864
FXUS65 KRIW 290450
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1050 PM MDT Sun Apr 28 2024

.KEY MESSAGES...

- Scattered snow/rain showers continue across parts of western
  WY. Showers and thunderstorms look to develop and spread east
  during the afternoon and evening.

- Showers dissipate during the overnight hours with a few
  lingering showers over western WY.

- Winds increase Monday as a quick moving system works it way
  into western WY. Scattered showers and thunderstorms will be
  possible during the afternoon and evening.

- Winds remain gusty through the first half of the week. The
  remainder of the week looks to be unsettled, with multiple
  chances for precipitation and cool below normal temperatures.

&&

.DISCUSSION...
Issued at 110 PM MDT Sun Apr 28 2024

The low that brought steady precipitation to parts of the state over
the past few days has finally moves east into the Northern Plains.
However, unsettled weather will remain over the region, as a weak
shortwave trails behind the low and moves across the Northern
Rockies today. Western WY currently is seeing some scattered snow
showers mainly over parts of YNP. The remainder of the state can
expect to see some periods of sun during the early afternoon, with
highs nearing normal values. This afternoon and evening will see
scattered showers and a (10-20%) chance for a few isolated
thunderstorms to develop across the state. Central and northern
portions of the CWA have the best chance to see some precipitation
with a (30-60%) of seeing a brief shower. Sweetwater, Sublette, and
Lincoln County look to likely remain mostly dry through the day
today. Similar to yesterday winds will increase slightly this
afternoon with most seeing breezy conditions. Parts of Sublette and
Sweetwater Counties look to see the strongest winds with a (40-70%)
chance of seeing gusts of 35+ mph. Showers dissipate overnight with
a few showers lingering into the early morning hours Monday. Winds
decrease after sunset light and variable overnight.

Another weak shortwave sweeps across the PACNW and moves
into the Northern Rockies by Monday afternoon. Showers look to
develop by the late morning 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
40+ 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. Temperatures
will briefly rebound for Monday, with near normal values for areas
east of the Divide.

Tuesday will be drier with an upper-level low staying north of WY.
Showers will still be possible but look to be very isolated with
chances remaining below (20%). 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 (30-60%) of seeing 45+ mph gusts. RH
values will also be rather dry with percentages around 20%.
Temperatures do look to remain cooler than normal with highs around
5-10 degrees below normal.

The remainder of the week is looking active with multiple quick
hitting systems moving through the region. Mid week is looking
interesting as an upper-level low develops over the PACNW and swings
down across the Great Basin into Colorado. Models are showing some
unseasonably cold air associated with this system. 700 mb
temperatures for Wednesday into Tuesday show values of -5 to -10
degrees Celsius across the state. As the low sweeps to the south of
the state a brief period of northeasterly upsloping looks possible.
Snow would be possible across parts of the Absarokas, Wind Rivers,
and Casper Mountain due to this favorable flow. There even looks to
be a chance for some lower elevation snowfall during the overnight
Wednesday into the early morning Thursday as snow levels fall below
5000 feet. Overall, there still is a lot of uncertainty for the
upcoming week, as models have little grasp on the tracks and impacts
for these systems.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1049 PM MDT Sun Apr 28 2024

VFR conditions prevail overnight, with relatively light winds. Winds
begin to increase Monday morning, with gusts to around 30 knots by
the afternoon for many sites. There is a possibility for higher
gusts for KBPI, KCPR, KPNA, and KRKS, possibly to 35-40 knots; will
have to reevaluate wind potential with newer model runs.

Precipitation begins over western Wyoming around 18Z/Mon. As a weak
cold front passes through, rain chances spread eastward through the
day, reaching the Continental Divide roughly around 00Z/Tues. All
sites have a chance of rain through the TAF period, but lower
confidence for locations east of the Divide, so have left mention
out for most locations for now.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

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

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Wittmann