997
FXUS65 KCYS 272050
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
250 PM MDT Thu Mar 27 2025

.KEY MESSAGES...

- Unseasonably warm and generally dry weather is expected this
  week with record highs and near critical fire weather
  conditions possible Thursday.

- Cool and unsettled weather will prevail for the weekend with a
  decent chance for rain and snow showers. Colder on Sunday.

- Warmer and windy early next week, with another weather
  disturbance bringing a chance for showers on Tuesday.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 249 PM MDT Thu Mar 27 2025

Afternoon radar and satellite over southeast Wyoming and western
Nebraska indicates a few very high-based convective cells drifting
generally eastward throughout the high plains. Short-term forecast
soundings from high-res guidance indicates deep inverted-V profiles
indicative of plenty of dry air near the surface and a moderate
increase in mid-level moisture as a wave of energy moves eastward
out of the Rockies. Such a deep inverted V profile as is the case
today generally will not result in much or any QPF at the surface,
however some gusty winds upwards of 40 mph near any convective
shower can not be ruled out, especially from areas including Pine
Bluffs to Sidney as we ll as in the Scottsbluff/Chadron areas where
consecutive runs of the HRRR have consistently supported convection.
Have modified forecast grids through the later afternoon to support
the low-end thunder and PoP threat in these areas. In addition to
the shower threat today, afternoon highs have met or exceeded record
high levels, including at Cheyenne where the old record of 72 was
exceeded by a high temp of 73 so far. Overnight, expect another very
mild period with temperatures running well above average and partly
cloudy skies.

An unsettled period of weather will begin on Friday and last through
the weekend as a broad trough with several embedded waves move
through the Rockies and eject into the high plains.
Ensemble forecast guidance is unusually dispersive with regard to
this system at such a near timeframe, adding uncertainty to the
forecast from Friday evening onward. Most guidance supports dry
weather on Friday morning across the entire CWA as heights fall and
cloud cover increases. Expect a mild morning however afternoon highs
will be slightly lower by about 5 degrees as clouds thicken through
the day and a diffuse cold front approaches from the northwest. As
better dynamics and support for lift arrive over the region later in
the day, showers with possibly some thunder will develop first over
the higher terrain of northern Colorado and southeast Wyoming. This
activity will spread eastward generally after 5pm possibly impacting
the I-25 corridor. Forecast soundings indicate a much more moist
profile after around 3z throughout much of the region and a wide
area of stratiform rain showers is likely through the evening and
overnight. Snow levels will remain quite high with this system on
Friday night into Saturday morning. Therefore, no accumulations are
forecast outside of the Sierra Madre and Snowy ranges, with a cold
rain likely for the remainder of the foothills, Laramie Range, and
high elevation basins of southeast Wyoming. QPF values have come up
with the latest round of guidance in the latest model cycle, with at
least a quarter to a half of an inch of rain likely by daybreak
Saturday. Overall, forecast confidence is only moderate with this
event, owing to a varied placement of the heaviest bands of rain and
the scattered, convective nature of precipitation on Friday
evening. |

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Issued at 249 PM MDT Thu Mar 27 2025

Saturday...The initial shortwave trough aloft moves from southeast
Wyoming in the morning, to eastern Nebraska by evening. With
dynamics and upslope, and plentiful moisture, we will see scattered
to numerous showers at lower elevations, with snow for the
mountains. With all the thick cloud cover and precipitation, maximum
temperatures will only be in the mid 40s to mid 50s.

Sunday...Even colder with 700 mb temperatures near -6 Celsius
yielding high temperatures from the mid 30s to mid 40s. With nearly
saturated low and mid levels, dynamics from a passing shortwave
trough aloft and upslope, we will still see scattered to numerous
showers, mostly snow, mainly in the morning.

Monday...Turning breezy to windy, and warmer as the flow aloft turns
westerly, inducing downslope winds. High temperatures mainly in the
50s. Enough moisture in the flow for some orographic showers over
the mountains.

Tuesday...A progressive and fast moving shortwave trough aloft moves
from Idaho to western Nebraska during the day, with an associated
cold frontal passage. Most of the lift with this system is progged
to remain to our north, however, we will still see enough lift for
scattered showers.

Wednesday...Low amplitude shortwave ridging aloft builds across
Wyoming. Will continue with a mention of a chance for lower
elevation rain showers and mountain snow showers, though this day
may end up being relatively dry based on the model projections.

Thursday...As southwest flow aloft strengthens considerably, it
looks like a windy day will occur, with some wind prone locations
possibly seeing near high wind criteria. Temperatures will also show
a warming trend with 700 mb temperatures near 5 Celsius yielding
maximum temperatures in the 50s to lower 60s.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1123 AM MDT Thu Mar 27 2025

Southwest flow aloft will prevail. Scattered to broken clouds
from 10000 to 15000 feet will occur. Winds will gust to 30 knots
at the Wyoming terminals until 02Z, and to 25 knots at Rawlins,
Cheyenne and Sidney after 15Z Friday.

&&

.FIRE WEATHER...
Issued at 400 AM MDT Thu Mar 27 2025

Critical fire weather conditions are expected this afternoon across
portions of southeast Wyoming, mainly along and east of I-25. Warm
temperatures will produce low RH dropping to 10 to 13% as wind gusts
of around 25 to 30 mph develop during the afternoon. Expect these to
overlap in Wyoming east of the Laramie Range. The NE panhandle will
see low RH, but winds should remain below critical. Briefly to locally
critical fire weather conditions are also possible in the valleys west
of the Laramie Range. In addition, high-based showers with a few rumbles
of thunder will develop mainly over the Wyoming high terrain and adjacent
valleys/plains. This activity could produce isolated dry lightning and
gusty/erratic winds.

Expect another round of elevated to near critical fire weather
conditions on Friday. Cooler temperatures moving in from the northwest
will reduce the risk for most of the area, but far southeast WY and
the southern NE panhandle may be close to critical once again.

Reduced fire weather concerns expected Saturday onward thanks to
cooler temperatures and a better chance for wetting rainfall and/or
accumulating snow.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 7 PM MDT this evening for WYZ417-418-
     430>433.
NE...None.

&&

$$

SHORT TERM...MAC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...MN