820
FXUS63 KLBF 102117
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
417 PM CDT Sat Aug 10 2024

.KEY MESSAGES...

- Scattered showers and storms tonight with a marginal threat of
severe weather in the panhandle due to hail and wind.

- Additional thunderstorms expected tomorrow afternoon and evening,
especially across the Sandhills, also with a hail and wind threat.

- Virtually daily thunder chances through the week as temperatures
gradually climb to near normal levels by late week.


&&

.SYNOPSIS...
Issued at 417 PM CDT Sat Aug 10 2024

Nebraska lies on the periphery of a transient upper ridge along the
spine of the Rockies, while a deep closed upper low continues to
spin just north of the Great Lakes. Thick cloud cover and well below
normal temperatures accompany broad northwest flow aloft. Toward the
surface, high pressure is centered over Kansas, which places most of
the forecast area in southerly return flow. A low near the Laramie
Range extends a weak trough across the northern Sandhills and a
quasi-warm front south along the lee of the CO Rockies. Temperatures
as of 20z range from the lower 60s in the Platte River Valley to
around 70F along the SoDak border.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 417 PM CDT Sat Aug 10 2024

This evening into tonight... A fairly substantial mid-level
shortwave begins to enter northwest Neb, while the surface trough
lifts north into So.Dak and the main front reaches the Neb.
panhandle. Despite the strong forcing aloft, the bulk of the surface
driven lift will be focused away from the heart of the forecast
area. Isentropic analysis also reflects this, with the steepest
gradients occurring either north of the state line or above 305K.
South/southeast near surface winds will help keep dew points steady
in the mid to upper 50s, but overall moisture advection appears
negligible. Confidence is not the greatest in widespread or
organized activity, but CAMS still suggest scattered showers and
storms coming in a couple different waves. One would be existing
activity from Wyoming and Colorado during the late evening, then
perhaps new development overnight closer to the area. Overall,
limited PoP to 40% throughout the night to message the scattered
coverage and conditionality of the event. As for the current
convection to the west that may enter the panhandle, a minor wind
and hail threat exists. Instability is weak overall, however an axis
of slightly greater MUCAPE values of 500+ j/kg stretches along Hwy
61. Deep layer shear is the main component as values reach 50 kts.
For min temps, stayed near the NBM mean. Strengthening southerly
flow at H85 helps lead to modest warm air advection, and generous
low cloud cover should limit boundary layer decoupling. Forecast
values range from mid to upper 50s.

Tomorrow... An active day could be on tap for western Nebraska as a
few synoptic features come together over the region. The
aforementioned mid-level shortwave crosses the Sandhills, following
the tail of a local H3 jet maximum. The surface low pushes toward
the NE/KS/CO border and extends the front through the heart of the
forecast area. A few items are at play, which would determine the
overall thunderstorm (and severe) threat. Any lingering rain showers
from overnight could be moving through north central Neb until
midday. The accompanying stratus deck may be pretty thick and only
slowly erode to the Hwy 61 corridor by mid-afternoon. These factors
would likely lead to another very mild day, especially east of Hwy
83 where forecast highs reflect the 25%ile of NBM, equating to
lower/mid 70s. Instability will be limited once again for areas east
of Hwy 83 with MUCAPE values generally held to 500 j/kg, perhaps
1000. However, farther west toward Hwy 61, additional clearing and a
big warmup to around 80F closer to the surface low will create a
steep gradient of convective parameters. A ribbon of greater
instability in the form of 2000 j/kg MUCAPE and 7-8 C/km mid-level
lapse rates will complement strong deep layer shear around 50 kts.
CAMS seem to support a couple focus areas for thunderstorm
development, with one being in So.Dak north of the warm front and
more aligned with the upper forcing, and one being directed toward
Kansas ahead of the surface low. Most of the activity in our CWA
will likely be derived from the northern setup. Forecast soundings
suggest the bulk of the CAPE east of Hwy 83 occurring above H7, but
plenty of low level veering. Initial storm mode may very well be
supercellular before cold pooling takes over and storms evolve into
clusters or perhaps a QLCS. Agree with the sentiment of MRGL risk by
SPC, but would not be surprised to see an upgrade to SLGT north of
Hwy 2 should later model trends point toward greater instability.
The threat of severe wind and hail certainly exist, but may be more
of a widespread low-end event more than a localized significant
severe threat. Most guidance pinpoints mid-afternoon (~21z) for far
northern Neb between GRN and VTN, early evening (~00z) from ANW to
BBW, and mostly exiting to the east by 03z or so.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 417 PM CDT Sat Aug 10 2024

The subtle upper ridge over the Western US shifts east onto the
Plains and builds midweek, with the axis bisecting the Sandhills on
Tuesday. The pattern turns progressive later in the week as a trough
pushes through on Thursday and then a more amplified ridge building
into the weekend. Nearby surface features also promote periodic
precipitation chances, especially the first half of the week.
Southwest Nebraska may receive a couple more rounds of wetting rain
Monday and Tuesday as storms originating from upslope flow spread
east off the mountains. As for temperatures, they should finally
warm up with the help of the upper ridge and breaks in cloud cover.
Guidance continues to support a gradual rise from 70s to 80s over
the next few days and potentially reaching 90F on Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1242 PM CDT Sat Aug 10 2024

Stratus continues to be present across western and north central
Nebraska. Model guidance is struggling to catch on to the
redevelopment of lower ceilings, which is being observed on
satellite. Tended to the more aggressive solutions on ceilings, as
MVFR to VFR conditions persist this afternoon and evening. Overnight
ceilings should remain VFR, with a drop to IFR and LIFR ceilings
along and south of Highway 2 tomorrow morning. As thunderstorms
track in from the west this evening and overnight, they are expected
to weaken and bring periods of showers around both terminals. Though
the winds are expected to remain fairly light, decaying
thunderstorms and showers may introduce some briefly erratic winds.

&&

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

&&

$$

SYNOPSIS...Snively
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Richie