Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 131748
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1148 AM MDT Fri Oct 13 2017

.SHORT TERM...Friday through Sunday night

Things will turn a bit more active today with two concerns. The
first is across the west as a Pacific trough and cold front approach
the area. This will lead to increased clouds as well as some rain
and snow showers across the northwest today. At this point, there is
not a tremendous amount of moisture or forcing with the system so
amounts should remain sub advisory for the most part. For tonight,
snowfall may enhance a bit more, especially a bit further south as
the trough axis approaches and a bit more upper level support
emerges in the form of the right rear quadrant of jet streak.
However, this looks to be a quick hitter so again amounts should
remain below advisory level except maybe in the very highest
elevations where effects will be minimal.

Concerns shift to the fire variety East of the Divide. Temperatures
will be seasonable. However, it will remain dry with low relative
humidity. In addition, there will be a gusty southwest wind
developing ahead of the advancing cold front. There could be
critical fire conditions for a short time. However, with the shorter
days it is unlikely we would reach red flag criteria. So for now, we
will stick to a special weather statement.

The cold front will swing across the area Saturday morning. The
models have some into better agreement with a brief period of
northerly upslope developing across the favored areas like Casper
and the Wind River Mountains. As a result, we raised POPS and QPF
and the day shift should consider raising them some more. As for
amounts, with the quick movement of the system, amounts should
remain sub advisory. However, there could be a brief period of tough
travel conditions with a period of moderate snow and a gusty wind
Saturday morning. All snow should end by early afternoon though.
With the cold advection and lingering cloud cover, it will be a cold
day, especially further east where the clouds will be slow to clear.
As a result we kept temperatures below guidance.

The area should enter into a quieter weather pattern starting Sunday
as dry northwest flow moves into the area and ridging builds across
the west coast. Temperatures should recover to near normal levels
with a good deal of sunshine leading to a nice finish to the
weekend.

.LONG TERM...Monday through Friday

Zonal flow to flat ridging is expected through middle of next
week. The flow is dry to very dry through Wednesday with no
precipitation. Temperatures will be above average with breezy
winds at times elevating fire weather conditions in the lower
elevations.

Global models show a trough pushing into the West Coast Thursday,
and then across the Rockies in various intensities Friday into
early Saturday. Ahead of the trough on Thursday looks to be
mainly dry, breezy with mild to warm temperatures with increasing
chances of precipitation (based on current timing) mainly over the
west Thursday night/Friday. For now, will keep areas east of the
Divide dry on Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1125 AM MDT Fri Oct 13 2017

VFR conditions will prevail across the area through 00Z Saturday.
A cold front will bring scattered to numerous snow showers into
the northwest mountains, vcnty and north of a KJAC-KDUB line,
late Friday afternoon into the overnight hours with increasing
mountain obscurations. Surface SW winds have started to increase
to 15-25 knots across much of southern and central Wyoming. The
cold front will push SE across the rest of the area 06z-18z
Saturday, spreading sct MVFR/IFR valley and numerous mountain
snow showers across the area. The main band of MVFR/IFR snow
showers are expected to be centered roughly along a vicinity KAFO-
KRIW- KCPR line 09z-12z Sunday. These showers will quickly end
from west to east after 15Z Saturday.

&&

.FIRE WEATHER...

...ELEVATED FIRE CONDITIONS FOR NATRONA COUNTY THIS AFTERNOON...

A Pacific Cold front will approach the area today and bring some
rain and snow showers to areas West of the Divide today and tonight,
spreading East late tonight and into Saturday. A gusty southwest
wind will develop today East of the Divide, especially from Rock
Springs through Casper. Relative humidity will fall into the teens
this afternoon. Although critical fire conditions are not expected,
fire danger will be elevated at times this afternoon in areas where
fuels are still critical. Mixing and smoke dispersal will be
generally fair to good.

&&

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

$$

SHORT TERM...Hattings
LONG TERM...Murrell
AVIATION...LaVoie
FIRE WEATHER...Hattings



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