Latest ZFP from WFO RIW

		
National Weather Service Local Forecast for Star Valley Ranch
Updated: Sun May 05  8:31 am MT

Today... Scattered showers, then showers and possibly a
thunderstorm after noon.  High near 54. Breezy, with a south wind 16
to 21 mph becoming west southwest 8 to 13 mph in the afternoon. Winds
could gust as high as 29 mph.  Chance of precipitation is 100%. New
rainfall amounts between a tenth and quarter of an inch, except higher
amounts possible in thunderstorms. 

Tonight... Rain and snow showers, becoming all snow after
midnight. Some thunder is also possible.  Low around 31. South wind 5
to 10 mph.  Chance of precipitation is 80%. New snow accumulation of
less than one inch possible. 

Monday... Snow showers before 11am, then rain and snow showers.
Some thunder is also possible.  High near 39. Breezy, with a west wind
8 to 13 mph increasing to 15 to 20 mph in the afternoon. Winds could
gust as high as 28 mph.  Chance of precipitation is 90%. New snow
accumulation of around an inch possible. 

Monday Night... Rain and snow showers, becoming all snow after
9pm. Some thunder is also possible.  Low around 30. Breezy, with a
west southwest wind 10 to 20 mph, with gusts as high as 30 mph. 
Chance of precipitation is 80%. New snow accumulation of less than one
inch possible. 

Tuesday... Snow showers. Some thunder is also possible.  High
near 36. Breezy, with a west wind 11 to 18 mph, with gusts as high as
28 mph.  Chance of precipitation is 100%. New snow accumulation of 1
to 3 inches possible. 

Tuesday Night... Snow showers likely, mainly before midnight.
Some thunder is also possible.  Mostly cloudy, with a low around 26.
Breezy, with a west wind 13 to 18 mph decreasing to 6 to 11 mph after
midnight. Winds could gust as high as 29 mph.  Chance of precipitation
is 70%.

Wednesday... A 50 percent chance of snow showers.  Mostly
cloudy, with a high near 40. West northwest wind 6 to 13 mph. 

Wednesday Night... A 20 percent chance of snow showers before
midnight.  Mostly cloudy, with a low around 29.

Thursday... A 40 percent chance of showers and thunderstorms
after noon.  Partly sunny, with a high near 50.

Thursday Night... A 20 percent chance of showers before
midnight.  Partly cloudy, with a low around 29.

Friday... A slight chance of showers and thunderstorms.  Mostly
sunny, with a high near 55.

Friday Night... Partly cloudy, with a low around 32.

Saturday... Sunny, with a high near 59.

		

Latest AFD from WFO RIW

		
756 
FXUS65 KRIW 051112
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
512 AM MDT Sun May 5 2024

.KEY MESSAGES...

- Showers develop across western WY this morning and gradually spread
  east as a cold front moves through the state this 
  afternoon/evening.

- High elevation snow will be possible after the frontal passage with
  chances for light snow in western valleys.

- Winds will be gusty late this morning through the evening with many
  seeing gusts of 30+ mph. Parts of Sweetwater, Fremont, and 
  Natrona Counties likely see gusts exceeding 55 mph.

- The first half of the week looks to be unsettled with chance
  for precipitation, breezy winds, and below normal 
  temperatures.

&&

.DISCUSSION...
Issued at 332 AM MDT Sun May 5 2024

Saturday saw pleasant and sunny weather across the Cowboy State. 
Unfortunately change is around the corner, as a potent upper-level 
Pacific low is currently making its way across the Great Basin this 
morning. This low will bring gusty winds, chances for precipitation 
and cooler temperatures over the next couple of days. Temperatures 
do make a brief rebound ahead of the FROPA today, with highs west of 
the Divide in the 50s/60s and highs east of the Divide reaching the 
70s. 

Today will be the start of an unsettled weather pattern, with the 
main culprit behind this pattern change being a deep Pacific low. 
The low continues to near the state during the morning and impacts 
look to begin to ramp up around the same time. There are two parts 
of this upcoming system. The first will be winds which are going to 
be the main concern, as a strong 100+ knot jet sets up over the 
region by the afternoon. Southerly winds begin to increase shortly 
after sunrise, with the first impacts seen across the southern CWA 
before gradually spreading north through the early afternoon. Gusts 
of 30+ mph will be widespread with a (70-90%) chance across most of 
CWA during the afternoon and evening. Stronger gusts of 50+ mph are 
likely (50-80%) in parts of Sweetwater, Fremont, and Natrona 
Counties. Models continue to indicate these strong wind gusts and 
due to that, the High Wind Watches have been upgraded to High Wind 
Warnings. Winds have slightly decrease for the Lander Foothills and 
much of Natrona County. So, the High Wind Watches for these areas 
have been cancelled. Winds look to decrease Sunday night and then 
once again increase after sunrise Monday. For this reason these 
Warnings will be in effect from Sunday afternoon through Monday 
evening. Some areas of concern will be along the I-80 corridor and 
South Pass. Gusts in these areas likely exceed 60+ mph on Sunday and 
Monday which may make travel difficult, especially for high profile 
vehicles.

