604
FXUS63 KGLD 230220
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
820 PM MDT Fri Aug 22 2025

.KEY MESSAGES...

- There is a marginal risk for severe storms this evening and
  possibly overnight generally north of Interstate 70 as showers
  and thunderstorms accompany a cold front. In addition, locally
  heavy rainfall leading to nuisance flooding is possible.

- Severe storms are possible Sunday afternoon and evening in the
  Kansas and Colorado border area.

- Rain chances and cooler weather are forecast to continue
  through most of the upcoming week.

&&

.UPDATE...
Issued at 810 PM MDT Fri Aug 22 2025

Corridor of instability continues to slowly slide south behind
the advancing cold front. Storm activity over NW KS has greatly
dissipated as the storms moved out ahead of the corridor into
the more stable air. To the north the corridor of instability is
over SW Nebraska. The storms have increased some in intensity as
they move through this instability. However midlevel lapse rates
are much lower, around 6C/km, which is preventing the storms
from becoming more intense.

Foresee the storm activity continuing to march southeast through
the rest of the evening. After midnight another upper level
short wave trough, currently over SE WY, should ignite another
round of storm activity over the northeast part of the forecast
area/bring storms in from the north-northwest. Due to mid level
lapse rates being unchanged from what they are now, and the
instability being less than what is currently available, am
anticipating storm intensity to be what is currently happening
if not less. This activity looks to slide southeast of the
forecast area before mid morning.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 1210 PM MDT Fri Aug 22 2025


A cold front is slowly sagging into the area from the northwest
where rain showers are already ongoing along the I-80 corridor;
an associated 500mb shortwave is also in place across southern
Wyoming along with a developing surface low across eastern Colorado.
As you can tell there are a ton of features at play in the next 24-
36 hours which will lead to a varying forecast of potential
outcomes. There is one thing for sure is that there will be
rainfall, but the overall coverage, amounts, and severe potential
are still in question unfortunately even at this range of the
forecast. The reason for this is due to so many variables at play
there is no one single deterministic or CAM that is handling the
current location of all of these features the best. With that said
this forecast is currently strictly ensemble based off of the ECMWF
at least for rainfall chances and the 15Z RAP as it is initializing
the current features the best.

Confidence is increasing in convection developing along the
Front Range and the Palmer Divide this afternoon aided by the
500mb jet and the low, the question is how far east will this
survive as this will depend on how the low evolves; a more
compact low will keep the bulk of the rainfall to the west and a
more elongated low which is currently developing should extend
the rainfall to the east quicker. Now comes into play the speed
of the front as well, as the front progresses to the south. An
axis of CAPE of 1500-2000 j/kg and 30-35 knots of shear will be
in play along the front as it progresses to the south which
should be after 23Z which will be our peak time for severe
weather this afternoon. There will be the potential for some
supercell structures in this environment with the main concern
for large hail residing along and north of Highway 36. The key
to our severe weather potential will be how widespread is the
rainfall which would limit overall instability due to competing
updrafts. Current thinking is that a window for severe weather
will be in place from 6pm-10pm MT then as we turn into more of
an upslope regime behind the front with northeasterly winds this
will help promote more showers and non severe storms;
confidence in that is around 60%.

Now is where the scenarios come into play, if the evening
storms and coverage of rainfall doesn`t come to fruition then as
we turn more into the upslope/isentropic enhanced regime
overnight the atmosphere won`t be as worked over and we may
have a severe threat with damaging winds and large hail
overnight as well, confidence in that scenario is around 25%.
There is also a scenario where very little to nothing happens
and the upslope flow leads to dense fog with the
climatologically favored northeast flow across the entire area
(15% chance.

