904
FXUS65 KCYS 081759
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1059 AM MST Fri Nov 8 2024

.KEY MESSAGES...

- Areas of freezing fog and/or freezing drizzle are possible
  along the I-80 corridor from the summit eastward tonight into
  Friday morning.

- The storm system will return to the area from the south Friday
  afternoon and continue into Saturday with wet snow
  accumulation possible in far southeast WY and the southern NE
  panhandle. See below for more details.

- An occasionally windy and mostly dry period will occur for
  Sunday through Thursday, with warmer than normal temperatures
  for each day except for Wednesday.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 245 AM MST Fri Nov 8 2024

Impactful weather ongoing this morning with patchy dense fog and
areas of snow/freezing drizzle along the Interstate 80 corridor
from Kimball to the Summit. WYDOT webcams showing dense fog in
the eastern foothills and here in central Laramie County. Went
ahead and issued a Dense Fog Advisory to cover the area
mentioned through 9AM this morning. Moisture streaming north
ahead of the closed low over western New Mexico this morning.
METARS in eastern Colorado reporting rain and some fog in their
reports. As this moisture encounters higher terrain up
here...we`ve been seeing burst of snow with light accumulations
so far.

GFS has come in line with the ECMWF this morning on the track of
this closed low. Low tracks almost due north...maybe a little
northeast into east central Colorado and eventually northeast
Colorado this afternoon and evening. QPF amounts have really
increased over solutions from 24 hours ago. Now seeing over an
inch of QPF over the southern Panhandle...with .5 to .6 inches
over Cheyenne late this afternoon and evening. Good isentropic
lift seen on both the GFS and ECMWF supports the higher QPF.
Limiting factor will be how cold it gets in the TROWAL feature.
Went ahead with Winter Weather Advisories from Kimball to the
I-80 Summit. Day crew will need to monitor temperatures and be
prepared for upgrades and expansions of winter headlines should
we get even 2-3C colder. Would not be surprised at all if
further upgrades/expansions are issued later today.

Rain and snow continue through Saturday morning before the low
tracks into central Nebraska. May not be until late Saturday
afternoon before rain/snow starts tapering off as the low moves
east and finally exits east Saturday evening.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 245 AM MST Fri Nov 8 2024

Medium to long range models in reasonable agreement through the
middle of next week, showing quasi-zonal flow developing over
the northern and central Rocky Mountains once this weekend`s
storm system moves east of the area. Some models, such as the
GFS and Canadian, show a weak front quickly moving across the
region. Other than some cloudiness and increasing winds, not
many impacts are expected. Temperatures are forecast to return
to normal for this time of the year with highs in the mid 50s to
low 60s for the eastern plains, and in the mid 40s west of the
I-25 corridor.

For the middle of the week, models show the next Pacific storm
system moving onshore and weakening as it moves into the
Intermountain West. With a northward storm track, expect low
chances for precipitation for the valleys and high plains and
more strong winds possible since the weather pattern for midweek
appears like a typical strong wind pattern for southeast
Wyoming with a 140 kt anticyclonic jet core at 300mb lifting
northeast across the region. May need some High Wind headlines
beginning Sunday night and Monday and likely Tuesday into
Wednesday. Started increasing winds for the wind prone areas for
now, but the secondary wind prone areas (Cheyenne, Laramie
Valley, Coleman/Converse County) may be next if current trends
continue. Temperatures will briefly lower behind the cold front
on Wednesday, back into the 40s to low 50s, but should rebound
later next week as all models show another ridge of high
pressure aloft building over the Front Range and Intermountain
West.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1042 AM MST Fri Nov 8 2024

Latest radar loop was showing the snowfall mostly in northern
Colorado, but there have some bands of snow that have been
crossing the I-80 corridor at times. These bands of snow have
reduced the visibility to near a mile or less at times and
reduced the ceilings to the MVFR category. This trend should
continue during the next two to three hours with more widespread
and heavier snowfall moving into the higher elevations above
5kft agl after 22Z. This includes areas between KIBM and KLAR.
LIFR ceilings and vsby are likely this evening and overnight.
Meanwhile, the lower elevations will experience mostly rain with
better visibility, but the ceilings will still most likely be in
the IFR category. KLAR may actually get shadowed by this event
due to northeast flow through much of the day into the evening.
The wind is expected to switch to the north at KLAR after 09Z
which may reduce the visibility and lower ceilings.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 11 AM MST Saturday for
     WYZ116>119.
NE...Winter Weather Advisory until 11 AM MST Saturday for NEZ054.

&&

$$

SHORT TERM...GCC
LONG TERM...TJT
AVIATION...REC