Area Forecast Discussion
Issued by NWS Riverton, WY

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327
FXUS65 KRIW 122053
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
153 PM MST Sun Nov 12 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 137 PM MST Sun Nov 12 2017

Dry high pressure will be over the western and central Wyoming
tonight and Monday. High and mid clouds will increase in southwest
flow aloft on Monday and Monday evening.  Downslope winds will
increase along and near the east slopes of the mountains and through
the wind corridor across Sweetwater, southern Fremont and Natrona
counties.  Monday night winds may reach high wind category across
the Cody foothills and across southern Fremont and Natrona counties
with the threat of high winds continuing through Tuesday.
Some light snow showers will develop late Monday night increasing
across the western mountains on Tuesday as southwest winds become
quite strong over the higher ridges and passes of the west as well.
The snow will end rapidly Tuesday evening with clearing through
Wednesday.

.LONG TERM...(Wednesday night through Sunday)
Issued at 137 PM MST Sun Nov 12 2017

Beginning of fcst, a shortwave ridge passes through and to the east
of WY while the upper levels begin transition to southwesterly
Wednesday night with an advancing broad trof on the way toward/into
the region. A brief strong wind pattern will become possible by
Wednesday night over the nrn Mountains and Foothills as mid/upper
level flow across this region (mountains) will be favorable to the
formation of good amplitude mountain waves, combining with 50 - 60
kt winds at ridgetop and lee side troffing. The Wind Corridor is
also expected to react to the approach of this system with increased
winds...along with another brief period of marginal High Wind
possible ahead of a cold front due to arrive across the FA later
Thursday. As the large/broad upper level trof continues to approach
WY, much of wrn,swrn/srn WY will be under increasingly favorable
upper level dynamics from the jet (110-140kt), combining with
increasing EPAC moisture and giving growing areas of clouds and also
increasing precip chances across wrn/swrn/srn WY overnight Wednesday
night, through Thursday morning and into/through Friday morning. As
the trof axis passes through WY later Thursday/Thursday night, an
associated front will get pushed through the FA with some lower
chances for precip arriving east of the Divide. Highlights likely
west of the Divide beginning sometime Thursday.

The significant/persistent GFS/EC temporal differences (GFS overall
quicker/EC slower) are still present although the gap continues to
slowly close. The GFS solution is "slowing slightly slightly faster"
than the EC`s continued slow down. Spatial differences, however,
seem to be at a minimum. This slow down trend within a quite
progressive upper level pattern has continued over the past several
days with both models well out of phase from a timing standpoint by
Friday. Pushing higher POPs through Friday morning and into the
afternoon is how this problem will currently be handled with respect
to both models. Of course, there are split expectations at this
point that in another 24 hrs either both models will finally be
within 3 to 6 hrs of each other, ending Friday afternoon...or the
slowing trend continues and significant POP chances will continue
into Friday night. Betting on the trend?

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday)
Issued at 137 PM MST Sun Nov 12 2017

VFR conditions will prevail through the forecast period at all
terminal sites. VCFG KWRL 11Z-15Z Monday morning. A gusty wind will
return to KCPR airport Monday morning, decreasing by 23Z Monday
afternoon.

&&

.FIRE WEATHER...
Issued AT 137 PM MST Sun Nov 12 2017

Dry high pressure will be over the western and central Wyoming
tonight and Monday. High and mid clouds will increase in southwest
flow aloft on Monday and Monday evening.  Downslope winds will
increase along and near the east slopes of the mountains and through
the wind corridor across Sweetwater, southern Fremont and Natrona
counties.  Monday night winds may reach high wind category across
the Cody foothills and across southern Fremont and Natrona counties
with the threat of high winds continuing through Tuesday.
Some light snow showers will develop late Monday night increasing
across the western mountains on Tuesday as southwest winds become
quite strong over the higher ridges and passes of the west as well.
The snow will end rapidly Tuesday evening with clearing through
Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baker
LONG TERM...Braun
AVIATION...Braun
FIRE WEATHER...Baker



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