Jackson, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

280
FXUS65 KRIW 202329
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
529 PM MDT Fri Sep 20 2024

.KEY MESSAGES...

- Breezy today, with elevated fire weather for portions of
  central Wyoming. A cold front moves through late today. A
  cool north to northeast wind follows.

- Saturday is much cooler, with a gusty northeast wind for the
  Wind Corridor and Sweetwater County. Patchy frost is possible
  Sunday morning for low-lying or cold prone areas.

- A quick moving system Monday brings a north wind and low rain chances.

- Warm-up for the latter half of next week, with little to no
  rain chances.

&&

.DISCUSSION...
Issued at 1226 PM MDT Fri Sep 20 2024

In the middle of high pressure over Texas and low pressure up in
Canada, today should be a fairly typical mid-September day. West to
southwest flow today brings a breezy afternoon, with gusts 10 to 20
mph for much of the area. The Wind Corridor, from roughly South Pass
to Casper, is a bit windier in this favored direction, with
afternoon gusts up to near 30 mph. High temperatures are the warm
side today, with the high pressure having a greater influence.
Temperatures in the mid-60s to mid-70s occur west of the Continental
Divide, with mid-70s to low 80s east of the Divide.

There are some fire weather concerns this afternoon and early
evening. The gusty winds of the Wind Corridor, in addition to the
drier air, brings elevated to critical fire weather to portions of
the area. Red Flag Warnings are in effect to cover this.

A cold front drops down from the north late this afternoon through
the overnight hours. The main impact from this will be a breezy
north wind and cooler temperatures. Starting with the wind, north
wind prone locations, such as the Bighorn Basin and Johnson County,
could see gusts up to 35 mph through about sunrise Saturday. A few
high-resolution models are developing very light rain showers with
the front. These would mainly be over Yellowstone National Park, the
northern Absaroka range, and the northern half of the Bighorn Basin.
If lucky, a hundredth of liquid may fall, but expect a few drops at
most, if a shower does pass over. Have kept chances mainly 15% or
lower, with some spotty 30% chances for Yellowstone into the
Absarokas.

Post-front Saturday features a cool northeast wind. Highs peak in
the 60s for most of area. An approaching low pressure system to the
south will aid in bringing a gusty northeast wind to the Wind
Corridor, and especially Sweetwater County, starting Saturday
morning. Gusts increase, with speeds of 30 to 35 mph by the
afternoon. These winds decrease into the night. That low to the
south remains out of the CWA as it tracks eastward. A very isolated
(15%) shower is possible over far southeast Sweetwater and Natrona
Counties late Saturday afternoon and through about sunrise Sunday.
Models continue to reduce these chances, however.

Sunday morning will likely be the coldest morning in at least the
next week. The focus for the colder temperatures is lower elevations
east of the Divide - places that haven`t seen growing season ending
temperatures yet. Overall, not looking at widespread freezes (32F or
less), but morning temperatures in the middle to upper 30s look to
be widespread. Models are hinting at the potential for a few colder
locations, such as near Worland and Casper, where temperatures near,
or less than, 32F could occur (about 40% chance based on NBM, but
less than 10% based on HREF). The takeaway here is that widespread
freezes are not expected, but there could be some patchy frost areas
for a few locations, and low-lying areas. For the day Sunday,
relatively light winds, with no precipitation chances. Highs will
climb a little bit, but are still seasonal.

A trough quickly sweeps down through the state Monday. Models are
still in disagreement on the strength of this system, though would
likely bring a breezy north wind, with low precipitation chances.
This system exits the area for Tuesday, which looks dry as high
pressure begins to build in. Temperatures are on the warm side for
the second half of the workweek, with little to no rain chances.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 529 PM MDT Fri Sep 20 2024

All terminals remain VFR through 00Z/Sunday. A shortwave over
Montana continues an eastward trek this evening and pushes a
cold front south through areas east of the Continental Divide by
06Z/Saturday. Gusty westerly wind ends early this evening, but
passage of the cold front leads to northerly wind 10-20kts
spreading from north-to-south between 02Z-08Z/Saturday. The
front does make it to KRKS around 08Z/Saturday, but fails to
reach other western terminals.

The pressure gradient tightens Saturday afternoon as an upper-
level low begins to eject northeast from the Desert Southwest.
KRKS should see a steady increase in east-northeast wind during
the day Saturday, with gusts 25 to 35 kt by mid afternoon.

&&

.FIRE WEATHER...
Issued at 1226 PM MDT Fri Sep 20 2024

Elevated to critical fire weather conditions today across fire zones
280, 281, 289, and 300. A southwest wind increases this afternoon,
with gusts 25 to 30 mph. Areas of critical RHs occur through this
evening, with values around 15%. A cold front passes through this
evening and overnight, bringing a north to northeast wind and cooler
temperatures.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for WYZ280-281-
289-300.

&&

$$

DISCUSSION...Wittmann
AVIATION...CNJ/VandenBoogart
FIRE WEATHER...Wittmann