464
FXUS63 KLBF 161152
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
652 AM CDT Mon Jun 16 2025

.KEY MESSAGES...

- An Enhanced Risk for severe weather (level 3 of 5) is in place
  for Monday with a Slight Risk (level 2 of 5) now in effect
  for southwest Nebraska Tuesday.

- Heavy total rainfall appears likely late Monday through late Tuesday
  where probabilities of exceeding 1" of total rainfall exceed
  60%.

- Heat builds in later this week as probabilities for afternoon
  highs > 100F climb to the 70-100% range for Friday and
  Saturday.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 402 AM CDT Mon Jun 16 2025

Early this morning, scattered light showers continue to shift east
in the wake of expansive outflow from Sunday evening`s
thunderstorms. Any shower activity across the area will likely
subside towards daybreak and leave a dry forecast for the late
morning into early afternoon.

Monday...a modest surface low will track east across South Dakota.
This will drag an attendant cool front south into western Nebraska.
Fairly large variability is noted in placement of this boundary as
it stalls this afternoon. This has large implications on today`s
thunderstorm threat including severe weather. Expectation is for
this boundary to line up southwest to northeast near a North Platte
to O`Neill line. This closely resembles latest HREF/NAM output but
is further south than consecutive HRRR runs. This will likely be
something to watch closely over the next 12 hours with the resulting
PoPs forecast and placement of greatest magnitude of severe weather
hinging on it. Ahead of this front, persistent southerly flow will
usher in rich low-level moisture as dew points climb into the middle
to upper 60s prior to convective initiation. Westerly flow aloft
will maintain a modest EML with steep lapse rates overspread the
frontal boundary. As afternoon highs climb into the upper 80s to low
90s across the warm sector (only middle 80s behind the front across
the Sandhills), strong destabilization is likely to develop with
mixed-layer CAPE (MLCAPE) values climbing above 4000 j/kg. Though
the greatest mid-level flow appears to reside post frontal across
South Dakota, h5 flow nearing 20-30 knots will lead to an
increasingly sheared environment through the late afternoon with 0-
6km BWD values around 25-35 knots which will support multicell and
at least brief supercell storm modes. Forecast soundings depict
residual capping issues but suggests these should be overcome with
daytime heating by late afternoon. Storms should develop by late
afternoon along the boundary but with shear vectors largely parallel
to the firing boundary, storms should grow upscale fairly quick.
Even so, and especially if backed southeasterly flow can occur into
the frontal boundary, am concerned that there may be a small window
for large and even very large hail and perhaps a tornado or two as
some streamwise vorticity is apparent in the low levels. Analogs
also indicate fairly significant hail as much of the instability
resides above the freezing level with surface based Lifted Index
values nearing -10 to -15C. As storms grow upscale by late evening,
concerns then focus on damaging wind gusts and heavy rainfall in an
anomalously moist environment (PWATs nearing 125-150% of normal). As
has been the case the past few days, the background environment is
very supportive of strong outflow wind gusts as DCAPE exceeds 1200
j/kg and 0-3km max theta-e differences near -35C. Various high
resolution guidance shows fairly expansive updraft helicity swaths
in addition to significant winds at the surface, lending confidence
to the expected severe hazards. The latest Storm Prediction Center
outlook maintains the Enhanced Risk from near Alliance east through
the Highway 281 corridor between I-80/Highway 20. Have no qualms
with this but do suspect and southeast trend may be necessary.
Storms will likely rip along the frontal boundary and as it becomes
convectively reinforced, it should quickly progress south into
Kansas by late evening. The severe threat will likely subside by
Midnight tonight with only general showers and thunderstorms
persisting through early Tuesday morning. There`s some indication a
second round of strong to potentially severe thunderstorms may move
in late out of eastern Wyoming, but confidence in this is low at
this time.

