Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 192056

Area Forecast Discussion
National Weather Service Cheyenne WY
256 PM MDT Wed Oct 19 2016

.SHORT TERM...(This evening through Friday night)
Issued at 255 PM MDT Wed Oct 19 2016

Current KCYS radar loop shows scattered showers north of I-80
early this afternoon as the secondary disturbance digs southeast
across Wyoming. Most of the precipitation is due to llvl
instability and some llvl convergence...with even a few thunder
showers from time to time from north of Rawlins eastward towards
the northern Nebraska panhandle. This activity will slowly
translate southeast towards the I-80 corridor by this evening with
secondary redevelopment possible across the mountains of southeast
Wyoming as the vorticity max associated with the disturbance
gradually moves eastward into western Nebraska late this evening.
The only minor concern is some high elevation snow showers through
this evening producing locally heavy snowfall and slick
roads...but do not expect snowfall rates to be all that high
since activity will likely be diminishing after sunset.

After midnight...drier conditions are expected with dry weather
lasting into this weekend. It will be cold Thursday morning with
lows in the 20`s across most locations...and even in the mid to
upper teens over the more sheltered valleys west of the Laramie
Range. Thursday will remain seasonably cool due to northwest flow
aloft but it will be near normal for this time of the year as
highs climb in the mid 50`s to lower 60`s. There is some concern
of a wind event for our wind prone areas across southeast Wyoming
late Thursday night and early Friday morning. Models show 850mb to
700mb gradients increasing with winds at 700mb around 40 to 45
knots. Subsidence increases in these areas as well with a moderate
llvl pressure gradient. For now...increased winds for sustained
between 25 to 35 mph and gusts as high as 50 mph over the wind
prone areas. Graidents and speeds for high winds are still below
critical thresholds so will just monitor for now. Models then show
the upper level ridge axis currently over the Great Basin
translating eastward into the central Rockys for
Friday...resulting in increasing 500mb heights and 700mb
temperatures with highs returning to the 60`s for most of
southeast Wyoming and low to mid 70`s further east across western

.LONG TERM...(Saturday through Wednesday)
Issued at 209 PM MDT Wed Oct 19 2016

Shortwave ridge over the area on Friday will transition eastward by
Saturday with flow aloft becoming more southwesterly.  It will be a
breezy day across southeast WY as the CAG-CPR gradient increases to
around 40 meters.  Could be some elevated to critical fire weather
conditions on Saturday aftn over the plains of southeast WY where
min RH values will be 15-20 percent.  Temps will continue to be
around 10-15 degrees above normal through Sunday.  Both the GFS and
ECMWF show increasing amounts of pacific moisture streaming into the
region by Monday evening and Tuesday.  The best chance of rain
showers (20-40 percent) will be across the Sierra Madre and Snowy
Ranges where orograhphics improve forcing.  While temps will cool a
bit by Tuesday, more significant cooling looks to occur by mid week
behind a fropa as an upper trough digs into the Intermountain


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1127 AM MDT Wed Oct 19 2016

Mostly vfr conditions through the taf period. West winds will
gust to 20-30 kts through the afternoon at the southeast WY sites.
Isolated showers and thunderstorms will develop by around 20Z for
areas to the east of the Laramie Range. While brief mvfr cigs in
any heavier showers will be possible, duration and coverage is not
expected to be high enough to include in taf.


Issued at 148 PM MDT Wed Oct 19 2016

No Fire Weather concerns through the rest of the week with
concerns increasing a bit for the weekend. Scattered showers and
isolated thunder will continue this afternoon and through this
evening. Drier weather is expected Thursday through Sunday with
temperatures gradually moderating. Mild temperatures are expected
this weekend with low daytime humidities around 15 to 20




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