474
FXUS65 KRIW 010414
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1014 PM MDT Fri May 31 2024

.KEY MESSAGES...

- Active mountain snowmelt will occur Saturday through Monday as
  daytime high temperatures climb to 5-10F above normal.
  Foothill creeks and streams see daily diurnal rises.

- Above normal temperatures combined with a breezy west to
  southwest wind could elevate rangeland fire conditions over
  central and southern Wyoming Monday.

- Temperatures across the region will be above normal the latter half
  of next week as a ridge of high pressure builds across the
  western United States.

&&

.DISCUSSION...
Issued at 1250 PM MDT Fri May 31 2024

Cloud cover dissipated across the far north and eastern zones late
Friday morning as cyclonic flow exited to our northeast. This
has left abundant sunshine and seasonal temperatures across the
forecast area early Friday afternoon. These conditions persist
through Saturday morning with little more than increasing high
clouds. Saturday finds mid-level moisture progressing into
southwest Wyoming from the Great Basin in zonal flow. Daytime
heating leads to isolated convection over the southwest mid to
late afternoon and after 5 PM for portions of central Wyoming.
Instability is limited and the sub-cloud layer is dry, so gusty
outflow wind around 40kts would be the primary convective
hazard. It appears this mid-level plume continues to traverse
southwest and central Wyoming through Saturday evening and into
the Sunday morning hours, so light showers may indeed linger
much of the night. Otherwise, cloud cover steadily increases
Saturday night helping to keep temperatures warm for Sunday
morning. Shortwave energy swings east-southeast across the
forecast area around midday Sunday. Showers look to be a decent
bet (30-50 percent) across the northwest and most areas east of
the Continental Divide, but extensive cloud cover Sunday
morning should hinder instability for stronger convection that
afternoon and evening.

A trough off the Pacific Northwest coast spins a stronger
shortwave toward western Wyoming Monday afternoon. Instability
is more favorable for deeper convection across the west and
north Monday afternoon and early evening. Breezy southwest wind
Monday helps to boost temperatures a few degrees from those of
Sunday, while also lowering relative humidity. As such, elevated
rangeland fire weather conditions are possible across portions
of central and southwest Wyoming Monday afternoon. The warmer
temperatures of the Saturday through Monday time period enables
active mountain snowmelt, with the bulk of the remaining
snowpack positioned 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.

West-northwest flow follows for Tuesday dropping temperatures to
more seasonal readings, while keeping isolated convection
mainly confined to northern Wyoming and the I-25 Corridor.
Ensembles continue to show a building ridge over the western
United States for the latter half of next week. Temperatures
rise into the 80s for many locations under the building ridge,
approximately 10F above normal. There is some hint that a weak
low in the Desert Southwest could circulate moisture north on
the backside of the ridge late in the week. Thus, it is
conceivable that isolated convection could still be present
Thursday and Friday even with the ridge in place.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1007 PM MDT Fri May 31 2024

Light winds and clear skies will prevail overnight. On
Saturday, mid level clouds will spread across the southern half
of the state after sunrise, including for sites such as KRKS,
KPNA, and KBPI. During the afternoon, isolated showers and weak
thunderstorms are possible (20 to 30% chance) in the Upper Green
River Basin into Natrona County, and the main concern with
these would be brief, erratic wind gusts to around 40 kt. The
threat of this shower activity ends around sunset, with a
return of light and variable winds for Saturday night.


&&

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

&&

$$

DISCUSSION...Jones
AVIATION...VandenBoogart