326
FXUS65 KRIW 112231
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
431 PM MDT Mon May 11 2026

.KEY MESSAGES...

- Well above normal warm temperatures prevail across the Cowboy
  State today with numerous high temperature records in
  jeopardy.

- A chance (10-30%) for a few showers and an isolated
  thunderstorm will be possible later this evening across
  northern WY, including portions of YNP, the northern
  Absarokas, and the northern Bighorn Basin. A brief light rain
  shower, a few rumbles of thunder and some gusty outflow winds
  will be possible with any of these showers or storms.

- Abnormally warm temperatures are forecast for Wednesday with
  highs likely to near monthly record high temperatures.
  Temperatures look to get into the 90s east of the Divide and
  upper 80s west of the Divide.

- Afternoon showers and thunderstorms will be possible Wednesday
  with the main concern being strong gusty outflow winds.

&&

.UPDATE...
Issued at 118 PM MDT Mon May 11 2026

Record high temperatures are expected across the Cowboy State
today. Highs look to get into the mid to upper 80s east of the
Divide and upper 70s west of the Divide. Most locations stay dry
today with the only exception being far northern WY, where a
few showers and possibly an isolated thunderstorm cannot be
ruled out. The best chances (10-30%) will be across portions of
YNP, the northern Absarokas, and the northern Bighorn Basin.
Models have indicated a push of moisture later this evening,
which may allow for precipitation to reach the surface in some
locations. Overall, the atmosphere is likely too dry to see much
moisture reach the surface. Strong gusty winds may be possible
with these showers but at this time concerns remain minimal. The
main focus shifts to Wednesday, where the heat really arrives
with the potential for monthly May high temperature records to
be met or even broken. Currently, models are showing 700 mb
temperatures getting around 13- 16C which would translate to
temperatures nearing 90 degrees at the surface. The locations
most likely to see these temperatures would be central WY such
as Fremont/Natrona Counties and portions of northern WY such as
the Bighorn Basin and Johnson County. Other locations, likely
see temperatures get into the mid to upper 80s. The concern
remains for showers and thunderstorms during the afternoon
Wednesday with the main hazard being strong gusty outflow winds.
Otherwise, the forecast remains on track with little change for
the end of the week into the weekend.

&&

.DISCUSSION...
Issued at 1252 AM MDT Mon May 11 2026

The strong ridge that will control our weather for the next several
days is noted on water vapor imagery across the southwestern US.
This will lead to very hot, dry, and breezy to windy conditions
through at least Wednesday. The ridge is being flattened slightly by
a shortwave currently sliding east from southwestern Canada into the
northwestern US. This shortwave will deal a glancing blow to Wyoming
as it slides east through Montana and into the northern Plains
Monday into Monday night. This shortwave will bring a weak cold
front with it Monday night leading to a slight cooldown Tuesday. The
ridge should amplify with a vengeance by Wednesday, with the
hottest temperatures of the year, by far. Wednesday`s high
temperatures will reach the low to middle 80s F west of the
Continental Divide and upper 80s to low 90s east of the
Continental Divide.

Concerns for Wednesday include, the potential for dry thunderstorms
and very strong downdrafts/outflows from convection. Mid-level
moisture will be funneled in from the southwest as the ridge shifts
east putting the area on the western side of the ridge. This mid-
level moisture should be enough for isolated rain showers and
thunderstorms Wednesday afternoon into Wednesday evening. A lack of
low-level moisture due to very dry air remaining in place from
earlier in the week will prevent much, if any, rain from reaching
the ground. Model forecast soundings depict impressive inverted-v
soundings across the area, with dew point depressions of 50-60
degrees. If this comes to fruition wind gusts from even little green
blobs (very light rain showers) will have the potential to produce
wind gusts of 50-60 mph at the minimum. The lack of precipitation
reaching the ground will also lead to the threat of dry lightning.
This will be discussed in more detail in the fire discussion below.

For Thursday and beyond the weather pattern becomes much less
certain. There is good consensus on a fairly compact upper-low
moving into the region, but the timing and exact location will be
the difference between another hot and dry day on Thursday vs a
cooler day with modest chances for precipitation. This probably
won`t be resolved until about Wednesday morning when this low
finally comes onshore somewhere from Northern California to Oregon.
Overall, expect it to remain warm, but be cooler from Thursday
through Saturday. High temperatures these days will range from upper
60s to mid 70s west of the Continental Divide to mid 70s to low 80s
east of the Continental Divide.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 431 PM MDT Mon May 11 2026

VFR conditions prevail through the period. Gusty winds Monday
afternoon decrease through 03z this evening. A cold front moves
through from the north to start the period, bringing a gusty
northerly wind shift to KCOD, KCPR, KRIW, and KWRL. Winds should
then decrease within a few hours of frontal passage. There remains
around a 30 percent chance for a shower around KCOD through about
04z, with lesser chances at KCPR. Gusty outflow winds would be the
main concern should a shower occur. Tuesday is less windy than
Monday, with the strongest gusts occurring around KBPI, KPNA, and
KRKS.

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

&&

.FIRE WEATHER...
Issued at 1252 AM MDT Mon May 11 2026

A strong ridge will keep skies mostly clear, with hot, dry, and
breezy to windy conditions Monday through Wednesday. Monday and
Wednesday are the days of greatest concern. Monday will feature high
temperatures about 15 degrees above normal, wind gusts of 30 to 40
mph on average through the afternoon hours, and RH of 8 to 15%
across all lower elevation zones. Tuesday will be a bit better east
of the Continental Divide thanks to cooler air behind a weak cold
front, but similar conditions to Monday will occur west of the
Continental Divide other than wind being much weaker. Wednesday
poses the widest range of threats as the ridge slides east
positioning the area on the west side of the ridge. This will lead
to mid-level moisture advecting in from the southwest. This coupled
with very dry conditions persisting in the low-levels of the
atmosphere will lead to possible (30%) dry lightning and very strong
downdrafts from any convection that develops Wednesday afternoon.
This convection could last well into Wednesday evening as well. This
is in addition to the already expected breezy, dry, and very hot
conditions on Wednesday. Beyond Wednesday the forecast becomes less
clear, so keeping the focus on the next three days for fire weather
concerns.

&&

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

&&

$$

UPDATE...Dziewaltowski
DISCUSSION...Rowe
AVIATION...Wittmann
FIRE WEATHER...Rowe