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000
FXUS63 KGLD 241108
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
508 AM MDT Wed Apr 24 2024

.KEY MESSAGES...

- Significant severe weather is possible Thursday for most of
  the area with the main threats being tornadoes and very large
  hail. The threat is conditional as a cap could prevent storms
  from forming.

- A Fire Weather Watch is in effect Thursday south of I-70 and
  west of Highway 25 for low humidity and strong winds.

- Blowing dust is also possible Thursday afternoon for near and
  south of the I-70 corridor.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 334 AM MDT Wed Apr 24 2024

For today, a fairly similar day to yesterday is in store with a mix
of clouds and sun through the day today and highs around 70. Showers
and storms would then return to the area this evening and overnight
as a shortwave moves through the larger flow. The main difference
today is that winds will be a bit stronger around 20 to 25 mph and
from the south which will help bring moisture into the area. For
tonight, will need to watch for fog in the area with the moisture
advection, especially since winds are forecast to have a slight
easterly, upslope component overnight. The other thing to watch will
be the potential for a second round of stronger storms just before
sunrise as some guidance suggests that there could be some elevated
instability. Even if tapped into, it is unlikely severe storms would
occur, but CAPE just shy of 1000 J/KG and shear around 45-55 kts
could allow hail to form.

Tomorrow is still forecast to be an active day, but will depend on
dryline placement and how long cloud cover lingers. Guidance has
come into better agreement on the low and dryline setting up on
KS/CO border in the area by the late afternoon and early evening
hours. This would leave most of the area in cloud cover (and
potentially fog) until the early afternoon hours. Some locales
closer to Central Nebraska and Kansas may have cloud cover persist
through the day which would limit temperatures to the 60`s.
Meanwhile, clouds would clear beginning from East-Central Colorado.
This would allow these locales to warm into the 80`s and also dry
out as the dryline advances. With this and the approach of the low
pressure system strengthening the winds, have opted to issue a Fire
Weather Watch for south of I-70 and west of Highway 25 where
critical fire conditions could be met late in the afternoon. The
main uncertainty is how fast will the dryline advance and will it be
enough to lower RH for 3 hours.

Also later in the afternoon tomorrow, will need to watch for a
blowing dust threat generally along and south of I-70. Local
research suggests that winds will become strong enough around 21Z
from the south to start generating some blowing dust. It looks to be
unlikely that there`d be a thick plume of dust or brownout
conditions (except right next to source regions) as lapse rates
around 2km are forecast to still be around 9 C/KM which could allow
dust to mix out further and not become concentrated.

The main threat for Thursday is the chances for severe weather. With
the moisture advection and the chance for multiple boundaries to be
in the area due to the low pressure system, storms will have the
possibility to form. If they do form, the biggest threats would be
large hail that could exceed 2" (CAPE around 2500 J/KG and effective
shear around 55-60kts would allow for longer lived supercells) and
tornadoes. The tornado threat has increased with the latest forecast
packages as guidance suggests that there will be ample 0-1km shear
and SRH along with low LCLs. The dryline and a potential warm front
across NW Kansas could also serve as focuses and a genesis point for
tornadoes with the NAM 3km suggesting that any dryline initiated
storms would be well favored to produce tornadoes (STP near 6). The
main uncertainty for severe storms is can they form and if they do,
how far can they move east before diminishing. Guidance has been
consistent with a cap (convective inhibition) developing around the
800-700mb level largely due to the cloud cover keeping near surface
temperatures cooler. If the CAP erodes near the dryline or any
boundary, storms should have enough forcing and instability to
develop. Significant hail would be more likely if the cap is weaker
than forecasted and is then overcome during the afternoon hours. As
for how long severe storms would last, the more of the area under
cloud cover until the mid to late afternoon hours, the more of the
area with little to no instability to sustain the storms which would
cause them to dissipate as they move east. In summary, significant
severe weather is possible tomorrow unless most of the area can stay
under cloud cover until the late afternoon hours or the cap is
stronger than forecast.

Going into the overnight hours, the low is forecast to begin lifting
north and east across the area which could temporarily stop
precipitation if the dry air is pulled north with it. The night
hours would then see winds slowly shift to out of the northwest with
lows in the 40`s and 50`s.

