Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 211741

Area Forecast Discussion
National Weather Service Cheyenne WY
1141 AM MDT Wed Mar 21 2018

.SHORT TERM...(Today through Thursday night)
Issued at 415 AM MDT Wed Mar 21 2018

Current KCYS radar loop shows some precip west of the Laramie
Range early this morning as there is some warm air advection and
jet energy aloft. Some snow mixed with light rain is reaching the
ground, but it isn`t amounting to much with generally trace
amounts observed. Expect this to continue this morning until the
upper level ridge begins to amplify along the Rockies later today
and subsidence increases. This will result in warmer temperatures
with highs in the 50`s to low 60`s as winds shift into the west
or southwest. Model soundings are favorable for some fog
development late tonight as warm air aloft moves across the area
and skies clear, so added some fog in the lower valleys from just
east of Lusk towards Chadron and Alliance Nebraska. Some fog is
possible across the lower North Platte River valley as well. For
Thursday, models show the upper level flow shifting into the
southwest ahead of a strong Pacific storm system moving onshore.
Highs in the upper 50`s to upper 60`s are expected Thursday
afternoon with a few locations reaching 70 degrees over far
eastern Wyoming and the southern Nebraska panhandle.

Models show a weak disturbance quickly moving northeast across
Wyoming Thursday night, resulting in an increase in shower
activity, mainly west of Interstate 25. Some cooler air will move
into the western zones, so expect some accumulating snow above
9000feet in the mountains. In the lower elevations, it will be
relatively mild at night with lows in the upper 30`s to upper 40`s
mainly because of increasing cloudiness.

.LONG TERM...Thursday Night - Tuesday

Medium-range models are in excellent agreement w/ deep upper-level
troughing over the Pacific NW early in the period. Moist southwest
flow over the central Rockies, coupled w/a fast-moving disturbance
traversing the flow should support at least scattered rain or snow
showers across much of the area Thu night/Fri. However, an overall
progressive pattern and fairly warm thermal profiles would suggest
limited potential for accumulations. Breezy conditions are likely,
especially along/west of the Laramie Range on Friday. An unsettled
pattern persists through the weekend as multiple weak disturbances
emanate from the western US trough. The GFS/ECMWF are in agreement
with a stronger low taking evolving over the southwestern US early
next week. It is much too early to go into any details, but expect
to see increased chances for precipitation around Mon/Tue with any
impacts depending heavily on how this system evolves. It will most
certainly be something we will need to keep an eye on. Chances for
precipitation may exist almost any given day this period. In fact,
there may be enough instability for a few thunderstorms as well as
we head through the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1137 AM MDT Wed Mar 21 2018

Upper level ridge will continue to dominate the area during the
next couple of days, resulting in VFR conditions. It will be
become a bit breezy at RWL and LAR on Thursday morning as the
upper level trof approaches the northwest Pacific coastline and
increases the pressure level gradient.


Issued at 333 AM MDT Wed Mar 21 2018

Minimal Fire Weather concerns through the end of the week with
minimum relative humidities between 20 to 35 percent and
relatively light winds across the eastern plains. Winds will begin
to increase late Thursday and early Friday ahead of the next cold
front, but temperatures will lower for the weekend with a chance
of rain and snow.




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