Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 261101

Area Forecast Discussion
National Weather Service Riverton WY
401 AM MST Sun Jan 26 2020

.SHORT TERM...(Today through Monday)
Issued at 350 AM MST Sun Jan 26 2020

The fast-moving pattern across the western US continues with
little change noted in the short term. Today will see a similar
day to yesterday for most of the region, as weak ridging takes
over, allowing temps to again rise into the 30s and 40s for lower
elevations. Temps will be a couple degrees below yesterday, mainly
due to increased high clouds. This high cloudiness is the signal
that the next shortwave is approaching. It will begin to impact
the western mountains later this afternoon, with increasing snow
chances through the night into tomorrow morning. Flow around this
system will be a bit more southwesterly as it moves through, which
will add a bit more moisture at midlevels. This will allow the
snowfall chances to spread eastward across the eastern Wind River
Basin, along with Sweetwater and Natrona Counties. These areas can
expect maybe an inch or two of snow, mainly overnight tonight for
Sweetwater County, and during the morning hours tomorrow for
Fremont and Natrona Counties. The complicating factor around the
Casper area will be temperatures, which will be near or just above
freezing most of the morning tomorrow. Thus the snow may mix with
rain, which will limit the accumulation of snow. This system is
moving fast, so all snowfall should be complete by noon Monday.

.LONG TERM...(Monday night through Saturday)
Issued at 350 AM MST Sun Jan 26 2020

The extended forecast continues to show an active pattern with a
series of shortwaves poised to traverse the region as we remain in
an onshore Pacific flow pattern. On the heels of the shortwave that
will be moving out early Monday afternoon, another shortwave pushes
across the state Tuesday into Wednesday. There continues to be less
confidence with this event regarding snow amounts east of the Divide
than the previous system, though there is confidence for snow
increasing across the west beginning Tuesday. The energy with this
wave is expected to split, as we have seen with previous recent
shortwaves in this pattern, and be concentrated to the south in CO,
UT and AZ and northwest in MT and the Dakotas. The back side of this
event may see some energy move across WY, so PoPs in eastern
Sweetwater and Natrona counties and in the Big Horns were increased
slightly between 12Z Wed and 00Z Thurs.

North/northwest upper flow will continue towards the end of the
period, with another embedded shortwave likely bringing more snow
to western Wyoming on Thursday. Models suggest modest ridging will
set up by the weekend which would bring a reprieve from the snow,
although there are hints at a more significant system arriving the
following Monday.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 350 AM MST Sun Jan 26 2020

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

The next round of snow and low clouds will develop after 19Z in
the mountains and far west valleys and continue through 12Z
Monday. This would include the KJAC terminal forecast. Mountains
will become frequently obscured by 00Z through 12Z Monday.

Snow and low ceilings will develop over the rest of SW WY between
00Z and 03Z and continue through 12Z. This would include KBPI, KPNA,
and KRKS terminal forecasts.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

VFR conditions will occur through most of the forecast period.
Late tonight into Monday morning, areas from KRIW and KLND east to
KCPR will see lowered cigs and vis as snowfall develops in those
region. Most impacts will occur between 12z and 18z Monday for
those locations.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.


Issued AT 350 AM MST Sun Jan 26 2020

Next weather system arrives tonight, spreading snowfall across the
western mountains through sunrise Monday. Snow will also develop
for 277, 279, 280, 289, and 300 overnight tonight, with an inch or
two possible through noon Monday. Winds are expected to start to
increase across 279 Monday afternoon, with west winds of 25 mph
gusting to 40 mph at times.




LONG TERM...Fisher
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