Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 151744
AFDRIW

Area Forecast Discussion...Update
National Weather Service Riverton WY
1045 AM MST Sun Jan 15 2017

.UPDATE...Extended dense fog advisory for sweetwater county
through noon Monday.

.SHORT TERM...Sunday through Tuesday night

Conditions will remain favorable for widespread fog across
sweetwater county and interstate 80 through noon Monday.

High pressure will control the weather through the next 48 hours
or so and keep conditions similar. That means a mostly sunny sky
for most areas with no chance of snow. Areas that can mix, like
around Cody or Casper, will see temperatures close to seasonal
averages. However, across the Basins and Valleys, inversions will
likely hold another day and keep temperatures chilly. Not brutally
cold, just cold, nothing unusual for January. Also, the fog
monster has reared its ugly head once again across Sweetwater
County. We will continue the advisory as is through noon monday.
Other areas will have to be watched as well.

A weak upper level disturbance will move into the area Tuesday. It
has little upper level support and just as little moisture to work
with. As a result, we could see some flurries or light snow in the
northwest but nothing of consequence. It will also increase cloud
cover a bit. The wind will also increase across the southwestern
wind corridor as well as the Cody foothills. It does not look like
high wind at this point, but it has to be watched. There is a chance
it could mix out the basins and raise temperatures a bit. For now,
we will keep them cool though.

.LONG TERM...Wednesday through Sunday

Wednesday looks dry for most of the region with breezy/windy
conditions in the central wind corridor, including Casper area.
Some light snow should develop in the Western mountains in the
afternoon. Long range models still indicate an unsettled period of
weather starting Wednesday night and continuing through Saturday
night and possibly into next Sunday. The first batch of precip is
still expected Wed night through Thursday night in the west and
southwest part of WY. It does not look like a big storm with
light to moderate snowfall expected. Will keep an eye on it and
see how it looks tonight. East of the divide, scattered light snow
Thursday night into Friday is the forecast. Sweetwater county may
see a better chance of snow Thursday night into Friday morning and
will need to watch this area. The next disturbance in the flow
should impact Western WY Saturday afternoon into Saturday night.
This feature is weaker in the models in this 00Z run. Some light
snow for the Western mountains seems good for now with not much at
the lower elevations. Not much weather expected east of the divide
Saturday into Saturday night. Next Sunday looks mostly dry at the
lower elevations with scattered light snow in the mountains.
Temperatures will be mild on Wednesday in the mixed areas and
still cold in the snow covered valleys/basins. Temps cool down
Thursday through Sunday but the airmass is not that cold. The snow
covered valleys/basins will get quite cold any night there is
partial clearing.

.AVIATION.../18Z ISSUANCE/

The Rock Springs /KRKS/ terminal remains in dense fog, and is
expected to remain at or below airfield minimums through most of
today, tonight and through Monday morning. Most of the mid-high
level clouds from the south will remain to the east of most of
Sweetwater County and KRKS. The slight westerly breeze that is
expected to develop this afternoon and evening over Sweetwater
County will only enhance the fog at KRKS from the localized upslope
flow on the west side of the butte that KRKS is situated upon.
Another stubborn patch of fog is entrenched from the town of
Riverton to Shoshoni to Boysen Reservoir and the south end of the
Wind River Canyon. This patch of fog does not appear to be shrinking
either but will likely remain just east of the KRIW terminal for the
most part today. With warm air advection aloft expected tonight and
Monday, patchy fog is expected once again at KBPI, KJAC, KLND,
KPNA, and KRIW tonight and Monday morning. Otherwise, winds will be
mainly light through the period except for KCPR where southwest
winds today will blow at around 10 knots and 12 to 22 knots Monday.

.FIRE WEATHER...

Fire Danger low for all of WY through Monday. Cold seasonal
temperatures, good existing snow pack, and relatively light
to moderate winds will characterize the next several days. Smoke
dispersion will also remain poor for all locations through the
weekend with inversions in the basins and valleys. Mixing may
improve a bit on Tuesday as a week upper level disturbance crosses
the area.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon MST Monday for WYZ028>030.

&&

$$

SHORT TERM...C.Baker
LONG TERM...AR
AVIATION...WM/lipson
FIRE WEATHER...Hattings



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