667
FXUS65 KRIW 082324
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
524 PM MDT Wed May 8 2024

.KEY MESSAGES...

- The upper low continues to rotate through the region, bringing
  more rain and mountain snow to much of the region today and
  tonight. Northeasterly upslope flow will cause showers to
  linger through much of the day Thursday across favored areas,
  particularly the east slopes of the Wind River Mountains.

- Northerly winds will continue to decrease through the evening
  as the low weakens. Strongest winds through the rest of today
  will be post-frontal northerly winds across the Bighorn
  Basin.

- Warmer, drier, and much less windy weather will finally arrive
  Friday and continue through the weekend.

- A series of shortwaves look to move through next week, which
  could produce scattered afternoon showers and thunderstorms,
  but confidence is low regarding locations or intensity of any
  of these shortwaves and associated shower activity.

&&

.DISCUSSION...
Issued at 330 PM MDT Wed May 8 2024

Rain and snow have spread across most areas east of the Divide late
this morning into the early part of the afternoon. The precipitation
is associated with the same upper low that has persistently been
plaguing the region for the past several days. , we should
be largely done with the wind impacts that have been the most
persistent, it seems, with this upper low. Now that we have moved on
from wind, we will now be dealing with some rain and snow that will
persist through tomorrow and even into Thursday night for some
areas. We are not entirely done with the wind, as gusty post-frontal
north to northeast winds will persist across the Bighorn Basin
through this evening. The Wind River Basin and locations across the
southwest will also see some breezy winds through the rest of the
afternoon, but these will continue to decrease through evening hours
and be mostly light by Friday morning. Then, easterly winds will
develop across the south tomorrow late morning, gusting through the
afternoon, but gusts will be in the 25 to 35 mph range, rather than
the 45 to 55 mph range that we have seen over the past few days.

As for precipitation, northeasterly flow over the next few days will
enhance the precipitation across favored east slopes, particularly
in the Winds and Casper Mountain. Note that precipitation amounts
have increased significantly across the Wind River Range, and thus,
snowfall amounts have also increased rather significantly. Peaks of
the eastern Winds could see over 2 feet of snow through Friday as a
result of the upslope. Hence, have upgraded that zone to a Winter
Storm Warning. Meanwhile, to the north, precipitation across the
Bighorns is not expected to be as heavy as previously thought. Have
thus decided to downgrade to an Advisory for those zones. All other
highlights remain the same from the previous shift.

Snow will be mostly relegated to the mountains, however, evaporative
cooling, particularly in foothill locations along the east slopes of
certain ranges (Lander, Casper) could lead to a period of wet snow.
Other higher low elevation areas such as the higher elevations of
20/26 between Shoshoni and Casper, as well as across Sweetwater
County could also see some snowfall. Overall, given time of year,
snow accumulations in these areas will be minimal and will mostly be
on grassy surfaces, while road surfaces should remain mostly wet,
especially during daylight hours.

The bulk of the precip will fall this evening through tonight.
Thursday, precipitation becomes more showery in nature, but steady
rain and mountain snow will still be ongoing for upslope favored
locations (Wind River Mountains, Casper Mountain, Lander Foothills,
Green Mountain/Rattlesnake Ranges, east slopes of the Absarokas)
through Thursday afternoon and even lasting through Thursday night
across the east slopes of the Winds. Elsewhere, precipitation will
mostly end by Thursday night, though lingering light showers are
certainly not out of the question.

Friday, we finally begin to see a warming and drying trend, which
will continue through the weekend. Temps climb to above normal
values by the weekend and winds will remain light as well.
Temperatures remain warm through about mid-week next week, but a
series of shortwaves could bring some scattered showers and
thunderstorms to the region through much of the week. Confidence
remains low regarding intensity or location of these showers. Models
hint at a cooler, more potent shortwave for mid-week, but again, low
confidence at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 524 PM MDT Wed May 8 2024

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals.

Multiple shortwaves and associated moisture will move southwest
across the region tonight and Thursday morning. Downsloping flow
should limit precipitation chances at KJAC, KBPI, and KPNA. VFR
prevails at these terminals with an outside chance of brief MVFR and
light rain or snow overnight. KRKS sees a northeast surface
wind arrive around 06Z/Thursday, which should encourage IFR/MVFR
conditions with light snow for several hours. Conditions and
ceilings improve late Thursday morning with VFR at all terminals
through the afternoon. Gusty east to northeast surface wind
15-30kts will be common at KRKS by late Thursday morning. KBPI
and KPNA see easterly wind 12-25kts develop around midday.
Mountain tops frequently obscured.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals.

Multiple shortwaves rotate southwest through the region tonight and
Thursday morning. Favorable north to northeast flow leads to upslope
precipitation at all terminals, the exception begin KWRL where
passing showers and low clouds allow -RA to linger. IFR/MVFR to
be common Wednesday evening with most areas still seeing rain.
Dynamic cooling and the loss of solar insolation should enable
light snow or a mix to develop at KCPR, KRIW, and KLND. The
upslope lingers longest at KCPR and KLND Thursday, and
conditions will be slow to improve. VFR likely does not return
on a widespread basis until 16Z-20Z/Thursday. Mountains
obscured, especially above 8K ft MSL.

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...
Winter Weather Advisory until 6 AM MDT Thursday for WYZ002-008-
009-022.

Winter Storm Warning until 6 PM MDT Thursday for WYZ015.

&&

$$

DISCUSSION...Hensley
AVIATION...CNJ