Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 260434
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1034 PM MDT Mon Mar 25 2024

.KEY MESSAGES...

- Cool today, with snow shower chances this afternoon and
  evening across central, and especially, western Wyoming.

- Near normal temperatures return Wednesday, with mainly dry
  conditions.

- A wet and active pattern starts Thursday, looking to continue
  through at least this weekend.

&&

.DISCUSSION...
Issued at 1233 PM MDT Mon Mar 25 2024

A cool day today, as clouds and cooler temperatures stick around
after a cold front passed through yesterday. Northwest flow persists
in the upper-levels, with a shortwave, and associated vorticity
maximum, passing through the state today. This shortwave helps
produce some isolated to scattered snow showers throughout the day
as it passes through from northwest to southeast. Taking a look at
high resolution models, as well as model (and the 00Z RIW)
soundings, convective snow bands are possible. Given the northwest
flow aloft, locations most favorable for these bands would be the
southern end of the Wind River Mountains, as well as the western
Wind River Basin with bands forming off the Washakie Needles area.
Models depict winds around 20 knots in the moist layer; though not
ideal (want stronger winds for bands to form) for strong snow bands,
isolated, weaker bands could form. The 700mb winds will be the key
player in if bands actually do form. Currently they are forecast to
be too weak for good bands to form, so developing snow may just be
convective showers moving off the mountains. Lapse rates in the 6.5
to 8 degrees Celsius per kilometer range are also supportive of weak
convective bands. Should actual lapse rates overperform a bit, more
cellular snow showers would be favored. Predicting locations of
these bands or showers is difficult; have blended quite a few high
resolution models in the forecast to try and cover multiple
"opinions" on where the bands or showers may form. Should bands
occur, narrow stretches of around an inch or two of snow are
possible. Isolated (30% or less) to scattered (30% to 60%) snow
showers are also possible across most locations west of the
Continental Divide, as well as isolated (20%-30%) chances in the
Bighorn Range.

Snow chances decrease this evening as the shortwave moves out of the
area. A few showers could continue over the western mountains as
moisture inflow continues in combination with a weak shortwave.
Tuesday, temperatures increase a little, with many locations hitting
the 40 degree mark, though these are still below normal. Snow
showers are again possible (20% to 60% chances) west of the Divide,
with 20% to 30% chances of a some showers moving off the mountains
and east of the Divide. The northern Bighorns have about a 60%
chance of snow, with lesser chances for the southern end of the
range.

A quick-moving ridge passes through for Wednesday. This greatly
limits precipitation chances, with only isolated snow chances for
the western mountains. Elsewhere, temperatures rebound to near
normal for the end of March. Gusty winds also return for the Wind
Corridor as southwest flow returns at the surface.

Thursday through at least the weekend will be influenced by an upper-
level low moving down the Pacific coast. This brings moist southwest
flow to Wyoming through that time period. Western Wyoming takes the
brunt of this to begin with on Thursday. East of the Divide looks
relatively dry at this time through a majority of Thursday, though
this could easily change. This wet pattern continues through the
weekend, with increasing chances of precipitation east of the Divide
as well. This far out, there is uncertainty in the details, but
there is good confidence in this wet pattern through at least the
weekend. Temperatures for this time period look to be near normal to
slightly cooler than normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1034 PM MDT Mon Mar 25 2024

Any lingering light snow showers continue to fade, and VFR
conditions generally prevail through the forecast period. Mid-cloud
decks remain overnight before another round of instability showers
Tuesday afternoon. Heavier showers will be accompanied by reductions
in cig/vsby and occasionally gusty winds. These again look to be
widespread, with impacts varying from terminal to terminal. These
instability showers are hard to pinpoint exact locations and timing,
so have left VCSH groups for now. Mountain tops will be frequently
obscured after 18Z Tuesday. Shower activity will wane towards the
end of the period for most terminals. The exception is KJAC, where
models hint at fog and/or low clouds developing, with lingering snow
showers, after 03Z Tuesday evening.

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...Wittmann
AVIATION...Hensley/LaVoie


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