703
FXUS63 KGLD 180630
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1230 AM MDT Sun May 18 2025

.KEY MESSAGES...

- Strong southwest winds will develop behind a northward
  advancing dryline Sunday afternoon, mainly along and south of
  I-70 where sustained winds at 30-40 mph and gusts up to 55 mph
  are possible.

- Severe storms are forecast to impact the area Sunday
  afternoon. Storms could form as early as 2pm and last until
  midnight. The main threat area is generally north of
  Interstate 70, but the entire area will have a chance for
  severe storms. Large to very large hail, damaging wind gusts,
  and a few tornadoes are possible.

- Severe storms are possible again Monday afternoon/evening,
  mainly impacting locales east of Highway 83.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 1226 AM MDT Sun May 18 2025

Current observations show showers decaying over Northeastern
Colorado as the lift and moisture supporting them are weakening.
Meanwhile, the next upper trough is centered roughly over Southern
Nevada, with broad surface low pressure along the Front Range and
into the Southern Plains ahead of the upper trough. For the
remainder of Saturday night and into early Sunday morning, the upper
low is forecast to slowly shift east and allow the surface pressure
gradient to remain fairly broad. With this, winds should stay from
the east/southeast around 10-15 mph. The low level moisture
advection from the easterly winds is allowing some low level stratus
clouds to develop. The low clouds that develop should linger through
the night and into early Sunday morning. Temperatures should remain
in the 40s and 50s.

For Sunday morning, a cloudy and potentially foggy start is forecast
for the area due to the continued low level moisture advection. Fog
looks like it would be patchy if it did form due to the insulation
from the low level clouds and winds around 15 mph keeping winds
mixed. Given how these setups have gone in the past, would not be
surprised if there are some dense patches of fog to begin the day.
Winds are forecast to strengthen through the morning as the upper
low is forecast to progress to the Four Corners region and deepen
the surface low and push it into Eastern Colorado. This could allow
winds to strengthen to around 25-35 mph with gusts up to 50-55 mph
by the early afternoon hours. Temperatures will likely be slow to
warm as long as the cloud cover is in place.

For Sunday afternoon and evening, storms are still expected to
impact the area with increasing concern for severe storms. The
current forecast calls for the surface low and dryline to push into
the western half of the area during the afternoon and help erode the
cloud cover. From ensembles and the different convective allowing
models, two main scenarios have seemed to emerge. The first scenario
is that the dryline pushes to about the midpoint of the area during
the afternoon, roughly around a line from Yuma, Colorado to Leoti,
Kansas. With this, the dryline and resulting differential
heating boundary from the cleared clouds would serve as the
focus for storms to develop. With the boundary in place and the
cap eroded, storms would have little issue firing up around
2-4pm MT. With the influx of moisture and daytime heating, CAPE
is forecast to be around 2000- 3000 J/KG along with mid level
lapse rates around 8-9 C/km. Combining the instability with
forecast effective shear around 45-65 kts should mean that
supercells would form, as long as they don`t get over sheared.
The initial threats would be large hail with sizes probably up
to 3 inches (likely around 1.5-2 inches), and wind gusts up to
85 mph (likely around 65-70 mph with winds around 55 kts in the
mid-levels). As the storms move northeast, the threat for
tornadoes would increase as long as the dry line does not surge
ahead and clear out the low level moisture. Forecast soundings
suggest that the storms would move into an environment that
supports lower LCLs and has slightly better low level shear. The
storms would then likely be out of the area by 8-9 pm MT as
they move north/northeast out of the area with the advancing
surface low and upper trough. The timing would depend on how far
south the storms are able to fire as they would track longer
across the area.

The primary alternate scenario where the surface low is drug more
south and delayed would keep more of the area under cloud cover with
maybe some breaks in the eastern and northern fringes of the area,
farther from the low. In this scenario, we`d likely have a
slightly later start time with storms initially forming just
west of the area. Late in the afternoon though, we could wind up
with multiple lines of storms moving through the area. We`d
have a line along the dryline, a line along the eastern break of
the clouds, and maybe a line over the area if the mid-level low
moves in slightly faster than the surface low. The issue is
that all of these lines would posses the potential for all
threats with plenty of shear and strong winds, though hail
chances may be a bit lower. With this, we could have a Quasi
Linear Convective System scenario where each line is mainly
producing swaths of damaging winds likely around 60-70 mph with
maybe an 80 mph. QLCS tornadoes would also be a threat with the
southeasterly surface winds and southwesterly low to mid level
winds from the advancing system leading to sufficient low level
shear. The lower LCLs would also help. This scenario could last
until midnight.

