Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 140515 CCA
AFDRIW

Area Forecast Discussion...CORRECTED
National Weather Service Riverton WY
1115 PM MDT Tue Apr 13 2021

.SHORT TERM...This evening through Wednesday night
Issued at 254 PM MDT Tue Apr 13 2021

The weather system over the western U.S. will spin off a weather
disturbance and send it toward WY tonight and Wednesday. An area of
snow will develop over southern WY tonight and progress northward
late tonight into central WY as well as far west WY. Then this area
of snow will hang around the central and far west zones Wednesday
morning, with breaks in the snow Wed afternoon for some places. The
far north may stay mostly dry on Wednesday with just scattered areas
of light snow. Snowfall from this first system will vary widely
across the region. Lower elevations can expect a trace to a few
inches, with the mountains of the central and southwest seeing as
much as 5 to 8 inches. Lows tonight will be in the teens and 20s
with teens in the mountains. Highs Wednesday will be in the 30s with
some 40s in the southwest.

Winds will also be an issue across the south this tonight and
Wednesday morning. As tonight system moves in the tightening
gradient will create northeast to easterly winds of 20 to 30 mph
with gusts in the 40 to 50 mph range. These winds with the expected
precipitation tonight will create difficult travel conditions,
especially along Interstate 80. Thus, we will be issuing a Winter
Weather Advisory across our southern areas for tonight through
Wednesday morning.

We will be upgrading to a Winter Storm Warning for the Salt River
and Wyoming Ranges, the East Slopes of the Wind River mountains, and
the Lander Foothills from midnight tonight through Thursday
afternoon. This was done to include the snowfall of late tonight and
Wednesday, as well as the larger snow event that occurs in these
zones Wed night through Thursday afternoon. More details on the main
snow event is covered in the section below.

.LONG TERM...Thursday through Tuesday
Issued at 254 PM MDT Tue Apr 13 2021

Snow showers will be ongoing across most of the area at the start of
this period as the trough slowly pulls east. While we expect the
bulk of the precipitation over Wednesday night, this will continue
the upslope flow across central Wyoming through Thursday.
Accumulations at lower elevations are still challenging during the
afternoon though as temperatures are again expected to rise into the
mid 30s. This will hopefully somewhat mitigate road impacts during
the afternoon. By Thursday evening showers should become more
isolated as the best dynamics and moisture move east with the low.
Precip will not shut off on Friday however, as models now indicate a
weak wave and cold front pushing down keeping isolated showers
across mainly the mountains. These will decrease Saturday, but
isolated snow showers are still likely. On Sunday weak ridging
will move in with dry conditions and slightly warmer highs. Models
are now indicating the next system arriving Sunday night, which
could bring another round of precip and cooler temperatures to the
area to start the work week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1100 PM MDT Tue Apr 13 2021

Waves of snow showers are expected across central and southern
areas through 00Z Thursday with significant lulls possible. A
more persistent snowfall is expected especially across central
areas Wednesday night. Also the northern terminals (KCOD and KWRL)
will then have better chances of snow.

MVFR or low VFR ceilings are expected to continue or develop
across terminals by 12Z, and remain in place through the
remainder of the TAF period with a trend to lower ceilings after
00Z Thursday.

KCPR, KLND, KRIW will likely have a prolonged period of IFR
visibilities in snow Wednesday night with the worst conditions at
KLND.

&&

.FIRE WEATHER...
Issued AT 254 PM MDT Tue Apr 13 2021

Snow will develop in the south after sunset this evening and spread
north during the late night hours. Wednesday will see a chance of
snow in the central and south zones with lesser snow coverage in the
north. Winds will continue to be quite gusty overnight and into
Wednesday across the south. Expect a northeast to easterly wind of
20 to 30 mph with gusts in the 40 to 50 mph range. Temperatures will
remain on the cold side Wednesday. Smoke dispersal will be poor to
fair tonight and Wednesday afternoon.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT Thursday for WYZ027>030.

Winter Storm Watch from Wednesday afternoon through Thursday
afternoon for WYZ007>011-016-017-019-020-022.

Winter Storm Warning until 6 PM MDT Thursday for WYZ015-018-024.

&&

$$

SHORT TERM...Hulme
LONG TERM...Myers
AVIATION...Murrell
FIRE WEATHER...Hulme


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