Area Forecast Discussion
Issued by NWS Cheyenne, WY

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

FXUS65 KCYS 131032

Area Forecast Discussion
National Weather Service Cheyenne WY
332 AM MST Tue Feb 13 2018

.SHORT TERM...(Today through Thursday)
Issued at 330 AM MST Tue Feb 13 2018

Concerns this period will be with an expected strong wind event
tonight through the day Wednesday. Currently quiet across the CWA
with snow pretty much over. A few snow showers still possible
over the higher mtns but little additional snowfall expected so
have cancelled the Winter Wx Advy that was in effect for the
Sierra Madre Range. SW to westerly flow aloft will continue over
the CWA through Thursday with weak impulses bringing some snow
showers at times to the higher mtns. Mainly dry elsewhere until
Thursday when the next cold front will move south across the CWA
and bring some post-frontal snow showers mainly across the north.

7H winds will increase over SE Wy this afternoon as lee troughing
deepens over the high plains today. Winds exceed 50 kt by late
evening, and with good downward motion, expect strong winds to
begin in the Bordeaux/Arlington/Muddy Gap areas this evening.
Strong winds look to spread east later tonight to include the Srn
Laramie Range area as well as the Laramie Valley with 60-65kt winds
at 7H over this area. Confidence is sufficiently high to go ahead
and upgrade these areas to High Wind Warnings. Will keep Converse
and central Laramie county watches in place for now but delayed
the onset as the stronger winds there should hold off until later
in the morning. Winds should diminish Weds evening as the pressure
gradient decreases.

Developing lee trough will erode the cold air out of the CWA today,
so warmer temperatures expected given sunshine and more downslope
flow. Continued mild Wednesday.

.LONG TERM...(Thursday night through Monday)
Issued at 330 AM MST Tue Feb 13 2018

00Z medium range models/ensembles portray an active, progressive
large scale pattern across much of the CONUS through the long term.
Fast west to northwest flow aloft will prevail through the weekend
with periods of strong winds likely for much of southeast Wyoming.
The period of strongest winds will be from late Friday night through
early Sunday morning when the CAG-CPR 700/850mb gradients peak
between 60 and 75 meters and 700mb winds increase between 55 and
65 kt. Wind-prone areas will be most susceptible, but cannot rule
out adjacent valleys and plains of southeast Wyoming. High wind
headlines will eventually be required by the end of this week.
Temperatures will moderate from Thursday`s cooldown with highs
back into the 30s and 40s, with even a few low 50s on Saturday.
Changes take place late Sunday into Monday as a long wave trough
digs southeast into the Intermountain West, with the flow aloft
becoming west to southwest. Pacific moisture will spread northeast
into the region as a resurgence of Arctic air pushes south. Model
differences occur at this time, with the ECMWF/Canadian solutions
further south with the Arctic frontal progression into Colorado,
while the GFS develops a wave along the front over southeast
Wyoming. ECMWF 700mb temperatures fall into the lower 20s below
zero Celsius, while GFS 700mb temperatures fall into the single
digits below zero Celsius. ECMWF is most bullish with QPF,
followed by the Canadian, and GFS the least. Since these model
differences for Day 6-7, generally followed a blend of the
SuperBlend and WPCGuide models for PoPs, QPF and temperatures.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 330 AM MST Tue Feb 13 2018

Lingering MVFR early this morning for portions of the Nebraska
Panhandle, becoming VFR. VFR elsewhere. West to southwest winds
increasing through the day across southeast Wyoming, with gusts
from 20 to 35 kt this afternoon and evening. Stronger winds with
mountain wave activity develops tonight along and west of the
Laramie Range. Light/variable winds wil become westerly around 10
kt for the Nebraska Panhandle. Snow showers will create occasional
obscurations over the Snowy/Sierra Madre Ranges through the TAF


Issued at 330 AM MST Tue Feb 13 2018

Warmer temperatures will return to the area today and Wednesday but
some snow showers will continue at times over the higher mountains.
Of more concern will be with increasing winds, which are expected
to occur later today and tonight around the mountains, and continue
through much of the day Wednesday. Overall fire weather concerns
will remain low however, with cooler temperatures returning by


WY...High Wind Warning from midnight tonight to 6 PM MST Wednesday
     for WYZ107-109-115>117.

     High Wind Warning from 6 PM this evening to 6 PM MST Wednesday
     for WYZ104>106-110.

     High Wind Watch from Wednesday morning through Wednesday
     afternoon for WYZ101-118.



FIRE WEATHER...RE is the U.S. government's official web portal to all federal, state and local government web resources and services.