993
FXUS65 KRIW 281936
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
136 PM MDT Tue May 28 2024

.KEY MESSAGES...

- Another mostly sunny and mild day across the Cowboy State.

- Isolated showers and thunderstorms will be possible over southern/southwestern
  WY this afternoon and evening.

- Wednesday will bring the possibility for scattered showers and thunderstorms
  with a few strong storms possible over parts of Johnson and
  Natrona Counties as well as the Bighorn Basin.

&&

.DISCUSSION...
Issued at 135 PM MDT Tue May 28 2024

Another beautiful late May day across the Cowboy State. Temperatures
will continue to warm today, with highs in parts of the Wind River
and Bighorn Basins having a (60-80%) chance of meeting or exceeding
80 degrees. Other parts of the state will still be warm, with highs
in the 70s. Much of the state will remain dry today with the only
exception being SW/S WY where there is a (10-40%) chance for showers
this afternoon and evening. These showers will create some breezy
winds with gusts of 20-30 mph but much of the CWA will see light
winds through the day. Wednesday sees the warming trend continue
with areas east of the Divide having a (60-90%) chance of seeing
highs at or greater than 80 degrees. These temperatures may create
some river flooding issues due to melting of mountain snow. Many
ranges across the state currently have snowpack values greater than
100%, which may overload rivers depending on how quickly the snow
melts. This is not expected to be a significant concern at the
moment but will need to be monitored over the next week.

Wednesday will see the upper-level ridging be ushered out by a
trough digging across the PACNW. The bulk of the disturbance is
expected to remain to the north of the CWA but a cold front will
begin to sweep across the region during that time. CAMs continue to
show the possibility of some convective showers and thunderstorms
developing ahead of the front. Any storms that do develop look to
initiate off high terrain during the late morning and afternoon.
Some instability will be present with highs in the 70s to low 80s
and dew points in some places being ranging from the mid 30s to low
40s. This combined with steep lapse rates across the region should
create CAPE values of 1000-1500 J/kg. Shear values are lacking
across most of the CWA, meaning storms will pop up then quickly
collapse. Overall, thunderstorms are possible with much of the state
seeing a (20-50%) chance during the late morning and afternoon
Wednesday. A few isolated strong storms cannot be ruled out with the
best chance being across parts of Johnson and Natrona Counties where
the most favorable dynamics may be present. Recent CAMs have begun
to show there being a possibility for an isolated strong
thunderstorm to develop across parts of western WY and especially
the Bighorn Basin. These areas look to have favorable dynamics with
dewpoints near 40 and some shear present through the low to mid
atmosphere. If any strong storms were to develop the main hazards
would be strong gusty outflow winds and small hail.

The cold front sweeps across the state during the evening Wednesday
and early morning hours Thursday. A few isolated showers are
possible across the northern CWA Thursday as the northern shortwave
slowly moves east. Temperatures for the second half of the week
return to seasonable values, with quiet weather returning through
Friday. Models are mostly coming into good agreement regarding the
weekend. The consensus seems to be scattered showers and
thunderstorms possible as a weak shortwave moves through the region.
Most of the CWA looks to remain dry with temperatures returning to
above seasonable values. Ensembles continue to agree on a pretty
large warm-up for the first week of June, with a large potent ridge
moving in over the western CONUS. The magnitude of this ridge and
the warm temperatures that come along with it are still uncertain.
However, early indications are showing possibly some of the warmest
temperatures so far this year. It is starting to look like there
will be a possibility (20-40%) of some areas seeing their first 90
degree temperatures of the year.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1131 AM MDT Tue May 28 2024

VFR conditions will prevail through today. There will be some
isolated convection across southwestern Wyoming this afternoon, but
low confidence on terminal impacts precludes mentioning this at any
of KRKS, KBPI, and KPNA. A leading shortwave from an approaching
trough will lead to some additional shower development after 06Z
tonight, moving northeast overnight. Again, with low confidence on
impacts we will not mention in TAFs for now. Better confidence
exists for shower and thunderstorm development across western
Wyoming late Wednesday morning; this activity will be introduced in
the next TAF period.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Myers