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000
FXUS65 KRIW 260921
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
321 AM MDT Fri Apr 26 2024

.KEY MESSAGES...

- Showers and isolated thunderstorms today and Saturday, most
  numerous in central and southern Wyoming. The steadiest
  precipitation will be tonight,

- Snow is likely in the mountains, with the heaviest in the Wind
  River and Absaroka Ranges.

- Remaining rather unsettled through Wednesday, with a few
  chances for showers and the potential for strong wind Monday
  through Wednesday.

&&

.DISCUSSION...
Issued at 316 AM MDT Fri Apr 26 2024

The pattern looks rather active over the next few days. Radar
currently shows some showers mainly across Johnson and Natrona
County as I write this around 2 am. And today looks rather damp as
we will be under the influence of two low pressure areas. The first
is a vertically stacked, low moving low that is moving out of
Colorado and into Nebraska at this time. The second is now moving
into the Pacific Northwest and will close off over the Great Basin
tonight and into Saturday. This will turn low level flow east to
northeast across much of the area and bring in moisture.  There are
some changes this morning though. For one, the QPF has trended down
across portions of the area, especially further east and north in
places like Buffalo where the core of the moisture would be further
south. Today looks to be more convective, with isolated
thunderstorms possible in most areas, but the chance of any spot
seeing one is 1 in 3 or less. The steadiest. more stratiform
precipitation still looks to be tonight, when moisture flow
would be the deepest. The highest amounts still look to occur in
the favored east to northeast upslope locations, especially
from the east slopes of the Absarokas to the Wind River Range to
to Salt and Wyoming Range. Heavier amounts are also possible in
southern Wyoming which will be very the best convergence will
set up. In the lower elevations, the most favored areas, like
Lander, Dubois and even Rock Springs have at least a 1 in 2
chance of picking up a half and inch of rain or more. Amounts
would then generally decrease further north and east away from
the deepest moisture. Temperatures will be cooler today, but not
cold given the Pacific nature of the air mass.

Now on to the S word, snow. With 700 millibar temperatures expected
to remain at minus 3 or warmer, snow accumulation would be largely
restricted to the mountains, with snow levels generally 7500 feet or
higher. We can`t rule out a small accumulation of snow in places
like Dubois or Lander if precipitation rates are very heavy, but
accumulation would likely only be on non-paved surfaces. The
heaviest snow still looks to fall in the Wind River Range, where
areas above 10000 feet may pick up 2 feet of new snow, with around a
9 in 10 chance of over a foot of snow in the highest elevations.
We will maintain the Winter Storm Warning here. The advisory for the
Absarokas will also be continued, but impacts here would be less,
with less than 1 in 3 chance of a foot of snow or more.

Unsettled weather will continue into Saturday, although intensity
should be less as the low moves away. A new wrinkle is what may
happen Saturday evening as the trailing trough axis swings through
western Wyoming. Some ensemble solutions are putting advisory
amounts of snow in places like the Salt and Wyoming Range. There is
poor agreement on this though, with less than a 1 in 2 chance of
reaching advisory criteria. This, plus the fact that impacts would
be limited, no new highlights will be issued at this time.

Things become somewhat, emphasis on somewhat, less active after
that. A few showers will linger into Sunday but coverage will be
about 50 percent less than previous days. The first part of the new
workweek will feature mainly zonal flow. A couple of shortwaves will
pass through the flow, most likely on Monday and Wednesday. These
may bring a few showers, especially to northern portions of the
area. Details on how far the reach are difficult to determine at
this time though. The main concern on these days may turn out to be
strong to potentially high wind. Flow is fast over the area and
the jet will be overhead, helping to enhance downward momentum,
especially across the southern half of the state. Way too early
for details, but it could be a few days of securing things like
trash cans, trailers and toupees. More settled weather is then
expected for the end of next week as ridging builds into the
area. Temperatures through much of next week should average near
to slightly below normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 950 PM MDT Thu Apr 25 2024

A very active weather pattern continues through the next 24 hours.
An area of rain showers will develop from the Bighorn Basin down to
Natrona County tonight/early Friday morning. Rain chances increase
at KCOD/KWRL/KCPR terminals near/shortly after sunrise, so have
prevailing -SHRA at that time. For other terminals it will remain
dry tonight with more convective showers developing late Friday
morning/early Friday afternoon across the area. For now have -SHRA
for most terminals Friday afternoon, but -TSRA may be added with the
next TAF issuance if confidence is high enough. There will be
thunderstorms, but the exact location/timing is too difficult to
pinpoint at this time. A more widespread -RA will develop Friday
evening from KRIW/KLND terminals down to KRKS/KBPI/KPNA terminals.
For KCPR/KWRL terminals showers exit to the southwest by mid-
afternoon Friday.

MVFR conditions are likely (70%) at KCOD by 10Z/Fri as low clouds
develop and hang around through Friday afternoon. Improvement should
occur at KCOD late Friday afternoon/Friday evening as clouds begin
to lift and -SHRA shift to the southwest. For most terminals VFR
conditions will prevail through the TAF period. Mountain obscuration
will increase Friday afternoon and be prevalent Friday evening. Have
VCTS at KRKS Friday afternoon and included a variable gusty wind to
account for thunderstorm downdrafts/outflows.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon today to 3 PM MDT Saturday
for WYZ002.

Winter Storm Warning from 6 PM this evening to 9 PM MDT
Saturday for WYZ015.

&&

$$

DISCUSSION...Hattings
AVIATION...Rowe