Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 150536
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1136 PM MDT Thu Sep 14 2017

.UPDATE...
Issued at 800 PM MDT Thu Sep 14 2017

Latest model data shows an upper level short wave trough giving a
glancing blow to the northwest corner of the forecast area this
evening. In addition the nose of the low level jet is moving up
from the south. This feature has caused a storm in Cheyenne County
KS to maintain its intensity despite the storm being behind its
own outflow. Radar shows the storm activity increasing as the nose
of the low level jet continues to move north and the upper level
short wave trough deepens just to the north. Soundings show the
potential for elevated severe convection during the evening for
the next hour or so on the leading edge of the low level jet.

So far the deep layer shear and instability have been just strong
enough for the severe thunderstorm to produce hail up to quarter
size, based on storm reports. See this threat continuing for the
next hour or so, mainly north of Highway 36, before the threat
for severe weather shifts north of the forecast area.

&&

.SHORT TERM...(This evening through Friday)
Issued at 226 PM MDT Thu Sep 14 2017

Broad ridging has shifted further east, with diffluent flow
developing into the southwest US. Lee trough extends from eastern
Colorado over our CWA, with several weak covergence zones/trough
axis over our east and south. CAP is still strong enough to limit
convection, though there is a small CU field beginning to develop
near covergence zone in our southwest.

This afternoon-Tonight: Best forcing remains well west of our CWA,
however vort maxes within SW flow will rotate around western extent
of ridge and may help support showers/thunderstorms lingering
eastwards as the move off the higher terrain. Stronger forcing
slides northeastwards as upper low over SW US moves northeastward
late tonight. As CINh continues to weaken this afternoon I can`t rule
out an isolated thunderstorm along trough axis further east this
afternoon, but favored timing/locations will be west in the evening
transitioning eastward overnight. Isolated to scattered activity is
favored, with higher resolution guidance favoring maxing trough axis
in our north as acting moves off the higher terrain in Colorado and
this is where I kept slight chance PoPs.

DCAPE has increased over 1500 J/KG in NW KS and SW NE,
and with well mixed/dry lower levels (sub 9kft) we may see a
enhanced risk for microburst potential. SB CAPE has increased to
2000 J/KG range, however ML is much less impressive over the same
locations. Considering the isolated/uncertain nature of convection
and timing where better convective indies line up I am not sure we
will se much of a severe threat. By sunset we should see any
limited/isolated severe/strong threat end with decoupling of lower
levels.

Friday: Surface trough begins to shift further south and east and
deep mixing will support lower Tds and breezy conditions. We could
see RH values in the upper teens, maybe a few locations near 15%. I
have questions on coverage and duration of 15% RH and whether 25 mph
gusts correlate with these lower RH values for 3hr. I decided
against issuance of fire weather highlights with elevated (not
critical) favored. If lower Tds mix further east then we may see a
potential, so this will need to be monitored.

.LONG TERM...(Friday night through Thursday)
Issued at 226 PM MDT Thu Sep 14 2017

Friday night-Sunday: Cold front passes through the area late Friday
night into Saturday morning. High temperatures Saturday will be in
mid 70s to low 80s across the area. It is possible that temps do not
even get that warm if the NAM verifies with its post frontal stratus
for the majority of the day (current run of the NAM MOS shows a high
of 68 in Goodland on Saturday). Will have a chance of showers and
thunderstorms Saturday evening and Sunday evening. No severe weather
expected at this time. Temperatures will continue to be close to
normal, which will be still feel cooler compared to what the area
has experienced the past week.

Monday-Thursday: Monday and Tuesday should be relatively quiet
weather days with temperatures returning to above normal values due
to persistent southwest flow. All global models are showing the
remainder of the week could be fairly active. GFS, JMA, CMC, and
ECMWF all show either a strong negatively tilted longwave trough or
a closed low approaching the CWA from the West. Currently, while
models are not in agreement on location, strength, and timing, all
are depicting a strong feature in the long term. This will be
closely monitored by future shifts as we head into next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1130 PM MDT Thu Sep 14 2017

VFR conditions expected for the TAFs. Storm activity has moved
north of the sites already. There should not be any storm activity
until Friday late afternoon/evening, and that would mainly be for
KMCK.

Due to the various outflow boundaries near KGLD, winds will be
variable through the night. Both sites will have LLWS due to a
strong low level jet overhead. Southwesterly winds Friday will
turn to the south and then northeast as the cold front moves in
from the northwest.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

UPDATE...JTL
SHORT TERM...DR
LONG TERM...SME
AVIATION...JTL



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