702
FXUS65 KRIW 170649
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1249 AM MDT Mon Aug 17 2026

.KEY MESSAGES...

- Chances for showers and storms increase today, and peak on
  Tuesday. The best chance for showers and storms will be across
  northern Wyoming.

- Drier air returns starting Wednesday and lasts through Friday,
  with only isolated convection, mainly in and near the
  mountains.

- Above normal temperatures return by Wednesday and last through
  at least Saturday, with widespread highs in the 90s East of
  the Divide Thursday, Friday and possibly through the weekend.

&&

.DISCUSSION...
Issued at 1246 AM MDT Mon Aug 17 2026

The monsoon continues today and, like last night, the models did
another bad job with the night time convection. There is less than
last night though with the air mass being drier than last night.
But, what I wouldn`t give for a nice, strong cold front to push
through and vanquish the monsoon until next summer. But, we have to
play the hand we are dealt so here we go.

Moisture will increase across the area today, although not be a lot.
Precipitable water values today look to generally run anywhere from
100 to 140 percent of normal, not excessively high. The result will
be a somewhat greater coverage of showers and storms that yesterday.
Most guidance is also fairly consistent in keeping the most numerous
storms across the northern half of the area, with mainly dry
conditions persisting in southern Wyoming. Not saying there won`t be
any there, but the chance is only around 1 out of 10. The best
chance looks to be across the northern border where the chance is
around 1 out of 3. As for hazards, dew point depressions are over 40
degrees so there could be some strong wind gusts. There could also
be some locally heavy rain but there is steering flow today and that
should help mitigate the flooding threat; it is not zero but it is
low. With somewhat higher thicknesses, temperatures should be a
couple of degrees warmer than yesterday, fairly close to what is
normal for mid August. Some convection lingers into as well, but
placement is uncertain given the poor model performance with the
monsoon.

Tuesday looks like the most active day for this round of the
monsoon. The highest precipitable water values are not the highest,
again topping out around 140 percent of normal. However, it is the
most widespread. As a result, just about all locations will have at
least a 1 in 5 chance of a shower or thunderstorm. Just about
everything else looks similar to today, the main threat would be
strong wind gusts, with a lesser chance of minor flooding with
decent steering flow mitigating that threat somewhat. A few showers
may linger into Tuesday night as well, but probably fewer than on
Monday night. Temperatures should also run fairly similar to Tuesday.


Drier air will then overspread most of the area for Wednesday and
Thursday. Precipitable water values fall back to below normal levels
for most of the area on Wednesday and even into Thursday as the
moisture gets suppressed to the south. The chance of convection on
these days is very small, less than 1 out 10 for all locations.
There is a slightly better chance of a shower or storm on Thursday,
but it would likely be restricted to the mountains. With the
associated ridge building northward, temperatures will be on the
rise as well. The forecasted temperatures may be a few degrees too
cool as well. Most of the lower elevations East of the Divide will
probably see high temperatures into the 90s possibly as early as
Wednesday and almost definitely from Thursday through at least
Saturday. Some of the warmer spots could be in the upper 90s Friday
or Saturday.

The chance of showers and storms also begins to rise on Friday as
monsoonal moisture moves back into the area. Most activity would be
confined to in and near the mountains on Friday though. Saturday may
be a day that needs to be watched. Some guidance shows precipitable
water values climbing to over 150 percent of normal, possibly
approaching 200 percent of normal. There is steering flow, so this
should mitigate the flooding threat somewhat. I would not be
surprised to some sort of Excessive Rainfall Outlook for this day
though. Above normal moisture also looks to persist into Sunday and
early next week, keeping the chance of showers and thunderstorms in
the forecast.
&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 958 PM MDT Sun Aug 16 2026

VFR conditions are generally expected through the period. Late
evening showers and thunderstorms are currently on the decrease,
with most of this activity coming to and end by 06Z. Lighter winds
and decreasing clouds are expected overnight with VFR conditions
then prevailing through Monday morning. Recent model trends have
increased convection coverage for Monday afternoon, and accordingly
have introduced PROB30 groups for several terminals. Brief heavy
rain could lead to occasional MVFR conditions, but the more likely
impact will be outflow wind gusts of 30 to 40 knots.

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...Hattings
AVIATION...Myers