309
FXUS65 KRIW 151058
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
458 AM MDT Thu Aug 15 2024

.KEY MESSAGES...

- Warmer today with less coverage of showers and thunderstorms
  this afternoon.

- Very warm and mainly dry Friday with elevated to possibly
  critical fire weather Friday afternoon.

- Above normal temperatures expected from this weekend into next
  week with daily chances of afternoon and evening
  thunderstorms.

&&

.DISCUSSION...
Issued at 239 AM MDT Thu Aug 15 2024

All in all, it has been a fairly quiet night here at the humble
Riverton weather abode. The main feature on the map tonight is a but
if a mesolow that has rotated from eastern Wyoming into southwestern
South Dakota. Just enough moisture wrapped around it to bring some
showers and a occasional rumble of thunder to eastern Johnson County
but this is moving away. Now will transition into a period of warmer
and drier weather, But notice the modifier in the word, thank you
all of my English teachers from many eons ago. Especially in the
word drier. That will be the rule of thumb through the next few days.

Ridging will build northward over the area today and bring warmer
temperatures. There will still be above normal precipitable waters
across the area though, especially East of the Divide and the north.
The ridging should help keep the morning dry, leading to a mainly
late show in the later afternoon and evening. Coverage will be less
than previous days as well, maxing out at around 2 out of 5 in
northwestern Wyoming. A few showers will linger into the overnight
hours as well.

Friday looks like the driest day of the period as the ridge bulges
north and pushes the deepest moisture out of the area. The only
chance for a shower or storm would be across the northern border but
even here the chance is only 1 out of 5. Temperatures will continue
as warm with highs in the 90s returning the warmer spots. The main
concern here shifts to fire weather. We considered some watches for
our southern and eastern counties with humidity falling to under 15
percent. We held off for now though. In Natrona County, wind is
borderline. In Sweetwater County, there has been a fair amount of
moisture the past several days. We will let the day shift take one
more look at it for potential watches. We can upgrade them tomorrow
night if needed. Elsewhere, wind will not reach criteria or humidity
will be too high.

Saturday looks like the warmest day with highs in the mid 90s for
many of the lower elevations East of the Divide. The chance of
thunderstorms will return to western Wyoming though as the ridge
axis shifts eastward and allows so moisture to ride up the back side
of it. Most of this should be restricted to west of the Divide, as
southwest, downsloping flow should keep areas to east largely dry
and hot. The increased humidity should also ease fire weather
concerns across southern Wyoming as well.

From Sunday into the middle of next week ridging will dominate the
weather across the area and bring above normal temperatures. A few
shortwaves will rotate through the flow and bring daily chances of
afternoon and evening showers and thunderstorms. Sunday looks fairly
active, especially across western Wyoming. For next week, there is
more divergence in the models so timing the shortwaves and picking a
more active day remains uncertain.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 458 AM MDT Thu Aug 15 2024

Mainly VFR conditions expected to prevail across central and western
Wyoming through the 12Z TAF period. Current guidance shows
thunderstorms developing between 20Z and 22Z before moving eastward
and potentially impacting terminals until 02Z to 08Z, tapering off
from west to east. Gusty and erratic winds are possible, as well as
frequent lightning, in thunderstorms.

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

&&

.FIRE WEATHER...
Issued at 239 AM MDT Thu Aug 15 2024

Fire weather concerns will below critical today with light to
moderate wind and humidity remaining above critical levels.
Increasing southwest wind and lower humidity will bring at least
elevated fire weather to southern Wyoming and portions of
central Wyoming with around a 25 percent chance of critical fire
weather on Friday afternoon.

&&

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

&&

$$

DISCUSSION...Hattings
AVIATION...Gross/Hattings
FIRE WEATHER...Hattings