Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 182124

Area Forecast Discussion
National Weather Service Goodland KS
224 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...(Tuesday through Friday)
Issued at 200 AM MST Sat Feb 18 2017

Tuesday-Wednesday: Shortwave ridging aloft transitions eastward with
westerly flow developing in the Central Rockies by Tuesday
afternoon. This will keep a deep dry and stable air mass in place
over our CWA. Deepening lee trough will result in good WAA and
models have been consistent on temps aloft reflecting very similar
conditions as our record highs this past Thursday (mid to upper
70s). I trended highs upwards to reflect this based on biases of
past warm ups. Highs Wednesday will also be quite warm (60s/lower
70s), but as surface trough shifts eastward there is less confidence
on where main axis of WAA will fall.

Winds may currently be underdone Tuesday as model mixing heights
might allow for gusts 20-25mph to mix in the morning before stronger
winds aloft transition out of the area. Timing does not seem to
support RFW as winds may decrease as lowest RH develops. Will need
to monitor due to the dry/warm conditions likely to occur.

Thursday-Friday: Change in pattern is still reflected during these
periods in current guidance. Trough is shown to move across the
Great Basin and deepen over the Plains, with a cold front dropping
through our CWA by Thursday night. Confidence is still high on
seasonably cold temperatures and windy conditions on Friday.
Magnitude of CAA is somewhat limited, but highs Friday could be near
freezing depending on timing of precip/cloud cover. While below
normal in a technical sense this is much more seasonal than we have
experienced in the last few weeks.

Regarding precipitation: 12Z ECMWF and 12z/00z GFS have reflected a
northerly track in the previous few runs which is generally
unfavorable for our CWA to receive meaningful precipitation (maybe
the far north/northwest). Latest runs of ECMWF/GEM have shown
opposite trends. GEM is much stronger and could support a winter
storm developing. The 00Z run of the ECWMF has shifted further south
in a similar manner to the GEM, but is more progressive and shows a
smaller window for moisture advection. I kept PoPs in place with
only adjustment to timing, as models support any precip ending by
midday Friday. Lots of uncertainty on amounts, with range of
possibilities from a barely measurable event to a winter storm. At
this range we will have time to fine tune details as consistency
hopefully increases.


.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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