Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 141658
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1058 AM MDT Sat Apr 14 2018

.SHORT TERM...Saturday through Monday night

The persistent low that brought the snow and wind of the past few
days as now moved into away to the east with mainly quiet conditions
across the area right. And for most of the area, this will be the
rule with sunshine mixing with high clouds and temperatures
remaining below normal. It will feel warmer however since there will
be MUCH less wind than previous days. And I say most since a weak
shortwave will move into northwestern Wyoming and bring a few rain
and snow showers this afternoon and evening. The system is a fast
mover and does not have a ton of moisture to work with so amounts
will likely remain light. We kept areas East of the Divide dry
since the models like do overdue precipitation over the Big Horn
Range. Sunday looks similar with another wave moving into the
western mountains with some showers while areas East of the Divide
remain dry. The difference will be temperatures will average about
10 degrees warmer than on Saturday with a few more clouds. It will
be breezy at times, but nothing really unusual for April in Wyoming.

On Monday, the weather looks to take a more active turn as a more
potent Pacific system moves in from the west. There are still some
differences in timing however. Most of the time, the models tend to
move systems in too fast. So it would not surprise me if the system
comes in slower than is now indicated. Nevertheless, almost all of
the precipitation would hold West of the Divide until after
midnight, with the new European keeping things dry until Tuesday.
The main story East of the Divide will be wind. With 700 millibar
winds reaching 50 knots at 700 millibars, there is the chance of
high winds in some locations. This combined with warm temperatures
with the southwest flow and low humidity could elevate fire danger
on Monday afternoon. Stay tuned.

.LONG TERM...Tuesday through Saturday

A cold front should quickly exit the area Tuesday morning. High
temperatures will be 20+ degrees colder than what occurred Monday.
In wake of the cold front, enough instability and moisture will be
present for continued chances of snow showers throughout the day.
The precipitation could be mixed with rain in the lower elevations,
but 700 mb, and thickness levels suggest mainly snow.

Dry and slightly below average temperatures are expected Wednesday
as a transitory ridge pulls across the area.

On Thursday/Thursday night, medium range models show an upper low
digging into the Desert Southwest, and then into the Four Corners
area on Friday before pulling into the central High Plains Friday
night/Saturday. Models continue to struggle on the details this
far out. Currently, this track would favor the central/southern
areas of the forecast area around Friday as moisture is wrapped
around the main system with an easterly/northeasterly upslope
conditions trying develop. The ECMWF is suggesting a mainly snow
event with the precipitation late Thursday night/Friday, while the
GFS is showing rain changing to snow with the bulk of the
precipitation Friday/Friday night. If the ECMWF timing is correct,
the forecasted high temperatures Friday will have to drastically
lowered by later shifts.

&&

.AVIATION...18Z Issuance

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

VFR conditions will prevail through the forecast period.

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

VFR conditions will occur at most terminal sites, except KJAC,
through the period. Snow showers will develop in the NW WY mountains
after 21Z and continue through 12Z Sunday. Expect some mountain
obscuration to continue from this afternoon through the end of the
forecast period. Additionally, isolated to widely scattered rain and
snow showers will occur across the lower elevations, including KJAC,
of NW WY from this afternoon into Sunday morning.

Please see the Aviation Weather Center for the latest information on
icing and turbulence forecasts.

&&

.FIRE WEATHER...

Today will be a somewhat warmer day with mainly dry conditions East
of the Divide. A weak disturbance will move into the western
mountains and bring some afternoon and evening rain and snow
showers. All areas will see less wind that yesterday. Relative
humidity will remain above critical levels. Mixing and smoke
dispersal will range from fair to poor in the basins to good to very
good across Sweetwater County.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...Hattings
LONG TERM...Murrell
AVIATION...Braun
FIRE WEATHER...Hattings



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