Area Forecast Discussion
Issued by NWS Riverton, WY

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957
FXUS65 KRIW 271702
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1002 AM MST Mon Feb 27 2017

.SHORT TERM...Monday through Wednesday night

Interesting forecast shaping up for today. Currently, some snow is
ongoing across the west as a front and trough move across the area.
We expect this to continue through the day. The models continue to
show that the system does not have a tremendous amount of moisture
to work with even through the jet dynamics are decent. Looking at
web cams, some areas already have an inch or two so we hoist a
winter weather advisory over much of the western mountains.

Another area of concern will be across Sweetwater County the front a
decent amount of left front quadrant jet energy this afternoon. The
models are showing a decent amount of QPF in that area this
afternoon. However, this looks to be a fairly quick hitter as most
of the precipitation should move out by dark with a bulk of the best
dynamics over areas east of Sweetwater County. In addition, the best
snow would likely be in southeastern Sweetwater County south of I-80
where the population is very sparse. We will issue a Special Weather
Statement for this area as well. The NAM does have some showers
creeping up toward Casper as well. With some decent instability, we
put at least slight POPS across the entire area this evening in case
some showers break out. An area that has to be watched is the Cody
area where we have been burned a few times. We increased POPS a bit
here as well. The snow should end fairly quickly after midnight as
the waves moves away.

Another wave will move into western Wyoming on Tuesday. At this
point, this wave looks weaker than the one today so only light to
occasionally moderate snow is expected. Most areas East of the
Divide should stay dry as this wave passes though. Winds will get
gusty once again across the southwestern Wind Corridor as well
although not of the high wind variety. Temperatures should drop a
few degrees behind the

The trend in precipitation should continue to decrease with only
some light snow in west. However, the wind machine may begin to
crank up again across the Lee of the Absarokas as mid level winds
increase to over 50 knots. The main area of threat would be, you
guessed it, around Clark. In addition, an Alberta Clipper will drop
southward into the Plains states. Most of the effects should remain
to the east. However, it should get close enough to possibly bring
some light snow to northern and eastern portions of the county
warning area. Temperatures starting Wednesday should then begin a
slow moderating trend.

.LONG TERM...Thursday through Monday

Northwest flow aloft for Thursday with some light snow in NW WY
once again. Some light snow for the northern Bighorn mountains and
possibly northern Johnson county. Dry elsewhere on Thursday. The
flow aloft turns west on Friday and Saturday with moisture in this
flow. This would keep periods of snow in the forecast for the
Northwest quarter of the state. This would include Jackson, Alpine
and Hoback Junction. South of these locations the snow looks to
be less at this time, but will have to see how this unfolds once
the pattern changes. Dry weather for the rest of the region Friday
and Saturday. Breezy to windy areas Fri and Sat, mainly in the
favored wind corridors of central and northwest WY. Will have to
watch a weather system for next Sunday as it crosses through the
region. Both the GFS and ECMWF have this potent system and it
could bring a decent snow event to the west from Saturday evening
through Sunday evening. East of the divide, the impact would be
Sunday afternoon through Sunday night. Expect brisk wind on Sunday
in many locations. Any lingering snow would end Monday morning,
followed by decreasing clouds. Temperatures will become more mild
Thursday through Saturday. Still not looking at a fast lower
elevation snowmelt during this period as 700MB temps only get to
near zero Celsius Friday and Saturday. Temps will be colder Sunday
and Monday as the weather system passes by.

&&

.AVIATION.../18Z ISSUANCE/

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

Widespread VFR/MVFR with areas of IFR conditions in light snow and
mountain obscurations will characterize the forecast period. Snow
showers will increase and drift south and east along a boundary near
and south of the Interstate 80 corridor through this afternoon.
Drier air will then move in this evening with isolated to scattered
snow showers mainly confined to the northwest mountains after 06z
Tuesday before then next upper level disturbance arrives across the
west late Tuesday morning, lowering CIGS and increasing snow chances
once again.

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR conditions will prevail through the forecast period for most
terminal sites. KWRL, however, will see MVFR to occasional IFR in
lower CIGS and possible reduced visibility between 03Z and 06Z
Tuesday. Isolated to scattered MVFR snow showers are currently
drifting along and south of vcnty KRIW-KCPR line along a boundary
today and can be expected to persist through this afternoon.

&&

.FIRE WEATHER...

Fire Danger low for all of Wyoming today as a good existing snow
pack combines with seasonal to below seasonal temperatures. Smoke
dispersion will be fair to very good across most of the forecast
area this afternoon. A period of light to moderate snow will
continue across the western mountains. Wind should remain moderate
today although gusty winds will return in the wind prone areas
tomorrow with strong winds possible by Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

Winter Weather Advisory until 5 PM MST this afternoon for WYZ012-
013-023>026.

&&

$$

SHORT TERM...Hattings
LONG TERM...AR
AVIATION...Braun
FIRE WEATHER...Hattings



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