620
FXUS65 KCYS 110459
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1059 PM MDT Sat Aug 10 2024

.KEY MESSAGES...

- Scattered to numerous thunderstorms in multiple rounds are
  expected across the area this afternoon and evening. Storms
  will have the potential to produce heavy rainfall, gusty
  winds, and isolated large hail.

- Expecting a gradual warmup through the week returning to near
  normal temps and daily chances for afternoon and evening
  showers and thunderstorms continuing.

&&

.MESOSCALE...
Issued at 221 PM MDT Sat Aug 10 2024

Isolated to scattered showers and thunderstorms have initiated
across portions of south and southeast WY early this afternoon.
Surface-based CAPE of 500-1500 J/kg has been created due to the
morning sunshine in WY, with the lower amounts across NE due to
the lingering low clouds in that region. A couple of strong
storms had wind gusts of 40-60+ mph shortly after 18Z through
20Z. Steep lapse rates in the low and mid-levels of 6.5 to 9.5
degrees C/km combined with 40-55 knots of 0-6km effective bulk
shear should allow for any additional storms remain organized.
DCAPE of 600-1100 J/kg across our cwa should also support strong
wind gusts through early this evening. Hi-res guidance depicts
the potential for a line segment to develop later this afternoon
and evening, but confidence in this occurring is slightly lower
due to the stable atmosphere in the NE Panhandle from the low
clouds through almost 18Z. With the afternoon insolation, this
should increase surface CAPE to assist with atmospheric
destabilization. Overall, a couple more severe thunderstorms
may be possible through this evening before the chances of
thunderstorms/convection dissipate near sunset.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 330 AM MDT Sat Aug 10 2024

The cool weather pattern is starting to break across the area, but
moisture remains plentiful. Current satellite imagery shows thinning
cloud cover across the area as the latest vort-max in the series
impacting the region over the last several days shifts east into
central Nebraska. As the high cloud cover moves out, this reveals
the lingering low cloud deck over the High Plains. Low clouds
are thinner and have less coverage this morning than the
previous several mornings. Cloud cover is expected to break by
midday for the vast majority of the forecast area, opening the
door for more sunshine and thus destabilization today. Forecast
soundings show the inversion mixing out leaving sufficient
moisture and instability to support scattered to numerous
showers and thunderstorms fueled by yet another vort-max passing
over the area aligned fairly well with peak heating.
Precipitable water around 1 to 1.5 sigma above normal along with
modestly steep lapse rates and sufficient vertical wind shear
will lead to a threat for isolated strong to severe storms.
While the main concern will be locally heavy rainfall, a few
storms will have the potential to produce strong gusty winds and
isolated large hail. The storm potential will also drag well
into the evening with modest isentropic lift continuing to kick
off shower and storm activity ahead of a more substantial upper
level shortwave traversing the northern Rockies. Showers and
thunderstorms are likely to continue overnight, winding down by
around 12z Sunday morning.

This more substantial shortwave will not be timed as well Sunday for
shower and thunderstorm activity. The axis passing through the area
Sunday morning will leave modest synoptic descent over a good
portion of the area during peak heating on Sunday. Moreover, drier
air in the wake of this will spill into Carbon and Albany counties,
and probably nudge the dryline just east of I-25 during the daytime
hours. The dryline`s eastward push may be able to kick off a few
showers and thunderstorms that could overcome the synoptic descent.
These storms may be operating in a fairly potent environment if they
manage to develop, but coverage should be considerably lower than
Saturday. Thus, we`ll be looking at a conditional threat for severe
weather Sunday, with only isolated storms expected but those that
manage to develop may be more likely to become strong to severe.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 330 AM MDT Sat Aug 10 2024

An active extended forecast period for southeast Wyoming and the
western Nebraska Panhandle w/ numerous mid and upper-level short
wave disturbances embedded within quasi-zonal flow aloft. Expect
daily chances for showers and thunderstorms as several pieces of
energy continue to emanate from the slow moving parent trough in
the Pacific Northwest. Multiple rounds of strong/severe thunder-
storms appear possible given substantial low-level moisture with
dew points in the 50s and 60s and occasional mid-level jet maxes
contributing to adequate deep layer vertical shear for organized
storms. Still too early to determine any specifics of which days
may feature a more organized severe risk as this will be heavily
dependent on the eventual timing of individual waves. Otherwise,
expect temperatures to be near seasonal norms with daytime highs
mainly in the 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 1059 PM MDT Sat Aug 10 2024

Scattered showers and thunderstorms will continue overnight across
the area. Light to moderate rain is expected, which could briefly
drop visibility down to MVFR criteria. Low stratus is also likely
with southeasterly flow overnight. IFR CIGs will be possible,
mainly at KSNY and KAIA. MVFR CIGs will be possible around KCYS
and potentially KBFF and KCDR. Expect an isolated storm or two,
mainly in the Nebraska panhandle during the afternoon.

&&

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

&&

$$

MESOSCALE...BW
SHORT TERM...MN
LONG TERM...CLH
AVIATION...SF