878
FXUS63 KLBF 060924
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
424 AM CDT Sun Jul 6 2025

.KEY MESSAGES...

- Strong to severe thunderstorms are probable each day Sunday
  and Monday with a Slight Risk (level 2 of 5) and an Enhanced
  Risk (level 3) in place for each respective day.

- Locally heavy rainfall is possible both Sunday and Monday with total
  rainfall amounts for the 48 hours of 1-2" likely across
  central Nebraska.

- Seasonable temperatures and recurring rain and thunderstorms
  chances continue through the extended forecast with the threat
  of severe weather returning on Thursday.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 424 AM CDT Sun Jul 6 2025

Early this morning, progressive outflow from Saturday evening
convection across western South Dakota was tracking south and east
into the Sandhills. This boundary was providing enough low-level
lift to overcome the stable low-levels and lead to scattered showers
and thunderstorms. A few storms, particularly near Valentine as of
0815z (315am CDT) were noticeably stronger and perhaps contained
some small hail but overall the threat for severe weather is low
with MUCAPE of around 1000 j/kg and lapse rates aloft fairly
marginal. Aloft, fairly zonal flow was in place as shortwave
troughing departed to the east into the Mississippi Valley and
another notable shortwave was apparent along the
Montana/Saskatchewan border. Placement and evolution of the low-
levels with respect to this outflow will have large implications on
how the threat for thunderstorms, including the threat for severe,
plays out today.

Sunday/Sunday Night...Early morning model guidance is already
struggling with placement and progression of outflow currently
located near a VTN to AIA line. This feature will continue to shift
south but will likely stall across the central Sandhills closer to
daybreak. This will result in a fairly notable spread in daytime
highs with upper 80s to low 90s across southwest Nebraska but only
upper 70s along the Nebraska/South Dakota border. Through the late
morning, surface winds will back to the south and then southeast
ahead of the boundary and this will maintain a ribbon of richer
moisture as dew points in the lower 60s persist within a relatively
narrow corridor. Warming temperatures in the mid-levels will promote
steepening lapse rates with magnitudes climbing to around 7.5-8.5
C/km. Within the narrow moisture tongue and as daytime temperatures
climb, moderate to strong instability will develop. As the shortwave
along the international border tracks east, enhanced mid-level flow
will overspread the Central and Northern Plains creating a strongly
sheared environment with ample instability. Latest Day 1 Storm
Prediction Center outlook maintains a Slight Risk (level 2 of 5) for
much of the area. A few flies in the ointment regarding the setup:


1) Outflow remains progressive and already appears to be further
south than what many CAMS suggest. This casts doubt on deterministic
solutions and taking their direct output as reliable.

2) Placement of eventual boundary stalling also remains somewhat
uncertain and could trim areas out of the severe threat should this
continue to shift south.

3) Recent trends have suggested that capping may not fully erode and
with fairly weak forcing in the warm sector, discrete storms may be
limited or not materialize whatsoever.

Given these lingering questions, have kept PoPs on the lower end
through the daytime Sunday. Should a storm develop this afternoon,
it`ll likely remain fairly discrete and all hazards of severe
weather will be in play with greatest concern being very large hail,
perhaps exceeding 2", damaging wind gusts of 70-80 mph, and a
tornado or two. It`s worth emphasizing this is likely the worst case
scenario and current confidence in this scenario materializing is
low. Later today though, within the southeasterly moist flow,
believe storms are more likely to develop off the topography to the
west of the forecast area. Reasonable theta-e advection off the
surface should fuel a complex of thunderstorms that quickly grow
upscale with merging cold pools. Given high DCAPE values focused
across southwest Nebraska, believe damaging winds gusts would be the
main concern. Given recent heavy rains from July 4th activity, did
briefly consider hoisting flood headlines in our southern zones.
Opted against this eventually as uncertainty with evolution of
storms today casts doubt on magnitude of rainfall amounts. On top of
that, storms should remain progressive and the threat for seeing
more than one round in the areas that saw heavy rain the other day
appears low. While a few locations could see 1-2" of rainfall from
activity tonight, belief is this will be rather spotty and not
present widespread issues warranting headlines. Storms should
quickly dive southeast into the strengthening LLJ. Believe most if
not all thunderstorm activity should exit the area around or shortly
after midnight.

