557
FXUS65 KRIW 301901
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
101 PM MDT Thu May 30 2024

.KEY MESSAGES...

- Daytime high temperatures 5-10F above normal Saturday through
  Monday initiate another period of active snow melt in the
  mountains. Foothill creeks and streams will see daily diurnal
  water rises.

- Breezy west to southwest wind on Monday and Tuesday could
  heighten rangeland fire conditions over central and southern
  Wyoming.

- Ensemble forecasts are in agreement with a ridge of high
  pressure developing over the western United States by the
  middle of next week. Temperatures will be well-above normal.

&&

.DISCUSSION...
Issued at 101 PM MDT Thu May 30 2024

Mid-level moisture within cyclonic flow draped over the northern
half of the forecast area has allowed for isolated showers and cloud
cover over the northern mountains today. Otherwise, plenty of
sunshine and more seasonable temperatures across the the remainder
of the forecast area Thursday afternoon. The cyclonic flow persists
across the north overnight enabling a few showers to linger over the
northern mountains into Friday morning. The parent trough over the
Canadian Prairie Provinces lifts northeast by midday Friday. This
leaves the forecast area with a mostly clear sky Friday afternoon
and night. There will be a breezy west wind across southern Wyoming,
but nothing out of the ordinary. Temperatures warm to at or just
above seasonal normals regionwide.

Zonal flow is found across the region through the weekend.
Temperatures will be running 5-10F above normal both days, which
allows for a period of active mountain snowmelt. Much of the
snowpack is now confined to elevations above 9K feet. Foothill
creeks and streams will see daily diurnal rises, but available
channel capacity and the fact this will be higher elevation melt
should limit flooding concerns. The exceptions would be the Salt
and Snake drainages where lower snow has yet to melt, and those
drainages fed by the northern Bighorn Mountains. Mid-level
moisture sneaks into southwest Wyoming Saturday and ignites
isolated afternoon and early evening showers and storms in that
region. A better plume of mid-level moisture arrives from the
west Saturday night and Sunday, leading to better coverage over
the northwest-quarter of the state during that time period.

A deepening trough off the Pacific Northwest coast generates
southwest flow aloft Monday leading to even warmer temperatures.
The above normal temperatures combined with a breezy southwest
wind and a drier airmass elevates rangeland fire weather
concerns Monday. However, many areas are still in greenup. The
flow flattens Tuesday as shortwave energy rolls through the
Northern Rockies with little noticeable impacts to sensible
weather. It may be a bit breezier Tuesday as the pressure
gradient tightens. Attention then turns to a building ridge
across the western United States. Much above normal temperatures
in the 80s and even lower 90s look increasingly likely. Current
projections have daily highs the latter half of next week
falling short of record highs that run in the lower to mid 90s.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1126 AM MDT Thu May 30 2024

VFR conditions will prevail through the period at all terminals.
Skies will remain mostly clear across the region through the period
as well, with only FEW to SCT high clouds. Breezy west-northwest
winds will develop early in the period at most terminals. Gusts 20
to 25kts will be common through the afternoon. Winds then decrease
to light and variable drainage flows toward sunset and light and
variable winds will prevail through much of the rest of the period.
A weak boundary will bring mid-level cigs into KCOD and KWRL this
afternoon. A few isolated rain showers may be possible with this
boundary at these terminals (20% chance at KCOD and 10% chance at
KWRL), but due to low confidence in these showers, have left
mentions out of the TAFs. The BKN mid-level decks will likely (80%
chance) persist through much of the rest of the period for the
aforementioned terminals.

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...CNJ
AVIATION...Hensley