316
FXUS65 KRIW 181827
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1227 PM MDT Wed Sep 18 2024

.KEY MESSAGES...

- Windy this afternoon, with lighter winds returning for Thursday.

- Light rain and mountain snow continues this afternoon,
  decreasing this evening and overnight.

- Thursday is dry, with slightly warmer temperatures.

- The next weather system comes this weekend. Most of its
  impacts remain outside the area, but cooler temperatures and
  isolated rain is possible.

&&

.DISCUSSION...
Issued at 1226 PM MDT Wed Sep 18 2024

Current satellite shows an occluding low pressure system, centered
over eastern Montana. Its influence today keeps cool temperatures
and gusty winds. The main impacts from it decrease starting mid-
afternoon through the overnight hours.

A tight pressure gradient keeps strong west to southwest winds this
afternoon. Gusts ranging from 20 to 70 mph continue across the area.
Recent model trends show that these winds should begin to decrease
after 3pm MDT this afternoon. Winds should be less than 20 mph by
midnight, with the exception of the higher elevations, which
continue to gust through Thursday morning. Wrap around moisture
keeps precipitation falling across northwest and northern Wyoming as
well. This should remain light. Snow levels are mostly above 10000
feet, but some areas are as low as 9000 feet. Precipitation
decreases through the afternoon, with some lingering showers lasting
until Thursday morning. All precipitation should be done by sunrise
Thursday. High temperatures remain on the cool side today, with 50s
to 60s west of the Divide, and 60s to low 70s east.

As the low exits the area, Thursday is much calmer with the winds.
Most areas are 10 mph or less. The Wind Corridor gets afternoon
gusts to around 20 mph. Otherwise, no precipitation is expected,
with high temperatures peaking a little warmer than today. Friday,
temperatures are a little higher. Some moisture could bring very
isolated (20%) showers to northwest and north Wyoming.

An upper-level low tracks into the Four Corner area Saturday. Most
of its influence should remain south and southeast of the area
through the weekend. That being said, temperatures decrease, with
highs returning to below seasonal values. No widespread
precipitation is expected given the current model tracks, but some
isolated (15% to 30%) showers could occur. These would be favored
for southeastern locations of the area.

Past this weekend, ensemble models are bringing in a ridge by the
middle of next week. This would favor warmer and drier conditions to
end the month.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1126 AM MDT Wed Sep 18 2024

Cloud cover and areas of light rain have been wrapping into
northwest and northern Wyoming Wednesday morning within counter-
clockwise flow around an upper-level low over Montana. Also, gusty
southwest surface wind 30G50kts has plagued KCPR and similar speeds
are likely to prevail there through about 22Z/Wednesday before
slowly decreasing by 02Z/Thursday. The counter-clockwise flow
leads to gusty westerly surface wind 15-30kts until around
01Z/Thursday at most other terminals, with 10-20kt winds
lingering longest at KRIW in favored west-northwest flow. As
for precipitation, KJAC will continue to flirt with MVFR/VFR
threshold of 030AGL through mid-afternoon, with VFR likely to
prevail after 21Z/Wednesday. All other terminals to be VFR.
Scattered light rain showers remain favored at KJAC in west-
northwest flow until 03Z/Thursday. KWRL has a less than 30
percent chance of seeing a brief light rain shower from 21Z-
24Z/Wednesday. Other terminals to remain dry. Cloud cover
gradually dissipates and ceilings rise from south to north
tonight. Any lingering light showers decrease between
06Z-12Z/Thursday.

Mountain tops frequently obscured above 10K feet MSL until
06Z/Thursday across the northwest quadrant of Wyoming.

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...
High Wind Warning until 4 PM MDT this afternoon for WYZ003-019-
020.

&&

$$

DISCUSSION...Wittmann
AVIATION...CNJ