283
FXUS65 KRIW 120356
AFDRIW

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

.KEY MESSAGES...

- Scattered rain showers and an isolated thunderstorm continue
  this evening across northern WY, including portions of YNP,
  the northern Absarokas, and the northern Bighorn Basin. Gusty
  downdrafts and strong outflow wind are the main threats.

- Abnormally warm temperatures are forecast for Wednesday with
  highs 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 as well
  as dry lightning.

- Remaining warm and mostly dry Thursday through Saturday, with
  a cooldown back to about normal by Sunday.

&&

.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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 956 PM MDT Mon May 11 2026

Prevailing VFR conditions continue through the TAF period, with
mostly clear skies by Tuesday morning. A few rain showers over
northern portions of the area linger for an hour or two to begin the
period. Gusty downdrafts remain a threat with these showers. A cold
front will continue passing through central portions of the area
early in the period, but should stall along the Continental Divide
early Tuesday morning.

Wind is northwest to northeast behind the front and will remain a
bit breezy for most of tonight. Wind will increase again Tuesday
afternoon, but will be much lighter than this past afternoon. The
front will finally reach KRKS by 05Z Wednesday with wind shifting
from the west to the east. Shortly thereafter this front will
dissipate heading into Tuesday night.

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...Rowe
FIRE WEATHER...Rowe