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Latest ZFP from WFO RIW
	
National Weather Service Local Forecast for Star Valley Ranch
Updated: Thu Apr 25 12:29 pm MT

This Afternoon... Showers and possibly a thunderstorm.  High
near 52. West wind around 7 mph.  Chance of precipitation is 80%. New
rainfall amounts between a tenth and quarter of an inch, except higher
amounts possible in thunderstorms. 

Tonight... Scattered rain showers before midnight, then a
slight chance of rain and snow showers after 5am. Some thunder is also
possible.  Mostly cloudy, with a low around 33. West wind around 6 mph
becoming east southeast after midnight.  Chance of precipitation is
50%. Little or no snow accumulation expected. 

Friday... A slight chance of rain and snow showers before 9am,
then rain showers likely. Some thunder is also possible.  Mostly
cloudy, with a high near 52. Southeast wind around 6 mph becoming
northwest in the afternoon.  Chance of precipitation is 70%. Little or
no snow accumulation expected. 

Friday Night... Showers and possibly a thunderstorm.  Low
around 38. North northeast wind around 7 mph.  Chance of precipitation
is 80%.

Saturday... Showers, with thunderstorms also possible after
noon.  High near 50. Northeast wind around 6 mph becoming west in the
afternoon.  Chance of precipitation is 90%.

Saturday Night... Showers likely and possibly a thunderstorm. 
Mostly cloudy, with a low around 36. Southwest wind around 6 mph. 
Chance of precipitation is 60%.

Sunday... A chance of showers, with thunderstorms also possible
after noon.  Mostly cloudy, with a high near 47. West wind 6 to 11
mph.  Chance of precipitation is 50%.

Sunday Night... Mostly cloudy, with a low around 34.

Monday... A chance of rain and snow showers before 7am, then
rain showers likely. Some thunder is also possible.  Partly sunny,
with a high near 50. Breezy.  Chance of precipitation is 60%.

Monday Night... A 30 percent chance of showers before midnight.
 Partly cloudy, with a low around 31. Breezy. 

Tuesday... A slight chance of rain and snow showers.  Mostly
sunny, with a high near 54. Breezy. 

Tuesday Night... Partly cloudy, with a low around 34.

Wednesday... A slight chance of showers.  Mostly sunny, with a
high near 63.

	

Latest AFD from WFO RIW
	
370 
FXUS65 KRIW 251908
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
108 PM MDT Thu Apr 25 2024

.KEY MESSAGES...

- More widely scattered rain showers and isolated thunderstorms
  this afternoon and evening. 

- Main system pushes through Friday night and into the weekend
  with ample mountain snow and low valley rain. 

- Warming trend and mainly dry next work week with another
  system late week and into the following weekend. 

&&

.DISCUSSION...
Issued at 1236 PM MDT Thu Apr 25 2024

IR currently depicts the deep trough over the western CONUS with
cooling cloud tops through the CWA advecting in from the
southwest. Radar shows a much more sporadic day ahead with
widely scattered rain showers and some isolated thunderstorms.
This will continue through the afternoon and early evening hours
before subsiding with radiational cooling and the eventual FROPA
of a cool front. This is pushing into northwestern portions of
the state and will slowly move southeast throughout the
remainder of the day. Temperatures behind it are not much cooler
around 10 degrees from yesterday, but more seasonable in the
days ahead over the weekend. 

With these rain showers and thunderstorms, there is enough
instability of DCAPE to see some gustier outflows for southern
counties and those east of the Divide from Wind River Basin to
the I-25 corridor. Updraft is not strong enough to see any type
of hail growth or potential for anything severe at this time. 
The prone area with the best potential will be well east of the 
CWA into far reaches of the state in eastern Wyoming and points 
southeastward. Otherwise, a decent rain fall, even for the 
higher terrain expected for the rest of today with the better 
bullseye further east from Casper to Buffalo dependent on where
any showers/storms entrain upon one another. 

This first initial shortwave off the main low coming in from 
the Pacific northwest overnight into much of Friday. Initial 
waves of snowfall to the higher terrain of the Absarokas and 
Bighorns expected by mid afternoon spreading to the Winds by the
evening. Fairly slow moving over the weekend, substantial 
snowfall expected with the Winds the highest amounts up to 1.5 
to 2 feet with other ranges up to a foot possible. The better 
dynamics and 700mb trough orientation looks to set up off the 
Absarokas to the Winds with the highest probabilities over 18 
inches of 80-90 percent. Over 12 inches with a 60-70 percent 
probability elsewhere at this time. Regardless, winter 
highlights have been issued to cover these ranges. Minor 
accumulations with little to no impacts with the warmer 
temperatures for lower areas west of the Divide.

Liquid precipitation is expected for the lower valleys east of
the Divide where the southern counties to be the possible
winners for the weekend. All areas need the moisture, but
especially this area. However, a minor flooding impact is
possible and something to keep an eye on where up to an inch is
possible. QPF amounts have come down as expected being a more
progressive than expected system. Less than half an inch for
other points to include the Wind River and Bighorn Basins, as
well as along the I-25 corridor. Confidence on the liquid
precipitation amounts are not as high as the snow, being more 
of medium confidence at this time as models are not in great 
agreement with one another.

Beyond the weekend, expect a warming trend and mainly dry
conditions for next work week as upper level ridging builds in
with increasing convergence aloft. Back to above average
temperatures and some windier days ahead for next week but
hopefully this overall system's QPF amounts helps to alleviate
any fire weather concerns in the more long term. Beyond that,
long term models and outlooks show another GOA low pushing down
that could affect the CWA by next weekend hopefully to bring in
more of the much needed moisture. 

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1128 AM MDT Thu Apr 25 2024

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals.

Terminals to generally remain VFR through the forecast period. 
Extensive cloud cover, with brief MVFR ceilings, over northwest 
Wyoming late this morning should hinder destabilization around KJAC 
this afternoon. As a result, have opted to avoid any TS mention at 
KJAC. However to the south where sunshine has been prevalent this 
morning, showers and a few thunderstorms were already erupting at 
17Z/Thursday. This convection should move northeast through the 
southwest terminals between 20Z-23Z. Brief MVFR is possible along 
with erratic gusts 25-35kts. Mid-cloud decks remain overnight, 
although there is a 30-50 percent chance of MVFR ceilings at KJAC 
between 06Z-12Z/Friday. Mountain tops frequently obscured.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals.

The first round of showers and isolated thunderstorms is lifting 
into northern Wyoming late Thursday morning. Clearing behind this 
wave will allow for destabilization and redevelopment of scattered 
showers and isolated thunderstorms by mid-afternoon. Additional 
convection over southwest Wyoming moves into the region late in the 
afternoon. Have generally opted for short TS TEMPO groups between 
about 22Z-02Z with erratic wind gusts 25-35kts the primary hazard. 
Lingering light showers persist until 06Z/Friday. Mid-cloud decks 
give way to lowering MVFR ceilings at KCOD around 10Z and eventually 
KWRL at 14Z as northerly surface flow strengthens. Other terminals 
to remain VFR through 12Z/Friday with possible localized MVFR after 
14Z. Mountain tops frequently obscured after 10Z/Friday. 

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 from noon Friday to 3 PM MDT Saturday 
for WYZ002.

Winter Weather Advisory from 3 PM Friday to 6 PM MDT Saturday 
for WYZ008-009.

Winter Storm Warning from 6 PM Friday to 9 PM MDT Saturday for 
WYZ015.

&&

$$

DISCUSSION...Lowe
AVIATION...Jones

	

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