636
FXUS65 KCYS 110945
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
345 AM MDT Tue Jun 11 2024

.KEY MESSAGES...

- Patchy fog may occasionally reduce visibilities to one half
  mile or less across the high plains of southeast Wyoming and
  the western Nebraska Panhandle through 8 AM MDT this morning.

- Increasing heat-related concerns for Wednesday and Thursday as
  daytime highs climb into the 85 to 95+ degree range across the
  entire area.

- Thunderstorm chances return to the region on Friday, along
  with the risk for severe weather.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 305 AM MDT Tue Jun 11 2024

Patchy fog has developed across the high plains of southeast Wyo
and the western Neb Panhandle given light winds and residual low
level moisture from earlier precipitation. Fog is likely to burn
off very quickly after sunrise.

A quiet forecast period ahead with hot and dry conditions likely
with minimal chances for precipitation. The overall mid & upper-
level pattern should remain zonal through the period with little
in the way of vort energy traversing the flow. The thermal ridge
builds into the region on Wednesday with H7 temperatures surging
to +16 to +18 deg C. This should easily support daytime highs in
the 85-95 degree range for much of the CWA, though we could very
well see highs approach the 100 deg F mark over the Platte River
Valley with the latest NBM spectrum suggesting a 50+% chance for
daily maximums exceeding 95 deg F in those areas. The warmth may
continue on Thursday w/ the flow pattern not supporting any cool
intrusions aloft. Aside from growing heat concerns, there is not
much to address over the next 24 to 48 hours.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Issued at 305 AM MDT Tue Jun 11 2024

The long term will start off active, with a strong shortwave trough
entering the central Rockies by Friday afternoon. This will increase
low to mid-level moisture across the area and provide lift for
storms to develop. Model soundings from the GFS show impressive
profiles across the Nebraska panhandle Friday afternoon. Eastern
panhandle soundings show upwards of 2000 J/kg of MUCAPE. This
certainly raises concerns for the potential of severe weather.
Large hail will definitely be a concern for storms, especially
for areas east of the Laramie Range where greater moisture,
higher CAPE values, and elevated large hail parameters exist.
With this current set-up, cannot rule out a few isolated storms
with significant hail. Aside from hail, it is worth mentioning
that effective shear values across much of the panhandle will be
around 40 kts, supporting supercells. MLCAPE values in the
panhandle are also approaching 1400 J/kg, so a tornado threat
cannot completely be ruled out. On top of all this, sounding PWs
are quite high, showing over an inch in the panhandle and
approaching 0.75 inches in much of southeast Wyoming. NAEFS mean
PWs fall into the 97.5th percentile for almost all of the CWA.
This means that storms Friday afternoon and Friday evening could
contain torrential rains that lead to flash flooding. Overall,
Friday looks to be an active day that will need to be monitored.

Headed into the weekend, both Saturday and Sunday look like warm and
dry days. With the shortwave moving off to the east on Saturday,
quasi-zonal flow will persist through much of the weekend. This will
keep conditions dry, albeit a bit breezy. 700 mb temperatures will
consistently stay in the 10C to 16C range during this time frame,
leading to widespread highs in the 80s. Mostly dry conditions look
to continue into the beginning of next week as a trough stays off to
the northwest of the CWA. Although dry, it may push a cool front our
way and drop high temperatures on Monday and Tuesday into the
70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1135 PM MDT Mon Jun 10 2024

Quiet across the area now that storms have pushed off to the
east. Conditions will remain calm overnight, which could lead to
the development of low stratus and potentially fog in some
areas. Ample low-level moisture and light winds will be the main
drivers in any low stratus/fog development late tonight/early
this morning. MVFR and possibly IFR conditions are possible
through mid-morning.

&&

.HYDROLOGY...
Issued at 300 PM MDT Mon Jun 10 2024

The slightly cooler temperatures the last few days have slowed the
melt just a touch, allowing flows to come down on area rivers and
streams. Therefore, the Flood Warning on the Little Laramie River
has been expired. Flows remain near flood stage on the Medicine Bow
River near Elk Mountain, so the Flood Watch was extended another
day. Temperatures will start to increase again Tuesday into
Wednesday, with more rapid melt anticipated. However, it is possible
we have passed the peak melt with a pretty significant loss in
snowpack over the last 7 days.

&&

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

&&

$$

SHORT TERM...CLH
LONG TERM...SF
AVIATION...SF
HYDROLOGY...MN