Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 190854
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
154 AM MST Sun Feb 19 2017

.UPDATE...
Issued at 841 PM MST Sat Feb 18 2017

Have updated the forecast to adjust cloud cover and temps based
off of latest obs and satellite trend. Currently over the
region...skies are mostly cloudy to cloudy as a mid and high cloud
deck works slowly over the area. Temps are ranging in the 40s to
near 50F with a south to southeast flow as area resides in the
vicinity of a warm front. Overall trend in forecast looks good at
this time but may have to adjust temp trend later.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 218 PM MST Sat Feb 18 2017

Latest upper air analysis shows a closed low over the lower
Mississippi River valley and a deepening trough over the West Coast.
Water vapor shows a large expanse of moisture ahead of the trough
over the Great Basin. At the surface a warm front was slowly
moving north through Kansas, just entering the Tri-State Area from
the south. Behind the front dew points quickly increased. An
expanse of low clouds could be seen behind the front as a result
of the low level moisture advection.

This evening the warm front will continue to move through the
Tri- State Area. Behind it dew points will gradually increase as
moisture advection follows the front northward. The highest dew
points will be over the east half of the forecast area. The cloud
cover and moisture advection will cause lows to be warmer than
last night, with readings closer to what the normal high would be
for this time of year. Before 6 A.M. fog will begin to develop as
temperatures approach the dew point. The fog will remain east of
the CO border where dew points will be higher.

Sunday morning the thickest fog will be along the southeast half
of the Tri- State Area south of a line from Sharon Springs to
Colby and Oberlin, with the lowest visibilities of a half mile or
less likely around 9 A.M. CT. As the morning continues
visibilities will improve from northwest to southeast, with the
fog completely gone before noon.

Sunday afternoon the higher moisture that is currently over the
Great Basin, and will be over the Tri-State Area tonight, will be
split in two as a dry slot moves over the forecast area ahead of the
upper level short wave trough that will be over the Four Corners
Area.  With little to no lift, drier air, and no surface feature to
focus convection except the developing dry line in far eastern CO,
have removed the mention of storms except for the far west along
the dry line.

Models have come into more agreement with the dry line being either
over or just west of the CO/KS border.  The dry line doesn`t really
become focused until the afternoon. As it does, minor short wave
troughs ahead of the main upper level trough over the Four Corners
Area will develop over and behind the dry line. Any lift behind
the dry line will likely result in very weak t-storms/showers with
little to no rainfall. Currently only have a low chance for rain
over the far west where storms may develop along the dry line.
While deep layer shear is very favorable for severe storms, the
drier air will greatly limit any storm development from occurring.
During the evening rain chances will be more favorable, when
higher mixing ratios and stronger lift move over the forecast area
with the upper level trough.

Aside from the lack of rainfall in the afternoon, south winds will
be breezy west of Highway 25.  The warmer air mass and breezy south
winds should contribute to warmer temperatures than today but the
thick cloud cover will mitigate some effects of the WAA.

.LONG TERM...(Wednesday through Saturday)
Issued at 154 AM MST Sun Feb 19 2017

Primary concern in the extended periods is the potential for a
winter storm to develop in the Thursday through Friday timeframe.

Wednesday: Surface trough shifts southeast, and main axis of WAA
should follow, however temps aloft remain very warm. Considering
biases and current trends we may see similar highs in our south and
east as on Tuesday with near daily records once again. Elevated fire
weather conditions are possible due to lower RH, however surface
gradient and winds aloft should be weak enough that winds should not
be an issue.

Thursday-Friday: Majority of guidance (discounting GEM) has trended
further south placing our CWA in a better position for precipitation
and a possible winter storm. There is significant disagreement on
mid level evolution even with favorable models, which impacts how
this event evolves and possible amounts. Strong cold front should
move through our CWA by late Thursday afternoon or Thursday
evening, possibly sped up by evaporative cooling under main axis
of precip as it spreads east. Based on wet bulb profiles on
GFS/ECMWF we may have a quicker transition to snow than currently
indicated (basically as precip begins rather than a delay). This
adds another layer of uncertainty to possible snow amounts and
timing of impacts.

Strongest winds will tend to be immediately behind the front
Thursday evening, however latest ECMWF could support a longer
duration of strong winds correlated with snow raising the potential
for blizzard conditions.

Regarding amounts: Even with a delayed start to snow accumulations
to the late evening period, lower end of blends would support snow
accumulations approaching advisory criteria (3") and a possible
period of blowing snow. The strongest solution (currently ECMWF)
shows a deformation zone forming and tracking across our north, and
this is associated with warning criteria amounts (6+). While GFS is
weaker on forcing and pattern is more questionable on duration of
better accumulations, adjusting for a faster transition could result
in 3-6" amounts in our north. Ground temperatures are warm, and
lower rates may struggle to overcome this initially negatively
impacting amounts. However this would have little impact if rates
are as high as whats possible, and by late Thursday night colder
air will begin to take its toll on warmer surfaces.

Confidence is increasing we will see winter weather impacts
(particularly north of I-70), however I have low confidence on how
this will unfold and what the magnitude of these impacts will be.

Saturday: Pattern should be dry with west-southwest flow developing.
This would also support lee trough development and WAA, however
colder air mass may be slower to transition east and lingering snow
pack could play a role in complicating high temps.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1000 PM MST Sat Feb 18 2017

Conditions...VFR with SCT-BKN100-250. SCT010 from 10z-16z Sunday
for KGLD.

Precip/Wx....Other than 6sm in fog for KGLD from 10z-16z
Sunday...none expected.

Winds........For KGLD...S 10-15kts. Gusts to 25kts possible from
16z Sunday onward. For KMCK...SE around 10kts thru 14z
Sunday...then south around 10-15kts w/ gusts to 25kts from 18z
Sunday onward.

Low Level Wind Shear(LLWS)...For KGLD 06z-10z Sunday 190@50kts.
For KMCK 06z-14z Sunday 200@45kts. Flight level 2KFT.


&&

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

$$

UPDATE...JN
SHORT TERM...JTL
LONG TERM...DR
AVIATION...JN


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