000
FXUS63 KLBF 271736
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1236 PM CDT Sat Apr 27 2024

.KEY MESSAGES...

- Precipitation chances will increase through the day Saturday, peaking
  around 85-95% Saturday evening into early Sunday. A few
  storms in the evening may be strong to briefly severe with
  isolated instances of large hail the main concern.

- Locally heavy rainfall is again likely tonight through early Sunday
  with QPF amounts of up to 1.00" and localized amounts closer
  to 1.5" possible.

- Wet snow may mix with rain early Sunday across the western Sandhills
  but no accumulations are expected.

- Fairly active weather continues into next week with recurring
  chances for precipitation with PoPs generally 50% or less any
  one day.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 402 AM CDT Sat Apr 27 2024

Round 2 of active weather will begin to encroach on the area later
today. This will include the threat for locally heavy rain and the
possibility of strong to severe thunderstorms favoring areas south
of Interstate 80.

Morning surface and satellite analysis depicts the area between two
distinct systems. The first of which produced the significant severe
weather across eastern Nebraska Friday, currently situated near the
northern Mississippi Valley. Northwesterly flow behind this feature
has propelled much cooler and stable air into the local area. To our
south, the next system is beginning to take shape across far
southeast Colorado into southwest Kansas. The trailing cool front
from the first system has settled south of I-70 in southwest and
central Kansas with broad southerly flow across the southern Plains
helping promote deep moisture advection which will support another
significant severe event across southeastern Kansas into eastern
Oklahoma. The developing surface low to our south will track along
the baroclinic zone settling across central Kansas. With converging
flow in the immediate vicinity of this, a warm front will sharpen
and gradually lift north as the surface low begins to shift east by
early afternoon today. Winds locally will veer to the northeast with
surface high pressure settling into the northern Plains. This will
help keep the local area on the cooler side north of the effective
boundary. As a result, high temperatures today will only range from
the upper 40s across the western Sandhills to near 60 in our far
south and east which falls about 5 to 15 degF short of
climatological highs for late April. Aloft, general southerly h5 and
h7 flow will advect another modest EML which will lead to steepening
lapse rates in the local area. With the warm humid airmass remaining
south of the area, potentially even south of the NE/KS state line
for areas west of Highway 183, am a little wary about our potential
for surface based convection. HREF probabilities of > 500 j/kg of
SBCAPE are zero for areas north of McCook. Forecast soundings show
elevated instability, generally rooted around h75 by mid to late
afternoon. Shear remains fairly strong in this layer, with 2-7km BWD
values of 35 to 45 knots. Believe this plays to at least a threat
for isolated large hail. Storms look to initiate across eastern
Colorado around midday and within southerly steering flow will track
north into southwest Nebraska by early evening. As they track north,
they will encounter more stable surface air and limited elevated
instability so the expectation is for this activity to weaken with
time. HREF storm-scale guidance shows fairly high probabilities of
notable mid-level updraft helicity, nearly 90% around I-70 west of
GLD, but rapidly decreasing to less than 30% once over McCook and
zero by the time storms arrive to I-80. Similarly, HRRR guidance
shows fairly notable weakening with storms once crossing into far
southwest Nebraska as storms congeal into a larger arc of moderate
precipitation. The latest SPC SWO Day 1 outlook grazes Frontier
County with a Slight Risk (level 2 of 5) and a Marginal Risk (level
1 of 5) generally along and south of a Grant to Oconto line.
Confidence in seeing severe weather locally is low enough that I
feel the Slight Risk can be removed from the local area. Heavy rain
will continue to be the greatest concern for western Nebraska
tonight through early Sunday. On the north side of the slow tracking
surface low, warm air advection will increase with a sharpening
gradient leading to strong fgen around h85 but extending up to h7.
With modest elevated instability remaining in place, general showers
and thunderstorms are expected as PoPs climb to 85-95% for much of
the area during the overnight. Even with high PoPs and convective
activity, rainfall amounts will be slightly limited due to fairly
average PWATs around 0.50-0.75". So slow and steady rain will again
be favored which will limit the overall flooding threat. Overall,
rainfall amounts of 0.50-1.00" with locally higher amounts closer to
1.50" possible. This generally lines up with HREF Probability-
Matched Mean values and the majority of this rain will fall in areas
typically more immune to flash flooding threats such as the
Sandhills but also areas that missed out on the heavier rainfall
Thursday night.

Turning to Sunday morning, cooler air will continue to filter in
from the north. This will promote low temperatures falling into the
middle 30s for the western Sandhills. With marginal h85 temperatures
around the freezing mark and low-level wet bulb temperatures maxing
out only a degree or so above 0 degC, will have to watch for a
rain/snow mix in our western zones. Antecedent warm conditions have
helped allow the ground temperatures to warm nicely across the area
so not expecting any wintry impacts outside maybe some marginal
visibility restrictions in areas that see the snow. Through midday,
the surface low to our south will lift north and east into the
middle Missouri Valley. As it does, it`ll weaken slightly which will
allow the pressure gradient to relax and forcing for ascent to
diminish. The combination of this and the focus lifting north into
South Dakota will help lead to decreasing precipitation chances
through the day. While low-end PoPs (< 30%) linger across north
central Nebraska late into the evening, believe most if not the
entire forecast area will be dry by mid-evening. Sunday night will
be the coldest night of the week with lows falling to around the
freezing mark. With the 50th Percentile last Spring freeze date
still a week or two away, no Frost headlines are expected at this
time.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 402 AM CDT Sat Apr 27 2024

Quieter conditions arrive for Monday as mid-level heights build in
and flow aloft favors a more zonal pattern. Continued southwesterly
flow will support increasing h85 temperatures and as a result,
moderating temperatures. Temperatures look to return to seasonable
values by Monday and Tuesday, with highs in the 60s and 70s. A
cutoff disturbance across the northern Rockies will gradually
translate east with a few stronger PV anomalies rotating on the
southern periphery of the main feature. This will push a few weaker
systems across the northern Plains which will drop a few cool fronts
south into the area during the week. For now, Tuesday and Thursday
look to be the best chances for these fronts to have the greatest
affect on sensible weather with not only a brief temperature drop
late Tuesday through Thursday but also recurring rain and
thunderstorm chances. Confidence in day-to-day details remains
fairly low given spatial and temporal discrepancies between
deterministic and ensemble solutions, but the overall pattern with
enhanced mid-level flow and a warm, humid airmass in the region
supports at least some potential for severe weather. More precise
details will likely not become apparent until we get to Monday so
continue to check later forecasts for the latest information.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1236 PM CDT Sat Apr 27 2024

For the KLBF terminal: Expect MVFR ceilings to develop this
afternoon with showers and thunderstorms likely this evening.
Ceilings will fall off to below 1000 FT AGL by late evening and
will persist through 18z Sunday. Expect periodic rain showers
overnight into Sunday morning with some visibilities down to 3SM
Sunday morning. For the KVTN terminal: Expect ceilings to remain
below 1000 FT AGL over the next 24 hours. Rain showers will
develop by evening and will persist through 18z Sunday. Some
visibilities may reach 3SM, especially Sunday morning.

&&

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

&&

$$

SHORT TERM...
LONG TERM...
AVIATION...Buttler