Area Forecast Discussion
Issued by NWS Riverton, WY

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014
FXUS65 KRIW 241715
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1015 AM MST Fri Nov 24 2017

.SHORT TERM...(Today and tonight)
Issued at 443 AM MST Fri Nov 24 2017

The high wind warning continues through 5 am for the Absaroka
mtns/Cody Foothills as well as the Green mtns through 5 am this
morning. 60 knot winds at 700mb ahead of a southeast bound trough
now over Montana and Idaho will surface during this time frame
along with a 4.5 30 decameter height lines at 700mb, as well as a
9 mb sfc pressure gradient between GCC and RKS to produce these
winds in these areas. In addition, there appears to be a gravity
wave pushing southeast ahead of the main trough. This wave is seen
seemingly gobbling up the lee enhanced clouds from nw to se. This
wave produced 40 to 50 mph wind gusts in Johnson County and now
that it is exiting our CWA, this wave just produced an all time
record wind gust of 95 mph at Camp Creek RAWS in the Green Mtns
between 11 amd and 12 midnight. In the next couple of hours, rain
showers should break out in far Western Wyoming with snow levels
dropping down to about 7000 feet after sunrise this morning. we
should see a quick shot of 3 to 6 inches of snow above 7500 feet
along with 9 inches above 10K in the higher Tetons. rain will fall
below 7000 feet but it will take a while for these elevations to
call down. Currently the temperature in Jackson is a balmy 50
degrees along with a warming southwesterly 36 knot wind gusts out
ahead of the approaching trough. we should witness an additional
spike in the winds in many areas between 12 and 15z this morning
with the 5mb 3 hourly sfc pressure rises just behind the cool
front. Some rain and mountain snow will spread across Northern
Wyoming this morning as well but with less QPF. Up to 3 inches of
snowfall is expected along the higher Big Horn Mtns. Clearing will
take place from northwest to southeast this afternoon along with
partial clearing in the far west after mid afternoon. Only spotty
showers are expected through the rest of the weekend in the far
west if any. Temperatures will cool slightly Saturday along with
warming on Sunday as the ridge rebuilds over the areas. The next
shortwave will move in from the west southwest and produce an
inch or two of snow in the far west Sunday night.



.LONG TERM...(Saturday through Thursday)
Issued at 443 AM MST Fri Nov 24 2017

The ECMWF was the first to pick up on this last night but it now
appears the Monday system will be splitting as it approaches
leaving us with a weakened system. Still a shot of mountain snow
out west Monday with rain or rain/snow in the far west lower
elevations. Much warmer system now than it looked a few days ago.
Amounts now look generally sub-advisory in the high country. Still
windy ahead of this trough but not as windy as it looked with a
more consolidated system. A chance of rain changing to rain/snow
mixture or brief snow east of the divide behind the cold front.
Brief shortwave ridging Tuesday before a new system dives down
from the se. GFS picked up on this last night and now the Euro and
GEM are also showing it. Could be a potent quick hitting system
with much colder air than our Monday system. Good shot of snow
across the wrn and nrn mountains and quite possible a period of
snow with fropa east of the divide. As mentioned last night, we`ll
have to watch this system with time as the chance of snow could
be much greater than the model blend. Brief shortwave ridging then
Thursday before a rapid flattening occurs ahead of another
potential system just beyond this period. Winds will be on the
increase once again as the ridge flattens and the next system
approaches. So increasing wind for many areas later
Thursday/Thursday night through Friday with temperatures warming
back up behind our midweek system. A chance of snow returning to
the far west Friday.

&&

.AVIATION...18Z Issuance

VFR conditions to prevail at the terminal sites for most of the time
through 00Z. A cold front dropping from north to south will bring
scattered rain showers through around 21Z. This front will push
through Central WY around 18Z. There will be MVFR ceilings at times
east of the divide. Conditions will improve over the north after 21Z
and in the central after 00Z. VFR conditions are to occur after 00Z
through 17Z Saturday.

Please see the latest terminal forecasts for more details.

West of the Divide...KBPI/KJAC/KPNA/KRKS Routes

VFR conditions will prevail at most places through the period.
Scattered rain showers with mountain snow showers in NW WY will
spread southward today and out of the area around 00Z. KJAC airport
should see a period of MVFR ceilings and rain showers today. A gusty
wind will occur at KRKS airport through 01Z, then decrease. Patchy
fog may develop in the vicinity of KJAC and KBPI after around 07Z,

Please see the latest terminal forecasts for more details.

Please see the Aviation Weather Center for the latest information on
icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 443 AM MST Fri Nov 24 2017

Strong west winds aloft will continue to surface and bring high
winds to portions of the Absarokas and Cody Foothills as well as
along the Green Mountains and Rattlesnake Range through 5 am this
morning. Pacific moisture in strong west flow aloft will bring
increasing snow to the higher mountains of western wyoming with
mainly rain below 8700 feet early this morning and then lowering
to 7000 feet later this morning, and then tapering this afternoon.
Most areas above 7500 feet can expect 3 to 6 inches of snow with
areas around 10 inches above 10000 feet with wind gusts tonight
around 60 mph. A cold front will move south this morning bringing
increased showers to the north and colder air with a wind shift
to the north and northeast bringing an end to the high winds.
Temperatures will drop 15 to 20 degrees in the east with many
areas falling around 10 degrees elsewhere from Thursdays
temperatures.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

SHORT TERM...Lipson
LONG TERM...Skrbac
AVIATION...Hattings
FIRE WEATHER...Lipson



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