360
FXUS65 KRIW 060915
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
315 AM MDT Mon May 6 2024

.KEY MESSAGES...

- Showers continue to spread across areas east of the Divide
  this morning. Moderate to heavy rain will be possible across
  parts of Natrona and Johnson County.

- Strong gusty winds continue today with widespread gusts of 30+
  mph this afternoon and evening.

- Showers will periodically continue across western and northern
  WY through the first half of the week. The remainder of the
  state will likely see a brief lull in action.

- Another round of precipitation looks possible for the second
  half of the week. Winds are expected to remain breezy or even gusty
  at times through most of the week.

&&

.DISCUSSION...
Issued at 314 AM MDT Mon May 6 2024

Winds howled across parts of the Cowboy State on Saturday, with some
locations, such as Lander and Rock Springs seeing gusts of 55 mph.
Besides the gusty winds, the day was a pleasant taste of typical May
weather, with highs east of the Divide reaching the 70s. However,
conditions quickly deteriorated as a cold front swept across the
state. Along the frontal passage showers and thunderstorms developed
and continued to linger after the front moved through. That leads us
to this morning where showers are still spreading across the state
and will linger through the day. The hardest hit areas look to be
western and eastern portions of the CWA.

The unsettled weather pattern continues today, with the main culprit
behind this pattern change being a deep Pacific low. The low
continues to track across the the state this morning and afternoon.
There are two parts of this upcoming system. The first will be winds
which are going to be the main concern, as strong 700 mb winds of 60
to 70 knots set up over the region by the afternoon and evening.
Similar to Saturday winds begin to increase shortly after sunrise,
with the first impacts seen across the southern CWA before gradually
spreading north through the early afternoon. There is a slight
deviation from Saturday, as the low is now going to be mainly east
of the CWA, which will create predominantly northwesterly/westerly
flow. 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. Due to the change in flow, places such as the
upper Wind River Basin and Northern Johnson County may see strong
wind gusts as well, with a (60-80%) chance of seeing 45+ mph gusts.
The High Wind Watch for part of Natrona County has been cancelled
due to the lack of confidence in criteria strength winds. However,
this area will still likely see periodic gusts around 50 mph. High
Wind Warnings remain in effect for parts of Sweetwater, Fremont, and
Natrona Counties through Monday evening. Special Weather Statements
have been issued for parts of Sublette, southern Lincoln, Fremont,
Natrona, and northern Johnson Counties. The SPS is due to strong
wind gusts that may be near or exceed 45 mph this afternoon and
evening. Some areas of concern will be along the I-80 corridor and
South Pass. Gusts in these areas likely exceed 60+ mph on Monday
which may make travel difficult, especially for high profile
vehicles.

Precipitation for West of the Divide...

Precipitation continues this morning across western WY and will
gradually ramp up intensity throughout the remainder of the morning.
Snow levels have dropped compared to Saturday, mainly thanks to
colder air from northwesterly flow. Snow is expected to continue
across western ranges through 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 remains in
effect 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
are now in effect for western ranges including the Wind Rivers as
they will likely see 6 to 12 inches of snow through this evening.
Lower elevation valleys in western WY will likely have a period of
snowfall starting early Monday morning. Periodic snow/rain showers
look to fall through Tuesday evening. Temperatures will likely climb
above freezing during the day and drop to or below freezing during
the night. This will limit most of the low elevation snow
accumulation to the overnight and early morning hours. Snow totals
range from 2-4 inches in parts of Jackson Hole and Star Valley.
There is a good chance that some of the snow in lower elevations
will melt in between showers, leading to lower amounts. Prevailing
westerly flow will likely keep showers over western WY through at
least Wednesday.

Precipitation for East of the Divide...

Showers continue to spread south to north this morning as the
Pacific low gradually moves across the state. Central portions of
the CWA will see showers dissipate after sunrise. Some showers are
possible through the remainder of the day with a (20-40%) chance of
an isolated shower this afternoon/evening. The main bulk of
precipitation will shift east across Natrona and Johnson Counties
this morning. Recent model guidance has indicated QPF amounts
greater than 0.50 inches by the evening in these areas.
Probabilities look good, with a (50-70%) chance of >0.50 inches of
QPF in parts of Natrona and Johnson Counties by the evening.
The eastern half of the Bighorn Basin looks to get a period of some
much needed precipitation this morning. Models are showing a (40-
70%) chance of QPF values >0.30 inches by the evening for places
such as Worland and Greybull. Another place seeing some much needed
moisture will be the Bighorn Mountains. Snow totals across the
Bighorns look to range from 6 to 14 inches with lower amounts in the
southern portion of the mountains. Winter Weather Advisories are in
effect through Monday evening as a result. The main bulk of
precipitation comes to an end by Tuesday morning with a few
lingering showers possible Tuesday and Wednesday.


Remainder of the week...

The remainder of the week is looking active and interesting in
regards to the track of this Pacific low. Models are showing this
low make its way north into Montana Tuesday and Wednesday as a
result of strong ridging over the Central CONUS. By Wednesday morning
things look to get interesting as models show the low being guided
back south moving over WY and ending up in the Great Basin by
Thursday. If this occurs flow would shift back to the
north/northeast by Wednesday evening, possibly bringing another
round of precipitation for the second half of the week. One thing to
monitor will be northeasterly flow prone areas such as the eastern
Winds. There are early indications of rounds of precipitation across
this area as a result of this flow shift. Winds will also likely be
sticking around as the low will keep the pressure gradient tight,
leading to breezy or even gusty conditions through a large chunk of
the upcoming week. Overall, most of the state will continue to see
breezy winds, below normal temperatures, and chances for
precipitation through most of the upcoming week. There may be a
light at the end of this unsettled, damp, and cool tunnel of weather
most of the state is currently in. While still numerous days out
models are showing a break in the action and a return to May-like
weather for the upcoming weekend. However, there are some models
which are showing the exact opposite, so that should give a good
indication of just how volatile the weather will be for the next
week or so.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1037 PM MDT Sun May 5 2024

Messy forecast overnight with rain and snow showers
overspreading the state. Areas west of the divide will fluctuate
overnight with showers, with cigs holding down to right near the
3000 foot level. Winds have relaxed overnight, but will jump up
again tomorrow morning, with gusts again 25 to 35kts, and even
higher at KRKS. Precipitation will gradually end at KRKS by 18z,
but will continue into the afternoon for KBPI/KPNA and all day
at KJAC. While showers will not be overly heavy, some brief vis
lowerings and variably gusty winds in the vicinity can be
expected.

East of the divide, showers have begun to spread into the
region, and will continue through the night. Winds here have
also relaxed, but will also jump back up to 25 to 40kts through
the afternoon. Showers continue at all sites through 00Z/07
before tapering off in the evening.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM MDT Tuesday for WYZ001.

Winter Weather Advisory until 11 PM MDT this evening for
WYZ008-009.

Winter Storm Warning until 11 PM MDT Tuesday for WYZ012.

Winter Weather Advisory until 6 PM MDT this evening for WYZ014-
015-024.

High Wind Warning until 9 PM MDT this evening for WYZ019-
028>030.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Straub