Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 221949

Area Forecast Discussion
National Weather Service Goodland KS
149 PM MDT Fri Sep 22 2017

Issued at 841 AM MDT Fri Sep 22 2017

Please refer to the Climate section below for record high
temperatures for today.


.SHORT TERM...(Today through Sunday night)
Issued at 416 AM MDT Fri Sep 22 2017

Forecast issues will be severe weather potential through this
evening followed by rainfall amounts for the rest of the period.
Satellite showing an amplified and slow moving pattern from the
Pacific into the western Atlantic. Analysis and satellite show that
moisture content through 700 mb is increasing from the south.

At jet level...models were close with maybe a slight advantage to
the Nam and Ecmwf. At mid levels...the Gfs and Ecmwf were starting
out slightly better than the remaining output. Nam looked to do
better at the surface. The Gfs and Canadian looked to start better
on the low level thermal field.

Today/tonight...Main jet axis and lift remains to the west, further
west than yesterday, of the area through the day. During the night
this axis is over the far western portion of the area to a little
west of the area. In general most every feature is further west.
Am concerned that the models are not far enough west with the dry
line. Considering where the deep upper low over the Great Basin and
continued big height falls from it, believe that the lee trough/dry
line will be further west.

This has two affects. Considering the strong winds expected today,
any location to the west of the dry line could see critical fire
weather conditions. At this time am thinking that will be to the
west of my area. Also if the dry line is further west, initiation
of thunderstorms will be further west as well. Because everything
is further west, models not showing as much rainfall over the
area. Am thinking the far western portion of the area will have
the best chance this afternoon into this evening with damaging
winds and large hail the big threats.

After a lull in the middle of the night, there looks to be
additional development late in the night due to the proximity of the
upper jet and another shortwave. Models have been consistent in
showing this for the last two days. So have pops increasing again
after midnight. In regards to high temperatures, considering how
warm it got yesterday, current mild readings, and 850 mb
temperatures, raised maxes a little from the previous forecast.

Saturday/Saturday night...Through the day the main jet axis/lift
remains just west of the area through the day with only weak upper
level lift indicated. That lift slowly strengthens and moves east
over the western half of the area during the night. Moisture
along with the mid level lift gradually increases through the day.
So the increasing pops through the day look good.

Moisture and lift continues to increase through the night. Depending
on which model you choose, Gfs further west, the PWs get as high as
1.5 to 1.8, mainly east of the Colorado border. This is 3 to 3.5
standard deviations above normal. Considering the instability,
negative theta-e lapse rates, and storm training, the heavy rainfall
risk is rather high. Wpc continues to have the area in a slight
risk for excessive rainfall.

Sunday/Sunday night...Right rear quadrant of the jet continues over
the area over through the period although there are some differences
in the models. There is some indication there may be a coupled jet
structure over the area. Mid level lift continues to increase
through the night as well as the upper system, which the models are
in very good agreement on, moves closer through the area. Front
finally starts moving into the area during the morning and then
stalls/lingers over the area until the overnight hours.

Models decrease the precipitable water values during this period
mostly into the 1 to 1.5 range which is still well above normal. Am
getting more concerned about this period due to the frontal boundary
that gets draped across the area. Surface moisture convergence maxes
out in this area with favorable theta-e lapse rates to allow for
deep lift of this very moist air mass. Sunday afternoon into the
night could see the heaviest rainfall along this boundary. Once
again Wpc has the area in a slight risk of excessive rainfall.
Have not issued any flash flood/flood watches but if trends
continue, a watch will need to be added soon.

.LONG TERM...(Saturday night through Friday)
Issued at 149 PM MDT Fri Sep 22 2017

For the extended period...the combination of the upper low over the
Rockies and the frontal boundary over the western Plains will
persist over the area...albeit with a slow trend eastward into
Monday as the upper system works off into the Plains region. As a
result...the potential for moderate to heavy rainfall...from
rw/trw...will persist from Saturday night right into next Monday.

For precip totals...the area could see a large range from 0.60" to
almost 2.00" for the Saturday night thru Monday timeframe. The
highest potential totals remain along central and eastern zones due
to proximity and positioning to the surface front. Some localized
amts over the aforementioned are possible...all of which keeps a
flash flooding/flooding threat in the forefront.

By Monday night as the upper system lifts north of the area...there
will be some wrap-around moisture affecting northern zones but
clearing out going into Tuesday. From Tuesday onward into next
Friday...models do keep mainly high pressure for the area w/ a few
weak shortwaves that do drop across portions of the region.
Scattered light rainfall/trw is possible.

For temps...with expected clouds/precip for the first portion of the or below normal temps will occur for all
locales...with near normal numbers returning for the latter portion
of the extended as high pressure returns.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1114 AM MDT Fri Sep 22 2017

VFR conditions are expected at MCK and GLD through the TAF period.
A steep pressure gradient will remain in place across the central
high plains region ahead of a very slow moving surface
trough/front/dryline. As the night time inversion sets up across
the region, surface winds will slacken and LLWS will develop as
the stronger winds remain above the inversion. Isolated showers
and thunderstorms are possible during the evening, but coverage
and probability of storms is low enough to leave them out of the
MCK and GLD TAFs for now. Moisture will increase and deepen aloft
over the region overnight. The probability of showers and
thunderstorms will increase after 14Z Saturday morning and will
continue to increase through the day on Saturday.




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