Area Forecast Discussion
Issued by NWS Riverton, WY

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327
FXUS65 KRIW 110546
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1046 PM MST Tue Jan 10 2017

.SHORT TERM...Tonight Through Friday (Issued at 115 PM MST)

Major winter storm continues out west with the final system moving
in this evening. This last round will be the most significant with
the best overall forcing and more favorable temperatures for snow
crystal growth. Jet support looks quite favorable with at least
right entrance region if not a couple forming overnight. Combine
that with the steep lapse rates and there should be a great
response. Heavy snow is likely tonight into Wednesday morning with
steady snow the rest of the day and into at least Wednesday evening
before possibly decreasing. Now we have to focus on the central
sections also. Cold front drops down into the north this evening
with increasing dynamics overrunning this area with steep lapse
rates above the cold dome. Heavy snow looks likely for the Cody
Foothills overnight into Wednesday morning with periods of mainly
lighter snows Wednesday afternoon through Wednesday night. Will
upgrade the Cody Foothills to a warning with the areas near and
especially west of Cody towards Wapiti, Pahaska and even Valley
looking quite good for heavy snow where over a foot could fall.
Further east, we`ll go with an advisory for zone 4 with the threat
of warning abouts north of Lovell and Deaver where better jet and
frontogenesis exists. Dubois should also get a good bout of snow and
wind developing this afternoon but especially tonight into Wednesday
morning with some lighter snows continuing into Wednesday night. The
Sweetwater/I80 corridor will also see a bout of strong west wind and
snow tonight into Wednesday with icy roads expected with
temperatures slightly below freezing and period of somewhat heavier
snow expected later this evening into early Wednesday. High winds
are also fairly certain in the Wind Corridor and Lander Foothills
again tonight. Temperatures will also be dropping in the north
behind this front into the single digits and in the far north
possibly below zero by morning. Otherwise, chilly day Thursday,
especially in the north and east where frontal boundary hangs tough.
Last upper low which drops swd across the Great Basin looks just a
tad too far west for any significant effect in our area. Maybe the
swrn corner could possibly see some light snow or flurries Thursday
into early Friday. A quick add on note: Snowfall totals are
actually ahead of schedule with most of the western mountains
already in the 2 to 3 foot range with a few over 3 feet. The
valleys vary from 7 to 15 in the Star Valley to 1 to 2 feet plus
in the Jackson Valley. The lower elevations of Sublette are
already in the 10 to 20 inch range. The storm tonight will add to
this substantially with another 1 to 2 feet in the mountains and
at least another 6 to 12 in the lower elevations with some spots
even higher.

.LONG TERM...Friday Night Through Tuesday

Beginning of FCST, split flow across the FA with western CONUS
trof/closed low now over the Desert SW and southern jet and WCB well
south and east of this area. The northern branch and weak trof over
the closed low now moving through WY with the flow aloft weakening
rapidly. Flow will remain relatively weak until Monday when the main
trof axis breaks far enough eastward to allow ridging to infiltrate
the western CONUS and NW flow to increase ahead of the next
developing Gulf of AK/EPAC system.

Temperatures will start out quite cold Friday night/Friday morning
but will be on the way to more moderate seasonal temperatures as the
weak upper level trof mentioned above scours the FA on its way into
the Plains...and then is replaced by modest ridging. Except for some
possible strong/high wind across the Cody Foothills late Sunday
night through Tuesday and across the Wind Corridor on
Monday/Monday night, the forecast will remain dry for most areas
until Tuesday night and the arrival of stronger jet flow aloft along
with increasing EPAC moisture.

&&

.AVIATION.../06Z ISSUANCE/

West of the divide...KBPI/KJAC/KPNA/KRKS Terminals

Periods of snow in the west through 00Z Thursday. KJAC airport
will stay in the snow through 06Z Thurs. MVFR to IFR conditions
will occur through the period. The other terminal sites in SW WY
will see improving conditions between 18Z and 21Z with VFR
conditions prevailing after 21Z. Expect a gusty wind at many
terminal sites through 00Z Thurs. Mountains will be frequently
obscured. Please see the individual terminal forecasts for more
details.

East of the divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

In northern WY areas of snow will occur through 00Z Thurs with
MVFR to IFR conditions prevailing. Conditions will be improving
in the north after 00Z Thurs as the snow ends and cloud heights
rise. Expect VFR conditions in most places by 06Z Thurs. For the
central area...scattered light snow will develop after 12Z with
MVFR to IFR conditions occurring. KCPR terminal will see the snow
from 13Z until 20Z with improving conditions toward 00Z Thurs.
KRIW and KLND should remain VFR, but some lower clouds could
develop after 13Z which would lead to MVFR CIGS until 18Z.
Mountain snow will continue along the continental divide with
some obscuration also expected through the period. Please see
the individual terminal forecasts for more details.

&&

.FIRE WEATHER...

Low fire danger out west continues with snow continuing through
Wednesday night. East of the divide there will still be very strong
winds around Lander, Jeffrey City and Casper. Significant snow is
expected in the far north around the Cody Foothills and northern
Bighorn Basin and also around Dubois (where winds will also be
strong). Sweetwater County will also see snow and wind tonight and
Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 PM this afternoon to 2 PM MST
Wednesday for WYZ028>030.

High Wind Warning until 8 AM MST Wednesday for WYZ018>020.

Winter Storm Warning until 5 AM MST Thursday for WYZ001-002-
012>015-023>027.

Winter Weather Advisory until 5 AM MST Thursday for WYZ016.

Winter Weather Advisory from 5 PM this afternoon to 5 AM MST
Thursday for WYZ004.

Winter Storm Warning from 5 PM this afternoon to 5 AM MST
Thursday for WYZ003.

&&

$$

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



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