418
FXUS65 KCYS 160008
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
605 PM MDT Mon Jul 15 2024

.KEY MESSAGES...

- Hot temperatures will continue through this afternoon for a
  majority of the area today before tapering off temporarily
  through mid-week.

- Increased precipitation chances and cooler temperatures are
  expected this afternoon through Wednesday.

- Isolated severe thunderstorms are expected today and Tuesday.
  The primary hazards are lightning, brief heavy rainfall, and
  strong winds to 60mph.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 235 PM MDT Mon Jul 15 2024

Cold front pushing into the CWA from the northeast this
afternoon...currently lays along a line from Bridgeport to
Douglas into central Montana. Radar beginning to show convection
developing just west of this front across northern Carbon/Albany
Counties...into Platte County. RAP analysis showing low level
CIN has eroded away with 20Z surface based CAPE 500 J/KG over
southeast Wyoming and just over 1000 J/KG over the Panhandle.

Looking at SBCAPE to continue increasing through the afternoon.
SPC mesoanalysis showing CAPE increasing to 1500-2000J/KG
through the late afternoon. Both HRRR and RAP simulated radar
showing a good coverage of convection across the CWA at 00Z.
Initially high based storms...main hazard will be strong
downburst winds of 60 mph or higher. By 00Z...PWATS looking to
be around 0.9 inch across southeast Wyoming and near an inch
over the Panhandle...so should begin to see rain hitting the
ground this evening for a time.

Front gets forced east Tuesday into western South Dakota and
western Nebraska. May be a bit less coverage of storms across
southeast Wyoming Tuesday as PWATS decrease in the drier air.
For the Panhandle however...their PWATS stay pretty high (over
an inch). May be dealing with marginally severe storms in the
Panhandle Tuesday afternoon.

Maybe better chances for convection Wednesday as ECMWF/GFS/NAM
and SREF all show that surface front surging west back into the
southeast Wyoming plains.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Issued at 235 PM MDT Mon Jul 15 2024

After a brief break from the heat on Tuesday and Wednesday, the
ridge aloft will re-consolidate on Thursday and warm 700-mb
temperatures back up to around +15C over the area. The intensity of
this round of heat is expected to be less than what we just saw over
the weekend. Still, expect above normal temperatures with highs in
the upper 80s to 90s for most of the area. Thunderstorm coverage on
Thursday will be a little less than Wednesday due to lack of
forcing, but dewpoints in the 50s will still linger in the Ne
panhandle and far eastern Wyoming. As a result, still expect PM
shower and storm activity, just with lower coverage. An uptick in
activity is possible on Friday as a shortwave skirts over the top of
the upper level ridge and moves down its eastern flank. The added
lift from the nearby shortwave could enhance storm coverage a bit,
though ensembles differ in handling the strength and proximity of
this system. Generally have PoPs in the 30-50% range across the area
for Friday, which looks like the best chance of the long term
period.

The axis of the upper level ridge over the west responsible for the
recent hot weather will retrograde westward over the weekend,
allowing cooler air to spill into the Plains east of the Rockies.
Temperatures on Saturday and Sunday will be near to slightly below
normal for this time of year as more surface cold fronts are
permitted through our area. Daily chances for afternoon showers and
thunderstorms will continue through the weekend, but it is difficult
to get into the details at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 605 PM MDT Mon Jul 15 2024

The first line of thunderstorms this afternoon will exit the western
Nebraska Panhandle over the next hour. A second round is developing
behind this line across the mountain of southeast Wyoming and is
forecast to impact most terminals between now and 05z, including
western Nebraska later this evening. Activity is expected to weaken
and push east after 05z late this evening.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail in between
thunderstorms. However, brief (Less than an hour) IFR conditions
are possible with these thunderstorms as they move rapidly eastward.
In addition, frequent lightning, small hail, and very gusty winds
are possible until 05z late this evening. Conditions will improve
by midnight (06z).

&&

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

&&

$$

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