Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 232208
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
308 PM MST Fri Feb 23 2018

.SHORT TERM...(This evening through Monday)
Issued at 256 PM MST Fri Feb 23 2018

A series of short wave low pressure troughs in westerly flow will
bring Pacific moisture into the western mountains of Wyoming with
light snow developing later tonight with very light accumulations
possible. As the moisture increases Saturday, snowfall will become
more widespread and increase in intensity snowfall of 3 to 5 inches
above 8500 feet is expected at this time.  Winds will pick up east
of the Continental Divide especially  in the Cody foothills,  over
and near the east slopes of the mountains and through the wind
corridor from Sweetwater county through southern Fremont and
southern Natrona county.  Winds will become stronger through Sunday
and Sunday night.  Periods of snow will then continue in the west
trough the weekend with a break late Saturday night and early Sunday
morning. Some snow may spread south east of the Continental Divide
through the day Monday.  Temperatures will gradually warm, with
the greatest warming in the windy areas.

.LONG TERM...(Monday night through Friday)
Issued at 256 PM MST Fri Feb 23 2018

The extended forecast period will be unsettled across the western
portion of the forecast area as a longwave trough should remain in
place across the region. The continued progressive upper northwest
flow will result in a a couple of weak cold fronts expected to move
through the region through the extended forecast period. This will
result in continued below average to much below average temps across
the region.

Between Monday and Tuesday, the extended models are in fair
agreement involving an approaching trough providing the necessary
uplift and moisture into areas west of the Continental Divide. This
will result in widespread snowfall over the west with possibly some
significant mountain snowfall during this time period. There is
still a slight probability that some of the snow could move east of
the Divide between Monday night and into Tuesday, but any snowfall
amounts at this point looks to be light. The rest of the forecast
area should remain generally dry through much of the extended
forecast periods.

The GFS and ECMWF models, to differing degrees, introduce another
trough into the region by the end of the extended forecast period by
next Thursday. At this time, it looks as though the areas west of
the Divide again will be the primary recipients involving the best
chances for snow, with the rest of the forecast area expected to be
mainly dry and continued cold.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday)
Issued at 256 PM MST Fri Feb 23 2018

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

Scattered snow showers will linger at KRKS until around 03Z along
with MVFR/potentially IFR ceilings/visibilities there also. Only VCSH
is expected at best, elsewhere into the same time period. Scattered
snow showers will slowly increase overnight at KJAC and have
increased probabilities through the rest of the forecast period to
reflect this. Expect MVFR ceilings/visibilities to occur at KJAC
after 16z and continue through the rest of the forecast period.

Expecting VFR conditions across the area elsewhere through the
forecast.

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

Will continue with MVFR expected visibilities/ceilings at KCPR until
around 06Z tonight due to scattered snow showers being expected. VFR
conditions are expected elsewhere through the forecast period. Will
continue with current trending of having southwest winds increase at
KCPR and KCOD after 15Z Saturday and through the end of the
forecast.

&&

.FIRE WEATHER...
Issued AT 256 PM MST Fri Feb 23 2018

A series of short wave low pressure troughs in westerly flow will
bring Pacific moisture into the western mountains of Wyoming with
light snow developing later tonight with very light accumulations
possible. As the moisture increases Saturday, snowfall will become
more widespread and increase in intensity snowfall of 3 to 5 inches
above 8500 feet is expected at this time.  Winds will pick up east
of the Continental Divide especially  in the Cody foothills,  over
and near the east slopes of the mountains and through the wind
corridor from Sweetwater county through southern Fremont and
southern Natrona county.  Winds will become stronger through Sunday
and Sunday night.  Periods of snow will then continue in the west
trough the weekend with a break late Saturday night and early Sunday
morning. Some snow may spread south east of the Continental Divide
through the day Monday.  Temperatures will gradually warm, with
the greatest warming in the windy areas.  Smoke dispersal will be
poor most areas through Saturday.  Better mixing will occur as winds
pick up in the foothills on sunday with areas of good smoke dispersal
developing.

&&

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

$$

SHORT TERM...Baker
LONG TERM...Troutman
AVIATION...Troutman
FIRE WEATHER...Baker


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