Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 120910
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
410 AM CDT Tue Mar 12 2024

.KEY MESSAGES...

- Elevated fire weather conditions are expected this afternoon due
to warm temperatures and low relative humidity, though winds remain
weaker from the west.

- A storm system is anticipated to impact the area Wednesday through
Thursday. This is a low confidence but potentially high impact
scenario, with a threat for strong winds, heavy rain, and
accumulating snow.

- Drier conditions persist late week into the weekend, with
 slowly moderating temperatures.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 409 AM CDT Tue Mar 12 2024

For today, the well above average temperatures persist, as H85
temperatures remain near the 90th percentile climo and westerly
downslope flow prevails this afternoon. Limited snow cover remains
across portions of southwest Nebraska, and this is expected to
finally erode this afternoon as temperatures again climb into the
60s and 70s. The well above average temperatures will again lead to
elevated fire concerns, as humidity values fall into the teens to
low 20s this afternoon. That said, winds remain weak from the west
today, generally below 20 miles per hour. Aloft, a weak shortwave
will push off just to the south of the area through late this
morning, though beyond some passing high clouds will lead to little
impact.

For tonight, flow begins to transition southwesterly aloft ahead of
an upper trough deepening across the Rockies. This will lead to
increasing cloud cover aloft, and will keep lows more mild
overnight, in the middle to upper 30s.
&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 409 AM CDT Tue Mar 12 2024

Attention then turns to a potentially high impact storm system
progged to impact the area Wednesday through Thursday.

By Wednesday morning, lee cyclogenesis will be well underway across
portions of southeast Colorado. Aloft, a low at H7 will begin to
drift slowly eastward across the Rockies, with a mid-level warm
front lifting into the Panhandle and northern Nebraska. Increasing
convergence near this boundary (and the encroaching H7 low) will
lead to increasing frontogenetical forcing across far western
Nebraska and the higher terrain of Wyoming. The system as a whole
does not have a tap of cold arctic air to rely on for any
precipitation changeover, and this will primarily depend on dynamic
cooling aloft. As for moisture availability, this system will have a
tap to the deep moisture of the Gulf of Mexico, and ensemble
guidance widely advertises PWAT values exceeding the 90th percentile
climo. This should promote widespread precipitation development
across the Panhandle through Wednesday morning, though snow levels
look to remain high enough to keep this as liquid rain initially.
The first round of this system looks to initially be confined to the
Panhandle and western Sandhills, with low confidence in the
progression of the rain/snow line through the day. A period of at
least rain/snow mix is expected across the western Sandhills, with
lessening confidence in a prolonged period of snow (and any
impactful accumulations) at this time. The heavier accumulations
look to remain over the western Panhandle/eastern Wyoming for now,
where increased elevation should help to overcome this and maintain
a pure snow p-type.

As we head into the afternoon hours on Wednesday, a deepening
surface low will begin to eject eastward across Kansas, with
precipitation coverage increasing from east to west. Aloft, a more
complex evolution looks to occur, and this is very low confidence in
how synoptic features evolve. The more robust guidance suggests a
quickly strengthening H5-H7 low, progged to pass off to the south of
the area. As a consequence, these solutions are also much less
progressive, lingering precipitation across the area longer.
This southward track is also climatologically favored for heavy
snow, though aforementioned cold air issues keep uncertainty
higher. The less bullish guidance suggests a weaker and much
further southeast surface low (and an open wave aloft), and
lesser deformation axis precipitation across the area.

The track and strength of the ejecting surface low will determine
the zone of highest impacts, and this will be monitored closely.
Should the surface low track further northwest and closer to
the local area - a lifting surface warm front looks to lead to
scattered thunderstorm development, and this could work into
areas south of HWY 23 Wednesday evening. Ample deep layer shear
and long hodographs could support a marginal hail threat with
storms, though confidence in storm coverage is higher off to the
southeast of the area over south central Nebraska at this time.
Winds will also increase substantially to the north and west of
the ejecting surface low, with increasing H7-H85 flow. As
mechanical mixing occurs (both in precipitation and in the cold
advection regime) wind gusts increase to 35-45mph from the
northeast. This will only add to impacts from any changeover to
snow, and could lead to blowing and drifting in areas of
accumulation. Speaking of snow, this will largely be driven by
enhanced dynamic cooling in areas of higher precipitation rates.
Surface temperatures look to remain marginal at best,
suggesting heavy and wet snow, with SLRs ~8-10:1. Most
concerning, in the more bullish guidance, cross-section analysis
shows a deep, strong frontogenetical circulation to the
northwest of the surface low, with a tap of negative EPV (and
slantwise instability) and even the potential for pure upright
instability. This is a low confidence, but most high impact
scenario locally. A narrow band of convectively enhanced
snowfall rates would lead to rapid accumulations of heavy snow,
and even the potential for localized blizzard conditions in the
strong northeast winds. Though not favored at this time, this
will be monitored closely and those with interests should
monitor later forecasts very closely.

The more likely scenario is for an area of heavier stratiform rain
to develop to the northwest of the surface low, with the potential
for widespread beneficial rainfall accumulations (0.50-1.0").
Embedded thunder would be possible in this regime as well. One
potential caveat would be the aforementioned further south and
east track of the surface low, keeping the majority of the area
drier and wind gusts weaker.

Precipitation should end quickly from northwest to southeast into
Friday morning, with dry conditions then persisting into the weekend
and early next week. Temperatures begin to moderate into Saturday
before a reinforcing shot of cooler air arrives for Sunday. This
looks to be short lived however, as it quickly pushes off to the
east and an upper ridge begins to amplify across the western CONUS.
As heights rise into early next week, temperatures return back to
near and above average across the area.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1222 AM CDT Tue Mar 12 2024

VFR will continue through the forecast period for western and
north central Nebraska terminals as mainly high clouds stream
by. Generally west winds will be present today with slight
strengthening during the afternoon and tapering again after
sunset.

&&

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

&&

$$

SHORT TERM...Brown
LONG TERM...Brown
AVIATION...Snively


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