Tuesday...with the surface front now displaced to the south,
easterly low-level flow will become established across the area.
Broad, moderate height falls will overspread the region as the
parent h5 trough crosses the central Rockies. As a secondary low
pressure center begins to form over the central and southern High
Plains, increasingly upslope moist flow will drive renewed rain and
thunderstorm development across southeast Wyoming. Though this is
typically a cooler weather setup, lingering steep lapse rates aloft
with daytime highs in the 70s and 80s should be enough to promote a
severe weather threat. Within this easterly flow, a moderate
instability gradient characterized by MLCAPE nearing 2000-3000 j/kg
will set up across northeast Colorado into far southwest Nebraska.
Strong orographic forcing will allow for scattered to widespread
rain and thunderstorm development. The HREF suggests strong to
severe convection as probabilities of exceeding 40kft Echo Tops nears
60-70%. Various high resolution guidance, particularly the HRRR,
shows a mature MCS diving east-southeast across western Nebraska.
With southeasterly flow at the surface and enhanced westerly flow
thanks to the passing shortwave, deep layer shear will again be more
than supportive of strong to severe thunderstorms. While not
displaying strong theta-e advection off the surface, a ribbon of
rich theta-e will extend from near CYS down through SYF. Do agree
with the SPC`s decision to upgrade the outlook to a Slight Risk.
Though the outlook displays equal outlooks for Hail and Wind,
believe winds will be the greater concern largely due to storm mode.
Expansive heavy rain will accompany this system as it moves off the
higher terrain with HREF probability matched-mean values showing
fairly expansive 0.50" or greater amounts across the area Tuesday
evening into early Wednesday. Cooler temperatures will follow the
rain and thunderstorms Wednesday morning with lows generally in the
50s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 402 AM CDT Mon Jun 16 2025

Wednesday and beyond...as the trough axis quickly shifts east
through the day Wednesday, strong height rises will fill in across
the region. This is due to amplifying ridging over the Great Basin.
This will foster a dry forecast which should largely remain in place
through the following weekend. As the ridge axis arrives onto the
Plains, h5 heights climb above 585 decameters which will top the
90th percentile in NAEFS climatology. At the same time, low and mid
level temperatures will climb with values from h85 through h5
exceeding the 90th percentile. ECWMF Extreme Forecast Index (EFI)
continues to advertise an anomalous heat wave for the area with
anomalies of 0.6-0.8 and non-zero Shift of Tails values. These
largely fall on Friday and Saturday where NBM probabilities daytime
highs exceeding 100F surpass 70% for much of the local area. The
resulting forecast ranges from 95 to 105F over the area which
closely resembles ECMWF/GFS output. These same solutions show
widespread upper 90s to lower triple digits for expected heat
indices both Friday and Saturday. Folks should be aware of the
expected heat and take adequate precautions to protect themselves if
necessary to be outdoors for extended periods of time. While ridging
will continue to amplify through the weekend, the ridge axis will
remain progressive and shift east to the Ohio Valley by Sunday.
Broad troughing will reestablish itself across the west and allow
for a reprieve from the heat. Though confidence in precise
temperatures on Sunday remains low, the expectation is for daytime
highs to fall back to the 80s or cooler by early next week. With
southwesterly flow aloft, recurring rain and thunderstorm chances
should dot the extended forecast. This generally resembles the
latest Climate Prediction Center outlooks which favor slight biases
towards above normal precipitation for both the 6-10 and 8-14 day
products.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 647 AM CDT Mon Jun 16 2025

Outside of convection, VFR conditions are expected. The main
concern will focus on afternoon and evening convection, some of
which could bring significant impacts to area terminals.

A frontal boundary will stall somewhere around a LBF to ANW line
later this afternoon. This will serve as the focus for vigorous
thunderstorm development in an environment supportive of
damaging wind gusts, large hail, and perhaps a tornado.
Similarly, heavy rainfall appears probable and various short-
term guidance suggests significant visibility restrictions under
stronger rain cores. Timing is perhaps the greatest uncertainty
with this, but believe that late evening arrival into LBF is
favored with VTN lagging by a few hours with weaker convection
from the west. Did include a +TSRA mention at LBF but limited
visibility impacts to 1SM for now as the strongest storms could
remain just east of the terminal. Will advise subsequent shifts
to closely monitor trends. Thereafter, believe a return to VFR
conditions is favored though the threat for MVFR cigs will need
monitored at either terminal.

&&

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

&&

$$

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