500
FXUS65 KCYS 192340
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
541 PM MDT Fri Jul 19 2024

.KEY MESSAGES...

- Severe weather is possible today as a cold front moves across
  the region. Damaging winds and isolated large hail are
  possible as the cold front moves through. Cooler temperatures
  for Saturday.

- Cooler weather expected this weekend into Monday ahead of a
  gradual warming trend to above average temperatures through
  next week.

&&

.MESOSCALE /THROUGH TONIGHT/...
Issued at 221 PM MDT Fri Jul 19 2024

Widespread thundershowers have popped up across portions of
southeast WY the past 1-2 hrs as we see sufficient daytime heating
ans surface convergence displayed well via satellite and radar.
Northwest flow aloft is providing weak steering flow at H7. Surface
temperatures range from the middle 80s to lower 90s for most of the
eastern tier of our cwa, with slightly cooler temperatures along the
I-80 corridor between the I-80 Summit and Rawlins. As of 20Z,
sub-severe thunderstorm activity remains ahead of the cold
front. SPC Mesoanalysis has low-level and mid-level lapse rates
8-10 degrees C/km. MLCAPE readings as of 20Z are 1000-1500 J/kg
for areas east of the Laramie Range where peak heating has
assisted with making the environment conditionally unstable.
Effective bulk wind shear is meager...20-30 knots from 0-6km.
Short term hi-res model data continues to suggest that we will
see convection through the 2z-3z hour for most of the cwa, and
then it will push further south. Can`t rule out an isolated
severe thunderstorm this afternoon to the early evening. The
strongest threat looks to be a marginal potential for strong
wind gusts via straightline winds from thunderstorm outflow. The
cold front should arrive much later this evening, and those
outdoors will see a much cooler weather pattern behind the
FROPA.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Issued at 221 PM MDT Fri Jul 19 2024

The models are in pretty good agreement in showing the upper
level ridge building over the area through mid week. This will
essentially strengthen the cap as the week wears on and limit
the convection chances. The precipitable water values are
progged to be closer to 1 inch on Monday over the Nebraska
panhandle while the rest of the CWA will be less than an inch.
NBM probabilities are showing CAPE values 500 j/kg or less over
the Nebraska panhandle. If we can get enough instability over
the the Laramie Range and Pine Ridge, we may be able to spark
some isolated convection with the main threat being gusty winds.
As we head into mid week, the WPC clusters are showing the upper
level ridge dominating the area which will limit any convection
development. Was tempted to lower pops over the higher terrain
during this timeframe, but will hold things off for now and see
how the ridge materializes. We did raise temperatures a bit
towards the end of the week which is when the models are trying
to flatten the ridge a bit which may enhance the downslope flow.
In addition, the flattening of the ridge will also tend to
increase the precipitation chances as we head into next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 540 PM MDT Fri Jul 19 2024

Northwest flow aloft will continue.

Wyoming TAFS...Scattered to broken clouds from 6000 to 10000 feet
will prevail, with occasional thunderstorms until 02Z, producing
wind gusts to 35 knots and visibilities to 5 miles. Outside of
thunderstorms, winds will gust to 25 knots until 02Z, and to
22 knots at Rawlins and Cheyenne after 18Z Saturday.

Nebraska TAFS...Scattered to broken clouds from 8000 to 10000 feet
will prevail, with occasional thunderstorms until 02Z, producing
wind gusts of 35 to 45 knots along with visibilities from 3 to 5
miles. Outside of thunderstorms, winds will gust to 25 knots until
02Z.

&&

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

&&

$$

SHORT TERM...BW
LONG TERM...REC
AVIATION...RUBIN