000
FXUS63 KLBF 151736
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1236 PM CDT Mon Apr 15 2024

.KEY MESSAGES...

-  Critical fire weather conditions are expected to develop
   across the eastern Panhandle and far southwest Nebraska
   today, with relative humidity values as low as 8 percent and
   south winds gusting as high as 45 miles per hour.

-  The potential for severe weather will quickly increase this evening
   into tonight across much of western and north central
   Nebraska. Large to very large hail, damaging winds, and
   isolated tornadoes are the primary hazards.

-  Strong northwest winds develop Tuesday afternoon and evening
   behind a strong cold front, with wind gusts as high as 60
   miles per hour across the southern Panhandle and far
   southwest Nebraska.

-  A quick moving system impacts the area Wednesday evening
   into Thursday morning, bringing a threat for rain changing to
   snow in the overnight hours.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 424 AM CDT Mon Apr 15 2024

A high impact weather system is anticipated to move through the area
through Tuesday evening, bringing a threat for severe weather,
critical fire weather, and strong northwest winds. Further details
on fire weather conditions can be found in the fire weather section
included below.

Currently, the area sits in broad southeasterly flow, as lee
cyclogenesis continues across eastern WY/CO. This is advecting
moisture richer low level moisture northward, with a plume of higher
dewpoints streaming northward through central and southeast KS.
Aloft, an upper low continues to push eastward across the Great
Basin, with flow aloft transitioning southwesterly across the
Plains.

For today, the primary focus will be on a strong surface low that is
anticipated to eject eastward out of northeast Colorado and into
southwest Nebraska this afternoon. As lee cyclogenesis continues
this morning, a warm front should lift northward across the area
into this afternoon, reaching central/north central Nebraska by
early evening. At the same time, a dryline will begin to slowly
translate northeastward into southwest Nebraska, leading to a narrow
corridor of middle to upper 50 dewpoints in the warm frontal zone.
It is in this zone where the threat for severe weather will be
maximized, and will need to be monitored closely this afternoon.

As for the environment, backed east-southeasterly surface winds
ahead of the dryline should lead to increasing low-level
hodograph curvature, especially as a low-level jet begins to
strengthen near and after sunset. As an upper level jet streak
translates eastward into the Plains by early evening, the area
looks to sit in the left exit region, promoting good divergence
aloft. Mid-level flow strengthens in response to the encroaching
upper wave, elongating hodographs with height. This all points
towards a background environment supportive of supercellular
development, though some lingering uncertainty remains to the
degree of forcing to overcome a capping inversion centered
around H7. That said, high-res guidance continues to come into
better agreement with the erosion of the cap, in response to
both continued moistening of the boundary layer (especially if
local pooling of dewpoints occurs near the warm front) and
gradual cooling aloft with the approach of the deepening upper
low.

It appears the cap should largely be eroded by early evening, and at
least scattered convective initiation should occur near/ahead
of the surface dryline and potentially in the vicinity of the
warm front. An initial supercellular mode looks likely, with a
threat for all severe hazards initially. Large to very large
hail looks to be the greatest threat, with steep lapse rates
aloft leading to ample instability. That said, mid-level shear
vectors (4-6km) do look rather weak, and this could impact
updraft width to a degree and hold back widespread higher end
(2"+) hail somewhat. Still, 1"+ hail looks like a probable
hazard in any sustained discrete updrafts. As mentioned, there
does appear to be a window for a tornado or two across
central/north central Nebraska as convection remains discrete,
with low-level shear more than adequate for storms to acquire
low-level rotation. The biggest limiting factors will be shallow
moisture depth and higher LCLs (which could be overcome in any
locally higher dewpoint pooling along the warm front). Eventual
upscale growth does appear increasingly likely, as the low-level
jet strengthens and more convective initiation gets underway
near and after sunset. This would limit the hail and tornado
threat to some degree, though increasing low-level instability
and shear points towards some threat for mesovortex production
and an attendant QLCS tornado and damaging wind threat.
Additionally, a cold front should overtake the dryline after
dark, leading to renewed convective development and additional
upscale growth. The threat should gradually wane into the
overnight hours as the boundary layer cools and storms have a
propensity to become elevated.

