908
FXUS63 KLBF 151815
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
115 PM CDT Sun Jun 15 2025

.KEY MESSAGES...

- Strong to severe thunderstorms remain possible (~15%) each day Sunday
  through Tuesday.

- Expansive rain and thunderstorms Monday night through Tuesday night
  will likely lead to locally heavy rainfall with 40-60%
  potential of seeing 1" or greater rainfall.

- Well above normal temperatures will return by late week with
  probabilities of daytime highs exceeding 100F of 50% or
  greater south of Interstate 80.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 423 AM CDT Sun Jun 15 2025

Early this morning, a complex of thunderstorms was tracking along
the Nebraska/South Dakota border. This activity has been pulsey in
nature, meaning cores strengthen quickly then wane just as quick.
This activity was largely being driven by modest WAA within an area
of ~1000 j/kg MUCAPE. While some of the stronger cores may be
capable of small hail, severe weather is unlikely. The WAA will
persist as a modest LLJ extends southwest to northeast across
Nebraska. The nose of this feature will quickly point into southeast
South Dakota by late morning. This should allow any lingering rain
and thunderstorm chances to focus to our northeast. Currently, an
elongated outflow boundary stretches from near Johnstown southwest
through Mullen then southwest towards Sidney. Velocity data from
KLNX depicts a fairly impressive undular bore quickly progressing
southeast towards Thedford. This outflow boundary will likely stall
across the Sandhills, then lift back north through midday towards
the South Dakota border. This may serve as the focus for isolated
afternoon thunderstorm development. Recent runs of the NAM Nest have
been quite bullish in this thinking but believe this is quite a bit
overdone and a more reserved output similar to the HRRR is more
realistic. This suggests the outflow boundary settling south of the
Niobrara Valley but low-level convergence insufficient to break the
cap aloft with h7 and h85 temperatures in the low teens and middle
20s degC respectively. The Storm Prediction Center maintains a
Slight Risk (level 2 of 5) for the local area west of Highway 281.
As troughing builds into the Western CONUS, subtle height falls over
the central Rockies will draw up low-level moisture to the Front
Range. Forcing off the Laramie Range should allow for scattered
thunderstorm development again in the afternoon hours with h5
steering flow helping push activity east. With afternoon highs in
the middle 80s/lower 90s and dew points maintaining the low to
middle 60s, moderate to strong instability is likely to develop. NWP
guidance suggests SB/MU CAPE of 4500 j/kg or greater for areas along
and west of Highway 61. Southerly surface flow with west-
northwesterly h5 flow will support adequate deep-layer shear as BWD
values generally reach 30 to 40 knots. HREF suggests another late
evening arrival as neighborhood probabilities for dBZ > 40 not
arriving until after 01z (8pm CDT) tonight. Similar to previous
days, damaging winds appear to be the greatest concern. This is due
to inverted-v soundings with DCAPE values approaching 2000 j/kg and
0-3km max theta-e differences of nearly -40C. Believe this
translates to a greater wind gust magnitude potential and believe a
few gusts could approach 70+ mph for areas largely west of Highway
61. Stronger updrafts may allow for isolated large hail but believe
storm mode will limit this potential. Activity will likely progress
quickly west to east with weakening likely to occur closer to
Midnight. Some lingering showers and general thunderstorms may
persist through daybreak Monday, but confidence remains limited so
will monitor trends going forward.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 423 AM CDT Sun Jun 15 2025

Monday/Tuesday...active weather continues into Monday with the
threat for severe weather as well an increasing threat for more
expansive heavy rain across the area.

Height falls ramp up markedly by early Monday as a northern stream
shortwave enters the Dakotas. A modest low pressure system will form
over western South Dakota with an attendant cool front shifting
south into the local area. This may allow for a larger temperature
spread across the region but highs should still climb into the 80s
and 90s. As the larger scale trough enters the Great Basin, a more
pronounced shortwave will cross Wyoming and lead to lee-cyclogenesis
over eastern Colorado. Ahead of this, southerly flow will increase
as precipitable water values increase to 1.00"+, or near the 90th
percentile of NAEFS Climatology. Increased forcing from upper-level
dynamics will allow for widespread rain and thunderstorm development
during the late afternoon and evening. Severe weather again appears
to be on the table with moderate to strong instability though
overlap of instability and shear appears limited with the greatest
shear being north of the boundary. Recent trends have been to
decrease low-level moisture quality along the front with a focus
more to the east. Regardless of this, large hail and damaging winds
appear probable with any strong to severe storm. In addition to this
with the frontal boundary serving as a source of low-level
vorticity, will need to monitor the threat for a tornado or two
though this threat appears greatest to the east. Persistent
southwesterly flow with multiple PV anomalies tracking through
should allow for rounds of rain and thunderstorms across the region.
ECWMF Extreme Forecast Index (EFI) continues to advertise a fairly
anomalous heavy rain event with positive anomalies of 0.5-0.7 and
non-zero Shift of Tails (SoT). Recent EPS/GEFS runs show fairly high
confidence as respective each QPF output generally matches the other
in terms of magnitude and placement. Similarly, higher percentile
output from each ensemble solution generally matches each other with
only slight spatial and timing variations. The going forecast right
now suggests widespread 0.50"+ rainfall with locally heavier amounts
closer to 2.00" probable. NBM probabilities of 1" or greater
rainfall remains fairly high, 40-60% for central to eastern Nebraska
and probabilities of exceeding 2" near 30% for the same areas.
Coarse deterministic output, such as GFS and ECWMF, aligns well with
the the ensemble output though higher resolution guidance suggests
more spotty QPF and this is likely due to the convective nature of
the rainfall. Overall, many locations stand reasonable chances to
see measurable rain and wetting rains at that. With the surface
front expected to shift south towards I-70 by Tuesday, temperatures
will cool considerably with highs only in the 70s and 80s.

Wednesday and beyond...troughing is expected to clear the area by
early Wednesday morning. Behind the trough axis, heights will build
as ridging amplifies across the western CONUS. Height rises continue
through the day Wednesday right into Thursday as high pressure aloft
centers over the Four Corners region. EFI begins to show MaxT
anomalies as early as Thursday with values then approaching 0.8 in
our western zones on Friday. This coincides with anomalous
temperatures aloft which culminates with h7 temperatures reaching
NAEFS climatological maximum values by midday Friday. Based on
respective climatology`s, forecast high temperatures at North Platte
and Valentine exceed the 90th percentile for both sites and near
record territory for Friday. Following collaboration with
neighboring offices, opted to boost high temperatures in this period
to bolster messaging. Experimental Heat Risk values reach highlight
much of Nebraska in the Moderate to Major risk levels Friday and
Saturday. Folks should be aware of the coming heat, especially if
necessary to be outdoors for an extensive time. Forecast Heat
Indices touch Heat Advisory criteria (> 100F) Friday and approach
these levels on Saturday so should the current forecast stand,
headlines may be necessary later this week. Fortunately, the heat
appears unlikely to linger much into the following week as the next
deep trough exits the Pacific Northwest. Though uncertain on precise
details, ridge breakdown appears probable in the Sunday to Monday
time frame and this should allow for the heat to subside and return
some rain and thunderstorm potential to the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1249 PM CDT Sun Jun 15 2025

Expecting another round of thunderstorms to move eastward across
the area tonight. Storms will move into the Panhandle very late
this afternoon and then continue eastward through the evening.
Strong gusty winds are expected with the storms. Otherwise
expect VFR conditions to prevail across all of western and north
central Nebraska. Winds will be south to southeast at 10-20 kts
outside of any thunderstorm activity.


&&

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

&&

$$

SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Taylor