Powell, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

321
FXUS65 KRIW 071646
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1046 AM MDT Sat Jun 7 2025

.KEY MESSAGES...

- Widespread warm temperatures with mostly sunny skies today
  with shower and thunderstorm chances (30-70%) across the
  Bighorn Basin, the Bighorn Mountains, and Johnson and Natrona
  Counties late this afternoon and evening.

- Near elevated fire weather conditions are possible this
  afternoon across southern Wyoming with low relative humidity
  values between 15-20% and gusty winds up to 30 mph.

- Much above normal temperatures are forecast the first half of
  the work week with multiple shower and thunderstorm chances
  Tuesday onward.

&&

.DISCUSSION...
Issued at 223 AM MDT Sat Jun 7 2025

As of 2AM local, water vapor imagery shows a weak shortwave
traversing the Intermountain West and bringing increased cloud
cover. The shortwave is expected to be east of the CWA shortly after
sunrise this morning, leaving mostly sunny skies much of the
day today. Wyoming will largely be situated between a building
upper-level ridge to the west and an upper-level trough the
northeast, leaving the region in northwesterly flow aloft today.
With mostly sunny skies, gusty winds between 20-30 mph, and
700-mb temperatures between 8-12C, temperatures will be allowed
to warm to slightly above normal today (70s to low 80s F). Gusty
winds and low relative humidity values between 15-20%,
especially across the southern portion of the state, supports
near elevated fire danger this afternoon.

In addition to the warm temperatures, an area of increased PVA is
forecast to round the trough and traverse the northern portions of
the state, providing support for isolated to scattered thunderstorm
chances primarily across the Bighorn Basin, the Bighorn
Mountains, and Johnson County. Convection chances (30-70%) will
increase during the late afternoon/evening. CAPE values are
forecast around 500 J/kg during this timeframe. However,
thunderstorms are not forecast to become severe with overall
height rises and modest mid-level lapse rates. The strongest
storms could produce gusty outflows up to 40mph. Storm coverage
diminishes after sunset with only isolated to scattered showers
possible (up to 50% chance) during the overnight hours across
Johnson County and the southern half of the Bighorn Mountains.

A somewhat similar pattern is in store on Sunday with the main
difference being that the upper-level trough is pushed farther
east as the ridge slowly shifts into the region. This ultimately
helps keep the area largely shower and thunderstorm free apart
from high elevation showers. High temperatures on Sunday are
forecast to be slightly cooler than today for locations east of
the Divide with 700-mb temperatures forecast to be less than
8C.

Ensemble guidance remains in consensus that the upper-level
ridge will be overhead Monday through Wednesday morning. Height
rises aloft and 700-mb temperatures around 12C will favor a warm
up to temperatures nearly 10-15 degrees above normal on
Tuesday. By Tuesday evening, there is consensus in a weak
disturbance rounding the ridge and bringing the next chance of
precipitation to portions of the area. However, there remains
uncertainty with the Tuesday system with the amount of
available moisture which will ultimately effect precipitation
chances. The ridge axis is forecast to be well east of the
Intermountain West by midday Wednesday leaving the region in
west-southwest flow through early next weekend. Deterministic
guidance is hinting at a frontal passage on Wednesday brining
more widespread precipitation, however, given how far out this
is, details remain unclear.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1045 AM MDT Sat Jun 7 2025

Mid- and upper-level northwest flow continues today across
western and central WY, with a shortwave trough moving from
southern Canada into eastern MT and clipping northeast WY
through the afternoon and overnight hours. VFR conditions are
generally expected at all TAF sites through the forecast period,
though there is a chance of MVFR conditions from KCOD/KWRL to
KCPR from about 08/03Z to 08/15Z due to lower ceilings with rain
showers. Gusty winds have already picked up during the morning
hours at several sites, and they will increase in strength and
coverage during the afternoon, though the highest gusts should
remain in the 20-28 kt range. The shortwave trough will bring
increased cloudiness and gusty north winds to KCOD early in the
afternoon, which will spread southward to KWRL later in the
afternoon and evening. Winds will become more northeast east of
the divide during the evening hours, with KWRL and KCPR having
the best chance (20-30%) of rain showers from about 08/09-13Z.
Gut feel is that there is a slight chance of some lower clouds
and very localized fog around KCPR after 08/12Z, though not
confident enough to include it in the TAF. The Bighorn Mountains
are likely to be obscured from 08/06-15Z.

The disturbance then moves to the southeast on Sunday, with
continued north-northwest flow becoming gusty during the
afternoon. Cloudiness will decrease through the day with
lingering clouds across south-central WY.

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...Gerhardt
AVIATION...McDonald