785
FXUS63 KGLD 200925
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
325 AM MDT Fri Sep 20 2024

.KEY MESSAGES...

- Briefly critical fire weather conditions are possible today in
  eastern Colorado.

- Showers and thunderstorms will develop over majority of the
  Tri-State area this weekend. Severe weather does not look
  likely, but there is a slight concern for flooding.

- Low temperatures in the mid to upper 30s are forecast for
  eastern Colorado by Monday morning.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 323 AM MDT Fri Sep 20 2024

This morning, a high pressure system over Texas is extending a ridge
over the Great Plains and Midwest. This will create mostly clear
skies for majority of the day, allowing temperatures to warm into
the low 90s. Winds will be south-southwesterly throughout the day.
In the far western CWA, around the Joes to Flagler, CO area, the
winds are expected to mix out surface moisture and drop RH values to
around 15% for a couple hours. The winds will have picked up at this
time and gusts around 25-30 kts are expected, briefly leading to
localized critical fire weather conditions. For more information,
see the fire weather section below.

Starting around 19-21Z this afternoon, a shortwave is forecast to
fire off some storms south of the CWA. Majority of this
precipitation will occur outside of the Goodland CWA, however, Gove,
Wichita, and Greeley counties could (~15% chance) see some light
showers late this afternoon. There is a low (~15%) chance that
lingering showers or sprinkles could last through the night in the
far eastern CWA. The best chance for showers over there would be
after 6Z Saturday.

Looking at isentropics, there is a well define moisture boundary at
315K around the 19-23Z timeframe near the Tri-State border. This
feature could set off an isolated storm or two this afternoon, but
confidence is only around 10-15% this will occur.

Overnight tonight, the pattern gets a bit more interesting as the
850mb LLJ will kick up to around 30 kts, moving Gulf moisture into
the area. A shortwave ridge will move back over the area, clearing
out the skies by morning. A low pressure system near the Four
Corners will be moving northeast to stir up the atmosphere
throughout the day Saturday. Lows look to drop into the low 50s in
the northwestern CWA where the winds will be weaker and skies will
be clear, but in the southeast, mid 60s are forecast where the cloud
cover will linger most of the night.

Saturday morning, the aforementioned low will be crossing over the
Rockies, but will extend a shortwave trough over the southern CWA to
cause some warm-front type showers. This shortwave will push out the
ridge from overnight, allowing clouds to form across a large portion
of the CWA. The shortwave will also cause a broad cold front to move
in from the northwest, shifting winds as it move in. The new
northerly winds and additional cloud cover look to bisect the area,
causing a fairly strong thermal gradient to setup. In the
northwestern CWA, temperatures will be capped in the lower to mid
70s, but southeast of the front, mid 80s are forecast.

Around 21Z Saturday, 500mb vorticity increases and begins moving
northward, indicating a start to the widespread forcing. This
forcing will cause showers and storms to form across majority of the
area with the precipitation lasting until Sunday morning. Severe
weather does not look likely (<5% chance) due to a lack of
instability, but deep shear and strong forcing could cause a storm
to over preform.

Saturday night, the low will move over the CWA causing widespread
precipitation. For more information about the rain, see the
hydrologic discussion below. Overnight lows will drop into the 40s.

Sunday morning and into the mid-day, the low will be moving out of
the area to the east-northeast. The following pressure rises will
cause the rain to cease in the west around 15Z with lingering
showers in the east likely until around 18-21Z. Northerly winds and
clouds will keep temperatures capped to the 50s for the area. The
skies are expected to clear in the evening, allowing efficient
overnight cooling.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 101 PM MDT Thu Sep 19 2024

For the extended period, the latest runs of the GFS/ECMWF both show
a cutoff 500mb set up in the Desert SW, allowing for NW flow aloft
initially. By midweek, amplified ridging occurs allowing for a
return to SW flow aloft, with the low still over the southwest
portion of the country. The two models do differ some on the
placement of the system during this time.

At the surface, high pressure will set up east of the area, with an
inverted trough over eastern Colorado. As the upper low swings south
through the Rockies on Mon-Tue, there is a 20-30% chance for rw/trw
to occur. Guidance has the pop chances out to the Highway 25
corridor, but should be focused closer to inverted trough although
it does shift a bit E/SE going into Tuesday. There is a weak
shortwave that could work into the upper ridge midweek, but after
the precip chances through Tuesday evening, the rest of the week is
mainly dry.

850 temps through Tuesday top off around +20c, increasing into the
20s midweek as the upper ridge becomes more assertive over the
Plains region. This will allow for a slow increasing temp trend, if
only by a few degrees from Monday`s to Friday`s highs.

For temps, the Tri State area will see mainly 70s for highs each
day. There could be some locales during the day Monday/Tuesday that
may only see the upper 60s. Tuesday`s numbers will be highly
dependent on how fast cloud cover breaks to allow mostly sunny skies
during the afternoon hours. Overnight lows will range mainly in the
40s each night, warmest areas east of Highway 25. Thursday night
could have low 50s stretch as far west as Highway 25, but cloud
cover/wind dependent.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1032 PM MDT Thu Sep 19 2024

VFR expected to prevail at both KGLD and KMCK through the TAF
period. Surface winds will be light tonight, increasing from the
southeast on Friday.

&&

.FIRE WEATHER...
Issued at 323 AM MDT Fri Sep 20 2024

This afternoon, in western Kit Carson and Yuma counties,
southwesterly winds are expected to pick up. Sustained winds around
15-20 kts with gusts up to 25-30 kts are expected. These winds will
work to mix in drier air, lowering RH values into the mid teens
across eastern Colorado. In the area mentioned above, local RH
values around 14% are expected for an hour or two. Widespread, long
duration critical fire weather conditions are not expected.

If the winds over perform and extremely dry air mixes down to the
surface, we could see some locations meet Red Flag criteria.
Confidence in the current forecast is moderate, around 60-70%,
meaning there is about a 30% chance three hours of critical fire
weather conditions could occur in the far western CWA.

&&

.HYDROLOGY...
Issued at 323 AM MDT Fri Sep 20 2024

An efficient 850mb LLJ is expected to set up around 21Z Friday-0Z
Saturday and continue until Sunday morning/mid-day. This LLJ will
provide a moist conveyor belt from the Gulf of Mexico into the High
Plains. As mentioned above, an organized low pressure system will
move into the region Saturday, creating a moderately strong forcing
mechanism to start precipitation.

Precipitation looks to start in the eastern CWA early Saturday
morning, intensifying Saturday afternoon, and begin weakening Sunday
morning/mid-day before moving out of the area by Sunday evening.
Between 21Z Saturday and 18Z Sunday, nearly the entire Tri-State
area will see at least a few tenths of rain with the potential
(~25%) of seeing 1.25+ inches in that timeframe. If the higher
amounts do occur, especially in the eastern CWA, there will be
increased flooding concerns. Concerns for flash flooding are low
(<10%) with the potential for areal or river flooding being slightly
higher at around 20%.

Throughout the entire event, locations along and southeast of a line
from Wallace, KS to Norton, KS can expect to see 0.9-1.6 inches of
rain, with pockets of 3+ inches being possible. Locations west and
north of that line will receive less precipitation, likely around
0.4-1 inch of rain, with some pockets up to 1.75 inches.

&&

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

&&

$$

SHORT TERM...CA
LONG TERM...JN
AVIATION...024
FIRE WEATHER...CA
HYDROLOGY...CA