Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 190442

Area Forecast Discussion
National Weather Service Riverton WY
1042 PM MDT TUE OCT 18 2016

.SHORT TERM...Tonight Through Friday (Issued at 137 PM MDT)

The snow covered Upper Green started out quite cold this morning as
expected with BPI dropping to 8 while PNA hit 14. Cloud cover and
snow showers around will likely help hold them up a little tonight.
Further west, where we have our winter weather advisory for the
Tetons/Gros Ventre ranges through tonight. Snow showers are
already spreading into the area and with steep lapse rates and low
to slightly negative li`s, we`ll have the potential for some heavy
snow showers and perhaps a lightning strike or two through the
evening. Could see some 1-2 inch per hour rates in the heavier
snow showers. Short lived storm though as their is little forcing
aloft after this afternoon and with daytime heating looks like
snow shower intensity and coverage will gradually taper off later
tonight. Across Sweetwater County, a vort max is helping with the
development of snow showers in the swrn corner and they will
spread across at least the south half of the area through this
evening with local light accumulations. A few snow showers or
mixed rain and snow showers will develop east of the divide later
this afternoon and evening but most will likely hold off for the
sewd moving shortwave on Wednesday. This has -26c air with it and
a front that works swd. Best chance will be along and behind the
front across the north and and east and favored nw flow areas (off
the sern Absarokas, srn Wind Rivers and srn Bighorns). Some light
accumulation will be possible with locally heavier bands where
convergence is more focused. gradual improvement Wednesday night
but chilly. Gradually warming temps Thursday into Friday and dry.
The only exception may be the high country near the MT border in
the nw where a few light showers/flurries may occur Thursday
afternoon and evening with a passing weak wave and some isentropic
upglide. Not much but enough to add slight chance pops. The other
thing to watch will be the increasing wind potential along the
Cody Foothills Thursday night as lee troughing develops to the
north, thermal gradient increases along the Absaroka barrier and
jet passes to the north. Plenty of time to watch and see how the
mesoscale guidance looks over time but added in more wind than the
guidance was showing and expect our normal area to at least be
windy with some potential for high winds in the gaps/Clark area.

.LONG TERM...Friday Night Through Tuesday

There is not much to talk about through the weekend other than that
it looks like a very nice, autumn weekend with mild temperatures and
light to moderate winds. There will be some high clouds at times,
especially across the north with a couple of shortwaves zipping by
across Montana. Otherwise, dry conditions and near to above normal
temperatures. The only concern would be elevated fire danger in
Natrona County but conditions at this time appear marginal at best
right now.

The more active weather and uncertainty creep into the forecast by
Monday. Both the GFS and European show a couple of systems moving in
from the southwest and the potential for unsettled weather Monday
and Tuesday, especially West of the Divide. As is expected, the
models are all over the place as to details. The European at this
point is the fastest and wetter model while the GFS is drier. At
this point with the uncertainty, we kept the low broad brushed POPS
in the forecast until things become clearer.




Areas of MVFR and IFR will occur due to lower ceilings and
visibilities due to snow showers through 15Z. Conditions will
gradually improve after 15Z as the snow showers will be mainly
in the mountains through 20Z. Expect mountains to be frequently
obscured through 23Z. After 00Z the snow showers end in the
mountains with clouds decreasing. VFR conditions will occur at
the KRKS terminal site through the period.


VFR conditions prevail through 12Z. Then scattered snow showers
will develop after 14Z and continue through 00Z Thursday. Areas
of MVFR conditions will occur in snow showers as ceilings and
visibilities will lower. Check the terminal forecast for more
details. VFR conditions will prevail after 00Z Thursday as the
snow showers end by 03Z Thurs.



Fire danger low all areas through Wednesday. Another upper level
disturbance and even a cold front will move through the forecast
area later tonight and Wednesday with more snow coming to the
western and northern mountains...with even a chance for light rain
or snowfall across the lower elevations east of the Divide. Modest
warming and drying will occur from Thursday onward. Some elevated
fire weather concerns on Thursday afternoon with breezy to windy
conditions in the wind corridor from Jeffrey City to Casper and min
rh`s in the upper teens to lower 20s (percent).


.RIW Watches/Warnings/Advisories...
Winter Weather Advisory until 6 AM MDT Wednesday for WYZ012.



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