687
FXUS65 KRIW 161731
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1131 AM MDT Tue Jul 16 2024

.KEY MESSAGES...

- Seasonable temperatures across the Cowboy State today with isolated
  showers and thunderstorms possible this afternoon.

- Gusty outflows of 30-40+ mph will be possible once again
  nearby any developing storms.

- Near seasonable temperatures and daily chance for afternoon showers
  and thunderstorms look to continue through the remainder of
  the week.

&&

.DISCUSSION...
Issued at 245 AM MDT Tue Jul 16 2024

Yesterday was quite the eventful and unsettled day across the Cowboy
State, especially in parts of Fremont and Natrona Counties.
Widespread showers and thunderstorms developed during the early
afternoon. A robust storm moved through the central CWA starting in
Lander and moving all the way into Casper. Severe wind gusts were
recorded in Lander with the airport recording a gust of 66 mph. This
storm produced widespread strong wind gusts of 55+ mph which led to
some downed trees and power lines in parts of Fremont County.
Fortunately, things are looking much quieter this morning with a few
lingering weak showers moving through parts of the CWA. Similar to
yesterday temperatures are expected to be warm but seasonable with
highs in the low to upper 80s and highs in the low 90s across parts
of the Bighorn Basin. Showers and thunderstorms are possible once
again this afternoon but are expected to be more isolated in nature
and remaining mainly across central and western parts of the CWA.

A weakening area of high pressure will continue to retreat to the
south for the first half of the week. This is largely due to a
longwave trough digging across the central CONUS, bringing with it
an active northern stream that aids in suppressing the high to the
south. As a result of this shift, westerly/northwesterly flow is
expected to develop, which will aid in funneling moist pacific air
into the region. PWAT values are forecast to remain above normal
over the next few days with amounts ranging from 0.75 to 1.00
inches. This flow combined with daytime heating and Pacific moisture
will create daily chances for showers and thunderstorms. The main
concern with any convection will be strong gusty outflows and brief
heavy downpours. Soundings for today are showing a drier overall
profile compared to Monday with a lower dewpoint depression. This
means that some storms may be capable of producing outflow winds but
weaker in nature compared to yesterday. Storms will likely be able
to produce isolated outflows of 30 to 40 mph with a few gusts near
50 mph possible. One thing to monitor will be upper steering flow
today as models are indicating a rather stagnant flow. This would
lead to storms stalling over one place or moving very slowly. Due to
the above normal PWAT values there is some concern for heavy
downpours over a brief period of time in the locations where storms
develop. CAM`s are showing most of the convection being limited to
the high elevation mountain ranges in the central and western part
of the CWA. There are some models showing these storms being able to
move off the mountains but due to the drier sounding profiles,
storms will likely weaken quickly over lower elevations. Overall,
showers and thunderstorms are possible this afternoon but will be
more isolated and restricted mainly to higher elevations. This does
not mean some lower elevations will not see a shower or two. The
best chance for showers in the lower elevations look to be along the
eastern slopes of the Wind River Range, western valleys, and the
Green River Basin. Precipitation chances in these locations range
from 20-40%. Thunderstorms are looking very isolated, with the areas
mentioned before having the best chance of seeing some with a 10-30%
chance. The majority of the CWA will likely remain dry today but
there is still the concern for some strong outflow winds developing
from the storms over the higher elevations. Showers and
thunderstorms will gradually dissipate by the evening with a few
lingering showers possible into the early morning Wednesday.

Due to the suppression of the high to the south and the development
of the potent northerly stream, unsettled weather is expected to
occur daily through the Wednesday. Pacific moisture along with
westerly/northwesterly flow will create daily chances for afternoon
showers and thunderstorms. Temperatures will also remain around
seasonable values with highs in the 80s to low 90s. The second half
of the week still has a lot of uncertainty as models differ on the
possible outcomes. Models are starting to lean towards the high
south of the region being pushed west over the Great Basin for the
second half of the week. This will leave Wyoming sandwiched in
between a large upper level low over the Hudson Bay and the upper
level high along the West Coast. Overall, temperatures look to
remain warm but still around seasonable values. Unsettled weather
will prevail through the remainder of the week with daily chances of
afternoon showers and thunderstorms.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1130 AM MDT Tue Jul 16 2024

An axis of upper-level high pressure remains just to the west
of Wyoming today, keeping warm, yet somewhat moist and unstable
air over the area. Mostly clear skies during the morning are
giving way to convective development by noon, with thunderstorms
starting over the eastern slopes of the Wind Rivers and Wyoming
range. Convection will focus today over west-central WY into the
Wind River Basin and southern Absarokas, and extend down to
Sweetwater County. Not as certain at KJAC but have included
vicinity showers in case some storms move around that airspace.
Winds are generally light, though thunderstorm outflows could
exceed 30 kts. As such, VFR conditions generally expected, with
brief MVFR is storms directly impact terminals. Showers are
expected to linger in the early evening hours, especially at
KPNA and KLND around the Wind Rivers. Winds will decrease
overnight, though skies should remain partly cloudy for some
areas. A couple of forecast models are indicating an area of
light showers early Wednesday morning over northwest WY,
possibly bringing some rain to KCOD around sunrise.

The high pressure axis shifts slightly eastward on Wednesday
which should bring showers and thunderstorms to areas along and
east of the divide. SW WY should remain mostly dry, though can`t
rule out an isolated storm or two. WNW winds will continue over
SW WY, while east of the divide will see NE to E winds Wed
afternoon, with stronger ENE winds pushing southwestward into
KRKS Wed evening.

Finally, smoke concentrations are increasing over the area due
to regional fires, but not yet enough to reduce visibilities at
the TAF sites. Will continue to monitor and adjust forecasts as
necessary.

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...
Air Quality Alert until 1 PM MDT this afternoon for WYZ010-023-
024-027.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...McDonald