Green River, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

504
FXUS65 KRIW 191801
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1201 PM MDT Thu Mar 19 2026

.KEY MESSAGES...

- Many locations are expected to break daily high temperature
  records and potentially all time March high temperatures with
  the ongoing record warmth. This record breaking warmth
  persists until Saturday.

- There is high confidence in critical fire weather conditions
  across low elevations of central and southern Wyoming through
  Saturday due to low humidity, gusty winds, and abnormal
  warmth. The most widespread fire weather conditions are
  expected to occur Saturday.

- A cold front brings a 30% chance for light snow showers across
  the northern mountains late Saturday/early Sunday. A brief
  cool down to closer to normal temperatures expected Sunday for
  the entire area.

&&

.UPDATE...
Issued at 1200 PM MDT Thu Mar 19 2026

18Z water vapor imagery shows the strong upper level high centered
over the southwestern CONUS that is responsible for the ongoing
widespread record heat and fire weather conditions. Abundant
sunshine today will allow for deep mixing to occur, and with 700mb
temperatures ranging from 5 C to 9 C, surface temperatures will have
no trouble reaching the upper 70s F and low 80s F today. Deep mixing
will also allow for winds to mix down to the surface and keep
humidity very low. As mentioned in the morning discussion, winds are
not expected to be as strong as they were the past two days due to
the strongest winds aloft being located over Montana. Regardless,
frequent wind gusts of 20 to 35 mph can be expected this afternoon.
Friday expect much of the same with slightly warmer temperatures
with 20 to 30 mph gusts as the upper high slowly begins to shift
east. More daily temperature records, and potentially all time March
records, are expected to be broken through Saturday.

The combination of much above normal temperatures, gusty winds, low
relative humidity, and dry fuels provides high confidence in
critical fire weather conditions through Saturday. Thus, the Red
Flag Warning remain in effect. It is important to note that Red Flag
Conditions are greatest each day roughly from 10AM through 7PM MDT
with some improvement overnight. Overnight relative humidity
recovery is forecast to be poor to fair, but winds will generally
follow the diurnal trend of weakening overnight. As the morning
discussion mentioned, a cold front will approach the region on
Saturday and tighten the pressure gradient and result in stronger
winds. So, there is greater concern for more widespread fire weather
conditions Saturday. The Saturday night/early Sunday cold front is
currently forecast to only bring snow chances (30%) to the northern
mountains and "cooler", closer to normal temperatures for Sunday.
Winds on Sunday are forecast to be relatively tame compared to what
we have been experiencing, but conditions will remain dry given the
lack of widespread moisture associated with the cold front. Thus,
elevated fire weather conditions are expected Sunday and Monday for
most low elevations.

&&

.DISCUSSION...
Issued at 120 AM MDT Thu Mar 19 2026

For those of us who do not like winter, today is a one of the
most looked forward to days (although some say we haven`t had a
winter this year, they do have a very good point). Today is the
last full day of astronomical winter, as the sun will move to
the north of the equator for the first time on Friday 8:46am
Mountain Time (the Vernal Equinox), ushering us into
Astronomical Spring (Meteorological Spring began March 1st).

However, as most people know around here, this time of year is
usually still rather cool. In addition, a majority of our huge
snowfalls climatologically occur from now through April. As you
may have noticed, this will not be the case over the next week
or probably the next 10 days or so. An abnormally strong ridge
will continue to bring temperatures over 30 degrees above
normal in some locations through Saturday. It will feel more
like the first day of summer, as in most locations most of the
high temperatures we see for the next three days, will be our
normal highs that we see in the middle or latter part of June,
not late March. Like the past two days, we will tackle each
concern individually, and we continue to have four of them.

RECORD HIGH TEMPERATURES: This portion of the forecast still looks
to be on track. Looking at the temperatures from yesterday, we had 8
daily record highs, with 5 sites tying or breaking the all time
March high temperature. I will include this data in the climate
section of the discussion. We were a bit too cool on most of the
highs yesterday, so we raised temperatures a bit. The NBM ensemble
gives at least a 1 in 2 chance of high temperatures over 80
degrees to most of the elevations under 6000 feet east of the
Divide. In areas west of the Divide, with the exception of the
western valleys, have at least a 1 in 2 chance of highs over 70
degrees. Most locations have at least a 4 out 5 chance of
breaking daily record highs (some locations it`s almost a
certainty), with a greater than 1 in 2 chance of breaking all
time March records. Conditions look similar on Friday as well.
Saturday may end up being the warmest day, as downsloping
increases ahead of an approaching cold front, except for maybe
the far north. Areas like Worland have a 1 in 2 chance of
reaching 85 degrees, with even a 1 in 5 chance in places like
Riverton, Thermopolis and even Casper. Temperatures should cool
from 10 to 20 degrees by Sunday, as the ridge weakens and moves
to the east and the aforementioned cold front sweeps across the
area.

