Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 182239

Area Forecast Discussion
National Weather Service Goodland KS
339 PM MST Sat Feb 18 2017

.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...(Sunday night through Saturday)
Issued at 239 PM MST Sat Feb 18 2017

Forecast concerns during an active long term period will shift
from a possibility of Thunderstorms Sunday night, to dry and
windy conditions during the first part of the work week, to colder
more seasonable temperatures late in the week with a possibility
of rain turning to snow on Thursday and Thursday night.

The upper low center lifts out across the far southwest U.S. and
phases into the upper trough in the northern branch as it moves
through the high plains region Sunday night into Monday. The
associated surface trough and dryline also lift out across the
forecast area late Sunday with a slight chance of thunderstorms
east mainly east of the dryline across the far eastern sections of
the forecast area.

Weak ridging will be in place through late Tuesday in the wake of
the exiting upper trough before the next upper trough begins to
deepen over the western U.S. and the jet stream begins to sag
south over the central U.S. Westerly flow across the Rockies will
induce a deepening lee trough along the Front Range on Monday and
Tuesday. With dryer air moving into the region as following the
passage of the dryline, expect RH values across the area, and
especially over the western half of the forecast area, to drop to
less than 20 percent during the afternoons as temperatures
increase. Temperatures will max out this week on Tuesday with
highs well into the 70s. Minimum RH values will hover around 15
percent briefly each afternoon from Monday through Wednesday.
These low RH values are of not too much concern Tuesday and
Wednesday with relatively light winds, but with higher winds
expected on Monday, Fire Weather conditions are expected to be
Elevated and be briefly near critical values. The key will be if
wind speeds remain higher as RH values drop through the afternoon
on Monday and will bear watching as Monday approaches.

Then as the next next upper trough swings through Central Rockies
and into the Central high plains by late Thursday, the persistent
surface trough deepens into a closed low over SE Colorado/SW
Kansas that lifts through eastern Kansas Thursday night.
Precipitation is expected to spread mainly across the northern
sections of the forecast area as the low moves across Kansas. As
colder air is pulled south on the back side of the low, rain
showers are expected to transition to snow Thursday night. With
the colder temperatures, temperatures will return to near normal
for this time of year.

Models solutions are somewhat out of phase by late Friday, but the
overall scheme has a series of low pressure centers rotating
through the western U.S. through next weekend.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1019 AM MST Sat Feb 18 2017

VFR conditions forecast for the TAFs. Low level wind shear will
develop at KMCK starting around 6z. During the overnight hours
higher dew points will move up from the south. Low stratus is
accompanying the higher dew points in Oklahoma currently. However
the bulk of the stratus may end up being east of KMCK. In addition
the low clouds may not arrive at KMCK before the warmer daytime
temperatures begin. Currently expecting the majority of the fog
to be south of KMCK and southeast of KGLD. However cannot rule out
a slight visibility reduction between 12z and 16z for both sites.




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