sat Dec 10 2016

Main concerns will be temperatures beginning Monday, and the chances
of snow beginning Tuesday night. Satellite showing a progressive and
nearly zonal flow from the Pacific into the western Atlantic.
Currently cold front still lying just to our south and west.

Commonly in such a strong westerly flow it tends to be unstable and
one has a hard time where the flow will buckle and will get trough
development. That is probably why the models are having a hard time
with the trough strength and speed next week.

Sunday night...strong upper jet will be over the area trough the
night. That looks to keep some kind of mid and high cloud cover over
the area. Winds will start light and then shift to the south through
the night. The mins will be a little tricky but the blend looks
reasonable and made little to no adjustments to it.

Monday/Monday night...strong jet will be over or near the northern
half of the area through the evening before moving a little to the
north of the area. This/strong mid level flow looks to create some
mid and high level cloud cover. Next strong and cold upper system to
usher in the next batch of arctic air starts moving into central
Canada during the day.

So then the question then becomes how much will it warm up. The day
starts with downslope winds. However models showing next arctic
boundary surging south. At the same time, strong lee surface trough
will lie to our south and west. A rather strong lee trough looks
good considering the strength of the cross mountain flow. So with
that strong lee trough where it is and the very cold air coming
in,that will encourage and probably speed up the arrival of north
winds and the dense cold air. Considering that and the possibility
of cloud cover will leave alone what the blend has given me.

The difference in the model output starts showing up during the
night and continues into the next period. The difference is on how
far south and west to take the front. By the end of the night the
Sref and Nam takes the front about half way through the area. The
Gfs takes it a little further south and west than those two. The
Ecmwf and Canadian have the front completely through the area.
Considering the above reasoning for the day, am thinking the front
should be through most of the area. Because of the speed/temperature
differences will either leave the blend alone or nudge the
temperatures down a little.

Tuesday...Very strong upper jet will remain not too far to the north
of the area. Per the discussion for Monday night, believe the most
if not the entire area will be behind the front with maybe the far
western portion the lone exception. However, to throw a wrench into
this, the forecast blend came in warmer than the previous run. After
collaboration and above reasoning will nudge the temperatures down a
little.

Tuesday night through Saturday...strong jet near the area Tuesday
night will move more north of the area Wednesday and Wednesday
night. Models start differing on the speed and strength of the
incoming upper trough from Wednesday night through the end of the
period. The 12Z Gfs is slower and stronger than the more progressive
and weaker 00Z/12Z Ecmwf. The 12Z Canadian is a combination of both
by being fast like the Ecmwf and just as strong or stronger than the
Gfs.

As a result the models differ on position/strength of a complex and
strong jet setup that will be over/near the area from Thursday
through the end of the period. The first good batch of lift on top
of a very cold air mass occurs from Tuesday night into Wednesday
morning. Then in general there looks to be a fairly dry period from
Wednesday afternoon through Thursday afternoon while shortwave
ridging aloft is over the area as the low levels prepare for the
next reinforcing shot of cold air.

From Thursday night through Saturday numerous shortwave troughs/mid
level baroclinic zones move through the westerly flow aloft. Couple
that with a very strong jet being around, should have a chance of
measurable snow through the entire time. The forecast blend captures
all of the above scenario nicely. However with the dendritic zone
near the surface, it may flurrie nearly continuously even when the
lift is not strong. Temperatures get progressively colder with
Saturday the coldest. The blend has given me a good starting point
and seems reasonable at this time and will make little if any
adjustments to it.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1034 AM MST Sat Dec 10 2016

VFR to MVFR conditions forecast for the TAFs. KMCK currently has
MVFR cloud deck. Further southwest KADT has an IFR deck. KOIN has
a MVFR deck. Based on the winds in the lowest 1kft, am thinking
these IFR clouds will remain west of KMCK. The MVFR deck should
clear out around mid afternoon. Tonight the winds will become
light ahead of a pre-frontal trough. Behind the trough winds will
turn to the northwest. The cold front will move through Sunday
morning. There could be some snow behind the front in the morning.
However, there should be little if any reduction in visibility and
no reduction in ceiling below VFR.

&&

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

$$

UPDATE...JTL
SHORT TERM...99
LONG TERM...BULLER
AVIATION...JTL


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