Monday...a greater severe risk appears likely for tomorrow. Latest
SPC Day 2 Outlook has added an Enhanced Risk (level 3 of 5) for much
of the forecast area. Inherited PoPs from the model blend painted
extensive Chance (25-55%) and even Likely (55%+) categories across
the region. Following collaboration with neighboring offices, opted
to trim these up somewhat as the day is not anticipated to be a
"wash out". As northern stream troughing translates east, a surface
cool front will settle south into the area by late in the day.
Southerly flow ahead of this feature will reinforce low-level
moisture and push afternoon highs into the low to middle 80s. Timing
of this front appears to favor late afternoon and early evening into
our northwestern zones. While broad warm air advection storms appear
possible ahead of this feature, forcing will be maximized along this
boundary and therefore have highest PoPs later in the day. An
approaching mid-level speed max will interact with this frontal
boundary around peak heating as moderate to strong instability
develops. Flow aloft exceeding 30 knots will support a strongly
sheared environment with 0-6km BWD of 35 to 45 knots. Forecast
hodographs exhibit long straight hodographs initially, elongating
through the evening as LLJ increases. This significantly increases
low-level curvature and bolsters 0-3km to around 200 j/kg. Given
shear vectors largely orthogonal to the surface boundary, believe
discrete storms may be sustainable for a few hours into the evening.
This increases concern for very large hail (2"+), damaging wind
gusts approaching 75 mph, and a tornado or two. Eventually though,
with ample unstable air feeding into the frontal boundary, upscale
growth appears likely and a transition to primarily damaging winds
is probable. SPC`s Enhanced Risk outlook is mostly driven by the
damaging wind outlook and believe this is valid. Given strong
forcing and anomalous moisture quality, believe heavy rain is also
possible though confidence in magnitude of rainfall is limited at
this time. Storms once again should depart to the southeast around
or shortly after midnight leaving the remainder of the overnight dry
for the area.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 424 AM CDT Sun Jul 6 2025

Tuesday and beyond...temperatures are likely to climb towards the
middle of the week as upper ridging across the Desert Southwest
surpasses 595 decameters. Though this is fairly anomalous values for
the area, the warmer air appears likely to remain bottled up in
closer proximity to the feature. Northwesterly flow will overspread
the Central Plains through the middle of the week. Highs will climb
into the middle to upper 80s for Tuesday and upper 80s to middle 90s
for both Wednesday and Thursday. While precipitation chances will
continue for both Tuesday and Wednesday, greater probabilities will
come Thursday as ridge breakdown begins during the day with a
stronger disturbance tracking out of the Pacific Northwest. Given
the expected warmth and an approaching cool front, have higher-end
PoPs in the forecast with Chance and Likely categories (45-60%) in
place. The SPC also highlights a Day 5 Outlook encompassing our
northern zones. Outlooks for Day 5 from SPC are fairly uncommon for
the local area, with a quick look showing the area averages maybe
one or two instances of this occurring a year. Active weather
continues through the end of the week as broad troughing remains in
place across the northern Plains through Friday and Saturday. This
should help maintain cooler temperatures through the time frame.
Temperatures should moderate by the start of the following week,
however, as mid-level heights build and ridging strengthens once
again across the west coast.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 1225 AM CDT Sun Jul 6 2025

For the KLBF terminal: Expect mainly clear skies through mid
late morning Sunday with increasing high clouds around midday.
The threat for thunderstorms will increase mid afternoon with
severe storms possible from mid afternoon through early evening.
Wind gusts up to 45 KTS along with hail and visibilities down to
2SM are possible from 22z to 02z. Conditions will then improve
after mid evening with broken ceilings around 20000 FT AGL after
03z. For the KVTN terminal: There will be a minimal threat for
thunderstorms in the vicinity of the termial overnight, however
forecast confidence is minimal as the CAM model solutions
tonight are divergent in their solutions over the next 6 to 10
horus. The threat for thunderstorms should end towar daybreak
but then increase during the early afternoon hours. Beyond late
afternon, expect broken ceilings around 20000 FT AGL.

&&

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

&&

$$

SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Buttler