Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 301057
Area Forecast Discussion
National Weather Service Goodland KS
357 AM MST Wed Nov 30 2016
.SHORT TERM...(Today through Friday night)
Issued at 123 AM MST Wed Nov 30 2016
Forecast concerns will be temperatures and a very low chance of
precipitation Friday night. Satellite showing progressive flow over
most of the Pacific then transitions to an amplified flow over North
America and western Atlantic. Slow moving and cold upper low over
Minnesota has moved little. A strong system is moving into the
Pacific northwest and southwest Canada and is starting to break down
Models started out okay at mid levels. However they were not
amplified with the western ridge and too far east/not deep enough
with the incoming trough. Overall the Gfs and Ecmwf were doing a a
little better than the rest. The Ecmwf and Canadian were doing a
little better than the Ukmet and Gfs on the low level thermal field.
Today/tonight...Clouds are expected to slowly decrease as system
over the north central portion of the country slowly pulls away.
Northwest winds will increase once again. However speeds look less,
in the 15 to 30 mph range, due to gradient decreasing and surface
ridge pushing in. Slight cold air advection to neutral will occur
through the day. High temperatures will be about the same to a
little cooler as a result.
Good radiational conditions result by later tonight as surface ridge
will create light winds and there will be little to no cloud cover.
So temperatures will be cooler than this mornings.
Thursday/Thursday night...Will have light and variable winds through
the day as mid and upper level cloud cover increases. This increase
is a result of a mid/upper level warm air advection pattern in
southwest flow aloft ahead of developing western trough. As a result
high temperatures will be about the same as todays. Latest data
supports the forecast blend and made no changes.
Will have light winds during the night but the mid and upper level
cloud cover continues to thicken. So at this time the current
blend/forecast looks reasonable and did not change.
Friday/Friday night...Thick cloud cover remains in advance of the
western trough and expect little to no sun. Boundary/light upslope
winds push through during the day. High temperatures look to be a
little cooler and that seems reasonable. However would not be
surprised if temperatures need to be adjusted down the closer we get
to this day. The forecast blend for this period looks good.
Upper trough that has developed to our west starts moving to the
east. The cutoff and stronger portion of this trough remains over
northern Mexico with the open wave portion of the system moving
across during the night. There looks to be plentiful mid level
moisture but not a lot of low level moisture. The forecast blend
brings a thin sliver of snow into my extreme southern portion of my
area. So that continuity is kept will leave this in but am thinking
that this snowfall will end up further south.
.LONG TERM...(Saturday through Tuesday)
Issued at 141 AM MST Wed Nov 30 2016
While model solutions are similar, the differences between the
ECMWF and GFS in the Long Term period appear to become
increasingly divergent through the period. The bottom line is
given the decreasing confidence through the period, little to no
changes have been made from the Model Blender solution as it seems
to identify the most significant features of the Long Term period,
which are warming temperatures through the weekend with a turn
towards sharply colder temperatures next week on Tuesday and
Wednesday. Will accept the precipitation fields as is for now.
The upper trough that has been deepening and swinging through the
western U.S. during the latter part of the work week will move
east of the Rockies and onto the plains on Saturday. The GFS is
initially more progressive moving the northern portion of the
trough onto the northern plains while the ECMWF is more
progressive than the GFS in moving the south end of the trough,
which has deepened into a closed low, into the the far southwest
portion of Texas on Saturday. This trend continues through Sunday
and into early Monday when the northern portion of the upper
trough moves into the Great Lakes region with a much larger
disparity with regard to the closed low at the south end of the
trough that eventually moves east as an open wave. The closed low
at the south end of the trough becomes mostly cut off from the
upper flow by Sunday. As such, the ECMWF has it moving into the
southern Mississippi Valley region while the GFS keeps it over
northern Mexico by Monday. This difference further propagates
through the forecast period as a difference in the resulting 500
MB height fields over the forecast area as the next upper trough
begins to deepen over the western U.S. The ECMWF produces lower
500 MB heights than the GFS over the central high plains region by
Tuesday with a more progressive and broader trough over the north
central tier of states than the somewhat less progressive and more
sharply defined upper ridge in the GFS.
The ECMWF seems to remain more progressive than the GFS with
regard to the surface features moving east of the Rockies through
the Long Term Forecast period. The tail end of a surface trough
moves across the forecast area late Friday while a deeper lee
trough forms along the Front Range by late Sunday. This deeper
trough moves across the Central High Plains by early Monday. Once
that surface trough moves east, it appears the region remains open
to receive surges of colder air with persistent northerly cold
air advection through the middle of next week.
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 354 AM MST Wed Nov 30 2016
Vfr conditions are expected through the period. Again the main
concern will be the gusty winds. However they will not be as
strong as yesterday. At both sites, sustained west to northwest
winds will start out near 15 knots. Around 16z those winds will
increase to near 20 knots with gusts to near 30 knots. Near sunset
those will lose their gusts and decrease to near 10 knots. The
winds will become west around 03z at around 7 knots and continue
through the rest of the period.