National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KRIW 182340
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
540 PM MDT Thu Apr 18 2024

.KEY MESSAGES...

- A few snow showers will continue in the mountains tonight.

- Temperatures will be below normal through Saturday, followed
  by near to above normal temperatures starting Sunday.

- Although there will be a few chances for showers, no major
  weather systems are expected for the next 7 days.

&&

.DISCUSSION...
Issued at 206 PM MDT Thu Apr 18 2024

The weather at the office today was a flashback for me, when,
many moons ago, I worked in the private sector at a company in
central Pennsylvania. Today, we had a combination of weak
upslope flow and unstable northwest flow in the Wind River
Basin. This leads to some morning sunshine followed by an
increase in stratocumulus clouds as the air heats up. We called
this phenomena "Self Destructive Sunshine" and it tends to
wreak havoc on temperatures forecasts. This is not as defined as
Pennsylvania, however, where the Great Lakes add moisture, but
it brought back memories. Drier air is moving in through, and
clouds are breaking up. We did lower temperatures this afternoon
though to account for this. If it gets warmer, no one will
complain.

We will be entering a period of quieter weather for the next several
days. Some snow showers will continue mainly in and near the
mountains, but impacts would be small. A weak shortwave will
bring a somewhat better chance of showers Friday. However, the
wave is week and moisture starved. The chance of any
accumulation is limited and mainly in the mountains. There is a
best a 1 in 6 chance of 2 inches or more and that would only be
the southern Absarokas and since there are basically no people
here, impacts would be slim to none.

Northwest flow will continue through Saturday, keeping temperatures
below normal. However, temperatures will gradually warm as the fair
mass modifies. Flow then turns southwest on Sunday as transitory
ridging passes across the area, and boosts temperatures back to
above normal levels. A weak cold front will then swing across the
area Sunday evening and bring another chance of showers, but again
the system is moisture starved. Gusty winds will occur ahead and
behind the frontal passage in the normal spots, but high wind is not
expected. The main effect would be to knock temperatures back down
to normal levels.

Early next week looks to be dominated by flat ridging to zonal flow.
A couple of shortwaves will move through with a small chance of
showers, but again these waves have little moisture to work with so
the chance is only about 1 out of 4. Temperatures should average
near to slightly above normal with a warmer day possible on
Wednesday as flow turns southwesterly again. A more substantial
system may approach for the end of next week, but details are
impossible to predict this far out.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 539 PM MDT Thu Apr 18 2024

Cool moist northwest flow continues this evening and overnight after
yesterday`s storm system moved off to the southeast.  Conditions are
generally VFR with localized MVFR due to lower ceilings.  Some light
showers continue also over the mountains and foothills, but have
very little impact or accumulation.  Winds are fairly light for the
rest of the day with some gusts 10-15 kts.  There is a small chance
of showers again at KCPR overnight due to the moist NNE flow, so
have added VCSH to that TAF.  Conditions Friday will be similar to
Thursday, with NE winds east of the divide, and NE winds pushing
into SW WY.  Cool northwest flow will aide boundary layer CU
development for localized MVFR conditions again at times.  Light
showers should remain confined to the higher terrain of the
Absarokas, Wind Rivers, and Bighorns Friday afternoon.

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...McDonald