Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 292032
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
132 PM MST Tue Nov 29 2016

.SHORT TERM...Tonight through Friday

Large upper low is slowly relinquishing it`s grip on our CWFA
this afternoon. Even with that said, there is still some
significant effects. High winds continue across Nrn Johnson County
where winds have gusted over 60 mph much of the day. This warning
is out through 5 pm and the timing looks pretty good. Otherwise,
we still have a few mainly higher terrain/mtn snow showers to deal
with. They will gradually decrease to mainly the higher peaks
overnight. On Wednesday a weak ridge moves into the west with a
rather weak moist upglide signature developing as the day wears on
in the far west. Looks like a high pop low qpf type event with a
couple inches of fluff for some of the mountains and a skiff to an
inch possible in the far west valleys. Before that, we may have to
deal with some patchy fog in the far west with brief clearing
tonight. Maybe more stratus for YNP. As our next system splits
with the building upstream ridge, we get a developing upper low
trying to develop near the Wrn Wyo border late Thursday into
Thursday evening. System is fighting the bigger picture of a ridge
so don`t expect this system to have a lot of punch. Favorable
track to bring some brief upslope to the Lander Foothills but not
sure it`ll be much more than a brief shot of flurries or very
light snow Thursday Night/early Friday. Otherwise, we`ll get some
higher elevation flurries/snow showers with a chance of snow over
the I80 corridor. System drops quickly swd with improving conds as
the day wears on Friday.

.LONG TERM...Friday night through Tuesday

Weak high pressure late Friday into Friday night will be short
lived as shortwave energy and moisture approach WY in NW mid
level flow. Mountain snow showers early Saturday morning should
spread to the far western valleys Saturday, with the snow moving
south as the day continues. All model guidance shifts the NW mid
level flow to westerly flow by Sunday afternoon. This looks to be
another good period of mountain snowfall for the western mountains
with the Bighorns perhaps picking up a couple and the basins east
of the divide remaining relatively dry. The western valleys should
pick up a fair bit as well. With the flow more westerly on
Sunday, temperatures should rebound to the 30s and low 40s in the
lower elevations, and wind through the RKS to CPR corridor will
be gusty and strong. The initial shortwave trough from the Pacific
Northwest looks to move through the state and into the northern
plains on Monday, although the model guidance is in disagreement
with the timing and strength. The GFS is currently trending faster
and stronger than the ECMWF. Regardless, the initial cold push
Monday is forecast to be followed by a Canadian push of cold air
on Tuesday. Details on snow potential are still uncertain, but
amounts don`t look too high unless the ECMWF forecast pans out
with the 500 mb low closing in southern WY. The shortwave energy
should still move quickly into the southern plains Wednesday,
with Wednesday morning looking to be the coldest thus far across
the state with subzero low temperatures.

&&

.AVIATION.../18Z ISSUANCE/

Back side of large scale storm system still influencing western and
central Wyoming today with northerly mid level flow.  Northern half
of Johnson county, especially around KBYG, expected to have strong
NW surface wind over 50 knots through 00z/Wed.  Other areas
likely to see gusts around 20 knots. Thickest clouds this afternoon
from Johnson into Natrona counties with mountains obscured through
about 06Z/Wed. Western WY will continue with light mountain snow
showers also through 06Z/Wed with partial obscuration. Expecting all
terminals to be VFR for next 24 hours, although possible patchy fog
around KJAC after 06Z/Wed. Wind forecast to prevent fog in upper
Green River basin. Next storm system will bring moisture and snow
showers to western WY mountains Wednesday afternoon, with MVFR
conditions at KJAC possible by 00Z/Thu.

&&

.FIRE WEATHER...

Winds will gradually decrease tonight but with some gusty wind
continuing in the mountains and east slope foothills. Some light
snow or flurries will develop again in the far west during the day
Wednesday into Wednesday night with a chance of snow in the upslope
favored areas east of the divide by Thursday night, mainly the
Lander Foothills and southward. The mountains, Cody Foothills and
wind corridor from Rock Springs to Casper look breezy to locally
windy on Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 5 PM MST this afternoon for WYZ010.

&&

$$

SHORT TERM...Skrbac
LONG TERM...McDonald
AVIATION...McDonald
FIRE WEATHER...Skrbac



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