480
FXUS63 KGLD 081124
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
524 AM MDT Sat Jun 8 2024

.KEY MESSAGES...

- There is a 60% chance for a significant, widespread severe
  event across the area this afternoon and evening. Very strong
  winds, large to very large hail, flooding, and maybe a tornado
  or two are all possible. The favored area is generally along
  and south of I-70 and Eastern Colorado. The entire area has a
  chance.

- Active weather pattern continues Sunday through Tuesday with
  similar trend of storms moving in from the west during the
  afternoon/evening.

- Potential break in the active weather pattern mid week with
  near triple digit temperatures.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 313 AM MDT Sat Jun 8 2024

Potential for a significant severe weather event this afternoon and
evening.

Current observations show showers and a few storms moving through NW
Kansas as moisture availability has remained high and MUCAPE has
remained around 500-2000 J/KG. Thankfully, storms should remains sub-
severe with a lack of shear which has kept the storms pulsey in
nature.

For the daytime hours, today is forecast to be cooler with some cold
air advection and some higher pressure trying to move in from the
north. The presence of cloud cover during the day will also help
with areas under cloud cover forecast to stay in the 70`s while the
rest of the area that sees more sunshine is forecast to warm into
the 80`s. Winds are forecast to out of the east (increasing moisture
advection) with higher pressure to the north east and low pressure
to the southwest.

For this afternoon and evening, the severe chances have increased
quite a bit given the moisture availability over the area, and the
potential for the low pressure system to remain nearby. The features
themselves are not forecast to generate storms over the area, but
any outflows from earlier storms may be able to pop up a few
isolated storms in the area (20% chance). The bigger problems is the
storms that will likely form along the higher terrain in Eastern
Colorado and move east into the area. These storms are forecast to
move into an environment with good instability (1500-3000 J/KG of
ML/MUCAPE), PWATS in excess of 1 inch, effective shear above 50 kts,
and corfidi downshear vectors of 50-70 kts. This environment would
be supportive of clusters to lines of storms moving across the area
that produce heavy rain and very strong wind gusts. Given the strong
downshear vectors, suggested linear mode, and flow within the cloud
layer to 70kts, wind gusts up to 90 mph are possible. Most gusts
will likely be in the 60-80 mph range, but higher values will be
possible. For the hail, any initial storm and any embedded supercell
will have the possibility of producing hail in excess of two inches.
While some analogs suggest hail up to 4 inches, I went with up to 3
inches given that the effective shear may be too strong (60+ kts) to
develop a good hail core. Storms may also quickly become
clusters/linear which would lower the chance for larger hail. So
most hail will likely be in the one to two inch range with isolated
instances of large hail (similar to yesterday). Another issue with
hail, especially with embedded supercells, is that accumulating hail
would be possible with right move motion forecast to be much slower
in the 10-20kt range. Any embedded supercell would also increase the
flooding threat as the high PWATs and potential for more skinny CAPE
at times suggest that these storms could be efficient rain makers.
Some guidance is trying to give up to 3-4 inches for areas that have
a supercell or slower cluster of storms. The flooding threat as a
whole remains on the low to moderate side as without embedded
supercells, the line would likely move to quickly for anything other
than maybe some urban flooding prone areas to be affected. Finally,
a tornado or two is possible, but the chances are generally low as
the low level flow and shear are forecast to be relatively weak.
Even if a QLCS/line of storms develops, the shear magnitude is
forecast to be 10 kts or less which isn`t very favorable short of a
spin-up or two.

In regards to timing and coverage, the storms look to initiate out
of the area by noon, but not move into the area until around 2pm-3pm
MT. Storms would then move through the area from west to east until
~11pm MT / 12am CT. The main batch could be out of the area by 9pm-
10pm CT if the storms stay more as lines and just sweep through the
area. For coverage, the entire has a chance, but south of I-70 is
favored. If the higher pressure and the low pressure both push
further south as guidance has been suggesting, the tracks and lines
of storms would also be pushed south. All of Eastern Colorado may
see storms irregardless of how the pressure pushes due to the terrain
aided storm development, but would struggle to make it into KS/NE if
the high pressure pushes in during the afternoon hours. As for
confidence, confidence in storms occurring within the area is 90%,
and 60% for a significant and widespread severe event.

