663
FXUS65 KCYS 231738
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
1038 AM MST Sun Feb 23 2020
.SHORT TERM...(Today and tonight)
Issued at 410 AM MST Sun Feb 23 2020
Light winds prevail today under increasing clouds and snow showers
along the I-80 corridor and towards the south. Temperatures will
generally cap out in the 30s and 40s across the region in stark
contrast to the warm weekend we've been having. This will all be
occurring as a cut-off low passes to our south, centered over the
CO-NM border. Snow showers will be light and should have little
impact, though roads effected could become slick at times. The
cold front associated with this system will pass quickly through
the region this evening, with clearing skies behind it for the
overnight period. As the front passes through it will couple with
a strong positioned shortwave directly behind it. Surface
gradients will tighten and low-level subsidence will increase for
strong winds across southeast Wyoming's wind-prone areas through
Monday. A High Wind Warning has been issued for the I-25 corridor
near Bordeaux and the I-80 corridor near the Summit, Arlington,
and adjacent foothills, beginning at 8 PM tonight. Please see the
Warning for further information.
.LONG TERM...(Monday through Saturday)
Issued at 410 AM MST Sun Feb 23 2020
A complex forecast is in store for the Monday and Tuesday period
behind an exiting system, and accompanying a strong and energetic
northwest flow aloft. Several components will factor in:
1. the aforementioned High Wind Warning will continue into the
day Monday across the wind-prone areas of southeast Wyoming.
However, strong gusts up to 50 mph are likely across areas west
of the Laramie Range early MOnday morning as a strong surface
front, coupled with an energetic shortwave descend quickly into
the region from the northwest. This energy will then transfer to
the east of the Laramie Range by mid-morning as the front and
shortwave pass through, and then continue into the afternoon as a
cut-off low passes over the southwest corner of South Dakota.
Winds will finally diminish slightly in the evening, ending the
High Wind Warning. Still winds will be sustained 20 to 30 mph with
gusts 35 to 45 mph through Tuesday east of the Laramie Range as a
strong 100 kt jet moves across the High Terrain and then the High
Plains from west to east Tuesday.
2. The northwest flow will bring generally light snow showers to
the region, though the Sierra Madres and Snowy Mountain Ranges
and our northern counties found along and near the Pine Ridge will
see higher amounts of accumulated snow. Under a northwesterly
pattern and an upslope flow, the mountain ranges do quite well in
terms of snow. We have issued a Winter Weather Advisory for these
areas, but will note that the winds expected over the same time
period will lead to low visibilities at times and difficult travel
conditions. Additionally, as colder air is ushered into the area
behind the front buried in the northwest flow, wind chill
temperatures are expected to drop to around 20 below zero by
MOnday afternoon - these conditions can lead to frostbite and
hypothermia. To the north, guidance is indicating that an area of
surface convergence will set up generally along the Pine Ridge
Monday morning. This feature will pair with increased CAPE, or
energy, and a 300 mb 70 kt jet aloft to produce an elongated area
of heighten snow production. Several inches of snow will be
possible along this elongated band of convergence. As winds rip
and roar over the course of the day Monday and Tuesday, it will
combine with winds for blowing snow and areas of reduced
visibilities. A Winter Weather Advisory has also been issued for
these conditions. Please see the text for further details.
As the 100 kt jet passes east Tuesday night, snow will tapper off,
winds will diminish, and overnight low will drop into the single
digits. Look for wind chill temperatures varying between 10 above
zero to the east, and 10 below zero to the west. A slow warmup
will ensue as winds turn westerly and a ridge of high pressure
moves off the Pacific coastline and pushes inland. A quick, weak
pulse will bring isolated shower activity Thursday, but otherwise,
dry conditions and a warming trend are expected for the end of the
week.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1038 AM MST Sun Feb 23 2020
VFR conditions currently at area terminals with ceilings around 8
kft for terminals near the CO/WY border. Recent radar imagery
shows echos across this region, however observed dewpoint
depressions and sounding profiles suggest no precipitation is
reaching the ground due to low level dryness. RAP forecast
soundings suggest low level moistening is possible during a short
window this afternoon which could bring ceilings down lower.
Otherwise, VFR conditions are expected for most area terminals
until late in the forecast period for KCDR as snow showers will be
possible after 12z Monday.
&&
.FIRE WEATHER...
Issued at 410 AM MST Sun Feb 23 2020
Westerly winds will soon turn northerly as a cut-off low passes
across southern Colorado, stopping the warming trend we've had
these last few days. Increasing clouds today and relative
humidities, with showers possible along the Colorado border and in
the mountains. Winds increase tonight and will remain heightened
through Tuesday as a strong northwesterly flow sets in aloft.
Winds will be accompanied by generally light snow showers.
Conditions become dry once again by the end of the week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 5 AM Monday to 8 PM MST Tuesday for
WYZ101-102-112-114.
High Wind Warning from 8 PM this evening to 5 PM MST Monday for
WYZ106-110-116-117.
NE...Winter Weather Advisory from 5 AM Monday to 8 PM MST Tuesday for
NEZ002-095.
&&
$$
SHORT TERM...AB
LONG TERM...AB
AVIATION...MB
FIRE WEATHER...AB
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