355
FXUS65 KRIW 012050
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
250 PM MDT Wed May 1 2024

.KEY MESSAGES...

- Afternoon scattered showers and weak thunderstorms are in the
  forecast daily through Friday. Light mountain snow
  accumulations are also possible over the next 48 hours.

- Elevated fire weather conditions exist this afternoon for
  Sweetwater and Natrona counties, due to a combination of
  breezy winds and a dry air mass.

- This weekend will be warm and dry east of the Divide, with
  cooler and wetter conditions for western Wyoming mountains and
  valleys.

&&

.DISCUSSION...
Issued at 250 PM MDT Wed May 1 2024

A longwave trough resides over the Intermountain West this
afternoon, with an approaching embedded shortwave. The cool air
aloft will encourage scattered shower development, but
accumulations from the short-lived showers will be minimal. This
afternoon and evening will also feature breezy winds in the
Sweetwater to Natrona county wind corridor as the shortwave
trough tightens the surface pressure gradient. When combined
with the relatively dry air mass, elevated fire weather
conditions will exist through sunset.

Thursday and Friday feature much of the same weather, with
temperatures about 5 degrees below seasonal averages, and
scattered afternoon showers. Accumulations will again be minimal
for lower elevations. Winds will be lighter these days, so fire
weather concerns are not as high.

On Saturday, a brief ridge moves through the Rockies, leading to
a quick warm up to about 10 degrees above seasonal normals. No
precipitation is expected, and winds are not overly breezy,
making conditions favorable for many outdoor spring activities.

On Sunday, a deep trough begins to push into the western Wyoming
mountains. This will bring a return of showers for locations
west of the Divide, but those in the basins east of the Divide
will enjoy a very mild day, with temperatures 15 or so degrees
above average.

On Sunday night into Monday, the weather system associated with
this trough will move across the state, bringing a noticable
cooldown, as well as more numerous showers and measurable
precipitation for many. Western Wyoming valleys could see light
snow during the overnight timeframe, but this would likely melt
quickly after sunrise Monday given high temperatures in the
40s. In the wake of this system, conditions moderate to near
seasonal averages by mid-week.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1115 AM MDT Wed May 1 2024

A weak weather system passes through today, with the main impacts
being precipitation chances and wind. Starting with precipitation,
chances will be limited to more northern Wyoming sites through the
afternoon. Chances (about 15%) sweep through KCPR, KLND, and KRIW
this evening. Best chances occur at KCOD and KJAC this afternoon.
Showers will be more scattered, so although the TAFs have prevailing
groups of snow, there may be times it is not snowing. Thunder is
also possible (about 10-15% chance), and given the most likely
precipitation type is snow, thundersnow is possible.

Wind-wise, gusts 20 to 30 knots are common this afternoon, with a
few sites favoring slightly higher gusts during peak heating this
afternoon. For the most part, gusts decrease after sunset, with most
locations ending the gusty winds by 05Z/Thurs. KRIW may see a
northwest drainage wind later than that time. Winds look to increase
again for Thursday.

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...VandenBoogart
AVIATION...Wittmann