The main threat area favors north of Interstate 70 in either
scenario, but the entire could see severe storms. Overall,
confidence in storms and severe storms occurring within the
area is high. Also worth noting, there is a low chance for
blowing dust, especially in a QLCS scenario. However, unlike
Wednesday, mixing is forecast to a bit high which would likely
limit the dust threat to near source regions and at the
beginning of the storms. A wall of dust looks to be unlikely
this time.

Tomorrow night, the system should push through and out of the area.
This should end the storm chances short of maybe a chance along
Highway 34 on the wrap around side of the surface low. Skies should
clear and winds lower as the system gets farther away and allow lows
to drop into the 40s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 133 PM MDT Sat May 17 2025

For the extended period starting Tuesday a surface low remains
in place around the South Dakota/Minnesota/Nebraska/Iowa state
lines as breezy to gusty NW winds are forecast to continue
across the area in response to this low. Wind gusts of 45-55 mph
are currently forecast with sustained winds around 25-35 mph as
30 knot 850mb jet remain in place during the afternoon and a
45-50 knot 700mb jet remains in place, assuming if some mixing
can occur then would not be surprised if a rogue 60 mph gust
occurs if these trends hold. At this time Tuesday is forecast to
remain dry but if the low sets up a little further west then
some vorticity maxima may lead to some spotty showers through
the afternoon as well.

Wednesday morning as this low moves it a cold front and
associated surface high is forecast to move into the area which
is forecast to drop Wednesday morning lows into the 30s. An
associated surface high also moves into the area with the front
which is forecast to bring a period of lighter winds before they
shift to the west. If this shift to the west is slower to occur
then temperatures may drop even further which may bring some
frost or maybe freeze concerns to portions of the area which
would be impactful given we are well past our climatological
last freeze date. Luckily this surface high is forecast to be
short lived as a lee trough ahead of western CONUS ridging
develops and pushes this out of the area. Some guidance does
indicate a weak wave moving through with this activity which may
try to spark some storms during the evening hours so will need
to keep an eye on this.

Thursday and through the remainder of the extended period weak
mid level ridging is forecast to take place across the Inter
Mountain west which if current placement holds puts the region
on the eastern periphery of this feature. Typically in these
patterns weak waves that are not handled well by long range
deterministic guidance moves through the area; what makes this
interesting is that there are already some signals are some
embedded waves which makes me think that another active pattern
may emerge late week and next weekend. With this still being 5-7
days out a lot can and will change but it does appear that
additional potential for severe weather may return again for
portions of the area.

As for temperatures for the extended period. Tuesday is
forecast to start out fairly cool with high sin the mid 60s to
low 70s across the area before warming back into the upper 70s
my Wednesday and into the mid 80s again Friday especially as
that ridge begins to make itself known. For low temperatures as
mentioned above, some concern for frost and maybe freeze to
start the period before a recover to more seasonable lows in the
upper 50s and mid 50s by the latter portion of the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1054 PM MDT Sat May 17 2025

For KGLD & KMCK... Rough flying conditions are forecast at times
through the period. VFR conditions are forecast for the first 6
hours with low level wind shear as the jet has been observed to
be a few hundred feet off the ground with speeds to 40 kts.
Lower ceilings around 1000-2000ft are possible from 09-18Z as
moisture is forecast to stream in from the southeast. VFR
conditions are then forecast to prevail through the period, but
with a risk for severe storms during the afternoon and evening.
There is still uncertainty as to where storms will form and how
widespread they will be. But between mainly 21-04Z, severe
storms will be possible with very large hail, wind gusts in
excess of 50-60 kts, and maybe a tornado. Use extreme caution
and be prepared for changing conditions. After 06Z, there is a
low chance for a final wave of storms to pass through KMCK, but
otherwise clear conditions are forecast.

&&

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

&&

$$

SHORT TERM...KAK
LONG TERM...Trigg
AVIATION...KAK