342
FXUS63 KGLD 290909
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
309 AM MDT Thu Jun 29 2017

.SHORT TERM...(This evening through Thursday)
Issued at 228 PM MDT Wed Jun 28 2017

Latest upper air analysis shows a deepening short wave trough over
Central Colorado.  Satellite imagery shows cumulus clouds increasing
in coverage over the mountains, with some storms developing on the
plains.  At the surface the cold front from this morning was
difficult to find due to the gradual cooling temperatures behind the
pre-frontal trough extending from near Liberal northeast to near
Hays. The dry line was running parallel along the pre-frontal
trough.

For the rest of the afternoon, isolated thunderstorms will continue
to develop over Eastern Colorado near the deepening upper level
short wave trough and where weak surface convergence will occur as a
surface low deepens.  The storms will increase in coverage due to
the short wave trough deepening.  Most of these storms are not
expected to become severe due to CINH capping off any mixed layer or
surface CAPE. However if storms develop as far south as I-70 or
further south, they may become severe due to very little CINH in
place there.

This evening the upper level short wave trough will continue to
deepen as it moves east.  Storms developing ahead of it will
increase in coverage as they move out of Colorado and into higher
CAPE in Kansas.  As the storms move east into higher instability the
threat for large hail will increase.  Meanwhile elevated CAPE will
develop near the warm front and nose of the low level jet over the
southeast part of the forecast area.  As the upper level short wave
trough progresses east, should see a second group of storms develop
along the warm front which will also coincide with an axis of
higher theta-e.  Am anticipating hail up to hen egg size with these
storms, although cannot rule out hail larger than that east of
Highway 83.  Severe winds will be possible with any storms that move
into Kansas.  Looking at 0-1 and 0-3 KM helicity and EHI, there is a
potential for a tornado to develop in the vicinity of the warm front
before midnight CT.  Have low confidence of this occurring, but
still bears mentioning.  However if severe weather is going to occur
it will be mainly in Northwest Kansas in the evening.

As the evening progresses the two groups of storms should merge into
a MCS or some sort of cluster before the overnight hours.  As the
storms merge into more a cluster, the size of the hail should become
smaller with severe winds becoming more of a threat along with heavy
rainfall.  Don`t have the confidence to issue a flood watch, since
the storm complex should be moving fast enough to negate flooding.

During the overnight hours the elevated CAPE shifts north into
Nebraska.  This may cause the severe thunderstorm activity to
transition north as the storm complex moves east.  However when the
CAPE axis shifts north it may be behind the storm complex. Generally
the later past midnight the lower the chance for large hail to occur
as the CAPE axis shifts north of the forecast area.

Thursday looks like another repeat of today with storms forming in
Eastern Colorado ahead of a deepening upper level short wave trough.
Isolated storms should begin to form in the early afternoon then
increase in coverage over East Central Colorado as they move east
later in the afternoon.  Main threat with these storms will be
large hail and damaging winds.

.LONG TERM...(Sunday through Wednesday)
Issued at 243 AM MDT Thu Jun 29 2017

Sunday and Monday: A shortwave will move across the region Sunday
afternoon and evening with PoPs increasing through the afternoon.
There will be good instability in place with enough shear to provide
an environment that will be favorable for strong to severe
thunderstorms. Showers and thunderstorms could persist into the late
evening and into the overnight hours, especially in the northeastern
portions of the CWA. For Monday, look for another chance of late
afternoon and evening thunderstorms as a developing upper low tracks
north of the CWA. Instability remains high; however, deep layer
shear will be lacking and will likely limit widespread severe
thunderstorms but we could see a few strong to marginally severe
storms develop.

Tuesday (4th of July): The upper trough, associated with the
developing upper low, will move to the east giving us northwest flow
aloft. There will be a narrow axis of instability along a dryline
that will set up just west of the KS/CO border. A slight chance of
thunderstorms is possible through the afternoon mainly for western
Yuma, Kit Carson, and Cheyenne counties in eastern Colorado. A few
strong thunderstorms are possible with a low chance of an isolated
severe storm.

Wednesday and Thursday: Northwest flow continues aloft through mid-
week with surface flow becoming southerly to southeasterly.
Instability will increase late Wednesday with thunderstorm chances
through the afternoon and evening over much of the CWA. Deep layer
shear will be relatively weak on Wednesday, once more limiting
widespread severe but allowing at least a low chance of an isolated
severe thunderstorm. For Thursday, instability and shear will
sharply increase as low level southeasterly flow increases; however,
there will be very little in the way of upper-level support and thus
there will only be a slight chance of thunderstorms through the
afternoon and evening. Any storms that are able to form on Thursday
could become severe.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1135 PM MDT Wed Jun 28 2017

Vfr conditions are expected through the period. For Kgld,
currently thunderstorms near and to the west of the site. Current
high resolution guidance supports having thunderstorms affecting
the site. At this time kept conditions vfr but may need to update
to make it mvfr. Winds will remain from north to around northeast
at 10 knots or less.

For Kmck, less of chance for thunderstorms for here. However,
currently weak activity near the site so have vcts for the first 3
to 4 hours of the forecast. Through the morning winds will be
variable below 10 knots. After that the winds will be northwest
to northeast at 8 to 14 knots.


&&

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

$$

SHORT TERM...JTL
LONG TERM...TL
AVIATION...BULLER