609
FXUS65 KRIW 272155
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
355 PM MDT Thu Mar 27 2025

.KEY MESSAGES...

- Temperatures continue to warm above normal this afternoon with
  highs nearing all time March records.

- Critical fire weather conditions continue along the I-25
  Corridor this afternoon, with the combination of wind gusts up
  to 25 to 35 mph, low relative humidity values (10-20%), and
  above normal temperatures.

- A weather system tonight will bring more seasonable
  temperatures and precipitation Friday through the weekend.
  These seasonable temperatures and precipitation chances are
  forecast to continue into next week.

&&

.UPDATE...
Issued at 211 PM MDT Thu Mar 27 2025

Satellite imagery (20Z) shows a mostly sunny sky across much of
central and eastern Wyoming that is allowing for sufficient
insolation across the region. Sufficient insolation and 700-mb
temperatures around 7C have translated to temperatures in the mid-
70s and these temperatures will continue to rise well above normal
this afternoon, with multiple record highs in jeopardy. As of
20Z, surface observations are showing relative humidity values
less than 15% with southwest wind gusts around 25 mph at many
locations east of the Divide. These dry conditions, gusty winds,
and warm temperatures continues to cause elevated to critical
fire weather conditions into the evening.

A cold front remains on track to impact the region tonight and bring
an end to the above normal warmth and dry weather. Locations across
western and northwestern Wyoming have the greatest chance (80-90%)
at seeing precipitation with the cold front. Precipitation is
expected to begin as rain but quickly transition to snow across
higher elevations and a rain/snow mix in lower elevations of
west/northwest Wyoming. Precipitation chances decrease as the
front pushes east early Friday morning. Rain and snow chances
increase areawide Friday afternoon as a shortwave traverses the
region.

&&

.DISCUSSION...
Issued at 131 AM MDT Thu Mar 27 2025

High pressure will remain in control across the CWA today, leading
to another day of above normal temperatures. Record high
temperatures are still expected across most areas east of the
Divide, with highs ranging from the middle 70s to near 80 degrees.
Elevated to critical fire weather conditions will return across the
Wind Corridor this afternoon (from Rock Springs to Casper) as well,
with wind gusts of 25 to 35 mph occurring over this area as well as
southern Lincoln and Sublette counties. Mid to high level clouds
will increase over western portions through the afternoon, as
moisture from an upper low off the West Coast streams over the
region. There will be enough moisture for a chance for rain showers
to occur (20% chance) over northwestern portions of the forecast
area. There is a 1 in 10 chance for a rumble of thunder to occur
within these showers as well. Chances for rain will increase (60-
80%) over these areas through the evening, as a cold front
associated with the upper low begins to move over the forecast area.
Winds will increase again as the front progresses eastward through
the night, with brief gusts of 35 to 45 mph expected (especially in
the central basins) and exiting far eastern portions of the forecast
area by 12Z Friday. An isolated shower (20% chance) could occur in
eastern portions of the Bighorn Basin with the passage of the front.

Temperatures will be 10 to 15 degrees cooler Friday, as a result of
the front, with highs returning to the 50s and 60s. Winds will not
be as strong either. A shortwave trough from the upper low will
approach the region, bringing the chance for widely scattered
showers back to the CWA. the best chances (30-50%) look to be over
far western portions and the Wind Corridor. There could be enough
instability with the showers over Sweetwater County for a
thunderstorm to occur. Showers look likely (40-60%) across the
forecast area Friday night, as the shortwave moves to the east-
northeast through the night. Snow levels look to range between 6000
and 7000ft during this time.

Precipitation chances will continue to be widespread across the CWA
Saturday, as the upper low moves onshore and over the PACNW,
weakening and filling as it progresses eastward. The best chances
will occur by late afternoon and through Saturday night, as the main
low moves over the area. Snow will be possible in the lower
elevations during this time, with accumulations only up to an inch
expected at this time. 3 to 6 inches are expected in the mountains,
with locally higher amounts of 8 to 12 inches in the Bighorns. This
will be due to a more favorable upslope component to occur over the
Bighorns as the low passes to the south.

Precipitation will end from the southwest to the northeast through
the day Sunday. A transitory ridge will be in place by Monday, as a
another upper low makes its way to the PACNW. This will keep
Pacific moisture streaming over the region and could result in
isolated rain showers over western and southern portions and
snow in the western mountains.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 354 PM MDT Thu Mar 27 2025

VFR conditions prevail through the period for most terminals. Clouds
will continue to increase in coverage through the afternoon and
especially after dark from west to east as a cold front moves
through. With the cold front, expect a 1 to 4 hour period of
rain/snow showers. Most likely chances (60%) for prevailing light
rain or snow is at KJAC. Showers are also possible at KBPI and KPNA
(40% chance) and KCOD and KWRL (25% chance) with the front.

Winds will be southwesterly for most terminals with gusts up to 20
to 25kts for most terminals to start the period. KCPR will see the
strongest winds with gusts around 30kts. With and behind the cold
front, winds will become westerly to northwesterly, but return to
typical nighttime drainage flows 2 to 4 hours after the frontal
passage. Southwest winds will increase again Friday late morning and
early afternoon for many terminals.

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 131 AM MDT Thu Mar 27 2025

Elevated to critical fire weather conditions will be in place
from zone 277 to zone 281. Wind gusts of 25 to 35 mph, minimum
RH values of 10 to 15 percent and near-record high temperatures
will occur in these areas today. Red Flag Warnings remain in
effect for zones 280 and 281 this afternoon between 1300 and
1900. Elevated fire weather conditions will also be possible in
the Bighorn and Wind River Basins.

A wetter pattern will begin Friday and continue through the
weekend and into the first half of next week.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for WYZ280-281.

&&

$$

UPDATE...
DISCUSSION...LaVoie
AVIATION...Hensley
FIRE WEATHER...LaVoie