West of the Divide... 

Precipitation arrives this morning across western WY and will 
gradually spread eastward throughout the day. Showers will be 
periodic with steady precipitation not arriving over this area until 
Monday morning. Temperatures on Sunday look to be too warm to 
support snow even at high elevations, with snow levels during the 
day exceeding 10,000 feet. However, snow levels look to quickly drop 
this afternoon/evening as a cold front sweeps across the state. 
After the front pushes through the heaviest snowfall is expected to 
fall over western mountains with snowfall rates nearing 1 inch per 
hour. Snow is expected to continue across western ranges through 
Monday into Tuesday evening. Snow accumulation will mainly be 
limited to the higher elevations with totals ranging from 6 inches 
to over 2 feet. A Winter Storm Warning has been issued for the high 
elevations of the Tetons and Gros Ventre ranges as they look to see 
1 to 2 feet of snow. Winter Weather Advisories have been issued for 
the remaining western ranges including the Wind Rivers as they will 
likely see snow totals of 6 to 12 inches. Lower elevation valleys in 
western WY will likely have a period of snowfall starting early 
Monday morning. Periodic snow showers look to fall through Tuesday 
evening, with snow totals ranging from 2-4 inches in parts of 
Jackson Hole and Star Valley. One thing to keep in mind is that the 
snow will likely have difficulty accumulating on surfaces due to the 
strong Sun angle. There is a good chance that some of the snow in 
lower elevations will melt in between showers, leading to lower 
amounts.  

East of the Divide...

Most of the CWA east of the Divide looks to remain dry for much of 
today. The best chance for precipitation comes with the nearing 
FROPA during the late afternoon and evening. Central portions of the 
CWA such as most of Fremont, Natrona and the Bighorn Basin will see 
little QPF as a result of the FROPA. Monday will be a slightly 
different story, as the low begins to shift northward due to a 
persist area of ridging over the central CONUS. As the low tracks 
north winds will shift to the NW, leading to enhanced upsloping for 
portions of the eastern Bighorn Basin. Natrona and Johnson Counties 
will also have a good chance seeing some showers during this time 
with a (40-70%) of seeing at least 0.20 inches of QPF by Monday 
night. Daily showers will be possible over the Bighorn Basin and the 
eastern portion of the CWA through midweek as the low wobbles around 
Montana.

Remainder of the week...

Uncertainty remains in regards to the impacts the low will have on 
the CWA as it moves over Montana during the first half of the week. 
The best chances of precipitation do look to remain across western 
and northern Wyoming, as flow and proximity to the low will be the 
most favorable. Overall, most of the state will continue to see 
breezy winds, below normal temperatures, and chances for 
precipitation through at least the first half of the upcoming
week.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 508 AM MDT Sun May 5 2024

Today will see numerous showers at KJAC through the day, with 
isolated thunder possible in the afternoon. Shower activity will
spread into KPNA/KBPI early afternoon, and to remaining sites 
late afternoon to early evening. Most periods will still remain 
VFR, but lower cigs will continue through the night, with tempo 
MVFR cigs expected. KJAC may see MVFR ceiling develop after 06Z
Monday as rain showers turn over to snow.

Other concern remains gusty winds during the day for all except
KJAC. Still expected at least 35 knot gusts for all sites west 
of the divide, with gusts approaching 60kts at KRKS during the 
afternoon. The strongest wind east of the Divide will occur in 
vicinity of KLND, KRIW and KCPR, where gusts to 40 knots will be
possible after around 16Z. Winds will relax some after 00Z, but
will still remain gusty at all sites through the overnight 
hours.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 6 PM MDT 
Tuesday for WYZ001.

Winter Storm Watch from Monday morning through Tuesday morning 
for WYZ008-009.

Winter Storm Warning from 6 PM this evening to 11 PM MDT 
Tuesday for WYZ012.

Winter Weather Advisory from 6 PM this evening to 6 PM MDT 
Monday for WYZ014-015.

High Wind Warning from 9 AM this morning to 9 PM MDT Monday 
for WYZ019-028>030.

High Wind Watch from Monday morning through Monday evening for 
WYZ020.

Winter Weather Advisory from 11 PM this evening to 6 PM MDT 
Monday for WYZ024.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Hattings