Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

622
FXUS65 KRIW 271003
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
403 AM MDT Fri Jun 27 2025

.KEY MESSAGES...

- Elevated to critical fire weather is likely across much of the
  area this afternoon and evening.

- Elevated fire weather remains likely on Saturday.

- Showers and thunderstorms are possible each afternoon across
  northern Wyoming, but the chance is generally less than 1 out
  of 5 at any particular location.

&&

.DISCUSSION...
Issued at 250 AM MDT Fri Jun 27 2025

All in all, there is little change in the reasoning of the
forecast this morning when compared to yesterday.

The main concern of the day is fire weather, both of the elevated
and critical variety. The set up looks the same, with a weak
shortwave moving across the area and a jet streak across Montana,
putting the area in the right front quadrant, enhancing downward
forcing. This will mix some mid level wind to the surface, bring
breezy conditions to much of the area. If this was August, we would
likely have fairly widespread Red Flag Warnings. However, most
locations don`t have critical fuels yet. Regardless, fire
weather conditions will be elevated to critical across the CWA.
Natrona County still looks good for the Red Flag Warning, so we
continued it pretty much as is. We did given some thought to the
other critical zone, 282, aka Washakie and Hot Springs County.
However, humidity will be a bit higher here and wind will not be
as gusty. A spot or two may get Red Flag conditions, but most
shouldn`t so we won`t issue. Critical conditions are likely in
southern Wyoming and portions of central Wyoming where humidity
will fall toward 10 percent as well. As for convection, a few
thunderstorms are possible along the northern border but the
chance is less than 1 out of 5. Any shower or thunderstorm would
be high based though, and with very high dewpoint depressions,
any shower or thunderstorm could have a wind gust of 50 mph.

The next question was if we should extend the Red Flag Warnings to
Saturday. For now, we held off. Most guidance is showing
dewpoints running 5 to 10 degrees above those on Friday. In
addition, the jet will shift a bit further north and wind should
be a bit lighter, making conditions more borderline. If trends
favor warnings, we can issue this afternoon or tomorrow morning.
Another shortwave moving through will bring a somewhat higher
chance of showers and storms across the north. However, the
chance will again be less than 1 out of 4.

A weak cold front then moves across the area Sunday. Moisture is
limited, but it could again bring isolated storms, with the best
chance in eastern portions of the area. It will knock temperatures
down a few degrees east of the Divide and raise dewpoints a bit
more, so the chance of Fire Weather headlines looks unlikely at
this point (less than a 1 out of 3 chance).

Ridging then builds back northward over the area for early next
week. Monday at this point looks like a nice day with near normal
temperatures and little chance of storms. Chances may increase
Tuesday and especially Wednesday as deeper moisture may try to
return to the area. Exact details are difficult to hash out
this far out, but PoPs have increased on these days.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 400 AM MDT Fri Jun 27 2025

VFR conditions throughout the period for all TAF sites remaining dry
throughout. Light winds and scattered mid to upper level clouds
over northwestern portions. Lee-enhanced clouds, BKN-OVC
FL150-250, have quickly developed over the east slopes of the
Absaroka Mountains. These clouds are expected to decouple by
15Z/16Z, with FEW-SCT over the northern half of the forecast
area. Winds will start to increase around this time as well,
then pick up with gusts around 25-30 kt at all locations after
18Z-19Z due to the stronger mixing with peak heating of the
afternoon. Winds will diminish after 01Z-02Z towards sunset
becoming around 8-12 kt through the end of the period and
overnight into Saturday morning. Any convection is expected to
stay over northern portions of Yellowstone NP this afternoon,
ending by 06Z. No other weather elements are expected at this
time.

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 250 AM MDT Fri Jun 27 2025

A weak weather system moving to the north will bring humidity
under 15 percent across much of the area. With a gusty wind
developing this afternoon, elevated to critical fire weather is
likely across much of the area this afternoon and evening, with
the worst conditions across central and southern Wyoming.
Elevated fire weather remains likely on Saturday afternoon,
although somewhat less wind and somewhat higher humidity may
improve conditions somewhat.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 9 PM MDT this evening for
WYZ280.

&&

$$

DISCUSSION...Hattings
AVIATION...LaVoie/Lowe
FIRE WEATHER...Hattings