926
FXUS65 KRIW 142151
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
351 PM MDT Sun Jul 14 2024

.KEY MESSAGES...

- Sunday afternoon and evening convection again has the
  potential to generate outflow wind gusts of 35 to 55 mph,
  although increasing moisture will lead to more rain-producing
  convection.

- Northerly near-surface wind flow tonight and Monday morning
  allows smoke to filter as far south as central Wyoming,
  especially along the Interstate 25 corridor in Johnson and
  Natrona Counties.

- Temperatures cool to seasonal averages Monday and Tuesday giving
  relief from the recent hot temperatures.

- Typical summertime diurnal convection is anticipated through
  the coming week.

&&

.DISCUSSION...
Issued at 121 PM MDT Sun Jul 14 2024

Water vapor imagery depicts moisture from the southwest pushing
into and then eastward across Wyoming early Sunday afternoon.
Cloud cover waned over the central and southwest during the late
morning allowing for better surface heating and the development
of convection over the higher terrain. This convection is
beginning to move off the mountains and into the basins. A dry
sub-cloud base layer will again generate gusty outflow wind of
35 to 45 mph. However, surface dew points have crept up so rain
will reach the ground with the stronger showers and storms. The
greatest temperature-dew point spreads will be across the high
southwest deserts where outflow gusts of 45 to 55 mph are
possible.

Drier mid-level air reaches the southwest Sunday evening leading
to a decrease in coverage in that region prior to sunset.
Shortwave energy over northern Nevada early Sunday afternoon is
eventually caught up in westerly flow aloft and makes a right
turn toward Wyoming tonight. While convection intensity and
coverage diminishes around sunset, this shortwave and weak jet
energy along the northern border enables at least isolated light
showers to prevail over the northern-third of the forecast
area tonight. A stronger shortwave over southern Canada tracks
east late tonight and Monday morning causing near-surface flow
on the backside to switch to the north along and east of the
Continental Divide. Wildfire smoke that has been plaguing
locations to our north Sunday should filter into northern and
central Wyoming. As a result, Johnson and Natrona Counties could
see reduced visibilities Monday morning before afternoon mixing
improves smoke dispersal.

The active northern stream flattens a dominant Four Corners high,
which elongates over the southwest US to begin the week. Heights
fall accordingly, and the aforementioned northerly push provides
cooler, more seasonal temperatures across the forecast area Monday.
Weakly cyclonic west-northwest flow and a persistent stream of mid-
level moisture combine to generate more widespread showers and
thunderstorms Monday afternoon and evening. The strongest storms
would be in Johnson and Natrona Counties where instability and shear
are greatest. These areas are highlighted in the SPC Day 2
Convective Outlook. The loss of solar heating brings an end to the
convection Monday evening, with only a few lingering light showers
around the Bighorns overnight. The only wind of consequence will be
15 to 25 mph west to northwest afternoon breezes over the southwest-
quarter of the state.

Seasonal temperatures continue Tuesday and Wednesday within west to
northwest flow aloft. Mid-level moisture favors typical diurnal
convection, with coverage greatest on Tuesday. The Four Corners
high begins to amplify north toward the Northern Rockies
Wednesday and builds through the remainder of the week.
Temperatures climb to above seasonal averages, but not as warm
as the heat at the end of this past week. Ensemble clusters
generally show the high retrograding to the Desert Southwest by
next weekend. This may cut-off the primary southerly flow of
moisture, but blended model solutions seem to favor a dirty
ridge. Thus, the trend of summertime diurnal convection
persists.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 351 PM MDT Sun Jul 14 2024

Showers and thunderstorms diminish most places this evening. Models
are indicating convection lasting longest at KCOD and KWRL, through
about 06Z/Mon at KCOD and 09Z/Mon at KWRL. KJAC may also see nearby
convection through that time, though is more likely to end closer to
04Z. Any outflow with these lingering shower/thunderstorms could
bring variable gusts 30 to 40 knots.

Winds become lighter overnight, before increasing again Monday
afternoon due to diurnal heating and thunderstorm outflows. Showers
and thunderstorms are once again possible Monday afternoon, with
gusty outflow being the main concern.

Smoke continues, mainly across the northern half of the area. VFR
conditions are expected to remain for all terminals, though some
mountain obscuration continues.

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

&&

.FIRE WEATHER...
Issued at 121 PM MDT Sun Jul 14 2024

Above normal Sunday afternoon temperatures combined with low
relative humidity and the potential for gusty outflow wind from
convection leads to continued elevated to near-critical fire weather
conditions, especially in Zone 280. Scattered showers and
storms through early Sunday evening will also produce rainfall,
although wetting rain would be scarce. Scattered showers and
thunderstorms ignite again Monday afternoon, with a 30 percent
chance of wetting rain in the Absaroka and Wind River Mountains.
Increasing dew points and cooler temperatures Monday and
Tuesday lead to higher relative humidity both days along with
improved overnight recovery.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM MDT this evening for WYZ004>006-010-
011-017-018-020.

&&

$$

DISCUSSION...CNJ
AVIATION...Wittmann
FIRE WEATHER...CNJ