Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 171033
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
433 AM MDT Tue May 17 2022

.SHORT TERM...Today through Thursday night

We still have some showers out there early this morning but they are
light for the most part. With a weak cold front slowly crossing the
area, we will continue to have some showers and thunderstorms around
today. The difference today being the main focus will shift to areas
East of the Divide with lesser chances further west. Most areas will
have at least a slight chance though. The main threat from any storm
will once again be strong wind gusts, especially across southern
Wyoming where there will still be fairly substantial dew point
depressions. However, temperatures will be somewhat cooler and the
atmosphere is a bit more moist, so potential high wind gusts
looks somewhat more diminished at this time. We gave some thought
to fire weather statements for southern Wyoming, but with
temperatures somewhat cooler than yesterday, criteria would be
hard to meet so we decided against it. All showers should end
around midnight or so.

Transitory ridging will then move across the state and bring a dry
day for Wednesday. This looks to be a warm day as well with some 80
degree highs possible in the warmer spots. The pressure gradient
will be tightening though ahead of a cold front advancing from the
northwest. This will bring a gusty wind to many areas Wednesday
afternoon, but with the lack of jet support, high winds are not
expected for this time frame. It will likely be sufficient for
elevated fire weather however, so we may be issuing some fire
weather statements for Wednesday afternoon as a result.

The threat for high wind will begin to increase Wednesday night
across the favored areas in the Cody Foothills. The area will begin
to get into the right front quadrant of an 150 knot jet for some
downward forcing. This, combined with 700 millibar winds climbing to
70 knots, may bring high wind to the favored areas near Clark.
The cold front will then move southward across the state on
Thursday. Guidance shows many locations having high wind potential
on Thursday afternoon. It can be a bit overdone this far out, but
the ingredients are there. There still some uncertainties in
other facets of the forecast though. One is temperatures, the NAM
is slower with moving the front in than the GFS and European and
as a result some locations have as much as a 15 degree spread in
highs on Thursday. Another variable is the chance of showers. Most
models keep most precip across northern Wyoming during the day
although there are varying areas of coverage. So for now we kept
POPS broadbrushed for now. All models do show much colder air
moving in for Thursday night with 700 millibar temperatures
falling to anywhere from minus 6 to minus 12. This is cold enough
for the S word, aka snow, to be possible even in the lower
elevations. Amounts look to remain on the light side, but it will
be a slap in the face after the past few warm days we have had.

.LONG TERM...(Friday through Monday)
Issued at 415 AM MDT Tue May 17 2022

A cold trough settles over the region Friday with high temps in
the 40s to lower 50s, which is much below normal, but not uncommon
for May. The GFS and ECMWF models give the area a chance of rain
and snow showers Friday into Friday night. Lows temps for Saturday
morning will be in the upper 20s and lower 30s with mainly 20s in
the west and south. Cold northwest flow occurs Saturday with a
weak weather system moving through the flow. This will generate
scattered rain showers for the lower elevations with snow showers
in the mountains. The precip will end Saturday night. High temps
Saturday will be in the 50s. Low temps Sunday morning will be in
the lower to mid 30s with some 20s in the west. The models
continue to suggest unsettled weather for Sunday with scattered
rain showers and mountain snow showers. High temps will be a
little milder with mid 50s to mid 60s across the region. Monday
looks dry per the ECMWF models, but the GFS model has yet another
weather system in the northwest flow aloft. For now will keep low
precip chances in the forecast Monday into Monday evening. Highs
Monday will be in the 60s with a few 50s in the west. It may be a
good idea to protect plants from the cold for several nights, if
possible.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday)
Issued at 415 AM MDT Tue May 17 2022

Cannot rule out a few showers this morning, but the main activity
will be this afternoon and early evening roughly along and east of a
line from Cody to Rock Springs. A weak cold front will move across
the area this morning turning winds northerly east of the Divide,
but westerly winds will continue west of the Divide. Winds will also
become variable and possibly strong at times due to the expected
convection.

VFR conditions are expected through the TAF period except very brief
MVFR/IFR conditions possible if a TAF site has a direct hit from
convection.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...

Expect another unsettled day today with a scattering of showers and
mainly afternoon thunderstorms, with the best coverage along and
east of a Cody and Rock Springs line. Like yesterday, the main
threat from any shower or storm will be strong wind gusts. All
showers and storms should end around midnight with mainly dry
conditions for Wednesday. Relative humidity should remain above
critical levels. A gusty windy will blow across southern Wyoming,
while other areas will have light to moderate wind. Mixing and
smoke dispersal will range from fair to poor in the north and east
to good to excellent in the south and west. A combination of warm
temperatures and windy conditions may bring elevated fire weather
to portions of the area Wednesday afternoon.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...Hattings
LONG TERM...AR
AVIATION...WM
FIRE WEATHER...Hattings


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