An overall strong signal for a swath of 1-2 inches of rainfall is
seen in ECMWF ensembles which favors locales north of I-70. The RAP
is also showing strong isentropic lift across the I-70 corridor
overnight as well which would line up well with the timing of the
heavier signal of rainfall seen in the ECMWF ensemble; so will be
interesting to see if that area shifts to the south a little bit on
the 12Z run as the only run available for this package was the
06Z. Not overly concerned for flooding but wouldn`t be surprised
if there was an instance or two of nuisance flooding as PWATs
increase to 1.4-1.5 and Corfidi vectors range from 15-28 knots
which supports some training potential. It is worth noting that
at least the past two runs of the HREF suggest a 10% chance of
3+ inches of rainfall targeted west of Highway 59 across Yuma,
Kit Carson and Cheyenne counties in Colorado so there is some
support for locally heavier rainfall.

Finally into Saturday, guidance has trended a little cooler which
isn`t overly surprising as cloud cover may be entrenched across the
area for the majority of the day. The way Saturday plays out is
completely dependent on how the overnight hours pan out. HRRR
suggests another 500mb trough moving through the area after 12Z
Saturday morning which if we are limited on storm chances
tonight may lead to a severe threat in the morning should this
materialize. RAP and NAM indicate a much weak wave but would be
the focus for the next round of precipitation with the chances
increasing south of I70 as it interacts with the front which
appears to stall out. A brief reprieve of precipitation may
occur NW to SE across the area during the late afternoon hours
through the evening as some drier air again pushes in. Saturday
night 850mb upslope flow again returns to the area increasing
rainfall chances for the area.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 1253 PM MDT Fri Aug 22 2025

Starting the extended period, Sunday and Monday at this time appears
to be the relative highest chance for rainfall for the area as the
upper level ridge that has been across the area for the past several
days shifts to the west and eventually breaks down. Severe weather
may be possible each day, but at this time Sunday appears to be more
favorable as bulk shear significantly increases to 35-50 knots
due to a developing surface low across eastern Colorado which
will also push some warmer air back into western portions of the
area due to downsloping winds. A surface high will be in place
across eastern portions of the area keeping showers and some
embedded storms in place but limiting any severe potential over
that way; the key question that will need to be resolved is how
far west will that feature set up which will limit the coverage
of severe weather potential during the afternoon. A better wave
comes off of the mountains during the late afternoon/evening
hours Sunday leading to a potential MCS developing. Increasing
PWATS to 1.7 and slower storm motions will then lead to an
increasing concern for flooding especially for any areas that
receive heavy rainfall or multiple rounds of rainfall over the
next few days. Rainfall is then forecast to continue through the
morning hours on Monday before ending. Additional rainfall may
occur during the afternoon and evening hours due to the
continued upslope flow but the better forcing will lie south of
the area.

Tuesday and through the remainder of the week, monsoonal flow
continues to feed into the Rockies as we see more waves from a
trough off of the western coast leading to the continued chances for
showers and storms. Surface high pressure across the Midwest stalls
out and continues to keep the cooler air in place. Temperatures may
need to be raised a little especially across western portions
of the area if subtle surface lows are able to develop which
will again bring in downsloping winds occur; at this range that
signal is so minute that being able to pick out a specific day
is unreasonable so will leave the forecast as is for now.
Towards the latter portion of the week the high pressure slowly
pushes to the east allowing the area to warm back up some into
the 80s but would not be surprised if our active pattern
continues as a more progressive upper air pattern ensues.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 545 PM MDT Fri Aug 22 2025

VFR clouds associated with a front and upstream showers and
thunderstorms are advancing on the area as of 5:40 pm MT/23:45z.
These clusters of showers and thunderstorms are poised to
affect MCK tonight, perhaps GLD. The best estimate for both
terminals is reflected in the TAFs, but may require some
adjustments pending trends. Guidance shows the potential for
another batch of showers and thunderstorms sometime Saturday
morning and/or afternoon; will need further assess this scenario
for upcoming TAFs.

&&

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

&&

$$

UPDATE...JTL
SHORT TERM...Trigg
LONG TERM...Trigg
AVIATION...Satterwhite