Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 132006
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
206 PM MDT Wed Mar 13 2024

.KEY MESSAGES...

- Snow will spread across much of the area today, with the
  heaviest snow expected tonight.

- Gusty to strong wind will accompany the snow at times,
  bringing difficult travel conditions.

- Quieter weather returns for Friday, with warming temperatures
  early next week.

&&

.DISCUSSION...
Issued at 233 AM MDT Wed Mar 13 2024

Things look like the are lining up for a decent snowstorm across
portions of the area. Things are quiet right now but radar is
showing snow loading up in Montana and this will dropping southward
into the area through the morning and afternoon as a cold front
moves southward through the area. And for the most part, reasoning
remains the same as yesterday. We have high confidence in time of
maximum impact, medium confidence in timing and low confidence in
snowfall amounts, although those huge ranges have shrunk somewhat
this morning.

The main drivers continue to be the cold front, an upper level low
dropping southward from Idaho into the Great Basin and lee
cyclogenesis that will occur over Colorado with low pressure moving
into the Plains states. The main driver to the location of the
snowfall amounts will be the northeasterly upslope flow. The upslope
northeast to east flow is fairly deep as well, ranging all the way
up to 500 mb. This will result in a good fetch of moisture moving
into the area. And places favored by this flow, like Lander and
Casper Mountain as well as the east slopes of the Wind River Range
look to be the most effected. To a lesser extent this is also for
the Bighorns. For the most part, snowfall amounts did not change
much. So, we left highlights for the most part as is. There were a
couple of things to consider though. The first was the Bighorns,
amounts increased somewhat. We thought about warnings but since the
areas with those amounts account for less than 10 percent of the
area, we stuck with advisories. We thought about an advisory for
Johnson County as amounts have increased, However, much of the snow
here would fall before 7 pm, aka when the strong March sun is out.
This, plus the borderline temperatures and warm ground, should keep
roads mainly wet. So, no advisories here as well. A small part of
southern Johnson has advisory amounts, but again this accounts for
less than 10 percent of the area. In addition, other areas will have
borderline temperatures and may mix with rain at times during the
day, again, limiting travel impacts somewhat.

The maximum impact still looks to be tonight as the snow gets
enhanced by a bit of a jet streak rotating into the area. We could
see snowfall rates over an inch an hour at times, with the best
chance of seeing this from western Natrona through Fremont County as
well as Sweetwater County. Models have come into somewhat better
agreement in ending the steadier snow Thursday morning. Some snow
showers will linger into Thursday night, but placement of these are
all over the place.

The other concern is wind. The wind will first hit in the favored
northwest flow / cold advection areas up north like Buffalo and
Greybull. High wind is not expected, but it will get gusty. The
stronger wind then shifts southward into central Wyoming tonight.
The strongest wind will be across Sweetwater County, especially on
Thursday with a tight pressure gradient between high pressure over
the Pacific northwest and the deepening low in the southern plains.
There is a 1 in 2 chance of wind gusts of 50 mph in this area
on Thursday. IF there is one saving thing, it is that the
heaviest snow will be over and the snow will be wetter, limiting
blowing snow somewhat. It will still not be any fun to travel
there on Thursday though.

Quieter weather should move in for Friday,although temperatures
will average around 10 degrees below normal. The recent model runs
have started to keep the potential weekend system east of Wyoming
now. We have kept some slight POPs as a hedge, but it does not look
like a major system. Dry weather looks to dominate the weather early
next week as ridging builds across the northern Rockies.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 156 PM MDT Wed Mar 13 2024

Scattered snow showers will continue through the day. This will
bring periods of MVFR to IFR conditions through Thursday
morning, especially across terminals east of the Divide.
Conditions will begin to improve toward the end of the period as
snow coverage decreases. Otherwise, wind will increase from
north to south late this afternoon through Thursday morning.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Thursday for WYZ008-009-
017-020.

Winter Storm Warning until noon MDT Thursday for WYZ015-018-
019-022.

Winter Weather Advisory from 6 PM this evening to noon MDT
Thursday for WYZ028>030.

&&

$$

DISCUSSION...Hattings
AVIATION...Myers


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