137
FXUS63 KLBF 160939 CCA
AFDLBF

Area Forecast Discussion National Weather Service North Platte NE
421 AM CDT Mon Sep 16 2024

.KEY MESSAGES...

- Windy (30+ mph) conditions today and Tuesday ahead of a potent
system  pushing inland across the western US.

- A cold front will bring increased precipitation chances  (40-70%+)
Tuesday night into Wednesday, with a threat for   severe wind gusts
for areas generally along and west of   Highway 83.

- High confidence (>90%) in above normal temperatures through  the
week ahead of a pattern change this weekend with cooler temperatures
and a secondary threat for precipitation.

&&

.SYNOPSIS...
Issued at 413 AM CDT Mon Sep 16 2024

Recent GOES-16 WV Imagery and RAP 500-mb analysis showed a Rex block
pattern across the eastern US with a large ridge of high pressure
centered over the mid-Atlantic to the north of a closed low pressure
system across the southeast. Across the western US, a deep trough of
low pressure was digging southward into northern California. All of
these features combined has resulted in southwesterly flow aloft
across western and north central Nebraska. A robust shortwave was
moving northeastward across eastern South Dakota which resulted in
showers and thunderstorms across the Sandhills overnight. Additional
scattered shower and thunderstorm activity has begun to develop
early this morning across northern Kansas into south central
Nebraska as a result of weak mid-level convergence on the eastern
edge of an increased lower-level jet (LLJ). As of 4 AM CT,
temperatures ranged from 57 degrees at Imperial to 72 degrees at
Valentine.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 413 AM CDT Mon Sep 16 2024

Today and Tonight...The aforementioned early morning activity
currently developing is expected to orient itself along a north-
south corridor east of Highway 183, waning through the early
afternoon. At most these showers and thunderstorms may produce some
gusty winds with hit-or-miss precipitation amounts of 0.5" or less.
Outside of this, dry conditions are expected across the local area
today. Surface high pressure will continue to hold strong across the
eastern half of the US with a surface trough of low pressure
deepening across eastern Wyoming into eastern Colorado.
Southeasterly flow ahead of the surface trough will amplify with a
tightened surface pressure gradient (SPG) between the two surface
features. As a result, southeasterly winds will increase with
widespread gusts up to 35 mph and locally higher gusts up to 40 mph
across northern Nebraska. High temperatures will warm into the above
normal range from the mid-80s to low-90s. Although low level
moisture will be prevalent across the area, limiting overall fire
weather concerns, any fire starts could spread quickly given the
gusty winds. Another shortwave ejecting northeastward across the
central Rockies combined with increased mid-level warm air advection
(WAA) and a strengthening LLJ will present another opportunity for
elevated shower and thunderstorm development late this
evening/overnight. Thanks to the LLJ, gusty winds up to 35 mph will
persist through the overnight period.

Tuesday...Similar conditions as compared to today will be on tap for
the area on Tuesday as the strong upper-level trough tracks
northeastward into the Great Basin on Tuesday with continued
amplified low-level flow. As the SPG tightens even further
(~15+ mb gradient across the state), widespread southeasterly
wind gusts will peak near 40 during the day on Tuesday. When
looking at recent NBM Probabilities, an overwhelming 75%+ chance
of wind gusts of 30 mph or greater exists across all of western
and north central Nebraska. However, when looking at
probability of wind gusts exceeding 40 mph, probabilities drop
to 30% or less across much of the area though pockets up to 60%
exist across northern and southwestern Nebraska. Given this,
locally higher gusts up to 45 mph cannot be ruled out for
portions of northern and southwestern Nebraska. Daytime
temperatures warm into the upper-80s mid-90s which is 15 to 20
degrees above normal for the middle of September. Dry conditions
are expected through the day ahead of an approaching cold front
which will bring an increased threat for precipitation Tuesday
night into Wednesday. &&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 413 AM CDT Mon Sep 16 2024

Tuesday Night and Wednesday...By Tuesday night, a strong negatively
tilted shortwave will lift into the northern Rockies and northern
Plains with strong lee-cyclogenesis across far northeast Wyoming and
southeast Montana, driven by mid-level height falls and upper-level
divergence. This will force a cold front to advance west to east
across the area. At the same time, a strong (40+kts) southwesterly
LLJ will ramp up over the northern Plains. Not only will the LLJ
support continued breezy winds through the night, it will also help
aid in the development of scattered to widespread shower and
thunderstorm development along and ahead of the frontal boundary.
Buoyancy will lack across the local area with more favorable
low-level moisture and mid-level lapse rates residing much
further north across Montana and North Dakota. Recent forecast
soundings show deep mixing and an inverted-v profile with DCAPE
values of 1,000-1,500 J/kg present across the area, suggesting
that strong to severe wind gusts will be the primary concern
with this activity. Convective initiation is expected to begin
across the higher terrain of Wyoming and Colorado forming
clusters of thunderstorms, tracking west to east across western
and north central Nebraska beginning around 00Z. Greatest severe
threat timing is from 6 PM to 3 AM CT with storms exiting the
area through sunrise on Wednesday. When looking at
precipitation totals, NBM Probabilities indicate a 40 to 60%
chance or greater for 24 hour (12Z Tue through 12Z Wed) 0.25"+
liquid equivalent precipitation across all of western and north
central Nebraska. Fortunately we will get another shot at
widespread meaningful precipitation as we head into the latter
end of the week into the weekend. The frontal boundary will also
bring an end to the gusty winds for Wednesday as the low-level
flow relaxes.

Thursday and beyond...The upper-level shortwave exiting into
Canada will be replaced by another trough of low pressure that
will drop southward across the west coast, pushing inland across
the Desert Southwest on Thursday. Additional frontal boundaries
advance through western and north central Nebraska through the
weekend resulting in unsettled conditions continuing and
ushering in cooler temperatures, falling into the 70s by
Saturday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1212 AM CDT Mon Sep 16 2024

There will be a limited threat for isolated thunderstorms into
the overnight hours mainly over northern and northwestern
Nebraska. There is a minor threat for thunderstorms in the
vicinity of the KVTN terminal through 10z overnight. Otherwise,
expect scattered high clouds to persist into the morning hours
on Monday. There is a secondary threat for thunderstorms Monday
evening, however at this time, the main threat is expected to be
off to the east of the KLBF and KVTN terminals. With low
forecast confidence in any storms impacting the terminals Monday
evening, will forgo mention in the 06z TAF forecasts. Winds
will be gusty from the south on Monday into Monday evening with
gusts reaching around 30 KTS for both terminals.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Buttler