Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 152209
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
309 PM MST Mon Jan 15 2018

.SHORT TERM...This evening through Thursday
Issued at 130 PM MST Mon Jan 15 2018

A cold Canadian air mass has moved in across the area
leaving areas of low stratus and fog in the valleys and basins
today.  Some light snow fell but is over now.  Temperatures
will be difficult with the dense stratus insulating some areas
while clearing mainly in the north and east will result in
below zero lows tonight mainly from -5 to -10.  The stratus
and fog will be slow to dissipate on Tuesday and may linger
in the valleys and basins longer than now expected with rather
light wind aloft as high pressure will dominate.  Some warming
will occur especially east of the Bighorn mountains where rapid
warming may occur.  The models are less bullish on precipitation
moving into the west mid week compared to the past few days.
now Thursday looks to be the arrival time oh scattered mountain
snow with warming east of the Continental Divide.

.LONG TERM...Thursday night through Monday night
Issued at 130 PM MST Mon Jan 15 2018

Models continue to trend toward a warm, southwest flow regime over
the forecast area Thursday evening into Friday, as a longwave trough
makes its way onshore over the PACNW. PoPs will steadily increase
across the NW Thursday night, with low snow ratios and valley rain
(or rain/snow mix) initially. Temperatures will finally begin to
decrease after 12Z Friday, as the associated cold front makes its
way toward the SE. As it does so, chances for precipitation will
increase east of the Divide. These chances will be widespread, with
lower elevations remaining rain or a rain/snow mix. Temperatures in
these areas will remain relatively warm ahead of the front, changing
over to snow by 00Z Saturday. Models also continue to prog this
system diving south over the Four Corners, with some energy
splitting over WY by 00Z Saturday. A slight chance for snow will
continue Saturday, but most of the focus will shift to the east,
with the best chances for snow possibly continuing over Natrona and
eastern Sweetwater counties. With lingering snow showers possible
Saturday night, the focus will return to the west Sunday and Monday.
The pattern will quickly reset, as another storm system quickly
follows on the heels of the Friday system. Associated moisture from
this system will again impact western portions, but at this point
only looks like isolated to scattered chances for snow. Apart from
western portions, temperatures Friday will be slightly above normal.
Otherwise, readings through the forecast period look to be at or
slightly below normal.

&&

.AVIATION...For the 00Z TAFS through 00Z Wednesday
Issued at 253 PM MST Mon Jan 15 2018

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

MVFR/IFR ceilings and fog vicinity KJAC has finally begun to
lift/clear this afternoon. Expect similar conditions from the past
24 hrs to repeat tonight/Tuesday morning. MVFR OVC clouds over
KRKS/KPNA/KBPI is also beginning to break up. Skies are expected
to stay clear through the TAF period at KRKS, but there will be a
slight chance for VCFG at KBPI/KPNA tonight.

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

Marginal MVFR clouds linger at KLND, but should break up in the
next couple of hours. Otherwise, clouds have mainly cleared out of
the other TAF sites. There remains a slight chance for patchy fog
to form vicinity KCOD and KWRL before sunrise Tuesday morning.
Otherwise, expect VFR conditions through the TAF period.


&&

.FIRE WEATHER...
Issued AT 130 PM MST Mon Jan 15 2018

A cold Canadian air mass has moved in across the area
leaving areas of low stratus and fog in the valleys and basins
today.  Some light snow fell but is over now.  Temperatures
will be difficult with the dense stratus insulating some areas
while clearing mainly in the north and east will result in
below zero lows tonight mainly from -5 to -10.  The stratus
and fog will be slow to dissipate on Tuesday and may linger
in the valleys and basins longer than now expected with rather
light wind aloft as high pressure will dominate.  Some warming
will occur especially east of the Bighorn mountains where rapid
warming may occur.  The models are less bullish on precipitation
moving into the west mid week compared to the past few days.
now Thursday looks to be the arrival time oh scattered mountain
snow with warming east of the Continental Divide.  Inversions
will be in place over the cold valleys and basins with light wind
resulting in generally poor smoke dispersal through Wednesday.

&&

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

$$

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



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