Damaging Winds in Wyoming, August 25, 2024

Area Forecast Discussion
National Weather Service Riverton WY
1132 AM MDT Sun Aug 25 2024

.KEY MESSAGES...

- Increased moisture today will increase chances of showers and
  thunderstorms through Monday.

- The coolest temperatures in a while move in for Monday, with
  frost possible in the western valleys Monday night.

- Other than fire weather concerns on Wednesday, much of next
  week looks tranquil with dry weather and above normal
  temperatures.

&&

.DISCUSSION...
Issued at 244 AM MDT Sun Aug 25 2024

We will have a variety of weather across the area over the next few
days. Things are mainly quiet this morning, as we transition
into a wetter pattern for the next couple of days. A weak cold
front is now dropping southward toward our office, but has
little moisture with it. It will bring some gusty northwest
wind, which does not line up well with balloon launch time that
I am tasked to do this morning. A surge of moisture will move
northward this morning in conjunction with an approaching trough
and upper level low over northwestern Utah that will move
northeastward toward the area and bring an increase in coverage
of showers and thunderstorms through the day. A few could become
strong as well. The Storm Prediction Center has the area in a
Marginal risk. As is usually the case in this area, strong wind
gusts will be the main threat. Some storms will likely linger
into tonight as well, as the low lifts northeastward into
northwestern Wyoming and into Montana tomorrow. Wind will
continue to be gusty through the day as well, but not as strong
as yesterday. One good thing is that the moisture will raise
dewpoints today, which should make for less erratic fire
behavior as compared to yesterday.

In addition, we have to talk about the S word. 700 millibar
temperatures will fall to around 2 Celsius in some locations in
the northern mountains. And with some moisture around, some
snow is possible above 9500 to 10000 feet. Accumulations for
most locations would be small or none, but some of the highest
peaks, especially in the Wind Rivers and Absarokas, could see an
inch or two of snow through Monday. Elsewhere, Monday will be
the coolest day many areas have seen in a while. This will
especially be the case in northern Wyoming, where there will be
more cloud cover as the low moves through the area. Places like
Cody and Buffalo have a better than 1 in 2 chance of staying in
the 60s for high temperatures that day. As for the convection,
the best chance will be in northern Wyoming as well, with
tapering chances further south (ranging from 1 in 2 along the
northern border to less than 1 in 5 in southern Wyoming.) This
will be an earlier show, with most precipitation ending around
sunset Monday evening. There is still the potential for some
frost as well on Monday night over the western valleys if the
sky can clear fast enough. Places like Big Piney, Pinedale and
even Jackson have around a 1 out of 2 chance at this time.

Ridging on Tuesday will bring a drier and warmer day for
Tuesday, with a chance for critical fire weather conditions
returning to central portions of the CWA. Then on Wednesday, a
fast moving trough and cold front will move from Canada and
into the Northern Rockies. The best forcing and moisture will
remain well north of the area, with any chances of showers less
than 1 out of 4 and confined to far northern Wyoming. It will
raise the chance of elevated to critical fire weather though, as
gusty winds will be widespread across the forecast area once
again. Additionally, the lowest dewpoints will be across central
and southern Wyoming. Following that, we should enter into a
period of tranquil weather as ridging builds over the area,
bringing dry weather with near to above normal temperatures as
we head toward the first day of September.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1131 AM MDT Sun Aug 25 2024

Conditions for the TAF period will remain VFR, except for a slight
chance of MVFR with a convective storm. South-southwesterly winds
increase from the south. Gusts of 20 to 30 kt will be common across
the forecast area, as showers and thunderstorms begin to develop.
The primary convective hazard for today will be the chances for
gusty outflow winds of 30-40 kt. TAF sites now have TEMPO groups for
the afternoon and evening, stating around 20Z and going as late as
02Z. Winds and thunderstorms will gradually subside through the
evening, ending for much of the area by 06Z. Additional showers look
to impact KJAC and possibly KCOD and KWRL between 04Z and 07Z, as
the main storm system tracks over eastern ID into southwestern MT.
These showers will then track across northwestern portions through
the rest of the TAF period.

&&

.FIRE WEATHER...
Issued at 244 AM MDT Sun Aug 25 2024

Fire weather should improve somewhat today. Increasing moisture from
the south will increase the chance of showers and thunderstorms,
especially this afternoon and into the evening. The increasing
moisture will keep relative humidity above critical levels,
generally the low 20s and higher. A gusty breeze will develop again
in central and southern Wyoming, but it will not be as windy as
yesterday. Mixing and smoke dispersal will be generally good to very
good in the afternoon. The next day of concern for elevated to
possibly critical fire weather will be Wednesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert until 1 PM MDT Monday for WYZ002-012-013-016.

&&

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

Hazardous Weather Outlook
National Weather Service Riverton WY
251 AM MDT Sun Aug 25 2024

WYZ001>020-022>030-261300-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn Basin-
Owl Creek and Bridger Mountains-Bighorn Mountains West-
Bighorn Mountains Southeast-Northeast Johnson County-
Southeast Johnson County-Teton and Gros Ventre Mountains-
Jackson Hole-Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
251 AM MDT Sun Aug 25 2024

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight.

Scattered afternoon and evening thunderstorms.

.DAYS TWO THROUGH SEVEN...Monday through Saturday...

Monday...Scattered thunderstorms across the north. Frost possible
in the western valleys Monday night.

Wednesday...Elevated to critical fire weather possible across
central and southern Wyoming.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.