668
FXUS65 KRIW 231841
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1241 PM MDT Sun Jun 23 2024

.KEY MESSAGES...

- Hot and dry will be the main story through mid-week.

- Slight chances (30%) of mostly virga showers across southern
  portions today and tomorrow. Gusty outflow winds would be the
  main concern.

- Better chances for showers and thunderstorms looks to come
  Wednesday and especially Thursday thanks to a shortwave
  drawing up Gulf moisture into the region. This should also
  provide a brief reprieve from the heat.

&&

.DISCUSSION...
Issued at 1236 PM MDT Sun Jun 23 2024

Today will be one of those days when you step outside into the dry,
hot, wind and feel like you stepped into a blast furnace. Get used
to that feeling because you`ll be feeling it through much of
the week. Today will be the warmest day of the week, but don`t
take that to mean that the rest of the week will be cooler,
because it certainly won`t feel that way. Temperatures today
will be in the upper 90s to near 100 across east of the Divide
basins. Best chances to reach 100 will be across the upper
Bighorn Basin near Greybull and Powell (60% chance) and across
the central Wind River Basin between Riverton and Shoshoni (20
to 30% chance). Chances of reaching tomorrow for those same
locations are 25% and 10% respectively. High temps will remain
in the upper 90s across basins east of the Divide and lows only
dropping to near 60 overnight through Wednesday. We should
finally get some short- lived relief late in the week, but more
on that later.

Similarly to yesterday, convection has begun to fire off of the
Uintas and across southern Sweetwater County as of 1230. Not
expecting much, if any, precipitation out of these popcorn
showers as dewpoint depressions are around 50 degrees. Given the
aforementioned large dewpoint depressions, gusty winds will be
a concern, even from seemingly weak virga showers. Convection
should spread a bit farther north than it did yesterday. Hi-res
models continue to prog weak convective activity across much of
eastern Sweetwater County, into eastern Fremont and Natrona
counties this afternoon. Again, not many of these showers to
even reach the ground. Tomorrow will see much of the same,
spreading across the same areas by mid-afternoon. There is a
better chance of showers reaching the ground from stronger cells
tomorrow, but precip continues to be limited and wetting rain
(>0.1") chances will remain nil.

By Wednesday and especially by Thursday, those wetting rain chances
will increase though, and we should start to see some relief from
the heat by Thursday. A low begins to slide into the PACNW Wednesday
afternoon and will help to draw some Gulf moisture into the
ridge. This will increase PoPs across the south and higher
terrain on Wednesday. As the shortwave moves east into northern
WA/ID Thursday, PoPs will become more widespread and wetting
rain chances significantly increase. This will be a similar set-
up to what we saw last Friday, so certainly monitoring the
potential for strong storms as well as the heavy rain threat.
WPC is already pushing a D5 Marginal ERO for Thursday across
southern WY, with forecast PWATs above normal across much of
the area and close to 1" across southern WY. For comparison,
"normal" PWATs are around 0.4". This trough not only has a
chance to bring some much needed moisture, but also some cooler
air. Not cold air, but GFS and ECMWF both indicate 700mb temps
in the +2 to +5 range, which certainly would provide some
relief. Unfortunately, this looks to be short-lived, with the
ridge rebuilding quickly behind it for next weekend, but we will
enjoy any relief we can get!

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1032 AM MDT Sun Jun 23 2024

VFR conditions are expected through the period as high pressure
persists across the area. Wind will become breezy this afternoon
with gusts of 20 to 25 knots at most terminals. While a few isolated
showers are possible during this time, mainly east of KRKS, little
to no precipitation is expected. The main concern with this activity
will be gusty outflow winds gusting over 40 mph. Wind and any
showers will subside after sunset, leaving clear skies through
Monday morning.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Hensley
AVIATION...Myers/Hensley