209
FXUS63 KGLD 210855
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
255 AM MDT Sat Sep 21 2024

.KEY MESSAGES...

- Showers and thunderstorms will develop over majority of the
  Tri-State area this weekend. Both severe weather and flooding
  chances are very low (<5%).

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

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 218 PM MDT Fri Sep 20 2024

Current observations continue to show some streaks of mid-
level moisture streaming from the southwest with storms
developing in Southwestern Kansas. The Tri-State area is more in
a dry streak which is keeping cloud cover and precip chances
low. There should be some sprinkles and showers for Greeley,
Wichita, Logan, and Gove counties, but not anything that should
be impactful. This evening and tonight, skies should clear out
with the moisture stream shifting more east/south. Winds should
lower to around 10 mph. Even with the clearing skies and
lowering winds, lows are forecast to remain fairly warm in the
50`s and 60`s as the southeasterly flow across a majority of the
area has brough dewpoints in the 50`s and 60`s to the area.

Tomorrow, the upper low currently near the CA/NV border is
forecast to shift east to near the Four Corners region during
the day. This will help push a surface cold front through the
area during the morning. With the frontal passage, winds will
strengthen to 20-25 mph with gusts up to 35 mph and bring in
some cooler and drier air to the area. Meanwhile, additional
mid-level moisture is forecast to stream in from the northwest
and help saturate the air column. The issue is that by the time
the air saturates, the front is forecast to be in the southern
part of the area. This will limit the better rainfall to the far
southern portions of the area. So for most of the area,
temperatures would likely peak around the noon hour, and then
remain steady or cool as cloud cover increase and colder air
advects in from the north. Rain looks to be limited through the
afternoon except for far southern portions of the area.

For the evening and overnight hours, the upper low is forecast
to begin swinging through the region. This will provide some
upper level support for showers and storms to develop along the
higher terrain in Eastern Colorado. Showers and storms should
then move through across the area with the saturated air unless
the higher pressure can move in quickly and undercut storms.
Once this line moves through the area, precipitation chances and
amounts are forecast to drop off as subsidence begins to take
over and drier air is forecast to move in the mid-levels.

Sunday, a dreary day is forecast as the lower levels remain
saturated and allow for fog and mist to develop. With the cooler
air and persistent cloud cover, highs are forecast to only be a
few degrees warmer than the lows in the 50`s. Temperatures may
end up being dictated by how low/high the dewpoints are. Winds
are forecast to slowly lower through the day as the higher
pressure moves over the area. The evening and overnight hours
are forecast to see skies slowly clear as the upper low pushes
east of the area and drier air moves in. This could cause a
potential issues where parts of Eastern Colorado could hit 36
degree or less for the first time this season. Looks to be
dependent on how low the dewpoints will get with clear skies and
light winds.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 245 AM MDT Sat Sep 21 2024

Monday: Guidance suggests that troughing/cyclonic flow aloft
will persist over the Central Plains.. on the eastern fringe of
an amplifying upper level ridge along the Pacific Coast. Clear
skies in the wake of the departing wave may eventually give way
to increasing cloud cover late Mon-Mon night.. via cyclonic
shear vorticity on the eastern periphery of a strong (~100-115
knot) northerly upper level jet extending southward from Alberta
and Saskatchewan to the central Rockies. Sunny skies during the
day will foster a warming trend. Expect temperatures warmer
than Sunday (albeit still cooler than average).. ranging from
the mid 60s (east) to mid 70s (west).

Tuesday-Friday: Below average forecast confidence. Forecast
confidence typically decreases with range -- `below average` in
this context is intended to communicate a further reduction in
confidence associated with /inherent to/ increased pattern
complexity -- e.g. patterns with cut-off waves, multibranched
wave interactions and potentially significant forms of
constructive/destructive interference or feedback.

Solutions from current operational runs of the GFS/ECMWF
continue to diverge on Tuesday.. albeit less-so than yesterday.
Both models suggest that [1] the aforementioned ridge will shift
eastward across the Intermountain West (Tue), Rockies (Wed),
Central/Northern Plains (Thu) and Mississippi River Valley
(Fri).. [2] that some degree of northern and southern stream jet
phasing (or interaction) within a complex split flow regime on
the eastern periphery of the advancing ridge will foster the
development of a closed low and [3] that said low will be
subsumed by /trapped within, cut-off beneath/ the ridge. The
ECMWF suggests that upper low development and subsumption will
occur over the Central-Southern Plains.. the GFS suggests it
will occur over the OH Valley. Steering the forecast toward
climatology appears to be the most prudent course of action at
this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1036 PM MDT Fri Sep 20 2024

VFR expected to prevail at both KGLD and KMCK through the TAF
period. A cold front will shift winds to the northwest then
northeast early Saturday morning, gusty through the afternoon.
Some showers may begin to move into the area towards the end of
the TAF period Saturday night, but with minimal, if any,
impacts.

&&

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

The forecast continues to call for precipitation this weekend
with the low levels becoming saturated through low level
moisture advection from the southeast and mid-level advection
from the southwest.

However, forecast amounts continue to trend down as the best
forcing does not appear to line up with when the air is most
saturated. The front is forecast to move through early Saturday
before the air can saturate. The best chance for rain during the
day Saturday is for southern parts of the area as the front
passes. Rainfall amounts and chances will be better if the front
stalls in the southern portion of the area. The next good chance
for rain is overnight Saturday into Sunday as the upper low
swings through and brings a chance for showers and storms off
the higher terrain in Eastern Colorado. However, a mid-level
dryslot may interfere with this round and weaken chances.

Amounts around a quarter of an inch or less are suggested with
this kind of a setup for the whole event. If the forcing and
moisture align better, than amounts of one to two inches become
more likely, especially if the front stays over southern parts
of the area. Flooding looks to be possible in scenarios where
the front over performs and produces a couple of inches early,
mainly from Wallace, KS to Norton, KS and south. Overall chance
is around 5 to 10%.

&&

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

&&

$$

SHORT TERM...KAK
LONG TERM...Vincent
AVIATION...024
HYDROLOGY...KAK