Rock Springs, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

863
FXUS65 KRIW 130140
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
740 PM MDT Tue Aug 12 2025

.KEY MESSAGES...

- Isolated thunderstorms will traverse far northcentral Wyoming,
  mainly northern portions of Big Horn and Johnson Counties,
  through 11 PM Tuesday. Wind gusts 35 to 45 mph will be the
  primary hazard.

- Elevated to critical fire weather conditions occur Wednesday
  afternoon across much of west, southwest, and portions of
  central Wyoming. Critical fire weather conditions are expected
  to persist Thursday across portions of southwest and central
  Wyoming.

- An increasing chance of thunderstorms through the week, with
  greatest coverage likely on Friday as moisture arrives from
  the southwest.

&&

.UPDATE...
Issued at 120 PM MDT Tue Aug 12 2025

It remains quiet this afternoon with relatively light winds and
mostly clear skies with scattered fair weather CU across
northern WY mountains. Overall, there has not been much change
to the forecast since the overnight discussion below. RHs did
trend lower a bit, and given other conditions in place, have
upgraded all of the Fire Weather Watches to Red Flag Warnings,
as well as have added several zones to Red Flag Warnings for
Wednesday, to include additional zones in western WY and central
WY. Though RHs look to be more marginal across those areas (15
to 20%), winds gusting 30 to 35+ mph across higher elevations
including the Absarokas and Wind River Mountains, and
thunderstorm chances, have leaned on issuing to cover the threat
of new fire starts and erratic fire behavior. RHs have also
trended lower for Thursday, and with gusty winds still in place
across portions of southwest and central WY, Red Flag Warnings
have been extended through Thursday for those areas.

PoPs have also generally increased for the next few days as
well, with isolated to scattered chances across much of the
northern half of the region for Wednesday. For Thursday, PoP
focus shifts towards more monsoonal flow and thus 20 to 35%
coverage exists across much of southwestern WY stretching as
far east as the Wind River Mountains and southern Absarokas.
Friday continues to look like the peak of this monsoonal
activity with widespread 30 to 40% PoPs across most areas west
of the Divide.

&&

.DISCUSSION...
Issued at 201 AM MDT Tue Aug 12 2025

Once again, things are quiet at this time across the area. And most
of the area should see this continue today. The only factor today is
a weak shortwave that will be brushing by to the north of the area.
CAMs do not show a lot of convection but there could be some,
especially in the favored areas in and near the Absarokas and in the
Bighorn range. Continuity had this covered pretty well and we didn`t
make many changes. Another area is the Upper Wind River Basin
where some weak southeast surface flow may bring enough upslope
for a stray shower or thunderstorm. Chances are small in all
areas through (generally less than 1 out of 5). Temperatures
will be warmer as well as flow turns to the southwest, with most
areas having high temperatures around 5 degrees higher than
yesterday.

We do have more concerns on Wednesday. Ridging will get flattened
and a trough and cold front approaching from the west will tighten
the pressure gradient across the area. This will bring downsloping
flow and also the hottest temperatures of the week, with many
locations seeing highs in the 90s, well into the 90s in the favored
areas East of the Divide. With dew points remaining about the same,
critical fire weather begins to become a possibility. In the area
from southern Lincoln county through Sweetwater, Natrona and eastern
Fremont Counties, models ensembles are showing a greater than 3 out
of 5 chance of wind gusts past 25 mph for 3 hours Wednesday
afternoon. This, combined with humidity falling under 15 percent, we
have hoisted a Fire Weather Watch for these zones. We also thought
about the western mountains, mainly the Salt and Wyoming Range as
well as the Tetons. However, most guidance has humidity remaining
above critical levels and even if it did, it would likely be for
less than 3 hours. So, we have held off on any highlights in this
area for now. There will be time for the day shift and tomorrows
night shift to issue if things trend drier. Mid and high level
moisture will increase on this day, as well as the chance of
convection, especially across the west. Surface moisture is
not there though, so any storms would likely be high based and
produce more wind than rain.

