963
FXUS63 KLBF 021125
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
625 AM CDT Sun Jun 2 2024

.KEY MESSAGES...

- Confidence continues to increase in thunderstorms producing
  significant damaging winds (75+ mph) and large hail (some >2"
  in diameter) across western and north central Nebraska late
  this afternoon and evening. A brief tornado or two will also
  be possible.

- A low confidence, but high impact corridor of wind driven
  significant hail will be possible this evening across western
  Nebraska, as initial supercells begin to grow upscale into a
  line.

- Thunderstorm chances persist into Monday and Tuesday, though
  the threat for severe weather appears low at this time. A lull
  in precipitation chances is then on tap as we head into
  midweek.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 405 AM CDT Sun Jun 2 2024

Currently, convection persists across portions of northern Nebraska
early this morning, in response to a broad southerly LLJ positioned
east of the Rockies across the High Plains. This is leading to
additional shower and thunderstorm development across portions
of northeast Colorado and the Nebraska Panhandle. Broad warm
advection persists this morning, with temperatures holding in
the low to middle 60s across the area.

For today, a potentially high impact severe weather episode is
possible across much of western and north central Nebraska. Aloft,
broad west-southwesterly flow prevails across much of the Plains,
with upper troughing established over northern Manitoba. This will
lead to broad, positive vorticity advection through the afternoon,
with a subtle shortwave trough embedded in the mean southwest flow
aloft, approaching the area by early this evening. At the surface, a
weak surface low will move northeastward across the Dakotas this
afternoon, dragging a dryline to near/just west of the HWY 61
corridor. Ahead of the dryline, broad southeasterly flow should
increase dewpoints into the middle 60s near/east of HWY 83 and as
high as low 60s dewpoints further west. As strong surface heating
commences through the afternoon, temperatures will climb into the
middle to upper 80s to the east of the dryline. This combination of
warming and moistening of the boundary layer and increasing
convergence along the aforementioned dryline should erode any
lingering CIN by mid-afternoon. Convection looks to initiate
primarily across the high terrain of the Laramie Range, moving east
with time late this afternoon. As this convection moves eastward
into western Nebraska, it will encounter much richer boundary layer
moisture in the largely uncapped airmass to the east of the dryline.
This should lead to rapid intensification, with an initial
supercellular storm mode for western Nebraska. Hodographs are
largely straight-line with height at least initially across
western/southwest Nebraska, with broad 35-40kt westerly H5 flow
aloft. Enough cyclonic curvature looks to exist in the lowest few
kilometers for right movers to dominate, though cannot completely
rule out a left split or two early on. These initial supercells look
to provide a threat for large to very large hail, with robust MLCAPE
2500-3000J/kg, very steep mid-level lapse rates, CAPE largely
distributed colder than 0C aloft, and mid-level storm relative wind
vectors favorable to both larger updrafts and limit hail embryo
seeding. That said, some weaknesses exist in the mid-levels of the
hodograph north of HWY 2, and could lead to a lesser hail threat
with northward extent.

As the aforementioned shortwave trough begins to overspread the
area, along with an approaching cool front, increasing forcing
for ascent should lead to gradual upscale growth, especially as
convection approaches and moves east of the HWY 83 corridor.
This leads to a low confidence, but potentially high impact
scenario for a corridor of significant wind driven hail, as
supercells begin to grow upscale. This potential will especially
be maximized on the southern end of any bowing segments, which
high-res guidance loosely paints somewhere in the vicinity of
the I-80 corridor late this evening. As supercells grow upscale
into clusters/bowing segments, the threat for significant
damaging winds looks to quickly increase across portions of
southwest into central and north central Nebraska. High- res
guidance continues to paint rather concerning signals for gusts
locally exceeding 80mph in the quick moving line as it
translates from west to east. Forecast soundings late this
evening support the higher end wind potential, with higher LCLs
above a very dry sub- cloud layer, dry adiabatic low level lapse
rates, and robust DCAPE values approaching 1500-2000J/kg. As
the low level jet strengthens by late evening, increasing low
level shear could lead to mesovortex production on the leading
edge of any bowing segments. Will have to watch the southern end
of the convective line should it maintain any supercell
characteristics as well, as this increasing low level shear
could locally enhance a brief tornado threat. As for failure
modes, will have to watch for the potential for outflow
outpacing any convective lines, though confidence in this
remains low for now.

Bottom line: Those with outdoor plans this evening should remain
weather aware, and confidence continues to increase in a swath of
potentially significant damaging winds and large hail across
much of southwest and central Nebraka this evening.

The line will quickly exit the area early tonight, with lesser
chances for and thunderstorms for the rest of the overnight period.
Additional chances for showers and thunderstorms will exist Monday
afternoon across the area, though confidence in the placement of
surface boundaries and associated corridors of higher instability
remain low confidence. Lesser deep layer shear should limit the
severe potential.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 405 AM CDT Sun Jun 2 2024

One more day of thunderstorm chances exists Tuesday as a cold front
sweeps through the area Tuesday afternoon, though again deep layer
shear and lesser instability should limit any widespread severe
weather threat. As we head into midweek, upper ridging begins to
amplify across the western CONUS, with heights rising locally. This
will lead to a lull in precipitation chances for Wednesday and
Thursday. Temperatures look to return to the upper 80s to low 90s
across southwest Nebraska on Wednesday as well. Confidence still
remains lowered for late week and into the weekend, primarily with
respect to the depth and positioning of a trough anchored across the
Great Lakes. Still, at least some potential for thunderstorms look
to return late week and into the weekend, as convection from the
high terrain should move into the area in the broad northwesterly
flow aloft.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 625 AM CDT Sun Jun 2 2024

A couple aviation weather concerns exist through the forecast
period for western and north central Nebraska terminals.
Scattered thunderstorms will continue to cross the Sandhills
this morning (through 14z or so) before fair conditions resume.
A more organized complex of storms is anticipated this evening,
likely taking the form of a line with high winds and heavy rain.
Gusts of 50+ kts and large hail are possible with the strongest
storms. In the meantime, ambient surface winds will gust to 20
kts from the south.

&&

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

&&

$$

SHORT TERM...Brown
LONG TERM...Brown
AVIATION...Snively