793
FXUS63 KLBF 132341
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
641 PM CDT Fri Sep 13 2024

.KEY MESSAGES...

- Isolated to scattered thunderstorms possible each evening through
the weekend with temperatures holding at near or slightly above
normal levels

- Stronger winds return Monday and Tuesday, but humidity should
remain well above critical fire weather thresholds

- Cool front may bring widespread thunder activity later Tuesday
  into Wednesday

&&

.SYNOPSIS...
Issued at 359 PM CDT Fri Sep 13 2024

Nebraska lies on the periphery of an upper trough digging into the
northern Rockies and Plains, with the accompanying low spinning over
Saskatchewan. Meanwhile, the remains of Francene are centered over
the Mississippi Delta and an upper ridge holds over the Great Lakes.
This pattern places Nebraska in primarily southwest flow aloft. At
the surface, a deeper low is stacked under the primary upper low
just north of the MT/Sask border, and a cool front stretches from
there to a secondary low stationed in the Sandhills. As of 20z, the
front lines up roughly along Hwy 83, with mainly dry northwest low
level flow behind it and relatively moist south/southeast flow out
ahead. The cumulus field has been building along and ahead of the
front, with the greatest convergence noted in north central Neb from
near BBW to ANW.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 359 PM CDT Fri Sep 13 2024

This evening into tonight... The main forecast challenge concerns
potential thunderstorms ahead of the cool front. Kept schc PoP from
previous forecast, but trimmed coverage to be mainly confined to
north central Neb. Very little model guidance suggests development
to the south, which appears to have a stronger cap in place per SPC
RAP Meso. Moisture transport at H85 also indicates greater advection
and convergence to the north on the eastern gradient of stronger
shear and instability. Nonetheless, surface dew point depressions
remain 25+ and overall CAPE/lapse rates are marginally supportive of
stronger convection. Any thunder should be isolated in coverage, or
scattered at best, with 00-06z being the most conducive timeframe.
Investigated the potential for fog and/or stratus with generally
light southeast low level flow in place overnight. Think the greater
potential lies east of the forecast area where isentropic upglide is
steeper within the moist layer and SREF probabilities are greater.
Can`t completely rule out patchy fog in the the usual spots in the
Platte River and lower Loup Valleys, but confidence in significant
impacts is low. Left fog mention out of the forecast for now. As for
min temps, stayed near the middle of the relatively small NBM
envelope, which trend toward the warmer numerical guidance. Felt it
seemed reasonable given consistent southerly low level flow
overnight and (very) weak warm air advection compared to last night.
Values range from near 50F along the Pine Ridge to upper 50s far
southwest and central.

Tomorrow... The Western US upper trough lifts somewhat,
transitioning the flow aloft to more broad southwest or bordering on
quasi-zonal for Nebraska. The surface cool front may retreat west
into the panhandle, which will allow for more widespread
south/southeast low level flow to continue. Temp advection at H85
weakens further and becomes negligible across most of the Sandhills.
Again used guidance near the NBM median for highs in the mid 80s,
which closely reflects today`s conditions. CAMS suggest a greater
potential for convective development tomorrow afternoon ahead of the
front. Some solutions hint at a small linear system or complex
following the Hwy 20 corridor. Increased chc PoP across the northern
Sandhills, which will likely lie toward the nose of higher CAPE with
supportive deep layer shear. A ribbon of nearly 2000 j/kg MUCAPE
stretches across western Neb, while mid-level lapse rates approach 8
C/km during the afternoon. Timing of the most widespread precip
doesn`t seem to correspond with the best severe parameters though,
with greater potential occurring after 00z when instability and
shear decrease.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 359 PM CDT Fri Sep 13 2024

For the start of the new week, the upper trough amplifies again as a
closed low follows the NW Pac coast and emerges onto the Great
Basin. Longer range guidance pushes the low back north from there,
placing it in Montana by midweek. This pattern places Nebraska
squarely in southwest flow and nearly meridional midweek. Another
cool front approaches the forecast area as the upper low passes to
the west, and then a surface low may sit over the Sandhills toward
late week. All in all, low level flow will be steady out of the
south and be nearly uninterrupted from the Gulf. A steepening
pressure gradient and strengthening H85 flow should result in
stronger winds Monday and Tuesday. At this time, humidity should
hold well above critical thresholds. Despite the limited threat of
official red flag conditions, the environment may still be conducive
for rapid fire spread, especially in areas with thick cured fuels.
Dew points should rise into the 60s, helping to aid additional daily
thunder chances. The best potential for precip comes late Tuesday
into Wednesday with the cool front passage and a stout mid-level
shortwave rounding the trough. Temperatures also remain near or
above normal levels through midweek with highs generally in the
mid/upper 80s and lows in the 60s.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 641 PM CDT Fri Sep 13 2024

VFR conditions will continue to prevail across all of western
and north central Nebraska tonight and Saturday. An area of
cloud ceilings around 7000 FT AGL will continue this evening at
KLBF, KANW, KBBW and KONL and should gradually become FEW-SCT
overnight. Isolated showers and storms are possible tonight,
mainly east of the KLBF and KVTN terminal and have not included
a mention attm.

&&

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

&&

$$

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