694
FXUS65 KRIW 291916
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
116 PM MDT Mon Apr 29 2024

.KEY MESSAGES...

- Scattered showers across western WY this afternoon, with a
  gradual spread eastward as a cold front moves through this
  evening.

- Gusty winds of 30 to 40 mph with isolated gusts of 40+ mph
  will continue through the afternoon today before decreasing
  after sunset.

- Breezy conditions remain through the overnight with a return
  of gusty winds for Tuesday.

- Cooler temperatures and chances for precipitation are in store
  for the Cowboy State through the remainder of the week.

&&

.DISCUSSION...
Issued at 114 PM MDT Mon Apr 29 2024

Another mostly quiet start to the day across the Cowboy State, with
only a few lingering showers in parts of the west. Near normal
temperatures are expected today before cooler air moves in for the
remainder of the week. A weak shortwave will sweep across the PACNW
and move into the Northern Rockies this afternoon. Showers look to
develop by the early afternoon across western WY before gradually
spreading east through the day. A few isolated thunderstorms will be
possible across the state during the afternoon and evening, with
most having a (10-20%) chance for a thunderstorm. The best chance
(40-70%) for showers and thunderstorms looks to come during the late
evening, as a cold front sweeps across the state. Dry air looks to
be ahead of the front, which may create some concerns regarding
strong outflow winds with any showers or thunderstorms that do
develop. This is due to inverted V signatures that indicate the
possibility for dry downbursts due to dewpoint depressions being 40-
50 degrees. Overall, winds look to increase Monday as the pressure
gradient tightens due to the approaching shortwave. Currently models
are showing a (40-80%) chance for most of the state to see gusts of
35+ mph during the day Monday. Weaker winds are expected in parts of
the Bighorn Basin and Powder River Basin. Winds look to remain
breezy after Monday, as the pressure gradient remains tight due to
another system nearing for the second half of the week.

Tuesday will be drier with an upper-level low staying north of WY.
Showers are possible but look to be isolated with the best chances
(20-40%) across the northern CWA. The main concern for Tuesday with
be near elevated fire weather conditions as a potent upper-level jet
crosses over the area. This will aid in mixing down strong winds
with wind prone areas seeing a (40-70%) of seeing 40+ mph gusts. RH
values will also be rather dry with percentages around 15-20%.
Temperatures are forecast to remain cool, with highs around 5-10
degrees below normal, which may limit any fire weather highlights.
Most of the state is expected to remain mostly dry Tuesday with the
exception being northwestern/northern portions of the CWA. These
areas have a (20-40%) chance of seeing a brief shower during the day
Tuesday. Other parts of the state have a much lower chance to see
precipitation, however an isolated shower cannot be ruled out.

The remainder of the week is looking active with multiple quick
hitting systems moving through the region. However, models are
continuing to lessen the impacts of these systems with each passing
day. A large potent upper-level low sets up over northern Montana by
Tuesday night. This low will aid in ejecting weak shortwaves to the
south, bringing chances for precipitation to parts of the state
throughout the week. These shortwaves will also usher in much cooler
air that lingers through most of the week. Looking at 700 mb
temperatures, models show well below normal values of -5 to -10
degrees Celsius across the state from Wednesday through Friday. Any
precipitation that moves into the state as a result of these
shortwaves would likely result in mountain snow, with the
possibility for low elevation snow mainly during the overnight
hours. One thing to note is that models have continued to lessen QPF
values with these disturbances. The tracks have shifted slightly so
that impacts will be mainly seen across the western and northern
portions of the CWA. The next chance for widespread precipitation
does not arrive until Friday. Based off how the upcoming mid week
system has shifted, it would not be a surprise to see something
similar happen for Friday`s. Overall, there still is a lot of
uncertainty for the remainder of the week, with impacts continuing
to trend towards remaining mainly across northern and western WY.
The one aspect that does look pretty locked in would be cooler below
normal temperatures through the remainder of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1138 AM MDT Mon Apr 29 2024

Shower activity starting to increase across western WY, and
will continue to impact sites into this evening. Have added some
tempo thunder into KJAC TAF, as lightning probabilities have
increased in latest model runs. As the latest system moves east,
showers will quickly move east across the divide, with a brief
round of showers between 00Z and 06Z at all sites. Thunder
should not be an issue overnight. Showers will be quickly
shifting east after 06Z, with sct high cirrus only cloud cover
remaining overnight and into Tuesday morning.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Straub