As the upper low continues to push eastward across the area Monday
night, continued widespread shower and thunderstorm development will
persist. A lull in activity can be expected early Tuesday
morning, as the dry slot translates across the area from west
to east. Wraparound showers and isolated thunderstorms can be
expected on the backside of the surface low into Tuesday, again
translating from west to east through the afternoon. The bigger
threat Tuesday will be the winds, as the cold front pushes
through the area during the day. Behind this boundary, strong
H7-H85 flow on the order of 45-55kts should be mixed downward,
as cold advection increases behind the front as well as inside
any precipitation. The area of greatest concern looks to be
near and west of HWY 61 and south of HWY 2, where both low-level
flow and stronger advections should be maximized. A period of
55-60 mile per hour gusts is looking increasingly probable in
this area, and have issued a High Wind Watch for Tuesday in
collaboration with neighboring offices. These gusts will
continue into Tuesday night, though should gradually weaken as
both cold advection weakens and the low begins to pull away from
the area. Precipitation also looks to quickly end from west to
east Tuesday morning, as dry air is ushered into the area
behind the departing low.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 424 AM CDT Mon Apr 15 2024

The lull in active weather looks to be brief, as another system
ejects eastward across Saskatchewan/Manitoba Wednesday, with an
associated trough axis pushing through the central Plains
Wednesday night. At the surface, a deepening low will eject
eastward across Manitoba, with an associated strong cold front
pushing through the local area by 06Z Thursday. This will usher
in colder temperatures and the potential for some changeover of
precipitation to rain/snow (and possibly all snow near the Pine
Ridge?). As the mid-level trough axis approaches the area, rapid
cold advection at H7 points to a quickly constricting thermal
gradient and FGEN increases markedly across the area in
response. This looks to lead to a narrow but potentially intense
band of precipitation, translating quickly from northwest to
southeast into Thursday morning. At least some convective
enhancement is also possible, with at least CSI and potentially
pure CI present. Thermodynamic profiles remain only marginally
supportive of snow at this time, though the enhanced rates could
lead to locally a switchover. SLRs will remain very low
(~6-8:1) and any snow that does fall would be heavy and wet.
Currently not anticipating much in the way of impacts with a
more mixed (rain/snow) p-type, but this will need to be
monitored going forward.

The active regime looks to persist into late week and the weekend,
with broad zonal flow gradually transitioning northwesterly. This
should provide additional precipitation chances, along with
continued below average temperatures to round out the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1232 PM CDT Mon Apr 15 2024


Winds will continue to be strong this afternoon out of the
southeast with winds of 20 to 25 kts and gust of 30 kts or more
possible. There will be some brief LLWS tonight, before midnight
across portions of southwest Nebraska. Thunderstorms will also
be possible late this afternoon through the overnight hours and
could impact both KVTN and KLBF terminals, along with terminals
across north central into central Nebraska.

&&

.FIRE WEATHER...
Issued at 424 AM CDT Mon Apr 15 2024

Critical fire weather conditions are likely this afternoon and this
evening across the southern Panhandle and southwest Nebraska. The
concern is humidity below 15 percent and southeast winds gusting to
40 mph. This will occur behind a dryline, and humidity values could
drop into the single digits across far southwest Nebraska during the
afternoon hours. Also, cannot rule out a scattered thunderstorm this
afternoon and evening, though the greatest chances should exist
further north and east of areas that will experience critical fire
weather conditions today.

Confidence in the placement of the dryline remains a little
uncertain, and further expansion of critical fire weather conditions
could occur further northeast of current Red Flag headlines. That
said, enough confidence exists in very dry air moving into the
eastern Panhandle near and south of HWY 2, and the Red Flag Warning
was expanded to include the eastern Panhandle and western Sandhills.
Of note, a wind shift from southerly today to northwesterly is
expected by Tuesday morning, and winds will quickly strengthen again
into Tuesday afternoon. Wind gusts of up to 60 miles per hour are
possible across the eastern Panhandle and far southwest Nebraska
Tuesday afternoon and evening, though cooler temperatures should
keep humidities higher.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 10 PM MDT this evening for NEZ204-210.
High Wind Watch from Tuesday morning through Tuesday evening
for NEZ022-023-035-056>058-069.

&&

$$

SHORT TERM...Brown
LONG TERM...Brown
AVIATION...Gomez
FIRE WEATHER...Brown