773
FXUS63 KGLD 191902
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
102 PM MDT Thu Sep 19 2024

.KEY MESSAGES...

- Thunderstorms confined to southeast CO and southwest KS could
  produce robust outflow that surges north toward the I-70
  corridor late Friday afternoon, resulting in an abrupt wind
  shift (from SW at 15-25 mph to S at 40-55 mph). Dangerous fire
  weather conditions and significant reductions in visibility
  assoc/w blowing dust would accompany such a wind shift, if
  present. Confidence is low that such a scenario will unfold.

- Showers and thunderstorms will develop over much, or all, of
  the Tri-State area this weekend as a potent upper level low
  tracks eastward across the Rockies and Central Plains. An
  instance of flash flooding or river flooding is possible,
  mainly Saturday afternoon through Sunday morning. Barring a
  significant change in the evolution of the upper wave, severe
  weather is unlikely in the Goodland CWA.

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

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 440 AM MDT Thu Sep 19 2024

Overview: A modest upper level ridge over the Southern Plains
will amplify and extend northward over the Central Plains today
and Friday. A potent upper level low stalled along the central-
southern California coast today-tonight will begin to track E
toward the Desert Southwest (Fri) and ENE toward the 4-Corners
(Fri night).

Today: Clear skies and unimpeded insolation assoc/w the
amplifying upper ridge over the region will foster dry
conditions. Modest cold advection /15-25 mph N-NW winds/ in the
wake of a weak cold frontal passage early this morning will
temper highs to some degree. Expect light/variable winds and
temperatures ranging from ~80-88F this afternoon, coolest in
northeast CO.

Friday: A modest, baggy lee cyclone will develop in the lee of
the Rockies during the aft-eve.. as upper level flow backs to
the SW and strengthens in advance of the aforementioned upper
low. Recent /00-06Z/ guidance indicates low-mid level flow
(winds from the surface to 10 KFT AGL) on the order of ~15-20
knots Friday afternoon.. suggesting SW winds on the order of
15-25 mph. Near-critical to locally critical fire weather
conditions are possible in eastern CO and adjacent KS-NE border
counties (mainly along/west of Hwy 27).. where deep vertical
mixing may yield very dry conditions (minimum RH readings ~10
percent). While isolated high-based convection cannot entirely
be ruled in far southern portions of the area (Greeley, Wichita,
Gove counties) where meager high-based instability may be
present during the late afternoon.. guidance continues to
indicate that diurnal convection will likely be relegated south
and east of the Goodland CWA. While convection itself may be
relegated to southeast CO and southwest KS.. simulated
reflectivity forecasts via recent runs of the HRRR and NAM NEST
suggest that said convection may produce robust outflow that
surges north toward the I-70 corridor during the late afternoon.
If such a scenario were to play out -- i.e. an abrupt
convective wind shift (from SW @ 15-25 mph to S @ 40-55 mph) in
the 22-02Z time frame -- dangerous fire weather conditions and
significant reductions in visibility assoc/w blowing dust would
both be `on the table`, especially along/south of I-70. Given
that this scenario highly depends upon specific aspects of
upstream convective development/coverage (in a weak forcing
regime, no less), confidence is quite low.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
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 /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 929 AM MDT Thu Sep 19 2024

With high pressure transitioning through the area during the
forecast period, VFR conditions are expected. Both terminals
(KGLD/KMCK) will see northerly winds around 10-20kts through
about 22z this afternoon, then becoming light/variable. By 07z
Friday, KGLD will see S/SE flow around 10kts. KMCK will see a
longer period of light/variable conditions, then becoming SE
around 10kts by 15z Friday.

&&

.HYDROLOGY...
Issued at 236 AM MDT Thu Sep 19 2024

An efficient 850mb LLJ is expected to start setting up around
21Z Friday and continue until Sunday morning. 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 Friday evening,
intensifying Saturday afternoon, and begin weakening Sunday
morning before moving out of the area by Sunday evening. Between
21Z Saturday and 12Z Sunday, nearly the entire Tri-State area
will see at least a couple tenths of rain with the potential
(~25%) of seeing 2+ 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 flooding being slightly
high at around 20%.

Throughout the entire event, locations along and northeast of a
line from Oakley, KS to Yuma, CO can expect to see 0.75-1.5
inches of rain, with pockets of 3+ inches being possible.
Locations southwest of that line will receive less
precipitation, likely in the 0.3-0.75 inches of rain.

&&

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

&&

$$

SHORT TERM...Vincent
LONG TERM...JN
AVIATION...JN
HYDROLOGY...CA