Friday, wrap around precipitation is possible through the day,
especially if the low elongates to the south and slows down. Winds
should strengthen behind the system, but currently have gusts around
50 mph with sustained speeds around 25 to 30 mph. There doesn`t seem
to be much of a chance of the winds getting to High Wind criteria
looking at how deep the low would get in ensemble members, but it
would be breezy for sure. Temperatures would likely stay near
average in the 60`s and 70`s with little to no cold air advection
behind the system.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Issued at 120 AM MDT Wed Apr 24 2024

Saturday...another low pressure system is forecast to move into
the area from the southwest during the late afternoon and overnight
hours. Easterly winds around 15 mph during the morning slowly back
to the northeast around 20 mph late in the day, becoming
northwesterly at 15 to 25 mph with higher gusts after midnight.

Shower/thunderstorm chances increase through the day from west to
east ahead of the approaching low with 40%-90% pops (east to west).
Overnight, we`ll have 50%-90% chances for showers/thunderstorms due
to wraparound precipitation behind the low. With above normal
precipitable water values, locations generally north of I-70 could
see 24 hour rainfall amounts in the 0.50 to 1.75 inch range, highest
in Yuma county.

High temperatures are forecast to be in the lower 60s to middle 70s
with low temperatures in the middle 30s to middle 40s.

Sunday...as Saturdays storm lifts northeast and away from the area,
we`ll continue to be impacted by wraparound showers/thunderstorms
during the day. Precipitation chances range from 20%-40% south of
Interstate 70 to 50%-60% near the KS/NE border. Overnight, rainfall
chances will have ended. High temperatures are forecast to be in the
middle 50s to middle 60s with low temperatures in the middle 30s to
around 40. Breezy/windy northwest winds are expected during the day
with gusts up to 35, maybe 40 mph. Presently, there is a 20% chance
for thunderstorms during the night across Norton/Graham counties.
This seems tied to increasing moisture in the 850-500mb layer moving
into those areas from the south and interacting with a strengthening
low level jet.

Monday...near zonal flow is forecast by the GFS/ECMWF/GEM/GEFS
models. Presently, the forecast is dry. However, GFS/GEM 700-500mb
relative humidity forecasts due show a disturbance moving across the
area from very late in the afternoon through the evening hours,
possibly supportive of some mention for showers/thunderstorms. Will
have to watch how this develops over the coming days. High
temperatures are forecast to bounce back up into the 70s with low
temperatures in the 40s.

Tuesday...broad upper level ridging is forecast to be over the area.
850mb temperatures from the GFS/ECMWF/GEM models continue to rise,
supporting highs in the upper 70s to middle 80s, possibly even
warmer if the GFS and ECMWF 850mb temperatures are realized under
typical mixing. Low temperatures are forecast to be in the middle
40s to middle 50s.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 501 AM MDT Wed Apr 24 2024

For KGLD & KMCK... VFR conditions are forecast through about
03Z. For the first few hours of the period KMCK may have some
lingering showers nearby and KGLD may have LLWS, but both are
forecast to end shortly. The rest of the day time hours will see
more sunshine and strengthening low level winds around 15-20 kts
with gusts up to 30 kts. This evening, ceilings are forecast to
lower after 03Z down to IFR. KMCK may drop a little later after
06Z as the moisture will be moving in from the south. Fog could
also develop, though the ceilings may already be below 500ft
when that occurs. The last note is the potential for showers and
storms again after 00Z. There is uncertainty with the
precipitation due to the presence of low clouds and potential
fog, so have not included them in the TAFs yet. McCook has the
relative highest chance for seeing storms tonight and small hail
wouldn`t be out of the question after 06Z if a storm can develop
and grow.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Fire Weather Watch from Thursday afternoon through Thursday
     evening for KSZ013-027-028-041-042.
CO...Fire Weather Watch from Thursday afternoon through Thursday
     evening for COZ253-254.
NE...None.

&&

$$

SHORT TERM...KAK
LONG TERM...99
AVIATION...KAK