Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 212338
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
535 PM MDT Thu Mar 21 2024

.KEY MESSAGES...

1) Strong westerly winds possible this afternoon with southeast
Wyoming wind-prone locations gusting around 50 mph.

2) Critical to near-critical fire weather conditions east of
the Laramie Range this afternoon.

3) A strong cold front will bring much cooler weather and widespread
precipitation chances Sunday into Monday. The unsettled weather
pattern is expected to continue through next week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 250 PM MDT Thu Mar 21 2024

Cold front lays along a line from extreme southeast Colorado to
near Sidney...then north northwest to a surface low near
Douglas. Pretty solid cloud layer north of the low and front
across Converse County into the northern Panhandle near Chadron.
North of the front...temperatures are struggling to get out of
the 40s. South of the front...Scottsbluff is at 71...Douglas at
65. Winds south of the front have been quite strong...with
Bordeaux reporting 50 mph gusts...Douglas at 37 mph and Laramie
at 41 mph.

Fire headline wise...the winds and low humidity have been having
a hard time lining up. Went ahead and cancelled the Fire Weather
Watches that were in effect. As for the Red Flag
Warnings...decided to keep them going as wind/RH combination
close at Douglas...Torrington and Wheatland. WIll let the
warnings continue through 6PM.

Front surges south after 00Z this evening. By 03Z...the front
looks to lay along a line from Bridgeport to Chugwater. By
06Z...the front looks to clear the Colorado stateline to south
of Laramie. Some light QPF showing up across our northern zones
behind the front. Kept low end chance (20-30 percent)PoPs going
across Converse and Niobrara Counties into the Pine Ridge area
of the northern Panhandle.

Cooler temperatures Friday as the front bisects the CWA from
northwest to southeast. Temperatures in the 40s north of the
front with 50s common across the southern areas.

Front begins to push east and northeast Friday night into
Saturday as a stronger shortwave approaches from the west.
Warmer temperatures Saturday with fairly widespread
precipitation overspreading the CWA through the day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Issued at 250 PM MDT Thu Mar 21 2024

Our streak of mild weather will come to an abrupt end this weekend
as a strong, but fragmented trough plows across the western US. Our
area will be in the warm sector of the approaching system Saturday
night, and overrunning on top of the leading warm front should be
enough to keep shower activity going into the night. We may also see
a few rumbles of thunder with this activity owing to some modest
instability in place. Meanwhile, moist southwest flow moving into
the mountains will return snow showers to the higher terrain, with a
few inches likely by morning. The upper level trough moving over the
mountains will support strong lee cyclogenesis over east Central
Colorado Saturday night into Sunday, with sea-level pressure
possibly reaching as low as 980-mb by Sunday afternoon. The surface
cold front is expected to push through the area Sunday morning, with
colder air wrapping into Colorado and strengthening the surface low
through the day. Expect the daily high to be reached in the morning
hours, with strong cold air advection and chilly northerly winds
behind the front. The fragmented nature of this trough will most
likely prevent a high impact winter storm for the High Plains. The
latest guidance continues to show the initial 700-mb low positioned
over north central Wyoming Sunday, putting isentropic descent over
much of the area during the morning hours. Once the secondary low
stacked on top of the surface low in Colorado takes over, this will
allow for some modest lift and moisture to wrap around the backside
of the low, but the best dynamics may already be to our east once
this happens. Still, fairly widespread snow showers are expected
Sunday afternoon and evening. About 10-20% of the latest suite of
ensembles wrap the moisture soon enough and far enough west to
deliver a warning criteria snowfall event for portions of the High
Plains, but the remainder show a more minor snowfall event. The
latest suite has also shifted slightly west and upward in QPF, but
not dramatically so. Current official forecast favors a widspread
dusting to 2" or so over the plains, but will need to continue to
monitor for the low probability but high impact potential with a
strong storm moving through. Regardless of snowfall outcome, it will
be much colder with chilly north winds continuing Sunday night into
Monday. Ensemble mean 700-mb temperatures plummet to -14C by Monday,
supporting a fairly potent shot of cold air for this late in the
season. Highs may struggle to reach freezing on Monday for much of
the area, with overnight lows in the teens or even single digits.

Beyond the first storm, the weather pattern is expected to remain
very unsettled through next week with several shortwaves behind
giving near daily chances for precipitation for some portion of the
forecast area. For Tuesday and Wednesday, shallow ridging will try
to build in in the wake of Monday`s trough, and we may have some
snow showers as a jet streak shifts from southwest to northeast
across our area. Any accumulation during this period looks modest.
The system behind looks a bit more potent, with another potent and
progressive shortwave moving across the west on Thursday or Friday.
There are considerable timing differences between models with this
system, but fairly strong agreement in a potent trough moving
through towards the end of next week. For now, PoPs will increase in
the official forecast on Thursday, but the temperatures forecast is
highly uncertain based on the timing of the front.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 535 PM MDT Thu Mar 21 2024

A surface cold front is currently just north of KBFF and KAIA late
this afternoon. This front is forecast to slowly move south and west
tonight with winds shifting into the north through 06z for most
terminals. Gusty winds will diminish late tonight.

HAZARDS/WEATHER TRENDS: VFR conditions are expected to prevail for
all terminals tonight with MVFR CIGS possible after sunrise for
KCDR. A brief thunder shower possible for KAIA, and to a lesser
extent KSNY, through 01z. Gusty westerly winds will shift into the
north and remain gusty for KCYS and all of the western Nebraska
Panhandle terminals this evening until 04z to 08z.


&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...None.
NE...None.

&&

$$

SHORT TERM...GCC
LONG TERM...MN
AVIATION...TJT


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