113
FXUS63 KLBF 232342
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
542 PM CST Sat Nov 23 2024

.KEY MESSAGES...

- Patchy fog development tonight into Sunday morning across southwest
  into south central Nebraska with visibilities of < 1 mile
  possible at times.

- A cold front moving in Sunday will bring much cooler
  temperatures, breezy winds, and a threat for light snow (<
  1") across portions of northwest Nebraska.

- Benign weather Monday and Tuesday before an even colder
  airmass settles into the central US by the middle to end of
  next week. A threat for wintry precipitation exists,
  potentially impacting Thanksgiving holiday travel, however,
  uncertainties remain in regards to snow accumulations.

&&

.SYNOPSIS...
Issued at 244 PM CST Sat Nov 23 2024

Recent GOES-16 WV imagery and RAP 500-mb analysis showed a broad
ridge extending across the central CONUS. An upper-level low was
centered over the north Atlantic, tracking northeast into Canadian
Maritimes. Just to the east of this feature, an upper-level trough
was sliding southeast across northern Ontario. A robust upper-level
low pressure system continues spinning off the coast of British
Columbia with a trough extending southwest into the eastern Pacific.
Multiple shortwaves and vorticity lobes were ejecting inland within
the southwest flow aloft over the Pacific Northwest and northern
Rockies. At the surface, a weak back-door cold front was draped
across western and central Nebraska. Widespread cirrus clouds
continue to move into the area with a stratus deck noted over
portions of northern Nebraska. Given the cloud cover, temperatures
have trended cooler than previously expected, especially for
northern Nebraska, with 2 PM CT temperatures ranging from 30 degrees
at Valentine to 54 degrees at Imperial.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 244 PM CST Sat Nov 23 2024

A potent upper-level shortwave will eject from the main system
centered off the coast of the Pacific Northwest into the northern
Rockies late tonight. As this shortwave moves eastward into the
northern Plains, a cold front will be forced southward, moving
through the area late tonight into Sunday morning. Ahead of the
front, patchy fog development appears increasingly possible
across portions of southwest and south central Nebraska
resulting in visibilities falling to 1 mile or less at times.
Although high clouds may pose a less favorable environment, it
appears breaks in the clouds and light winds may be just enough
to allow fog to development. Visibility may change rapidly
while driving, so Sunday morning travelers over the
aforementioned areas should stay alert. As the front clears the
forecast area Sunday morning, northwest/north winds will
strengthen behind it with 3 to 4mb/3 hour pressure rises and
cold air advection (CAA) increasing across western and north
central Nebraska. Widespread gusts in excess of 20 mph will be
common during the day on Sunday with the strongest gusts of 30
to 35 mph expected across northern Nebraska. As for Sunday`s
highs, temperatures will range from the upper-30s behind the
front across northern Nebraska to the mid-50s ahead of the front
across southwest Nebraska. This frontal passage will bring the
first of a series of cold air intrusions expected through the
week with Sunday night`s temperatures falling near 10 degrees
across northwest Nebraska to near 20 degrees across southwest
Nebraska. With breezy northwest winds gusting up to 25 mph
through the night, we will see some chilly wind chills falling
into the single digits by Monday morning. The cold overnight
temperatures, increased moisture and mid-level forcing will
present a threat for light snow/flurries across northwest
Nebraska Sunday night, potentially extending east into north
central Nebraska. Little to no accumulation is expected with
current NBM Probabilities of 24 Hour Snowfall > 1" remaining at
20% or less for northwest Nebraska. At this time, any winter
weather impacts appear low, though this will lead to much colder
temperatures as we head into Monday.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 244 PM CST Sat Nov 23 2024

As the flow aloft becomes zonal and surface high pressure builds
southward out of Canada, quiet conditions will settle into the area
Monday and Tuesday. With CAA continuing across the region,
temperatures will fall into the 30s to low-40s on Monday. Although
temperatures moderate back into the 40s as the upper-level ridge
flattens over the northern Plains on Tuesday, an even colder airmass
settles into the region for Wednesday and beyond.

The main focus in the long term revolves around the next system
ejecting out of the Rockies mid-week, potentially impacting
Thanksgiving holiday travel across our area. This mid-week threat
for snow remains low confidence as the deterministic ECMWF, GFS, and
Canadian continue to have run-to-run differences on the evolutions
of this system. As a heavily tilted upper-level trough extending
from the northern Rockies into northern California advances eastward
into the Plains through Wednesday, a lee-cyclone will develop across
southeast Colorado driven by mid-level height falls and upper-level
divergence. The main surface low will track southeast into the
Oklahoma/Texas Panhandles, remaining well south of the area.
Despite this, a cold frontal passage will bring increased mid-
level forcing, resulting in a threat for light snow across
western and north central Nebraska. Although discrepancies
exist amongst deterministic guidance, 50% or more of the GFS and
ECMWF ensemble members highlight the potential for light snow,
perhaps accumulating snow. Although uncertainties remain, with
such cold air in place, the threat for accumulating snow is non-
zero across the area with NBM Probabilities continuing to
highlight a 15% chance or less of 1"+ of snow. Thanksgiving
travelers should continue to stay up to date on the latest
forecast and be prepared to make adjustments to your plans if
needed, especially those who may be headed to Colorado where the
greater potential for winter impacts exists.

The one thing that appears more certain with this system is the
northern Plains seeing the most significant cold air outbreak
of the season thus far. Ensemble guidance shows a ridge
developing over Alaska and northern Pacific, favoring surface
high pressure to build southward into the central CONUS by late
next weekend, continuing into the 7 to 10 day range. Just how
cold it will get remains uncertain at this time, however,
confidence continues to increase in a period of sub-freezing
and perhaps well-below freezing temperatures to be felt across
the region as we head into the first part of December. This is
highlighted by CPC`s 6-10 Day Temperature Outlook favoring
below normal temperatures across the eastern third of the CONUS.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 541 PM CST Sat Nov 23 2024

For the KLBF terminal: Lower clouds will move into the area
overnight with ceilings around 2500 FT AGL. There is also a
threat for patchy fog at the terminal with visibilities as low
as 2sm during the overnight hours. Skies will scatter out on
Sunday with scattered ceilings around 20000 FT AGL. For the KVTN
terminal: Expect ceilings below 1000 FT AGL through 08z
overnight. Skies will remain cloudy, however, ceilings will
increase to around 12000 FT AGL as winds shift to the west then
northwest overnight. Lower ceilings will then set back in by mid
to late morning Sunday with cloud decks around 2000 FT AGL.

&&

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

&&

$$

SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Buttler