Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 222157

Area Forecast Discussion
National Weather Service Riverton WY
257 PM MST Thu Feb 22 2018

.SHORT TERM...(This evening through Friday)
Issued at 211 PM MST Thu Feb 22 2018

A prominent circulation now spinning along the Pacific Coast
within the base of an elongating trough will eject a shortwave/vort
lobe along the southern stream energy toward the Central Rockies
and will be responsible for delivering several hours of steady
light snow late tonight and Friday from RKS to CPR and points
south and east of there. Most of this snowfall will amount to 1 to
2 inches worth. Embedded within this area of stratiform snow
could be some heavier snow showers, especially in Eastern
Sweetwater County where lifted indices will be negative. In the
meantime, only light snowfall will occur in the west as the asct
troughiness tracks across the area. West winds will pick up
somewhat in Sweetwater County Friday.

Otherwise expected below normal temps to continue through the
weekend across the CWA through the weekend, although temps will
embark on a slow warming trend. Periods of light snow or flurries
will continue in the far west Friday and Friday night as the flow
off the pacific continues.

Then on Saturday and Saturday night, the snowfall in the far west will
increase in intensity as the flow off the Pacific becomes more direct
and strengthens out ahead of a prominent Pacific shortwave.
However, it appears that the only zone that may experience
advisory amnts at this point in time would be the Tetons/Gros
Ventres. Expect a short respite from the significant snowfall
Sunday before the next strong upstream Pacific shortwave
approaches Wyoming along with the strengthening backing westerly
difluent flow off the Pacific delivering more significant snowfall
to the far west by late Sunday. West winds will increase on
Sunday along the Southern Wind Corridor ahead of this next
approaching trough.

.LONG TERM...(Sunday night through Thursday) Issued at 215 PM
MST Thu Feb 22 2018

The forecast area will remain under the influence of an upper level
trough through the balance of the extended forecast period. Will
continue with a slightly below normal temp trend as a result.
Initially in the extended forecast period, western areas are
expected to continue to see some light snow during the day on Sunday.
A weak ridge is expected over the rest of Wyoming with an increasing
low level southwest wind flow across the wind corridor from Natrona
county extending southwest into Sweetwater county.

The models are in fair agreement involving a large trough being
expected to move southeast into the west coast between Sunday
night/Monday. Increasing snow pops are expected ahead of the
west/southwest flow out ahead of the trough also between Sunday
night and lasting into the day Monday across areas mainly west of
the Divide. The 12Z model runs today further indicate that a cold
front will weaken as it move southeast through the forecast area on
Tuesday. If current trending continues, the majority of the
accumulating snow will be west of the Divide.  Another storm system
than could impact the western areas at the end of the extended
forecast period by Thursday. Based upon model timing and trending, I
am most confident confident on snow across the west Sunday
night/Monday with low confidence on timing/location of snowfall
after Monday due to continued model run to run variability involving


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 211 PM MST Thu Feb 22 2018

West of the Continental Divide...KJAC, KBPI, KPNA, and KRKS

MVFR ceilings are expected at KJAC and KPNA after 03Z and KBPI after
06Z tonight and KRKS after 10Z. Will keep VCSH in at KJAC, KBPI,
KPNA after 20Z through the end of the forecast period. MVFR ceilings
and visibilities due to light snow are expected at KRKS between 10Z
through the end of the forecast period.

East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

Will continue with VFR conditions at all terminals through the
forecast period. Expect mid and high clouds to increase into
broken conditions through the end of the forecast period. Will
keep in VCSH conditions at KCPR, KRIW and KLND after 10Z through
the end of the forecast period as some scattered light snow
showers are expected.

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


Issued AT 211 PM MST Thu Feb 22 2018

Cold conditions continue across the region for another few days.
Expect light winds. Expect winds to increase again across the
eastern portion of zone 279 late Friday. Still, most locations
will see quite cold morning lows below zero. While slow warming
is expected over the next few days, temperatures will still be
below seasonal through the weekend. Smoke dispersion will be poor
to fair east of the Divide and fair to good west of the Divide
both today and Friday.





LONG TERM...Troutman
FIRE WEATHER...Lipson is the U.S. government's official web portal to all federal, state and local government web resources and services.