FIRE: The forecast remains on track here as well. Relative humidity
was a bit lower yesterday than forecast, so we lowered by a few
percent. Reasoning remains the same. Wind will be a bit lighter
today as the jet gets pushed further north. Most of the areas in the
Red Flag Warning have at least a 2 out of 3 chance of wind
gusts reaching critical conditions (>25 mph). The only question
is tomorrow, when some zones may not reach the wind criteria.
However, since it continues to be unseasonably warm and
humidity well below 15 percent, we will likely keep the
Warnings going even if wind does not make it. Saturday still
looks like the most impactful day though, as wind increases
ahead of an approaching cold front, with some wind gusts over 40
mph possible and humidity remaining in the lower teens. Fire
weather concerns should at least drop below critical for most
locations as cooler temperatures move in for Sunday.

WIND: With the jet moving further north, strong wind looks less
likely today. However, most areas should still have at least a
1 in 2 chance of gusts past 30 mph, mainly in the afternoon
during peak heating and mixing. Wind reaches a nadir on Friday,
with chances of wind gusts past 30 mph falling anywhere from 10
to 15 percent. Saturday continues like the windiest day ahead of
the cold front with many areas, especially those prone to west
to northwest flow, having at least a 1 in 2 chance of gusts past
45 mph. This is the day some locations may need some high wind
highlights. At this time, northern Wyoming has the best chance
of this with the cold advection / northwest flow pattern with
the frontal passage, along with some jet stream enhancement. We
will cross that bridge in future shifts.

RISING RIVERS AND STREAMS...Some streams and rivers are already
seeing some rises with snow melt beginning. However, concerns for
flooding remain low at this time for the same reasons as yesterday.
For one, with the recent dry weather, the soil will soak up
some of the water. Also, almost all of the snow is of the high
elevation variety, and temperatures will still fall in to the
30s at night, slowing the melt somewhat at night. Reasoning
remains the same as yesterday, with rises likely but flooding
remaining unlikely.

As for the rest of the forecast, Sunday will be a cooler day but
temperatures will remain above normal for all locations except for
possibly northern Johnson County. The front has little moisture to
work with so any precipitation amounts would be on the light side,
with the southern thirds of the area likely seeing none. Even
in northern Wyoming, almost now areas have a greater than 1 in 2
chance of a tenth of an inch or more of liquid precipitation
through Sunday except the western slopes of the northern
Bighorns. And with most guidance keeping the best forcing to the
north, this may trend downward. Temperatures then trend well
above normal again, but not to the levels we will see this
week. A few members of the ensemble have another front moving
through for midweek next week, but uncertainty is high. With the
zonal flow, the western mountains would have the best chance of
any meaningful precipitation. Looking further out, most
guidance shows a generally zonal to flat ridging pattern across
the area through the end of next week. So, unfortunately, the
prospect of a widespread precipitation event is looking highly
unlikely for the next 10 days.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1129 AM MDT Thu Mar 19 2026

VFR conditions will continue through the period as high pressure
dominates the region. The main aviation concern continues to be
wind, with most terminals seeing gusts of 20 to 30 knots through the
afternoon hours. Wind will decrease after sunset. Other than a high,
broken cloud deck moving in east of the Divide this evening,
skies will remain mostly clear.

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 120 AM MDT Thu Mar 19 2026

A combination of relative humidity falling in the teens and in
some locations the single digits, dry fuels, record high
temperatures and a gusty breeze will continue to bring elevated
to critical fire weather to much of the area, especially east
of the Continental Divide and in southern Wyoming. Wind may
decrease somewhat tomorrow, but conditions should remain
similar. Saturday continues to look like the most concerning day
with continued warm temperatures and increasing wind ahead of a
cold front moving in from the north. Conditions should improve
somewhat on Sunday as slightly cooler temperatures move in
behind the cold front.

&&

.CLIMATE...
Issued at 120 AM MDT Thu Mar 19 2026

Eight more daily records were tied or broken yesterday, all of
our main climate sites with the exception of Buffalo, bringing
the total in the warm spell to 11. In addition, three sites
(Casper, Lake Yellowstone, and the Riverton airport) set their
all time March high temperatures and two other sites (Big Piney
and Rock Springs) tied the all time March high temperature. Worland
had it`s earliest 80 degree high temperature, breaking the old
record by 10 days (March 28, 1986). It is likely (greater than a
4 out of 5 chance) that 35 or more daily high records will be
broken from Wednesday to Saturday and that all major climate
sites, except for possibly Buffalo, set their all time March
high temperature. Some locations may set the all time March
record high three times or even four.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT Saturday for WYZ276>283-287-
289.

&&

$$

UPDATE...Gerhardt
DISCUSSION...Hattings
AVIATION...Myers
FIRE WEATHER...Hattings
CLIMATE...Hattings