Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 200944

Area Forecast Discussion
National Weather Service Goodland KS
344 AM MDT Tue Jun 20 2017

.SHORT TERM...(Today through Thursday night)
Issued at 329 AM MDT Tue Jun 20 2017

Forecast issues will be chance of thunderstorms/severe weather along
with the heat through Thursday. Satellite showing an amplified
pattern from the Pacific into the western Atlantic. A high amplitude
ridge is over the western portion of North America, with center of
strong ridge over the desert southwest, while a trough is over the
eastern portion. This leaves the area in northwest flow aloft.

At jet level...models did fine. At mid levels...models again were
not quite strong enough with the ridge. The Canadian was doing a
little better than the Gfs and Nam with this and the overall
pattern. Rap/Sref were starting off well at the surface. The Nam,
Canadian, and Sref started off the best on the low level thermal

Today/tonight...models remaining consistent on where the surface and
shortwave troughs are plus where the thunderstorms will develop,
basically along and east of a line from Sharon Springs to Colby to
McCook. Surface and shortwave trough then progress east through the
night. Models also consistent in developing a convective circulation
at 700 mb over the eastern portion of my area. So raised pops in my
eastern areas.

Ahead of the surface trough, CAPE is 2500 to 3500 with the Nam much
more robust. Considering this along with shear and other instability
indices, once thunderstorms develop they should become severe.
Forcing does appear weak however the air mass becomes uncapped by
21z. Looks to be hail and damaging winds as the main threats.
However would expect the winds to be the bigger threat since DCAPE
values are in the 1000 to 2000 range. SPC has the eastern portion in
a slight risk and that looks reasonable.

Another threat will be locally heavy rainfall with PWs from 1 to
just above 1.5 inches which is almost 2 standard deviations above
normal. Storm motions look to be near 15 knots. So locally heavy
rainfall will be a threat. Will be putting in a mention of severe
and heavy rainfall into the forecast.

If convection/cloud cover do not start too early, temperatures will
be quite hot. Guidance has been running cool for the last 2 to 3
days. Based on recent trends, better performing guidance, and 850 mb
temperature changes, will raise maxes slightly.

Wednesday/Wednesday night...a weaker further south jet segment is
near the area late in the day. At that time, the left front quadrant
looks to be just northwest of the area or over the northwest portion
of the area. Models differ on details during the night, but most of
the output has a left front quadrant affecting the northeast/east
half of the area after midnight. This could possible keep
thunderstorms going or reignite them.

Convective setup is very similar to todays. However, features and
initiation look to be further west than today. Another shortwave
trough and the surface trough will once again move from west to east
across the area during the afternoon and night. Models want to have
the instability less than they do today. That may be due to higher
700 mb temperatures, otherwise see no reason why instability should
not be the same as todays especially over the eastern portion of the

So expect large hail and damaging winds to be the main threats.
Again SPC has our area outlooked for severe weather, mainly the east
half again, and that looks reasonable. Model guidance is also
hinting at a major squall line to move from west to east across the
area. At this time, what the builder gave me looks reasonable but is
possible pops may need to be raised.

Precipitable water values actually go up. Values range from 1 inch
over the far western end to near 2 inches in the eastern portion.
Storm motions are slower than the todays. Will have to watch this
closely in case the same places get a couple of days of heavy
rainfall. Feel confident enough about this that I will add heavy
rainfall wording into the forecast.

Based on latest guidance, trends, and biases, high temperatures will
be a little warmer on Wednesday with most locations along and east
of the Colorado border 100 or slightly above. Some guidance is a
little warmer than what I have but did not go that far. Depending on
how fast thunderstorms/cloud cover develops, that may slow down the

Thursday/Thursday night...In general this day looks to be the most
active due to having deeper and strong lift/features involved. A
little uncertainty creeps in on this period. Models are consistent
in bringing a boundary from the north and west. It is looks like a
preliminary/initial front may be pushing through later in the
afternoon and especially during the night.

Above mentioned left front quadrant continues to affect the
northeast portion of the area in the morning. For the rest of the
day, models differ on details and also are getting messed up by
convective feedback. However it looks like there will be some jet
help, more than likely a right rear quadrant from midday into the
evening. A stronger shortwave trough looks to move through as well.
So in general the higher builder pops look on track, and with a lot
of moving parts do not feel comfortable in making any major changes.
However, if mesoscale influences do not have an effect on what I
have just talked about, pops will probably need to be raised.

Moist and unstable air mass will still be in place. Considering the
much stronger/deeper and more widespread lift that will be in the
place, this day could have the most widespread and significant
severe weather. The new day 3 outlook from SPC has a slight risk
over the entire area with a higher than normal threat for very large
hail. This definitely looks reasonable. Also precipitable water
values will remain 1 to around 1.5 inches. This will also continue
the threat for heavy rainfall. Again I will put in a mention of
heavy rainfall into the forecast.

Will also be leaving the temperature forecast alone, which are
cooler, since convection and the incoming front will be major
influences on this.

Will be issuing a very strongly worded HWO this morning addressing
these three days.

.LONG TERM...(Friday through Monday)
Issued at 201 AM MDT Tue Jun 20 2017

Ridging just west of northern California will help maintain a very
broad trough that will influence the entire northern half of Country
as we head into Friday. Shortwaves will propagate from northwest to
southeast, across the rockies, and into the Plains. A cold front
will push across the region late Friday afternoon with a chance of
thunderstorms across much of the CWA. There will be minimal
instability in place; however, it is enough to allow a mention of a
few stronger thunderstorms as forcing will be enhanced preceding the
frontal passage.

The weekend will bring very pleasant temperatures in the 70s to
lower 80s across the entire CWA in the post-frontal environment.
Both Saturday and Sunday will be much cooler than average with
slightly lower moisture levels. Temperatures and moisture will
rebound very quickly as we head into next week. An isolated
thunderstorm or two will be possible on Monday as a weak shortwave
traverses the region. Very little model agreement is presented
between the global contributers at this point. There will be a
concern of severe thunderstorms on Monday as CAPE very quickly
climbs to over 2700 J/Kg east of a developing dry line that will set
up along the Kansas/Colorado border. The setup for severe
thunderstorms is agreed upon by both the ECMWF and GFS; however,
they are about 24 hours apart with the GFS highlighting a risk for
Monday afternoon and the EC leaning more toward Tuesday afternoon.
For now, staying with a slight chance of storms on Monday
afternoon due to the influence of an approaching ridge, but this
will need to be revisited as new data is made available.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1122 PM MDT Mon Jun 19 2017

VFR conditions forecast for the TAFs. Fairly light south winds
will continue into the afternoon then will turn either to the east
or southeast, depending on the TAF site`s location relative to the
surface trough. Isolated to scattered thunderstorms will develop
along the trough in the latter half of the afternoon. They may
impact the TAF sites, but KGLD may be too far west. The storms
will be east of the TAF sites by 6z.




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