For Thursday, the monsoonal plume may deeper a bit across
southwestern Wyoming, with precipitable water values possibly
rising to 125 to 150 percent above normal. This would increase
the chance of thunderstorms here, and some could produce some
badly needed rain if this works out. Deepening moisture will
also allow for a few more clouds, knocking temperatures down a
few degrees. As for fire weather concerns, things are looking a
bit better. Humidity will be a bit higher and wind does not look
as strong as previously. The main area of concern looks to be
from eastern Fremont through Natrona County, but not enough
confidence to extend the watch into Thursday.

As for the rest of the week, Friday still looks like the most active
day for convection as the trough moves through the area, with an
emphasis on southern Wyoming as a push of drier air moving in
from the northwest may limit activity somewhat. This also looks
like the least warm day of the period, although temperatures
will still average near to somewhat above normal. The rest of
the forecast reasoning looks the same with gradually decreasing
coverage of convection as drier air builds across the state.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 529 PM MDT Tue Aug 12 2025

VFR flight conditions are anticipated this TAF period. There remains
confidence in isolated showers along the northwest Wyoming
border through 04Z/Wednesday as shortwave energy treks eastward
across this region. However, there is low confidence (15-20%)
in direct impacts at KCOD, so have continued with VCSH for
showers in the area. Cloud cover decreases around sunset before
mid-level cloud cover makes a return after sunrise Wednesday morning.

Winds increase at all terminals after 18Z/19Z/Wednesday with
gusts between 20-25kts at KJAC, KCOD, KCPR, KRKS, KPNA, and
KBPI. Isolated showers and thunderstorms develop across the
higher terrain of western Wyoming between 18Z-20Z/Wednesday.
KRIW, KLND, and KWRL have the highest chance (30%) at direct
impacts and this is communicated with the inclusion of a PROB30
group at each. Other terminals have a 10-20% chance, so there
is no mention of shower or thunderstorms in the TAF.

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 120 PM MDT Tue Aug 12 2025

Continued light winds, despite critical or near critical RHs,
will keep fire concerns to a minimum across the region through
the rest of Tuesday. However, winds will begin to increase
Wednesday late morning, with critical RHs. Thus, Fire Weather
Watches have been upgraded to Red Flag Warnings across
southwest and portions of central WY for Wednesday. Across Fire
Zones 277, 278, 279, 280, 283, 289, and 300, RHs as low as 10
to 12 percent coupled with west winds 10 to 15 mph gusting 25 to
30 mph Wednesday afternoon will result in critical fire weather
conditions. Red Flag Warnings have been issued for these areas.
Notably for zones 279, 280, 289, and 300, similar conditions
will return Thursday afternoon, so Red Flag Warnings for those
zones are in effect through 8 PM Thursday. Conditions are
expected to improve Wednesday night with winds decreasing to
mostly light and variable, however, overnight recoveries will be
fairly poor, with RHs only recovering to around 30 to 45
percent.

Across mountain zones in western and northern WY, including
zones 414, 415, and 416 along with 286 and 288, RHs will be much
more marginal for Wednesday, generally 14 to 16 percent in the
valleys and around 20 percent across higher elevations. Despite
this, winds gusting 30 to 40 mph across higher terrain and the
thunderstorm threat (20 to 30% chances) across those regions
Wednesday afternoon necessitated the issuance of Red Flag
Warnings for those zones. In particular, there is increased
concern for new fire starts and erratic fire behavior with any
new starts, given the thunderstorm chances. Though there should
be some rain with any thunderstorms, precipitation will not be
enough to extinguish any lightning starts that may occur, as
wetting rain chances remain near zero. Thursday, the
thunderstorm threat shifts to southwest WY, but storms should
have more notable moisture with them on Thursday as monsoonal
flow begins to become more dominant.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 8 PM MDT Wednesday for WYZ277-
278-283-286-288-414>416.

Red Flag Warning from noon Wednesday to 8 PM MDT Thursday for
WYZ279-280-289-300.

&&

$$

UPDATE...Hensley
DISCUSSION...Hattings
AVIATION...CNJ/Gerhardt
FIRE WEATHER...Hensley