Area Forecast Discussion
Issued by NWS Goodland, KS

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094
FXUS63 KGLD 220551
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1051 PM MST Mon Jan 21 2019

.UPDATE...
Issued at 918 PM MST Mon Jan 21 2019

Updated the forecast to include Greeley County and Wichita
County, Kansas into the Winter Weather Advisory. Visibilities
have reduced due to freezing fog impacting the areas. Reports of
slick roadways have also been received.

Additionally, started the advisory now for Cheyenne County,
Colorado and Wallace County, Kansas, as Winter Weather Advisory
conditions have arrived sooner than previously forecast.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 257 PM MST Mon Jan 21 2019

Latest satellite and upper air analysis show a trough over the Great
Basin.  At the surface a warm front was located over East Central
Colorado along the west edge of the stratus.  West of the warm front
the sky was clear and temperatures were in the 40s to 60s.  East of
the warm front the sky was overcast with temperatures in the 20s
along with areas of freezing fog.

For the rest of the afternoon am expecting the warm front to move
southeast, causing clouds to clear and temperatures to warm for the
southwest 1/3 of the Tri-State Area.  Little to no change is
expected to the north.  Moved up the start time of the winter
weather advisory to the afternoon to account for the freezing fog.

This evening visibilities will fall quickly from the east as the
freezing fog moves in.  Currently thinking the majority of the
freezing fog will be east of Highway 25 due to the winds changing to
the north and west over the west half of the Tri-State Area.

Around midnight the strong cold front will move in from the
northwest.  Behind the front the environment will saturate
vertically through the night.  This will cause the precipitation to
start out as freezing drizzle until the saturated environment
deepens/cools enough to have ice crystals form, changing the
precipitation to snow.  Freezing drizzle will change to snow from
west to east through the night and into Tuesday morning.  The change
over will occur first in the Blizzard warning area.

Meanwhile as the upper level low moves over the forecast area
isentropic lift will strengthen on the backside of the trough.
Current data indicates the isentropic lift will remain nearly
stationary to the northwest of Yuma County, which is where the
highest snowfall amounts will be.  (On a side note, current data has
shifted the track of the trough slightly to the south, which has
also shifted the axis of higher snowfall amounts south.  So far the
higher amounts remain northwest of Yuma County.)  Am expecting most
of the snow to fall between midnight and 6 AM MT before moving east
over the rest of the forecast area.

Tuesday morning the freezing drizzle will finish transitioning to
snow over the forecast area before mid morning.  Northwest winds
will quickly strengthen as stronger winds mix down behind the upper
level trough as it moves eastward.  The highest gusts will be in the
morning over the blizzard warning area.  However winds will increase
east of the blizzard warning area in the afternoon behind the
exiting upper level trough.  The higher wind gusts should occur as
the snow intensity declines.  Around 6 PM local time the winds will
rapidly decline as the inversion develops.

Regarding the wind, the forecast area is in a great position to have
high wind gusts due to the trough moving over the forecast area.
However most of the forecast area has 50 kts at the top of the mixed
layer, which lowers confidence that these winds will reach the
ground; even on a sunny day.

Impacts...
Dangerous driving conditions are expected in Yuma County
and adjacent parts of neighboring counties after midnight and well
into Tuesday due to zero visibility from the snow and blowing
snow.  Thus the upgrade to blizzard warning.

Ice accumulations of a few hundredths of an inch should occur over
most of the Tri-State Area prior to the snow occurring.  Highest
amounts will be north of I-70.  Bridges/overpasses will be the most
susceptible.  However untreated paved roads may also become slick.
(Greeley/Wichita counties were not added to the advisory at this
time due to low confidence of ice accumulations occurring).

Reduced visibility from freezing fog east of Highway 25 this
afternoon and evening before the freezing drizzle occurs.  This may
cause a glaze of ice to form on bridges/overpasses.

Confidence...
Confidence is high that blizzard conditions will occur for Yuma
County.  Confidence is between moderate and high for blizzard
conditions occurring in counties adjacent Yuma County.  Due to the
potential for dangerous driving conditions, decided to error on the
side of caution and include Sherman, Cheyenne KS, and Dundy County
in the blizzard warning.

Confidence in ice accumulations is between moderate and high for the
entire forecast area.  With up to 10 hours of freezing drizzle
possible, this is plenty of time for a light glaze of ice to form.
The threat for ice accumulations increases to the east due to the
longer window of time before the snow moves in.

Confidence in wind gusts around 60 MPH is moderate.  Would not be
surprised to see a few gusts around 60 MPH during the morning
Tuesday in the blizzard warning area.  However confidence is not
high enough at this time to warrant a high wind warning.  Could say
confidence is highest for high wind gusts to occur at Goodland given
the current data and high wind climatology.

.LONG TERM...(Tuesday night through Monday)
Issued at 157 PM MST Mon Jan 21 2019

The central plains will be under northwest flow this period,
caught between a ridge over the western CONUS and trough near the
Great Lakes, neither of which will be moving. Weak waves embedded
in the flow will provide occasional chances for light snow. No
significant impacts are anticipated from any of these fast moving
systems.

Temperatures are a bit up and down through the period, although
there are no extremes. Highs will generally be in the 30s and 40s
with lows in the teens and 20s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1044 PM MST Mon Jan 21 2019

A cold front will continue to move through the Tri-State area
tonight. Conditions will prevail as sub-VFR first due to low
visibilities from freezing fog and drizzle at both terminals. They
will then remain poor at the Goodland terminal due to blowing
snow.

Conditions will improve first at the McCook terminal, as they
will be less impacted by this event. However, as Goodland will be
expecting Blizzard conditions, the terminal will see periods of
LIFR conditions due to blowing snow. Winds will be 40-45kts
around the area.

By Tuesday afternoon, snow will come to an end with MVFR
conditions by 18Z and VFR after 22Z.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Blizzard Warning until 5 PM MST /6 PM CST/ Tuesday for KSZ001-
     013.

     Winter Weather Advisory until 5 PM MST /6 PM CST/ Tuesday for
     KSZ002>004-014>016-027>029-041-042.

CO...Blizzard Warning until 5 PM MST Tuesday for COZ090-091.

     Winter Weather Advisory until 5 PM MST Tuesday for COZ092.

NE...Blizzard Warning until 5 PM MST Tuesday for NEZ079.

     Winter Weather Advisory until 6 PM CST Tuesday for NEZ080-081.

&&

$$

UPDATE...EV
SHORT TERM...JTL
LONG TERM...024
AVIATION...EV



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