Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 181142
Area Forecast Discussion
National Weather Service Goodland KS
442 AM MST Wed Jan 18 2017
.SHORT TERM...(Today through Friday night)
Issued at 325 AM MST Wed Jan 18 2017
Forecast concerns will be fog potential through Thursday night and
the chance of precipitation at the end of this period. Satellite
showing a progressive but somewhat amplified wave train from the
Pacific into the west coast of North America. The flow becomes more
amplified and split over the country. The models started out
well at jet level. At mid levels the Gfs, Ukmet, and Ecmwf were
doing a little better than the other output. Gfs was doing a
little better on the low level thermal field.
Today/tonight...Not a lot of fog going at this time, and it may end
up being mostly frost. There is still some potential there so kept
the mention of patchy freezing fog. Models underdid the warming
yesterday. The surface winds will not be as favorable as yesterday.
At this time I raised the high temperatures a little.
Models indicate a large increase in low level moisture during the
later half of the night. Model output shows fog developing but
differs on timing. The most aggressive, the Nam and Nmm, seem to
be a little to aggressive. However, there is enough model
consensus and supported by the Sref probabilities that fog plus
the pattern supports it as well that fog was added to the forecast
for after mid night.
As yesterday the models are showing the movement of a closed off mid
level circulation into the area, slower than yesterday, and looks
like it will be about half to two thirds of the way through the area
by the end of the night. The lift is weak and the lapse rates are
not that good. Also soundings show the moisture is shallow so
believe no drizzle or any measurable precipitation will occur in
addition to the fog.
Thursday/Thursday night...Per the discussion above, fog will
continue through mid morning with any drizzle or measurable
precipitation remaining to the east of our area.
Models showing that surface winds will be weak, especially in the
eastern portion of the area. Also models show that low level
moisture stays rather high in the eastern portion as well. At the
very least it looks like that stratus may linger well into the day
which could cut back on the heating and how warm it gets.
For the night for the eastern portion of the area, the low level air
mass does not change much with a continued light wind field. So
expect fog to develop again in the far east and introduced fog
Friday/Friday night...Fog will continue through mid morning once
again. Variable cloud cover will make it difficult to get a good
handle on the high temperatures. At this time made little to no
changes to what the forecast builder gave me.
There is now become a rather big difference in how fast the models
bring the next system through the area for this time period. Not
only that they differ on the strength, position, and how much they
close off the system as it progresses across the area.
First the models for the most part are slower in taking Thursday
system out. Very strong jet is moving into the west side of the
upper trough. At this time am leaning toward the slower arrival of
this system along with being more closed and little further
southwest. In general this would favor the Gfs. In addition model
sounding do not really saturate the column until the mid and late
afternoon hours. This would make sense since the previous would have
pulled the moisture to the east with it.
Whenever the lift and moisture arrives, favorable theta-e lapse
rates will be in place to allow a good response to that lift.
Considering the differences in timing, will keep the blend pops
confined to the afternoon hours but am thinking that precipitation
will wait to the mid and late afternoon hours. At this time will
keep the phase rain. The lift and moisture moves across the area
through the evening with some lingering in the far northeast after
midnight. There will be a transition to a mixture or to all snow.
.LONG TERM...(Saturday through Tuesday)
Issued at 325 AM MST Wed Jan 18 2017
A couple closed upper level short wave troughs will be of interest
for this period. The first one will be dry while the second will
bring another chance for precipitation beginning Monday night.
Saturday one closed upper level low will depart the Tri-State Area
while another one remains south of the area. Based on its current
path of moving straight east the majority of the low level moisture
below 500mb will be well south of the forecast area. If the closed
low ends up shifting more northward, the Tri-State Area will have a
chance at some precipitation. A cold front moves through late
Saturday night behind the closed low as it continues southeast.
A short wave ridge moves across the Tri-State Area behind the closed
low. This will negate the cooling effect of the cold front almost
completely, with temperatures remaining slightly above normal
despite the cold front passage.
Monday night a second closed upper level low will approach the Tri-
State Area from the west. The low will deepen as it moves through.
Currently models vary widely with the path of the closed low. The
ECMWF and GEFS mean are further north with it compared to the GFS.
The further north solution would mean lower precipitation chances
for our area Tuesday and Tuesday night. The individual GEFS members
mostly supported the GEFS mean which was more in line with the ECMWF
than the operational GFS, but there were several leaning toward the
operational GFS. However there is still a wide range of possible
outcomes advertised with the individual members. Overall have high
confidence a trough will approach the Tri-State Area toward mid
week, but low confidence regarding the path it will take.
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 436 AM MST Wed Jan 18 2017
For Kgld...light fog reducing visibility to 6sm is expected
through 15z. Otherwise vfr conditions and light and variable winds
are expected through the period.
For Kmck...light fog reducing the visibility to 6sm is expected
through 15z. More fog is expected to develop at 06z tonight. After
that happens Mvfr conditions are expected until the end of the
period. Light south to west winds are expected through the period.