703
FXUS65 KCYS 021141
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
541 AM MDT Tue Jul 2 2024

.KEY MESSAGES...

- A few showers and perhaps a rumble of thunder will remain
  possible across the region through mid-day. Gusty winds can be
  expected mainly along and west of the Laramie Range today w/
  gusts up to 45 MPH.

- Thunderstorms are possible on Wednesday afternoon, especially
  across east central Wyoming & the western Nebraska Panhandle.
  Any storms which develop will have the potential to become
  severe with all hazards possible.

- A cool and pleasant Independence Day is expected in the wake
  of a strong cold front set to sweep across the area on
  Wednesday night.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 413 AM MDT Tue Jul 2 2024

Scattered showers are expected to persist across southeast Wyo &
the western Neb Panhandle through mid-day as the axis of the mid
level short wave traverses the central Rockies. Gusty winds near
55 MPH may occur beneath some of this activity. Otherwise, gusty
winds are expected for areas along/west of the Laramie Range for
today as 700-mb CAG to CPR gradients climb to near 35 meters. We
should see a brief warm up on Wednesday w/ short wave ridging in
advance of the next sharp trough. Substantial WAA at 700-mb will
contribute to some questions w/ the eastward extent of the EML &
thus the impact of capping on overall coverage of storms in some
portions of the CWA, but the primary focus for Wednesday will be
northern & eastern zones along the edge of the thermal ridge for
potential thunderstorm development. SSE near-surface flow should
support dew points in in the mid/upper 50s by 18-21z assuming we
do not see the dryline mix eastward too quickly. Very steep mid-
level lapse rates combined w/ the moist boundary layer will help
to support MLCAPEs of 1500-2000 J/kg while increasing flow at H5
supports 35-45 knots of effective bulk shear. As such, organized
supercell structures will be possible with all hazards possible,
including very large hail & damaging winds. Notable veering wind
profiles in the low levels suggests a few tornadoes will also be
possible if storms can remain at least quasi discrete. Expect to
see a strong cold frontal passage late Wednesday night w/ 700-mb
temperatures plunging to +5 C or less by 15z Thursday. While the
overall thermal profiles should rebound nicely by afternoon, the
net result should be a cool and pleasant Independence Day w/ day
time highs only in the 70s for many.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 413 AM MDT Tue Jul 2 2024

Looking at a relatively quiet long term as the region makes the
gradual transition from broad troughiness to strong ridge.

With an upper-level low ejecting into the Great Lakes Region Friday
afternoon, expect a warm-up in temperatures as the CWA sits just
downstream of a ridge building over the west coast. This will usher
in both warmer, and drier 700 mb air into the region, contributing
to about a 5 degree warm up from Thursday`s comfortable highs.
Overall, looking at dry weather on Friday with gradual 500 mb height
rises, despite the weak vort maxes passing aloft.

Heading into Saturday, both the deterministic GFS and ECMWF show a
distinct cold front dropping down from the north as a strong
shortwave moves into Montana and the Dakotas. GFS and ECMWF are
roughly in agreement time wise, with the GFS bringing that front
through a tad faster than the ECMWF. Based on frontal timing, still
expecting a warming trend through the day Saturday, with another 5
degree jump in high temperatures compared to the previous day.
Frontal passage appears to be Saturday evening or night, either of
which leads to a cooler day on Sunday. 700 mb temperatures drop into
the +4C to +10C range, likely leading to below average highs. Did
bump temperatures below NBM guidance as they seemed too warm for
this magnitude of cold front. Highs on Sunday could be in the 70s to
low 80s. Cannot rule out some light precipitation with the front, as
well as behind the front since mid-level moisture does increase in
the presence of forcing. So, did increase PoPs Saturday night and
into the day Sunday, but went with slight chance wording.

With a strengthening ridge building over western CONUS, expect
warming temperatures and dry conditions through the beginning of the
work week. Increasing 700 mb temperatures will likely lead to the
return of 90 degree temperatures by Tuesday of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 540 AM MDT Tue Jul 2 2024

Some scattered showers are possible this morning across most of the
terminals in southeast Wyoming and western Nebraska. Showers will
end this morning for southeast Wyoming, leaving a breezy day with
gusts over 30 kts possible. In western Nebraska, showers will
transition to isolated thunderstorms during the early afternoon
hours, wrapping up by mid to late afternoon.

&&

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

&&

$$

SHORT TERM...CLH
LONG TERM...SF
AVIATION...SF