375
FXUS63 KLBF 180610
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
110 AM CDT Tue Jun 18 2024

.KEY MESSAGES...

- Thunderstorms this afternoon and into the overnight will lead
  to an increasing threat for severe weather, with very large
  hail, damaging wind, and isolated tornadoes.

- The redevelopment of heavy rainfall this evening and overnight across
  north central Nebraska could lead to an increased threat of
  flooding where heavy rains fell last night.

- ECMWF EFI values point to an unusually cool day relative to the
  M- Climate on Wednesday. There is nearly a 30% chance that
  high temperatures remain at or below 65F in North Platte.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 357 PM CDT Mon Jun 17 2024

Latest analysis from 20z shows that the warm front has been slow to
lift north, this is due to abundant stratus remaining across the
Sandhills and north central Nebraska.  To the south, temperatures
have warmed into the lower 90s across far southwest Nebraska, but
still hang in the upper 70s and lower 80s along I80 in Lincoln
County.  Looking regionally, very little developed cumulus is noted,
though there are signs of increased agitation across southeastern
Colorado and High County of the central Rockies.  Overnight there
was an abundance of heavy precipitation across north central
Nebraska with widespread reports of 3" or greater from eastern
Cherry to Keya Paha County.  The flood advisories that were out for
much of the day have been allowed to expire.  A special thanks to
the NSSL group who gave us an early look at their 19z sounding. As
expected with the delayed burnoff of the stratus, the capping
inversion is quite strong near LBF.

Uncertainty is the word of the day with the CAMs very bearish on the
severe potential for later this afternoon and evening, though the
environment would suggest otherwise.  Looking aloft, southwesterly
flow prevails, which is currently ushering increasing PVA as noted
by the developing CU over SE Colorado. Cyclogenesis has ensued over
the High Plains and subjectively now sits over far NE Colorado or
south of KOGA, near Grant. Southeasterly flow at the surface has
ushered TDs into the lower 70s as far north at KBBW and KLBF with
mid 60s as far west as the Highway 61 corridor.  The warm front is
subjectively north of KLXN, but not as far as KBBW.  Steep lapse
rates along the front are contributing to nearly 4k MLCAPE where
moisture is pooling just south of the boundary.  HRRR soundings
reveal an uncapped solution, but we know that is not the case,
especially north where substantial CIN remains.  That being said, we
believe with the increasing upper level support, isolated to
scattered severe storms will form eventually, which will be in the
vicinity of the lifting warm front and sfc low.

Once CI occurs, the environment will be very supportive of rotating
updrafts, which given the current situation, the Sandhills looks
prime, with the latest soundings indicating near pure streamwise
vorticity in the lowest few KMs of the hodograph.  This is due to a
strengthening low level jet as evening progresses.  With
southwesterly flow in the mid levels, hodographs will be quite long
which would point to all hazards with any supercell that develops,
though south of the boundary, large hail/wind will be the primary
concerns.  As sunset occurs, increasing CIN would lead to elevated
storms with the concern being hail, wind, and heavy rainfall.

The storms should weaken as nightfall arrives, but if storms
maintain into north central Nebraska and/or eastern Cherry County,
will need to monitor for flooding as heavy rainfall occurred last
night.  Lastly, mechanical mixing will allow for gusts of 40-45 mph
overnight south of the lifting front.

A cold front slides across the area tonight and tomorrow, but
remains a focus for storms Tuesday afternoon.  At this point, most
of the activity will be east of the forecast area, but locations
along and east of a Frontier to Custer to Eastern Holt County could
see additional storms.  Otherwise temperatures will be cooler in a
post frontal regime tomorrow afternoon with highs largely in the
70s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 357 PM CDT Mon Jun 17 2024

A cold front is projected to be east of the area by the start of the
forecast period, though additional showers and storms are possible
as convection forms on a mid-level area of convergence. The area of
concern would be from Hayes County northeast through Custer, Wheeler
and eastern Holt Counties, though the heaviest QPF is expected to be
just outside of the forecast area.

A post frontal regime will usher in unseasonably cool temperatures
mid-week.  The latest guidance suggest widespread 60s to lower 70s
across the entirety of the forecast area.  Climatologically, highs
on Wednesday will run some 10-20 degrees below normal.  The threat
for light showers continue, though continues to have highest chances
to the east.

Deeper low level moisture returns Wednesday night with easterly
upslope flow projected.  WAA spreading from the west may aid in the
continuation of precipitation /thunderstorms/ well into Thursday
morning.  The return of southerly flow late week and early next
weekend will keep the atmosphere unsettled with daily chances for
QPF, though late Saturday into Sunday, coverage looks less
promising.  Severe weather, at least isolated coverage, would be
possible as the the pattern switches from southwesterly to
northwesterly aloft.  Building heights from a central Rockies dome
of high pressure and decreasing cloud coverage would allow a return
to above normal temperatures early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 105 AM CDT Tue Jun 18 2024

The primary concern this TAF period will be strong southerly
winds gusting at or above 40kt along with low level wind shear
through the first part of the valid period. A cold front will
push through TAF sites toward daybreak and push the axis of the
low level jet eastward, shifting winds to the northwest and ending
the low level wind shear. While winds behind the front will
still be gusty for a while, speeds will gradually relax behind
the front through the afternoon.

Flight conditions will be VFR except for a couple of hours
either side of the frontal passage as a band of clouds moves
through with the front. KVTN will see CIGs on the lower side of
MVFR but the best potential for IFR is just to the north in
South Dakota. KLBF will be on the low side of VFR with
probabilistic guidance indicating only a 30 percent chance for
sub-VFR conditions. Will monitor sky trends closely and amend
if needed before the new TAF issuance at 12Z.

There may be some widely scattered showers with the frontal
passage, along with potential for some diurnal convection later
this afternoon. However indications are that the coverage will
be quite sparse so will maintain dry conditions this valid
period and amend if trends in radar or surface observations
begin to favor more coverage of precipitation.


&&

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

&&

$$

SHORT TERM...Jacobs
LONG TERM...Jacobs
AVIATION...MBS