Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 180005
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
605 PM MDT Sun Mar 17 2024

.KEY MESSAGES...

- High Pressure will keep very quiet weather over the region
  through the middle of the week.

- Mild temperatures will begin to melt low-land snowpack, but
  concern for ice jam/snowmelt flooding is low at this time.

- The ridge starts to break down late in the week, with
  increasing chances for precipitation towards next weekend.

&&

.DISCUSSION...
Issued at 1246 PM MDT Sun Mar 17 2024

As the Rex Block becomes fully established today, areas east of the
Divide will remain under the influence of a weak boundary associated
with a trough axis digging across the Great Lakes region this
afternoon. In light northeast flow, mid-level Cu and strato-cu will
exist across most areas east of the Divide this afternoon as a
result. Models over the past few days had indicated that there may
be some light showers or virga showers with this boundary, but even
the wet-bias high-res models (such as the NAMNest) have mostly
removed any precipitation chances, although a few light rain/snow
showers are still possible (< 20% chance) across the Bighorn
Mountains during the afternoon.

By sunset, PoPs drop to 0% across the region and winds become light
and variable. Skies also clear through the night. The aforementioned
Rex Block will then keep the first half of the work week mild and
sunny with light winds. The Bighorn Basin and eastern Johnson County
will see temps near the 70F mark both Monday and Tuesday while other
east of the Divide Basins approach the 60s. West of the Divide,
highs will be in the upper 40s to low 50s. The warm temps will begin
to melt some of the low-land snowpack (and even foothill snowpack).
East of the Divide, persistent mild temps over the past month or so
have led most of the main-stem rivers, as well as many of the
tributaries, to be ice free. With the exception of near Lander and
the surrounding foothills, low-land snowpack is mostly absent east
of the Divide as well. Thus, flooding or ice jamming is not likely
(<10% chance) east of the Divide. West of the Divide however, there
is an increased risk of overland snowmelt and possibly minor
flooding due to the mild temperatures during the day, especially as
temps increase to near 50F. However, the cool nighttime temps (low
to mid 20s) should limit this threat and confidence is low (less
than 20%) for any flooding.

The Rex Block will begin to breakdown Wednesday and especially by
Thursday. As expected, models continue to slow this breakdown, and
thus, delay any precip chances. The first precip chances will come
Wednesday night across the north, associated with a weak shortwave.
Precipitation chances and associated QPF remain low at this time.
This shortwave will, however, act to further breakdown the ridge a
messy zonal flow pattern looks to develop through the weekend.
Confidence remains low regarding any details on this pattern
change.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 604 PM MDT Sun Mar 17 2024

VFR conditions expected for all TAF sites throughout the period.
Relatively light winds and a few to scattered mid level clouds
through the afternoon and evening. Increasing upper level clouds by
12Z ahead of a weak, subtle shortwave that will pass the CWA to the
north. Winds will also increase at CPR with gusts up to 25kts after
15Z with the aforementioned shortwave coupled with daytime heating
and mixing to the surface through the afternoon heating hours.
Otherwise, dry conditions 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 icing and turbulence forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Hensley
AVIATION...Lowe


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