375
FXUS65 KRIW 061101
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
501 AM MDT Sun Apr 6 2025

.KEY MESSAGES...

- Sunny, dry, and seasonal to warm temperatures today and tomorrow.

- Breezy Monday, then widespread gusty winds 25 to 35 mph
  Tuesday and Wednesday, with higher gusts for favored
  locations. Combined with low relative humidities, elevated
  fire weather conditions are possible.

- Precipitation chances late Monday through Wednesday, favored
  for western and northern Wyoming. Thunderstorms possible.

&&

.DISCUSSION...
Issued at 109 AM MDT Sun Apr 6 2025

High pressure is in place today. As a result, temperatures will
trend up, with highs forecasted in the 50s west of the Continental
Divide (upper 40s for western valleys), and upper 50s to mid-60s
east of the Divide. These temperatures are just a few degrees above
normal for early April. Some passing high clouds move through, but
otherwise a mostly clear sky and dry conditions persist through the
day. Afternoon relative humidities (RH) will again be dry, ranging
from around 15 percent to 25 percent across the area. North to
northwest winds today will bring some breezy gusts (15 to 25 mph)
for some areas, like the Green River Basin and from around Buffalo
to Casper.

The ridge axis passes over the area Monday, meaning the warmest
temperatures associated with this high pressure system. Highs trend
3 to 8 degrees warmer than they will be today. Later in the day, the
next approaching weather system begins to flatten the ridge. This
tightens the pressure gradient, so increasing afternoon winds will
occur across the Wind Corridor and higher elevations. Afternoon
gusts from about South Pass to Casper will generally be 30 to 40 mph.

A broad trough then moves through late Monday through Wednesday.
This will bring two main weather elements, precipitation chances and
wind. Starting with precipitation, chances begin across western
Wyoming around 6pm MDT, spread eastward into Monday night. Models
continue to favor chances over western and northern Wyoming. Initial
precipitation type may be snow or rain/snow mix for the western
valleys, with snow for the mountains; daytime highs will mean rain
for the valleys and basins. Overall, not expecting a great amount of
rain or snow, with model NAM PWAT values around 100% of normal.
Precipitation chances continue through Wednesday, with highest
totals currently forecasted for the Tetons, Yellowstone, and
Absarokas, where snow totals are generally under 7 inches (isolated
higher amounts). This is still subject to change in the next couple
days as better high resolution guidance becomes available. Some
instability may also produce thunderstorms Tuesday and Wednesday.

The other element is wind. Winds increase Tuesday morning. Some
decrease is expected Tuesday night, before increasing again for
Wednesday. Probabilistic guidance favors Wednesday to be the slightly
stronger wind day, but both days will be quite windy, with
widespread gusts 25 to 35 mph Tuesday, with a little higher for
Wednesday. Favored areas, like the Wind Corridor or central
mountains, will likely see higher winds. As mentioned previously,
moisture will be limited with this system, so afternoon RHs will be
on the dry side, with values of 18 to 30 percent Tuesday and
Wednesday. This could bring areas of elevated fire weather
conditions, with wind being more more influential factor as RHs are
more marginal.

High pressure then returns for the end of the week. Model 700mb
temperatures would support Friday or Saturday being the warmest day.
With this, river rises are looking likely with snow melt. However,
this is fairly typical for this time of year, and with normal-ish
mountain snowpack (most water basins around 100% snow water
equivalent amounts) and no large precipitation events expected,
there is little concern for flooding at this time - so expect just
typical, spring river/creek rises associated with snowmelt.

Long range models hint at another system for the end of next weekend
into early next week, which would favor cooler temperature and
maybe precipitation. As expected this far out, details are
lacking.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 500 AM MDT Sun Apr 6 2025

VFR conditions prevail throughout the TAF period across all
terminals. Skies will remain mostly SKC with FEW to SCT high level
cirrus streaming across through much of the period. Winds remain
light across all terminals with a slight uptick expected during the
late morning to early afternoon at KBPI, KPNA, and KRKS, where gusts
around 20 knots are expected at times. These winds weaken by the
evening and become light, less than 10kts, after sunset.

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

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

&&

$$

DISCUSSION...Wittmann
AVIATION...Hensley