For tonight, the main line is forecast to push off before midnight.
However, additional storms could develop if the low pressure nose
remains too far north and keeps some surface convergence behind the
main line along with outflows. Some shortwave energy may also move
through and help a few storms form. As long as the storms earlier
sweep through and don`t fall apart, most of the environment should
be worked over and maybe up to 1000 MUCAPE may remain and give a
small hail threat. But cloud cover and storm could linger through
much of the night, keeping lows a bit higher in the upper 50`s and
60`s.

Tomorrow, the ridge is forecast to begin amplifying which will weaken
our flow aloft will high pressure remains near the surface. This
would allow cloud cover to clear slowly through the day and keep
temperatures mainly in the 70`s. Will need to watch for some
afternoon/evening thunderstorms moving into Eastern Colorado with
lower pressure trying to build back up along the Front Range and
moisture availability remaining high. As of right now, no threats
are expected, but could maybe see a marginal risk for severe weather
in the far western portions of the area.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 232 AM MDT Sat Jun 8 2024

At the start of the long term period, looking at another shortwave
moving through the flow, which continues the stormy pattern for the
region; however, currently not anticipating severe weather for the
CWA. Going into Tuesday morning, upper low pressure will move
through the OK/TX Panhandle region, followed by high pressure
building in over the Four Corners region through mid-week all the
while low pressure meanders off the West Coast. It`s during the
latter part of the work week this upper low begins its inland
progression, breaking down the ridge, and allowing a return of more
active weather to the area. Details at this range are uncertain, so
continue to monitor the forecast.

Cloud cover and showers/storms on Monday will keep temperatures
below normal for this time of year - currently forecast in the 70s
to low 80s. Tuesday will begin a warming trend with highs forecast
in the low to mid 80s. Overnight lows Monday-Tuesday will be in the
middle 50s to low 60s. With ridging really getting underway mid-
week, will be looking at afternoon highs in the 90s and overnight
lows in the upper 50s to middle 60s. Regarding shower/storm chances
for the period, Monday`s chances will linger into Tuesday morning-
afternoon before a drying trend thereafter - at least until Thursday
evening-night when we`ll see daily chances return through the
remainder of the long term period as the next system nears and
subsequently moves through the area.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 518 AM MDT Sat Jun 8 2024

For KGLD... VFR conditions are forecast for the period, but do
need to watch for sunrise low ceilings or fog this morning.
Otherwise, the main hazard will be clusters of storms or a line
of storms that is forecast to move through somewhere around 00Z.
These storms could produce significant severe weather with winds
in excess of 75 mph and hail above 2 inches. They could also
miss the terminal with some rain and gusts to around 40 kts.
After that, will need to watch for where a line of storms behind
the main line sets up, but no other hazards currently forecast.

For KMCK... IFR conditions are possible this morning with fog
and/or low stratus clouds. The showers and storms earlier in the
night appear to have lowered the chances for fog and stratus
along with winds having a more northwesterly component the last
hour or two. However, nearby sites to the northeast are
reporting worsening conditions, so have left it in the TAF for
now. Otherwise, the main hazard will be a line of storms moving
through just after 00Z. These storms could produce significant
severe weather including winds above 75 mph and hail above 2
inches. But the chance at KMCK is lower compared to the rest of
the area with chances for storms around 60% instead of 80%.
After that, will need to watch for some showers or an isolated
storm, but no other hazards are currently forecast for the rest
of the night.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.

&&

$$

SHORT TERM...KAK
LONG TERM...CC
AVIATION...KAK