771
FXUS65 KCYS 070750
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
150 AM MDT Mon Jul 7 2025

.KEY MESSAGES...

- There is an Enhanced Risk (Level 3 of 5) for severe weather
  today across portions of western Nebraska. All modes of severe
  weather are possible today: large hail, damaging winds, and
  tornadoes.

- Hot temperatures and dry conditions return Tuesday, limiting
  precipitation chances across the CWA.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 148 AM MDT Mon Jul 7 2025

Fairly quiet across the region once again tonight as skies slowly
clear on the backside of afternoon and evening convection. Some low
stratus is attempting to develop across southwestern Laramie County
as of 07Z. Winds are fairly gusty at Cheyenne at this time, with
southerly winds gusting around 25mph. Breezy conditions are ongoing
across much of the area, with locations in the southern Panhandle
gusting around 25mph and portions of southeast Wyoming gusting
around 20mph. Temperatures are mild with current temperatures in the
mid-50s to mid-60s across the CWA.

Another active severe weather day is expected this afternoon into
the evening hours, especially across western Nebraska where SPC has
highlighted a portion of the CWA in an Enhanced Risk (Level 3 of 5)
for severe weather. A very similar setup is expected today across
the region, with westerly flow remaining in place aloft. The CWA
remains sandwiched between a trough moving across southern Canada to
the north and a ridge moving northward across the southern CONUS.
The 500mb high over the southern CONUS will slowly meander northward
towards the Four Corners Region, potentially signaling the start of
the monsoon. Prior to this, however, several 500mb vorticity maxima
will eject out around the high and traverse across the CWA this
afternoon. One especially strong vorticity maxima will provide
enough CVA that a 500mb shortwave develops and slides across this
region this afternoon, starting between noon and 3pm. This shortwave
and the induced shortwave at 700mb, will be the primary forcing
mechanisms again today, along with the terrain-induced dryline
surging eastward during the afternoon hours. Ahead of the surging
dryline, southerly to southeasterly winds will keep dewpoint values
in the mid-50s to low-60s this morning into the afternoon hours.
Surface temperatures will rise into the mid-80s to low-90s again
with daytime heating allowing for daytime destabilization. A weak
backdoor cold front will drop down into the region this evening from
South Dakota, likely increasing lift and leading to thunderstorm
activity later into the night. Storm motion looks to be a bit faster
than previous days as a 500mb jet streak develops and winds in the
mid-levels increase to around 50kts. 700mb flow remains weak once
more, though winds should be around 20 to 25kts at 700mb, slightly
better than the 15 to 20kts of the previous days.

Current HRRR runs suggest around 1800 to 2000J of SBCAPE this
afternoon across the Panhandle, with the highest values on a line
from Chadron south through Sidney. 0-6km Bulk Shear is progged to be
a little lower with forecast soundings from the HRRR and RAP
suggesting only around 30 to 40kts of bulk shear across the
Panhandle. However, ample low-level turning is expected with 0-3km
SRH values in the 100 to 120 range. 0-1km SRH remains low again,
only around 25 to 35 in the northern Panhandle. The southern
Panhandle boasts 0-1km SRH values around 50 to 75, suggesting a
better environment for tornadoes across the southern Panhandle.
Steep mid-level lapse rates across the region once again favor large
hail, especially with a rather fat CAPE profile in the -10C to -30C
hail growth range. Strong winds will also be favored a forecast
soundings from the RAP and HRRR suggest around 1500 to 1700J of
DCAPE, all with strong lapse rates throughout much of the
atmosphere. Despite all of this, there is one featuring appearing on
several forecast soundings that may result in convective inhibition
remaining in place and prevent storms from forming. Several forecast
soundings from the RAP suggest a warm nose around 1km above the
surface, which would increase CIN significantly and potentially
prevent storms from forming. The HRRR on the other hand does not
have this warm nose, with steep lapse rates from the surface
throughout much of the atmosphere. This potential warm nose will
need to be monitored throughout the morning and afternoon hours as
it could prevent convective initiation if it does show up in the
late morning to early afternoon hours.

The upper-level ridge across the southern CONUS will advect
northward as the 500mb high moves over the Four Corners Region on
Tuesday. With multiple vorticity maxima ejecting out from the high
into the CWA, afternoon showers and thunderstorms will once again be
possible. However, forcing will be much weaker Tuesday, leading to
storms likely struggling to develop. Temperatures will soar into the
mid-80s to mid-90s across the entire CWA Tuesday, leading to a hot,
dry day across the CWA. Breezy conditions are possible out west of
the Laramie Range, leading to continued elevated fire weather
conditions across Carbon and Albany Counties Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 207 PM MDT Sun Jul 6 2025

The upper level ridge over the Four Corners states will amplify for
the middle part of the upcoming week. On Tuesday, 500-mb heights
will climb close to the 90th percentile of climatology as the ridge
strengthens. Expect highs to reach the mid 80s to mid 90s across the
area. The surface dryline will nudge off to the east Tuesday, but
not move completely out of the area. Current model guidance shows
the dryline setting up near the WY/NE state line Tuesday afternoon,
with ample moisture still present in the Nebraska panhandle despite
drier air moving in aloft. There will be somewhat of a capping
inversion in place once again, but a weak vort-max moving over the
top of the ridge may be able to kick off isolated thunderstorms in
far eastern Wyoming and into western Nebraska. Expect coverage to be
much more limited, but we probably won`t be completely in the clear.

The dryline will nudge further east on Wednesday as the magnitude of
the heat reaches its peak. 700-mb temperatures will climb close to
+18 to +20C, with the highest values over south central Wyoming.
Ensemble mean 700-mb temperatures are around the 90th percentile of
climatology. Considering this is the climatological hottest time of
the year, record highs are fairly unlikely at this time, but hotter
scenarios would put a few daily record highs in jeopardy. With drier
air over most of the area, expect PM thunderstorm activity to be
more limited, and likely confined to our far eastern zones. The next
shortwave trough will move in from the west on Thursday, adding a
bit more moisture aloft and cooling temperatures down by several
degrees. PM storm activity may be more in the form of gusty high-
based showers and thunderstorms as low levels look to remain on the
dry side. A potent surface front will move through late Thursday or
early Friday, leaving much cooler and more moist conditions in place
for Friday. This may suppress instability too much over much of the
High Plains, but scattered PM showers and thunderstorms may still be
possible against the higher terrain as the surface front pushes
against it. Temperatures will begin to rebound on Saturday, with
continued chances for scattered PM shower and thunderstorm
activity.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1037 PM MDT Sun Jul 6 2025

Outside of isolated showers moving west to east across the area
through 07Z, expecting a relatively calm overnight period. With
a moist boundary layer in place across the plains along with
south-southeasterly upslope flow, pockets of MVFR stratus will
likely develop after 05Z. Conditions will improve after sunrise.
A cold front moving south across the area late morning through
the afternoon will shift winds to the north-northeast and spark
another round of showers and thunderstorms for the plains
terminals after 20Z.

&&

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

&&

$$

SHORT TERM...AM
LONG TERM...MN
AVIATION...WFOCYS