477
FXUS65 KCYS 161641
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1041 AM MDT Thu May 16 2024

.KEY MESSAGES...

- Warm & dry conditions prevail through Saturday. Daytime highs
  on Friday may reach the lower to middle 80s for areas along
  and east of I-25.

- Windy on Friday as a strong disturbance tracks across the
  northern high plains. Wind gusts 45-55 MPH are expected for
  Arlington and Bordeaux. A couple brief gusts in excess of 60
  MPH cannot be ruled out.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 410 AM MDT Thu May 16 2024

A generally quiet forecast period ahead for southeast WY and the
western NE Panhandle as split upper-level flow prevails w/ short
wave energy remaining well to the north and south of the CWA. As
a result, any chances for precipitation are likely to remain low
to almost nil through Saturday. 700-mb temperatures are expected
to climb to +6 to +8 deg C across the CWA today, and continue to
rise to +10 to +12 deg C by 00z Saturday. As such, expect to see
a substantial warming trend over the next couple of days w/ high
temperatures likely reaching the lower 80s over areas along/east
of I-25 on Friday afternoon. Strong winds are possible from late
Thursday night through Saturday morning across the southeast Wyo
wind corridors as height falls spread across the western Dakotas
ahead of a vigorous mid-level short wave, resulting in 850 & 700
mb CAG-CPR gradients of 45 to 55 meters. Modest 700-800 hpa flow
only peaking around 45 knots should preclude any widespread wind
gusts over 60 MPH, but in-house RF models do suggest appreciable
probabilities of 45+ MPH wind gusts at both ARL and BRX. At this
time, do not anticipate the need for wind headlines. However, we
will need to pay close attention to model trends during the next
few cycles as a marginal warning-level wind event is certainly a
possibility.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Issued at 410 AM MDT Thu May 16 2024

A longwave, upper-level trough will begin to develop over the
Pacific Northwest on Saturday evening into Sunday. Several 500mb
vorticity maxima will eject out ahead of the incoming trough,
promoting scattered shower potential across southeast Wyoming and
western Nebraska. Widespread precipitation does not look likely at
this time for the end of the weekend. By Monday, the upper-level
trough will be over Idaho, with two separate jet branches overhead.
The northern jet branch will stretch from southwest Wyoming to the
northeast towards southwest North Dakota, while the southern branch
will stretch from Baja California northeast through western
Nebraska. The positioning of these two jets will support synoptic
life across the region Monday ahead of the advancing cold front.
700mb temperatures will drop from the 6-9C range to the -1 to 3C
range leading to temperatures on Monday dropping approximately 10 to
15F. With the rather strong cold front, showers and likely
thunderstorms will develop out ahead of the front, leading to area
wide PoPs in the 40-60% range. At this time, CAPE values do not look
to be impressive at all, so while some thunderstorms may develop
they will likely not be long lived or overly strong. However, winds
will be rather gusty behind the cold front, though should remain
below high wind criteria.

The upper-level trough will continue to push across the region
Tuesday into early Wednesday morning before a brief ridge develops
over the western CONUS. On Tuesday, PoPs will remain across the
region as the residual forcing associated with the upper-level
trough continues to push out of the region. 700mb temperatures will
remain cool, in the -2 to 3C range, leading to another cooler day on
Tuesday. Highs in the upper-50s to mid-60s are likely for Tuesday.
Once the upper-level trough clears the region and the shortwave
ridge moves overhead for Wednesday, temperatures warm once more.
Warm air advection will be present at 700mb as the ridge moves
towards the region, favoring lift across the region for Wednesday.
The GFS is much quicker will the development and progression of the
ridge, while the ECMWF does not show ridging until Thursday and
instead favors zonal flow. Given some of the disagreement, but both
models showing WAA at 700mb, kept PoPs around 20-30% across the
region. Temperatures will increase with this WAA into the mid-60s to
mid-70s for Wednesday.

Thursday morning, the next upper-level trough is progged to continue
its progression from the Pacific Northwest. The GFS and ECMWF are in
relatively good agreement on the development of this trough and its
movement across the CONUS, but the ECMWF suggests a more negatively
tilted trough while the GFS keeps the trough neutral. Ahead of the
incoming trough, 700mb temperatures on Thursday surge into the 6-8C
range, favoring surface temperatures in the mid-60s and mid- to
upper-70s across the region. As the trough pushes towards the
region, several 500mb vorticity maxima will eject out ahead and
favor precipitation chances again Thursday afternoon into the
evening. Kept PoPs in the 20-30% range at this time. Cold air
advection at 700mb late in the day Thursday will favor cooler
temperatures once more for Friday.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1038 AM MDT Thu May 16 2024

VFR expected for all terminals through the forecast period. KRWL
will see wind gusts up to 25 knots this afternoon before
tapering off to less than 12 knots overnight. KCYS and KLAR will
have occasional gusts up to 10-15 knots this afternoon before
dissipating this evening. The NE Panhandle terminals will have
winds of 12 knots or less through early Friday morning, with
wind gusts picking up after 15Z Friday to 20-25 knots.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...CLH
LONG TERM...AM
AVIATION...BW