523
FXUS65 KRIW 210841
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
241 AM MDT Fri Jun 21 2024

.KEY MESSAGES...

- An isolated shower or thunderstorm before sunrise this
  morning. Precipitation dissipates by the mid morning.

- Another round of showers and thunderstorms develop during the
  late morning becoming widespread and intensifying by the
  early afternoon. A few strong to severe storms will be
  possible this afternoon, especially in parts of Johnson and
  Natrona Counties.

- Hot and dry weather returns for the end of the weekend and
  through much of the upcoming week. Highs may near 100 degrees
  in parts of the CWA by Sunday.

&&

.DISCUSSION...
Issued at 240 AM MDT Fri Jun 21 2024

Showers and thunderstorms continue to develop across the state early
this morning. Convection is expected to remain weak, with some
capable of producing small hail, heavy rain, gusty winds, and
frequent lighting. A few may linger towards sunrise but the majority
will dissipate before than. The week concludes with seasonable
temperatures, partly sunny skies, and the chance for afternoon
showers and thunderstorms.

June has been rather dry across many parts of the Cowboy State with
little to no rainfall in places. The good news is some much needed
moisture looks to make its way into the region today. Unfortunately,
this moisture will come in the form of convective showers and
thunderstorms. Figuring out where convection develops and this
moisture ends up is like throwing a dart at a dartboard with a
blindfold on. So even though we may see some widespread convection
occur this afternoon, there will be places who see little to nothing
and places who see a much needed dose of rain.

This convection is due to a weak shortwave moving across the Inter-
Mountain West today. A strong high pressure over the southeastern
CONUS will funnel gulf moisture into the region. Combine this warm
gulf moisture with the favorable dynamics from the shortwave and you
get widespread showers and thunderstorms. The 06Z SPC convective
outlook has upgraded parts of WY to Slight/Marginal chance for
severe thunderstorms. Parts of Natrona and Johnson counties have a
(50-70%) chance of seeing thunderstorms and will likely be the spot
with the best chance for strong to severe thunderstorm development.
The remainder of the state has a (20-50%) chance of seeing
thunderstorm development but a lower chance of seeing stronger
storms. There are a few things to be concerned about with any strong
to severe storms that do develop. These concerns are small hail
(possibly nearing 1 inch in the strongest storms), strong gusty
winds, frequent lightning, and heavy downpours. There is a small
chance for some flooding to occur depending on the track of the
storms that develop this afternoon. PWAT values are high for this
time of year, ranging from 0.75 to 1.00 inches which is around 150-
200% above normal.

Now to summarize how today looks to play out, a few showers and
thunderstorms linger till around sunrise. During the morning, skies
will remain patchy in areas but the sun will likely break through at
times. High temperatures are forecast to remain slightly below
normal for today. By the mid-late morning, convection is expected to
start developing across the southwestern CWA and gradually move
northeast. Showers and thunderstorms will become more widespread and
likely begin to intensify by the early afternoon. The best chance
for strong to severe storms will be in parts of Natrona and Johnson
Counties during the mid to late afternoon. Most of the convection
will move out of the CWA by the mid to late evening with a few
lingering showers until midnight.

The weekend will see a return of warm and mostly dry weather as a
potent area of high pressure builds back into the region.
Temperatures return to the 80s and even 90s for Saturday with some
of the warmest temperatures arriving by Sunday. Models are showing
parts of the Bighorn and Wind River Basin having a (40-70%) chance
of seeing 95 or higher temperatures. These warm above normal
temperatures are expected to persist through the upcoming week with
many seeing highs of 90+ degrees for much of the week. This trend
towards hot and dry weather really highlights the importance of rain
from the showers and thunderstorms that develop this afternoon, as
we may not see another chance of precipitation for a while. There
will likely be elevated to near critical fire weather conditions as
we head into the end of the weekend and the first half of the
upcoming week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 933 PM MDT Thu Jun 20 2024

Scattered rain showers and thunderstorms have developed in central
Wyoming this evening. These rain showers and thunderstorms will
impact KCPR/KRIW/KLND for a few hours overnight before shifting
north toward KWRL later tonight into Friday morning. Have prevailing
-SHRA and VCTS at KCPR through 07Z/Fri and TEMPO groups with -SHRA
at these other terminals where convection will be more isolated
tonight. Wind direction varies greatly across the area and this will
continue through Friday afternoon.

The main weather system will push through Friday afternoon, which
will lead to widespread convection. Current thinking is convection
will begin developing around 18Z/Fri and travel east, exiting the
area by 02Z/Sat. Thunderstorms will be strong Friday afternoon, with
strong outflow/downdrafts likely (80%) and isolated severe wind
gusts/large hail possible (10-20%), especially near KCPR. Very
little convective activity is expected near KJAC, so only have a
period of VCSH Friday afternoon. At all other terminals there
is a PROB30 group with -TSRA and variable gusty wind. Conditions
will be mostly VFR, but MVFR conditions appear likely (70%) at
times Friday afternoon as showers and storms move through the
area. The strongest storms will be able to drop VIS down to IFR,
especially if they produce hail.

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

&&

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

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Rowe