528
FXUS65 KRIW 021149
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
549 AM MDT Sun Jun 2 2024

.KEY MESSAGES...

- Isolated thunderstorms are possible today with strong wind
  gusts the main threat.

- A good chance of showers tomorrow, especially in Western
  Wyoming. Increasing wind Monday and Tuesday.

- Mainly dry Tuesday through most of Friday with warming
  temperatures. Elevated fire weather and rising river levels
  are expected at this time.

&&

.DISCUSSION...
Issued at 306 AM MDT Sun Jun 2 2024

It looks like we have at least a chance of our usual charcuterie
board of late spring / early summer weather across the area over
the next week or so. They are, in rough order, convection, very
warm temperatures, elevated fire weather and rising rivers and
possible flooding from high elevation snowmelt.

Convection will be the first concern of the period. We still have
some light showers in the south and west as the second in a series
of three shortwaves approaches the Cowboy State. The second wave is
similar to the wave yesterday in that it has little moisture to work
with so chances of showers would be 1 out of 3 at the best with most
lower elevation locations having a 1 in 5 chance at best. We still
have dry low levels though, especially East of the Divide. And with
the large dew point depressions and model soundings showing more
inverted Vs, any thunderstorm or even shower could have a strong
wind gust past 45 mph. Most areas will be dry most of the day and
many areas will see nothing. Temperatures will be similar to a
degree or two cooler with somewhat more clouds than yesterday. And
showers should end fairly quickly this evening with a balance of the
night mainly dry.

The last wave will approach on Monday and Monday night. This one
will be the most potent. For one, precipitable water values will be
higher, approaching 150 percent of normal Monday afternoon. In
addition, there will be more upper level forcing courtesy of an 120
knot jet moving into the area. Strong thunderstorms look unlikely
though. Surface CAPE is rather limited and with more cloud cover,
instability will not be that high. There could be some decent rain
across the west though, with a greater than 1 in 2 chance of a half
an inch of rain across the western mountains. This should fall over
an 18 hour period though, with an emphasis on the afternoon hours
for the heaviest. The risk of flooding is low though. There have
been several days of dry weather. The main threat would be rain
falling on high elevation snowpack though. So, the threat is low but
not zero. Models have trended drier East of the Divide though, We
kept some POPs in but again, the chance is limited, generally less
than 1 out of 3. The main concern will be gusty wind. The 700
millibar wind does not look sufficient for high wind, but gusty to
strong wind is a possibility. This will be in the usual favored
areas, like Casper ahead of the trough, and places like Buffalo
post frontal.

A few showers will linger into Tuesday morning before ending.
Ridging will then begin building in Tuesday and begin to bring an
increase in temperatures. Now, we have to start looking at possible
fire weather concerns. Fuels are still in green up, so warnings are
not expected. Nevertheless, elevated fire weather will be possible
Tuesday and Wednesday as ridging will remain flat and gusty
wind will continue across the area with relative humidity
falling in the teens. The ridge should then become more
amplified on Thursday over the area, decreasing the wind.
Temperatures will rise through the week, with the warmest
weather of the year expected Friday and Saturday. Some of our
warmer spots, like Worland Greybull, could see the first 90
degree highs of the year. Things should remain dry through at
least Thursday. The chance of convection may return Friday or
Saturday as some moisture moves in from the southwest but
coverage of storms looks sparse right now. And finally, we have
rising rivers to worry about. A good rule of thumb for higher
elevation snowpack to melt is three consecutive days in the 80s,
and we should have that by Friday. So, we will have to keep a
close eye for rising rivers and possible flooding.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 543 AM MDT Sun Jun 2 2024

VFR conditions will prevail through the period. Winds will begin to
increase across the area from 16Z to 20Z, with gusts of 20 to 25 kt
occurring through the afternoon for most terminals.
Showers and thunderstorms will once again be possible across the
forecast area, becoming more widespread around 20Z. However, chances
remain too low to mention at any site. If a shower or thunderstorm
does move over a terminal, it will be fast moving and not last
more than 20 min or so. This convection will end or exit the
area by 02Z.

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...Hattings
AVIATION...LaVoie/Myers