-- Discussion containing changed information from previous version are highlighted. --
559
FXUS63 KGLD 291930
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
130 PM MDT Wed May 29 2024

.KEY MESSAGES...

-- Changed Discussion --
- Strong/severe thunderstorms possible the next few days with
  all modes of severe weather possible along with excessive
  rainfall that could produce flooding/flash flooding.

- A bit drier with less shower/thunderstorm coverage Sunday
  through Wednesday with afternoon temperatures well into the
  80s. Lower to middle 90s are forecast Sunday and Tuesday.
-- End Changed Discussion --

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Issued at 130 PM MDT Wed May 29 2024

Tonight...showers and thunderstorms are forecast to move into parts
of far eastern Colorado in the 5-6 PM MDT timeframe aided by
sufficient moisture in the 850-500mb layer, modest instability and
modest 250mb jet divergence. These isolated to scattered
thunderstorms will move toward Highway 25 by 03z, increasing in
coverage east of Highway 25 after midnight. Primary hazards through
midnight look to be large hail, damaging winds and perhaps some
locally excessive rainfall. The 06z-12z GFS and prior runs of the
HRRR were showing signs in the 0.5-1km wind speeds of a potential
blowing dust threat associated with any convection moving into the
far southern/southwestern zones from southeast Colorado (generally
00z-02z timeframe). After midnight, the threat becomes locally
excessive rainfall that could produce flooding/flash flooding.

Low clouds and likely some fog will be present a few hours prior to
sunrise Thursday morning. Dense fog cant be ruled out.

Low temperatures are forecast to be in the lower 50s to lower 60s.

Thursday-Thursday night...lingering morning showers and
thunderstorms east of Highway 25 in the morning look reasonable
given sufficient moisture in the 850-700mb layer despite mid level
dry air moving overhead. During the mid afternoon, looking at 20%-
30% chances for showers/thunderstorms east of Highway 27 with
continued chances through late afternoon with focus then shifting
toward far eastern Colorado as the next weather system moves in.
Overnight, this feature, aided by sufficient lift, instability and
upper jet divergence moves generally to the east although specifics
are a bit more difficult to pinpoint. High temperatures are looking
to be in the middle 70s to lower 80s with low temperatures in the
upper 40s to upper 50s.

Friday-Friday night...we`ll have 20%-40% chances for showers and
thunderstorms although a bit more specific timing would be east of
Highway 25 in the morning and early afternoon as Thursday nights
wave moves through. The next weather system moves into far eastern
Colorado during the late afternoon hours then east across the
remainder of the area through midnight before moving southeast and
out of the area. High temperatures are forecast to be in the lower
to middle 70s with low temperatures in the lower to middle 50s.

Saturday-Saturday night...shower/thunderstorm chances increase in
the afternoon from the west and southwest (20%-40% chance) then east
and out of the area near sunrise Sunday morning with continued 20%-
40% chances. High temperatures rise into the lower to middle 80s
with low temperatures in the middle 50s to lower 60s.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Issued at 100 PM MDT Wed May 29 2024

Shortwave trough comes through the zonal flow on Sunday with
convective initiation in the afternoon along a lee trough or dry
line draped over western portions of the forecast area. Deep
layer shear is forecast to be weaker than it has been, around
20-25 kts, suggesting more of a pulse storm mode. Nonetheless,
should see a low end risk for severe storms as they move east
Sunday evening. For areas west of the dry line Sunday afternoon,
near critical to critical fire weather conditions will be
possible due to low humidity, though wind appears to be lacking
at this point.

For early next week, a ridge over the southern plains is
forecast to gradually build northward. If the ridge axis is over
the Rockies as forecast, then the central plains will be
transitioning to a northwest flow aloft. The door will still be
open for disturbances coming over the ridge axis, especially
eastern areas, though as you get into Colorado the ridge might
start to suppress convection. Another impact of the building
ridge will be lighter flow aloft, with deep layer shear
generally in the 20-30 kt range each day. This would tend to
somewhat limit storm organization and severe risk. However,
instability does not look like it will be lacking with moderate
instability forecast just about every afternoon in some part of
the forecast area. So, daily thunderstorms chances appear to
continue but with some decrease in storm intensity and severe
risk.

Temperatures will be above normal with proximity to the upper
ridge. Highs will be in the 80s and 90s and lows in the 50s and
60s.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1115 AM MDT Wed May 29 2024

KGLD...VFR conditions are expected from taf issuance through 01z
then again after about 16z. Southerly winds gusting to 35kts are
expected from taf issuance through 01z. From 01z-07z, the
terminal could be impacted from showers and thunderstorms with
gusty winds, perhaps some hail and locally heavy rainfall that
could produce sub VFR visibilities. From 08z-16z, southerly
winds gusting to around 20kts will subside while slowly veering
to the southwest. Stratus and fog are anticipated, producing sub
VFR conditions. After 17z, VFR conditions return with winds from
the north around 10kts.

KMCK...VFR conditions are expected from taf issuance through at
least 09z. Southeast winds gusting to 30kts are expected from
taf issuance through 02z, decreasing to around 10kts through
08z. There is a chance for showers and thunderstorms to impact
the terminal from 03z-08z. After 09z, stratus and fog will
develop, creating sub VFR cigs/vis with winds from the southeast
under 10kts.

&&

.HYDROLOGY...
Issued at 358 AM MDT Wed May 29 2024

Highly efficient moisture return has already began and will continue
into the end of the workweek with aid from the 850 mb LLJ. This
moist conveyor belt will cause PWATS to increase above 1 inch
starting Wednesday and potentially remain that way until Sunday. The
highest values will be in the eastern CWA, but the majority of the
Tri-State area will have a good chance (70%+) at seeing PWATS above
1 inch. Throughout this active pattern, a high melting layer is also
expected, generally 11,000-15,000 feet agl.

Tuesday evening saw 2-3+ inches of rain in Cheyenne county Colorado,
and a few other locations in eastern Colorado. This rain did not
cause any flooding, but it will make it easier for flooding to occur
over the next few days. Locations that received heavy rainfall are
not fully primed for flooding (SAC-SMA soil saturation is around 30-
45% in these area), but will become susceptible to flooding sooner
than normal.

Based on what the CAMs are showing, the southern cluster of storms
would be a slower mover and larger in size, meaning based on its
projected path (south of I-70 across the CWA) and potential for
heavy rainfall, it will need to be watched closely for flash
flooding.

Thursday is currently the best day for training storms to create
heavy rainfall that could lead to rate-driven flash flooding and
duration-driven areal flooding. Friday and Saturday are also at risk
for flooding potential due to a combination of efficient rain
producing storms and potentially multiple days of heavy rain
saturating the soil.

Current confidence in localized flooding occurring through Saturday
is around 25-45%. Confidence in widespread flooding is about
20%.

&&

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

&&

$$

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