777
FXUS65 KRIW 162050
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
250 PM MDT Fri Aug 16 2024

.KEY MESSAGES...

- Elevated to critical fire weather conditions through sunset
  this evening for portions of central and southern Wyoming.

- Monsoonal moisture returns west of the Divide tomorrow
  afternoon, with scattered afternoon showers and thunderstorms
  expected Saturday through Monday.

- Temperatures about 5 degrees above seasonal averages through
  the weekend.

- No major weather systems or weather pattern changes through
  the end of next week.

&&

.DISCUSSION...
Issued at 246 PM MDT Fri Aug 16 2024

The jet streak that caused some overnight and morning showers
and weak thunderstorms is slowly moving northeast and out of the
state this afternoon. Isolated precipitation currently over the
Bighorn Basin, Bighorn Mountains, and Johnson County will soon
move out of the area, leading to mostly clear skies and minimal
precipitation this evening through mid-day tomorrow.

Afternoon mixing will bring mid-atmosphere breezes down to the
surface across southern Wyoming, and combined with the dry air
mass in place, fire weather conditions will be critical, leading
to a Red Flag Warning for portions of the state through 8 PM
MDT this evening.

The large-scale upper-level ridge will amplify over the
weekend, bringing warmer temperatures to the region, but no
exceptional heat is forecast. The southwesterly jet stream will
remain just west of Wyoming, and vorticity maxima moving through
the flow are likely to cause enhanced periods of lift and
increased shower and thunderstorms activity, especially west of
the Continental Divide starting Saturday afternoon. Moisture in
this flow pattern will be monsoonal in nature with high PW, so
the stronger storms could cause brief heavy rain (less than 10%
chance for any given location) and isolated flash flooding,
especially over southwestern Wyoming where soils are slow to
absorb incoming moisture. WPC highlights this same threat,
showing a Marginal Risk for excessive rainfall over the Saturday
through Monday timeframe.

The weather pattern changes little in the Tuesday through
Friday timeframe. A trough over the Pacific Northwest will keep
southwesterly flow in place over Wyoming, and isolated to
scattered afternoon thunderstorms will be commonplace.
Temperatures fluctuate between near normal and about 5 degrees
above normal for the work week. A larger and more impactful
trough looks to edge into Wyoming next weekend, but details on
this system are still of very low confidence.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1032 AM MDT Fri Aug 16 2024

VFR conditions are expected for the entirety of the TAF period.
Some gusty winds at RKS and CPR with the stronger gradient to
the south for these areas. Some mid level clouds to the north
with low confidence storms on station at COD and WRL between
21-23Z with initiation. TEMPO groups are carried here with the
isolated nature of these storms that will completely push
northeast by the next cycle run. Otherwise, light winds and
clearing skies overnight and into the rest of the period with no
other weather elements expected at this time.

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 246 PM MDT Fri Aug 16 2024

Relative humidity in the lower to mid teens and winds gusting
20 to 30 mph will bring critical fire weather to portions of
Sweetwater, Fremont, and Natrona Counties this afternoon and
evening. Red Flag Warnings are in effect through sunset for the
driest and breeziest locations. Elsewhere, winds will likely be
lighter and RHs above critical thresholds. No thunderstorms are
expected this afternoon or evening for the Red Flag Warning
area.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ279-289.

&&

$$

DISCUSSION...VandenBoogart
AVIATION...Lowe
FIRE WEATHER...VandenBoogart