Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 260854
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
254 AM MDT Tue Sep 26 2017

.SHORT TERM...Today and Thursday night
Issued at 245 AM MDT Tue Sep 26 2017

Showers have ended across the area this morning, as the main
circulation continues its eastward trek into SW SD. Overcast skies
of 5000 to 9000ft AGL are in place predominately over NW portions,
but are also streaming over central and southern portions. The only
notable cloud-free area is the Upper Green river Basin, where
temperatures dropped to freezing as early as 10pm Monday night. Will
have to keep an eye on these clouds through the rest of the morning
hours. Freezing temperatures, will also be dependent on these
clouds.

Otherwise, the forecast remains on track through the period. Dry and
unseasonably cool conditions today and Wednesday, with a gradual
warming trend through the week. Another upper low over the Desert
Southwest will make its way over the Four Corners by Wednesday.
Models have sped up the timing of this low to begin impacting
southern portions of the forecast area by Thursday. Clouds and rain
showers will be possible through Thursday night, with these showers
moving over portions of the Wind Rivers and upper Green River Basin.
Isolated embedded thunderstorms will also be possible Thursday
afternoon and evening. Models also continue to prog a weak cold
front entering the state during the day Wednesday. This will keep N
winds through the area, as well as drier air over northern and
central portions.

Winds will be light through the period across the area, except over
South Pass and eastern Sweetwater County where NE winds will gust 15
to 20 mph.

.LONG TERM...(Friday through Tuesday)
Issued at 245 AM MDT Tue Sep 26 2017

This upper low tracks through WY Friday. Some showers and isolated
thunderstorms Friday into Fri evening. The models have changed
once again to a more unsettled weather pattern Saturday and
Sunday. Saturday will be dry and breezy east of the divide. The
west will see increasing clouds Saturday with showers and isolated
storms in the afternoon into Saturday night. Snow in the western
mountains Saturday night and into the valleys once the cold air
arrives. Will have to watch and see how strong this system becomes
as that would elevate the potential hazard out west. A vigorous
cold front swings through the areas east of the divide Saturday
night with scattered showers and isolated storms. Much cooler
Sunday with lingering rain and snow showers. Monday looks dry east
of the divide with scattered rain and snow showers in the west.
Next Tuesday appears dry for most locations. Isolated showers are
possible in the far north where moisture lingers. High temps will
be mild Fri and Saturday with some cooling the west due to the
precipitation. Much cooler Sunday, then milder Mon and next Tue.

&&

.AVIATION...For the 12Z TAFS through 12Z Wednesday
Issued at 245 AM MDT Tue Sep 26 2017

Patchy fog could impact most terminals through 16Z. However, not
expecting widespread fog at the moment as progged boundary layer
moisture is marginal, and there is not a dry layer above the BL to
facilitate fog formation. Having said that, recent moisture over
the past few days will help to get some fog to develop especially
in low- lying areas or near bodies of water with clearing skies
and light wind. Thus will have VCFG on most terminals to account
for the fog possibility. Will look at the latest observations and
satellite trends before taf issuance to decide if prevailing
lower conditions are needed anywhere. Otherwise, VFR conditions
are expected with light winds.

&&

.FIRE WEATHER...
Issued AT 245 AM MDT Tue Sep 26 2017

Clearing conditions will begin today, with partly cloudy skies
returning by Tuesday. Areas of fog will also be possible in the
valleys and basins Tuesday morning. Dry and unseasonably cool
conditions will be in place through Wednesday. Clouds will increase
from south to north Thursday, with increasing chances for showers
and storms. Precipitation is expected to remain confined across
southern portions, but may move over the Wind River Mountains and
the Upper Green River Basin.

&&

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

$$

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



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