Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 262146
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
346 PM MDT Wed Apr 26 2017

.SHORT TERM...(This evening through Saturday)
Issued at 310 PM MDT Wed Apr 26 2017

A low pressure storm system moving across the Pacific northwest
will spread increasing snow into the west tonight and Thursday.
Through Thursday the snow will spread east of the Continental
Divide across the north. The storm system will then strengthen
and close off over south central to southeast Wyoming Thursday
night with potential heavy convective snow developing over the
Big Horn mountains, Johnson, Fremont and Natrona counties.

The mountains may see 10 to 20 inches of snow with 5 to 10 inches
in the lower elevations with local 12 to 15 inch amounts possible
in the foothills areas around Buffalo, Casper and Lander. The
storm system will dig south across northern Colorado and
eventually into northern New Mexico by Saturday when the storm
will be too far south for major impacts in Wyoming. Saturday
should be cold with some lingering showers, mainly over the
mountains.


.LONG TERM...(Saturday night through Wednesday)

Any left over snow shower activity in the mountains Saturday evening
will be dissipating as the low and trough exit to the southeast and a
positively tilted ridge builds in from the Great basin reflecting the
location of the long wave ridge over that region by then. Expect precip
free weather for most of the weekend, except over the far west as well as
across the Big Horn Mountains as a weak shortwave tracks southeast across
the Northern rockies behind the ridge axis where some mountain snow and
valley rain showers will occur beginning Sunday morning and continuing
through Monday. Then, yet another cold wet weather system will pay us a visit.
The next stronger shortwave will be tracking southeast behind the first
one and will dig a bit more with a string of vorticity tracking southeast
along the Idaho and Wyoming border to northwest Colorado, which is a decent
track for the East slope of the Wind river Mtns and Lander Foothills to
capture measurable precip so have kept the idea of shading the north half
of CWA from late Monday night (under a jet couplet), then through Tuesday
with higher pops across the north half of the CWA. Precip will then spread
south to include Southern Wyoming during the day Tuesday. The Canadian
appears to dig the trough the most, but the models seem to be in general
agreement. The snow level will likely, once again, reach the basin and valley
floors with this weather event once again with h7 temps running between -5 and
-6c over much of the area. Precip will diminish Tuesday night as a prominent
high tries to build in from the west. Wednesday looks to be precip free along
with a warming trend along with highs at the lower elevations in the 60s east
and 50s west.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 310 PM MDT Wed Apr 26 2017

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

The next Pacific storm system will continue to spread valley scattered rain
and mountain snow showers becoming more numerous into the western Wyoming this
evening with areas of MVFR ceilings and increasing mountain obscurations. A few
thunderstorms possible. Snow levels will lower to near valley floors
this evening as showers reach peak coverage with MVFR conditions becoming
widespread, areas of IFR conditions also pushing into vicinity KRKS by 02z
Thursday. These conditions will persist across the area through 18z Thursday.
Lcl MVFR conditions will persist after 18z, especially at KJAC with a few
showers lingering in the area. In Sweetwater County including KRKS, expect
lifting cigs with mainly VFR conditions after 14z Thursday along with
west winds of 28 knots gusting to 38 knots.

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

The next Pacific system and associated cold front will spread scattered
showers and isolated thunderstorms off the mountains into central Wyoming
through this evening. Rain and snow showers will gradually become
more numerous along with widespread MVFR/local IFR conditions vicinity and
north of a KRIW-KCPR line 03z-18z Thursday. IFR conditions will
become more widespread after 18z Thursday.

&&

.FIRE WEATHER...
Issued AT 310 PM MDT Wed Apr 26 2017

A low pressure storm system moving across the Pacific northwest
will spread increasing snow into the west tonight and Thursday.
Through Thursday the snow will spread east of the Continental
Divide across the north. The storm system will then strengthen
and close off over south central to southeast Wyoming Thursday
night with potential heavy convective snow developing over the
Big Horn mountains, Johnson, Fremont and Natrona counties.

The mountains may see 10 to 20 inches of snow with 5 to 10 inches
in the lower elevations with local 12 to 15 inch amounts possible
in the foothills areas around Buffalo, Casper and Lander. The
storm system will dig south across northern Colorado and
eventually into northern New Mexico by Saturday when the storm
will be too far south for major impacts in Wyoming. Saturday
should be cold with some lingering showers, mainly over the
mountains. Sat the storm spreads across the area, clouds will
lower and snow showers will become widespread with low mixing
heights producing poor smoke dispersal through Saturday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Thursday evening through late Friday
night for WYZ010-011-015-017>020-022.

Winter Weather Advisory until noon MDT Thursday for WYZ013-023.

Winter Weather Advisory until noon MDT Thursday for WYZ012-024.

Winter Weather Advisory from 6 AM Thursday to noon MDT Friday
for WYZ003-004.

Winter Weather Advisory until 6 AM MDT Friday for WYZ001-002.

Winter Storm Watch from Thursday morning through late Friday
night for WYZ008-009.

Winter Weather Advisory from 6 AM Thursday to 6 AM MDT Saturday
for WYZ005>007.

&&

$$

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


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