491
FXUS63 KLBF 182327
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
627 PM CDT Thu Jul 18 2024

.KEY MESSAGES...

- Periodic thunderstorm chances through Monday, including isolated
strong/severe storms this evening in the west and more widespread
activity tomorrow with an even greater wind risk

- Seasonable temps tomorrow, then a dip into mild territory (70s
  for highs) this weekend before rebounding to summerlike
  conditions midweek

&&

.SYNOPSIS...
Issued at 353 PM CDT Thu Jul 18 2024

Western Nebraska lies between the Rockies amplified upper ridge and
the Great Lakes trough, resulting in broad northwest flow aloft.
Toward the surface, the high pressure center has moved east toward
the Upper Midwest and a trough stretches along the Front Range. Per
20z sfc obs, a tongue of slightly better moisture shown by dew
points in the lower 60s roughly lines up the Hwy 83 corridor, as
opposed to mid/upper 50s to the west. A couple cumulus fields have
developed this afternoon, with one over north central Neb and the
other along the KS border. A light southerly breeze helped push
highs into the upper 80s across the west and lower/mid 80s east.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 353 PM CDT Thu Jul 18 2024

This evening into tonight... The main forecast concern revolves
around thunder potential, primarily for western Nebraska (near and
west of Hwy 83). Initiation is underway along the higher terrain in
WY/CO, and will need to monitor that activity as it slowly pushes
east toward the Neb panhandle. Near term CAMS guidance diverges on
overall coverage and intensity of thunder in the CWA. Some solutions
suggest isolated convective activity focused near the Pine Ridge and
the CO/NE/KS border areas. Other guidance suggests more scattered
activity across the western half of the CWA. Went ahead and
broadbrushed schc (20%) PoP along/west of Hwy 83 from 00-06z.
Thinking the lack of defined surface forcing, and mid-level
shortwave for that matter, should keep coverage fairly isolated, but
did not want to just focus on two confined distinct areas. As for
severe potential, agree with SPC assessment of marginal risk. The
relatively greater parameters are west of Hwy 83, including mid-
level lapse rates of 7+ C/km, 30-35 kts of deep layer shear, and
1000+ j/kg MLCAPE. Moisture seems to be lacking somewhat in the
lower levels though, and forecast soundings show an inverted-V esque
profile. Given the borderline shear magnitude for supercells and
DCAPE equal to MLCAPE, strong winds will be the main threat.
Overnight, a low level jet develops over the High Plains and quickly
redirects toward central and eastern Neb. Remaining moisture
convergence and the added wind shear may be enough to kick off new
activity over north central Neb heading into the early daylight
hours. Cannot completely rule out hail with that activity.

Tomorrow and tomorrow night... A potentially more volatile setup
will affect the forecast area, consisting of the surface trough
(cold front?) passage coinciding with a stout mid-level shortwave.
The prefrontal H85 thermal ridge will push temps above 20C in the
Sandhills, roughly 2-3C warmer than today. Blended in some warmer
guidance for max temps using NBM 75%ile and MAV, resulting in mid
80s north central to lower 90s southwest. Betting on early sunshine
and decent southerly flow to achieve these values as new convective
initiation may be earlier than typical late afternoon or evening
setups. Most CAMS are honing in around 18z for development near the
Pine Ridge and quickly overspreading the Sandhills through 00z and
exiting the CWA by 03z. Increasing shear and ample instability
should support organized convection, some of which likely reaching
severe levels. Forecast soundings seem to quickly transition from
profiles conducive for supercells to more linear modes as fat CAPE
in the mid levels give way to skinny CAPE and nearly unidirectional
flow in the low levels. Remnant showers or storms are possible for
central Nebraska overnight in the vicinity of the upper level
wave.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 353 PM CDT Thu Jul 18 2024

The Western US upper ridge amplifies further this weekend, resulting
in nearly meridional flow over Nebraska as a low attempts to close
over Iowa. The general synoptic pattern remains in place through
midweek with the quasi-low drifting into the Great Lakes and the
ridge expanding in the west. At the surface, high pressure builds in
the wake of tomorrow`s front. However, cooler temps aloft in the
vicinity of the upper low combined with differential heating at the
surface may spark scattered showers and storms early in the week.
Long range guidance trends drier and warmer midweek for Nebraska
with highs gradually returning to the mid/upper 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 627 PM CDT Thu Jul 18 2024

VFR conditions are expected tonight through Friday morning at
the KLBF and KVTN terminals. Scattered thunderstorms will
develop across northern Nebraska by 18Z and track southeast
during the afternoon. Storms may affect the KVTN terminal after
18Z, with a tempo from 18Z-21Z for 5SM -TSRA BKN070CB. At KLBF,
storms may affect the terminal 21Z-24Z. Timing and intensity of
the storms will continue to be adjusted if needed.

&&

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

&&

$$

SYNOPSIS...Snively
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Roberg