489
FXUS63 KLBF 052050
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
350 PM CDT Sun May 5 2024

.KEY MESSAGES...

-  A strong storm system crosses the area Monday, bringing a
   threat for strong winds and strong to severe thunderstorms.

-  The greatest risk for severe weather Monday will reside
   generally east of Highway 83 during the mid to late afternoon
   hours ahead of a fast moving frontal boundary.

-  Strong winds and low humidity values are anticipated across western
   Nebraska Monday afternoon, leading to at least elevated fire
   weather concerns.

-  Monday`s storm system lingers over the Plains through much
   of the upcoming workweek, keeping winds elevated and near
   daily precipitation chances.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 347 PM CDT Sun May 5 2024

The primarily concern for the short term will revolve around a
strong storm system, progged to impact the area tonight and
tomorrow. Currently, the aforementioned upper low is centered
over northern Nevada, with broad southwesterly flow in advance
of this wave aloft, entering the Plains. At the surface, broad
cyclogenesis has begun across portions of the Rockies, with an
increasing pressure gradient noted across western Nebraska. Flow
from the southeast has increased in response to the deepening
surface pressure, and is leading to increasing low level
moisture advection. Dewpoints have increased into the upper 40s
across southwest Nebraska this afternoon amid gusty southeast
winds.

For tonight, expect the increased southeast winds to persist, as a
strong low level jet develops across much of the Plains. Forecast
soundings suggest limited to no boundary layer decoupling overnight,
and even strengthening winds as the strong flow aloft is
mechanically mixed downward. Will have to watch for the potential
for high wind gusts (60+ mph) near the Pine Ridge at higher
elevation, though confidence in this is low for now. The boundary
layer remaining mixed will also promote mild overnight lows, in the
low to middle 50s across the area. Closer to sunrise tomorrow
morning, the increasing warm advection will lead to lowering cloud
decks, and a period of drizzle through late tomorrow morning.

As we head into the early afternoon, a pacific front will begin to
push quickly into the area from west to east, reaching the HWY 83
corridor around Noon. Ahead of this boundary, upper 50 to
potentially near 60 degree dewpoints will stream northward into the
area, with a narrow corridor of instability developing near the HWY
183 corridor. This (HWY 183) is where convective initiation is
anticipated by 1-3pm CDT. That said, questions remain regarding the
degree of destabilization that can occur with northward extent,
though guidance continues to suggest at least some MLCAPE for
convection to work with ahead of the advancing Pacific front.

As the upper low continues to deepen aloft, it begins to take a
negative tilt and mid-level becomes largely meridional with height.
Shear vectors show near boundary parallel storm motions, suggesting
quick upscale growth when combined with increasing forcing for
ascent with the approaching wave. This points towards a line of
thunderstorms initiating near HWY 183 mid-afternoon, quickly
moving east by late afternoon. The primary hazard with this
looks to be damaging wind gusts, though some hail risk will
exist with initial discrete updrafts. Any QLCS tornado threat
would be tied to low- level thermodynamics, and meager low-level
lapse rates could be in place due to persistent stratus. Will
have to monitor for any clearing closely, and better low-level
thermodynamic profiles could support at least a brief window for
an isolated QLCS tornado threat.

Behind the Pacific front and exiting convection, strong west winds
are anticipated amid clearing skies and quickly warming
temperatures. This, combined with increasing dry air advection,
should lead to quickly falling relative humidity values by late
afternoon. The combination of the strong west winds and low humidity
will lead to at least an elevated fire threat, with the caveat of
this being maximized in areas where green up is most delayed.
Will also have to watch for the potential for another period of
high wind as diurnal mixing leads to good momentum transfer.
That said, confidence remains higher further north in South
Dakota in closer proximity to the surface low center. North of
the tongue of dry low-level air, scattered wraparound
precipitation is possible near and just after sunset, though
should end prior to midnight as the upper low begins to pull
away to the north.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 347 PM CDT Sun May 5 2024

The upper low that impacts the area Monday is anticipated to
continue to influence weather locally through much of the workweek,
as it remains anchored over the northern Plains. This looks to keep
winds elevated each day, as additional frontal boundaries pass
through the area this week. Precipitation chances exist nearly each
day as well, though confidence in placement and amounts from any one
day remains lowered for now. Highs remain nearly average, generally
in the 60s each day this week. As we head towards the weekend, upper
level ridging will begin to amplify across the Pacific Northwest,
with northwest flow developing aloft across the Plains. As the ridge
begins to slide eastwards, this could bring a brief lull to the
active pattern.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1250 PM CDT Sun May 5 2024

Low stratus across the western zones including the LBF terminal
will gradually scatter early in the period leaving VFR
conditions for both terminals until more expansive stratus
develops tonight. For now, timing of this favors Midnight or
shortly after with a quick drop to IFR and LIFR conditions in
the area. This stratus may also pose the threat for DZ through
the early morning hours Monday. Ceilings will gradually lift as
winds quickly veer to the west around the end of the valid
period as a surging cold front clears the area west to east.
Winds will remain strong over the next 24 hours with gusts in
the 30 to 35 knot range through Sunday night then increasing to
35 to possibly 45 knots, mainly for VTN, after sunrise on
Monday.

&&

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

&&

$$

SHORT TERM...Brown
LONG TERM...Brown
AVIATION...NMJ