589
FXUS65 KRIW 071729
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1129 AM MDT Tue May 7 2024

.KEY MESSAGES...

- Showers continue across western WY with moderate to heavy
  snowfall possible in higher elevation through the morning.

- Scattered showers and isolated thunderstorms develop this afternoon/evening.
  Winds are expected to remain gusty across most of the state.

- Another round of precipitation is expected to move through the state
  Wednesday and Thursday. Mountain snow and low elevation rain
  with a few areas possibly seeing a transition to light snow by
  Thursday morning.

- Quiet and mild weather returns to end the week, with the possibility
  for a sunny, mild, and pleasant weekend.

&&

.DISCUSSION...
Issued at 259 AM MDT Tue May 7 2024

IR this morning shows a well defined circulation over parts of of SE
Montana, NE Wyoming, and W South Dakota. This circulation was the
main culprit behind the soggy start to the week in many places east
of the Divide. Showers spread across the state during the morning
hours on Monday, as an upper-level low tracked across the area.
Moderate to heavy rain fell across parts of Johnson and Natrona
Counties, with rainfall amount by Monday evening nearing and even
exceeding 1.50 inches in places. Winds continued to gust as well,
with periodic winds gusts of 50+ mph in parts of Fremont and
Sweetwater Counties. Unfortunately, showery activity continues today
across the Cowboy State today but does not look to be widespread.
Winds look to remain gusty in much of the same parts of the state as
Monday.

As mentioned earlier, the pesky Pacific low continues to bring
impacts to the state whether that be in the form of precipitation or
gusty winds. The low has moved into the Dakotas and eastern Montana
this morning but impacts will continue to be seen. The pressure
gradient remains tight with widespread gusts of 30+ mph during the
day today. Areas that experienced strong winds yesterday will likely
see another round today, with parts of Sublette, Sweetwater,
Fremont, and Natrona Counties having a (50-80%) chance of seeing 45+
mph gusts. Due to the position of the low, flow will continue to be
from the west/northwest. During the day today moisture will be
wrapping back around into the state, which will aid in creating some
instability in the atmosphere. Showers are expected to continue
across western mountains especially in westerly/northwesterly flow
favored areas such as the Tetons. Due to this winter highlights
remain through the morning and afternoon across YNP, the Tetons, and
the Gros Ventre. Lower elevation western valleys can expect to see
some convective showers develop during the early afternoon, with a
few rumbles of thunder possible. Some recent CAMs have shown showers
developing in other parts of the CWA as well this afternoon. While
these showers are not expected to be widespread most of the state
will have at least a (20-40%) chance of seeing a shower this
afternoon/evening. Temperatures remain on the cooler side across the
whole CWA with highs being 10-15 degrees below normal.

Unsettled weather continues through the overnight into Wednesday
morning. The next round of precipitation develops during the morning
Wednesday and becomes more widespread by the afternoon and evening.
Winds are expected to decrease compared to the past few days but
still remain breezy across most of the state. All of this is due to
the low or its residual energy returning back into the CWA and
moving across the state Wednesday. The remnants will gradually make
their way over the state and end up near Utah by Wednesday evening.
Flow will begin to shift as a result of this, with winds becoming
north/northeasterly by late Wednesday evening. Areas that favor such
flow like the eastern slopes of the Wind River Range, Absarokas, and
Bighorns may see winter highlights issued, due to possible snow
accumulation greater than 6 inches. At the same time northerly flow
will help usher in some cooler air, with 700 mb temperatures ranging
between 4-7 C for Thursday morning. This will be something to
monitor especially in parts of the Wind River Basin along the slopes
of the Wind River Range. Lander may see temperatures cool enough to
see rain transition over the snow during the early morning hours
Thursday. Currently the forecast remains to warm for this to happen
but if there was a slight shift of 2-3 degrees lower than this may
be a possibility. However, impacts would remain minimal with the
only concern being slick roads mainly during the morning commute.
These temperatures will need to be monitored as mentioned earlier, a
shift of a few degrees may be the difference between all rain or
morning snow in Lander come Thursday morning.

Remainder of the week...

Showers continue through most of the morning on Thursday, especially
in northerly/northeasterly favored areas. Conditions begin to dry
out by Thursday afternoon, as the low moves south into the Desert
Southwest. A large area of high pressure looks to begin to build in
by Friday, with a return to milder and quieter weather for the
weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1130 AM MDT Tue May 7 2024

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

Broad trough remains across the region today with gusty westerly
wind again the primary hazard. Frequent surface gusts of 28-40kts at
KRKS, KPNA, and KBPI into the evening hours. Meanwhile, southwest
wind 15-28kts will be common at KJAC until sunset. Weak orographic
flow to aid snow showers in the vicinity of KJAC through the
afternoon with occasional MVFR conditions. KJAC to temporarily see
VFR conditions before snow showers return in northerly flow aloft as
a shortwave spins south across the state late tonight and Wednesday.
Other than scattered brief MVFR snow showers this afternoon around
KBPI and KPNA, VFR to prevail at the remaining terminals. A
brief rain shower at KRKS to start the period, then quiet except
for the winds. Breezy westerly wind persists overnight with an
increase in speeds around 15Z-16Z/Wednesday. Mountain tops
frequently obscured above 10K feet MSL through the period.

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

A broad trough persists over the Northern Rockies today leading to
gusty west-northwest surface winds until around sunset. Gusts of 25-
40kts will be common during this time. Shortwave energy within the
broad trough pinwheels south across the region late tonight and
Wednesday. VFR conditions gradually give way to lowering ceilings
and a better chance of rain and snow showers over the Bighorn Basin
after 08Z/Wednesday. MVFR or low-end VFR to develop at KCOD and KWRL
between 12Z-15Z/Wednesday, while other terminals remain VFR through
18Z/Wednesday. Mountain tops obscured after 09Z/Wednesday.

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 PM MDT this evening for WYZ001.

Winter Storm Warning until 11 PM MDT this evening for WYZ012.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Jones