692
FXUS65 KRIW 151943
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
143 PM MDT Mon Jul 15 2024

.KEY MESSAGES...

- Scattered thunderstorms will produce brief heavy rain and
  gusty outflow wind of 35 to 45 mph through early Monday
  evening.

- A secondary surge of northerly surface wind arrives Tuesday
  afternoon and evening. This will allow wildfire smoke to
  increase along the Interstate 25 corridor in Johnson and
  Natrona Counties. Oregon wildfire smoke will reach western
  Wyoming tonight and Tuesday.

- Temperatures at or just above seasonal averages along with
  typical diurnal convection prevails much of the period.

&&

.DISCUSSION...
Issued at 143 PM MDT Mon Jul 15 2024

Scattered convection is ongoing as of 130 PM Monday across western
and central Wyoming. The strongest storms and greatest areal coverage
is across southwest Wyoming where a lack of cloud cover earlier
today has allowed for better destabilization as mid-level lapse
rates are ranging from 8-9C/km. Further destabilization is
expected across central Wyoming through mid-afternoon as solar
radiation has increased the past few hours. With precipitable
water values topping 0.80 inches, these storms will be producing
rain Monday afternoon and early evening. Temperature-dew point
spreads favor wind gusts 35 to 45 mph with the stronger
convection. CAMS show most of the stronger storms relegated to
locations over Natrona and eastern Sweetwater Counties by 5-6
PM. Showers and isolated storms eventually develop over
northcentral Wyoming late this afternoon. This activity tracks
east-southeast through the evening, lingering longest in
Natrona County. To the west, drier westerly flow aloft brings an
earlier end to the convection this evening. However, western
wildfire smoke, mainly from Oregon, is likely to filter into
the region in this flow regime.

Tuesday finds enough lingering mid-level moisture to trigger
convection around midday. Orographics favor the Absaroka and Wind
River Mountains for the best coverage Tuesday afternoon. Drier west-
northwest flow aloft should limit convection in the basins east of
the Continental Divide.  Surface high pressure dropping south
through the Northern Plains provides a secondary surge of northerly
surface wind east of the Divide Tuesday afternoon. Wildfire smoke
from southern Montana fires is likely to make a push farther south
into central Wyoming along the Interstate 25 corridor in Johnson and
Natrona Counties given this wind direction. Temperatures will
be around seasonal normals with the exception of cooler readings
in Johnson County. The north to northeast wind reaches
Sweetwater County and points westward Tuesday evening, but
speeds will generally be only 10 to 15 mph. Convection decreases
in coverage early Tuesday evening leaving a clearing sky and
seasonal temperatures overnight.

The remainder of the week finds a building ridge across the Great
Basin, which retrogrades closer to the West Coast late in the
forecast period. For the most part, temperatures at or just above
seasonal averages prevail through next weekend. Enough mid-level
moisture remains trapped under the ridge to keep isolated/scattered
diurnal convection in the forecast through at least Friday. As the
ridge retrogrades, Wyoming may end up in northerly flow aloft with
any southerly moisture surge possibly being tempered. Therefore,
next weekend may end up a bit drier.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1145 AM MDT Mon Jul 15 2024

With slightly above normal atmospheric moisture and moderate
instability, scattered to widespread showers and thunderstorms
are expected this afternoon across the entire forecast area. The
primary threats are brief heavy rain and gusty outflow over 40
kts. Some of the storms in central WY (KCPR-KBYG) may become
stronger and also produce hail over one inch. For the most part,
the convection will end before sunset with lingering showers
possible from west-central WY toward east-central WY. VFR
conditions are generally expected, though MVFR conditions are
likely if showers/thunderstorms move directly over or near TAF
sites. Some mid-level clouds will remain overnight and move
southward before sunrise. As the storm-producing weather system
moves eastward, some northerly flow will move into sites east
of the divide and increase Tuesday afternoon. WNW winds will
increase west of the divide. Isolated showers and thunderstorms
are expected over the southern Absarokas and Wind Rivers and
other mountain areas during the afternoon with sites across
central and southern WY the most likely to see isolated storms.

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 Tuesday for WYZ010-023-024-
027.

&&

$$

DISCUSSION...CNJ
AVIATION...McDonald