874
FXUS63 KLBF 132359
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
659 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Recurring chances for rain and thunderstorms are likely with strong
  to severe thunderstorms possible Friday and Saturday.

- Some uncertainty remains but more severe weather is possible
  on Sunday.

- Fairly active pattern continues into next week but confidence
  in temperatures is low at this time.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 346 PM CDT Thu Jun 13 2024

Mid-afternoon surface analysis depicts much of the area in general
east-northeasterly flow behind a cool front that passed early this
morning. This helped bring a swift end to the heat that was observed
Wednesday and the quick progression with cooler air filtering in
behind has held afternoon highs into the low 80s with locations
south of Interstate 80 still managing near 90 degF.

Surface high pressure will shift east across the Red River Valley of
the north. Low-level fetch will originate from this source through
late today which is supportive of the cooler temperatures. Flow will
continue to veer to easterly by late afternoon which will help drive
the formating of rain and thunderstorms off the Front Range to the
west. With the effective front well to the south, the bulk of any
instability will be removed to the south and this is where the Storm
Prediction Center (SPC) has placed their latest Day 1 Marginal Risk
(level 1 of 5). This outlook clips our far southwest corner but
confidence in seeing a notable thunderstorm potential, much
less severe threat, is low. HREF probabilities are quite low
with ensemble max QPF output showing less than 0.10" anywhere in
our forecast area. This is likely due to the fact that the
local environment is fairly hostile to convection with
significant capping thanks in part to h85 and h7 temperatures in
the low 20s and middle teens degC respectively. As temperatures
cool this evening, low-level capping will only increase which
should help keep most if not all locations dry. Lows tonight
should fall into the upper 50s to low 60s.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 346 PM CDT Thu Jun 13 2024

Friday and Saturday...likely the more noteworthy period of time in
the forecast period. Upper-level ridge of high pressure to the south
will slowly shift east with upper ridge axis approaching western
Nebraska by early Friday morning. A disturbance will track into the
Desert Southwest and carve its way through the ridge aloft. This
will prompt ridge breakdown during the day Friday. Southerly flow
will enhance ahead of this feature as low pressure begins to develop
across central Wyoming. This stronger flow will help usher in richer
boundary layer moisture as dew point values quickly recover back
into the 60s. Combined with modest lapse rates aloft, moderate to
strong instability will develop as MLCAPE values are progged to
climb into the 1500-2500 j/kg range by 00z Saturday (7pm CDT Friday)
as afternoon highs reach the low to middle 80s. Under a localized
speed maximum, deep layer shear will be supportive of organized
convection with 0-6km BWD values in the 25 to 35 knot range. This
should support multicell storm modes with a few embedded supercells
possible. Forcing for ascent will quickly ramp up by evening as the
main PV anomaly crosses the Central Rockies. Subsequent height falls
will peak Friday evening into Saturday morning. By early to mid-
evening, expectations are for thunderstorms to quickly track north
and east out of Colorado/northwest Kansas and into southwest
Nebraska. Primary concern will be damaging wind gusts as hi-res
guidance indicates a fairly quick upscale progression of
thunderstorms into an environment with moderate DCAPE (800-1200
j/kg) and delta theta-e differentials of greater than 25 degC.
Extended HRRR guidance (12z and 18z runs) shows areas of enhanced
wind gusts exceeding 40 knots and even peaking around 60 knots.
While large hail will also be possible, this will primarily reside
in storms that can remain discrete which will be a decreasing
probability as the evening progresses. Though a tornado cannot be
ruled out given modest curvature in the lowest levels, confidence in
seeing one is quite low given storm mode and quickly invading cold
pool conglomeration. The latest SPC Outlook for Friday has much
of the area in a Slight Risk (level 2 of 5), and generally have
no qualms with this. Precipitation will persist overnight into
Saturday with PoPs peaking around Midnight CDT Friday night
around 80%. Forcing wanes as the trough axis clears the local
area around sunrise Saturday and as such have PoPs quickly
decreasing from west to east through the morning Saturday.
Uncertainty exists around how the afternoon hours Saturday play
out. With clouds and precipitation chances potentially lasting
into the early afternoon, environmental recovery is somewhat
uncertain. The latest SPC Outlook for Saturday show our far
north central zones in a Marginal Risk (level 1 of 5) and
believe this is adequate for now given some lingering
uncertainties. It`s interesting to note that the operational NAM
and GFS keep any afternoon redevelopment east of the forecast
area so we`ll need to monitor for increasing/decreasing
probabilities. Depending on pace of clearing, temperatures
remain somewhat uncertain though forecast highs are likely to
return to above normal values reaching the middle 80s east to
low 90s west.

Sunday...an interesting day with a clash of cooler and more mild
airmasses across the central Plains. Behind the departing trough, a
fairly progressive cool front will dive south along the lee of the
northern Rockies. Further south, southerly flow will reinforce low-
level moisture with dew points likely to remain in the lower 60s.
Eventually, the cool front will win out with moderate CAA
overspreading the area. How far south this front reaches is the
subject of greatest uncertainty as temperatures remains more mild to
the north and hot to the south. Eventually, this frontal boundary
will still and lift back north slightly as a warm front. Easterly
upslope flow immediately north of the surface boundary will support
orographic lift across northeast Colorado while the front itself
will be a possible focus for thunderstorm development. NWP guidance
varies quite widely about placement of this boundary and thus where
greatest PoPs set up. For now, believe inherited Chance PoPs (up to
50%) are adequate though subsequent forecasts could introduce large
changes to these values. The NAM is furthest south with this frontal
boundary whereas the GFS/ECWMF shows it settling around the I-80
corridor. Capping will be strong but strong forcing from low-level
convergence may be enough to overcome this especially as the evening
low-level jet ramps up. Strong instability and deep layer shear will
be in place and suggest an organized severe weather event but
confidence in realizing thunderstorm initiation is low. Will need to
closely monitor this potential in the coming days.

Monday and beyond...continued southwesterly flow with a steady
parade of northern stream disturbances should keep the extended
forecast on the active side next week. While day-to-day
predictability will remain low given model guidance variations,
recurring afternoon and evening thunderstorm potential appears at
least probable for the foreseeable future. Persistent fetch
from the Gulf of Mexico should provide adequate moisture to
support this idea. NBM guidance for temperatures next week show
large spread in 25th to 75th percentile values and this is
likely due to some uncertainty on how far east the upper-level
troughing encroaches on the area. For now, deterministic
solutions show daytime highs remaining in the 80s for most but
large swings are possible as confidence in evolution of the
extended becomes more certain.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 659 PM CDT Thu Jun 13 2024

VFR conditions will prevail across western and north central
Nebraska through the period. Scattered showers and a few
thunderstorms are possible Friday after 12Z. Have included a
mention at KLBF from 14Z through 00Z/14th. Confidence however
is low on specific impacts to either terminal site at this time.

&&

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

&&

$$

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