Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 151925
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
125 PM MDT Wed Aug 15 2018

.SHORT TERM...This evening through Thursday

Currently, the exiting circulation appears to be over the South
Dakota/Wyoming border. This low and asct trough will continue to
exit east into the Northern Plains this evening with confluent
flow behind it. Good radiational cooling is anticipated tonight
under clear skies, except for the smoke. Several valley locations
plummeted into the mid and upper 20s early this morning, so we
should see similar readings tonight in YNP as well as other
favored cold spots like Bondurant. Thursday will feature a warming
trend by about 5 degrees for high temps east of the Divide with
areas west remaining roughly the same for highs. Once the ridge
axis shifts off to the east later Thursday, some instability and
moisture will begin to make its way into the far southwest reaches
of our CWA for isolated afternoon thunderstorms in Southern
Lincoln/Southwest Sweetwater Counties.

.LONG TERM...Thursday night through Wednesday

A trough and cold front will approach the area on Friday. The
models have continued with the trend of a slower progression. As
a result, most of the area will remain dry through the day Friday.
Precipitation will break out across the front over E ID, which
will continue as the front progresses eastward over W WY through
the overnight hours. Isolated to scattered showers will occur
east of the Divide by 12Z Saturday. As the front exits the
forecast area Saturday afternoon, isolated to scattered showers
and thunderstorms will continue east of the Divide, including
Yellowstone.

Precipitation will end from NW to SE Saturday night, as the upper
low moves over the Central Plains. NW flow and drier air aloft
will keep conditions dry Sunday. Another system moving south from
Canada could begin to impact northern portions by Monday
afternoon. The cold front associated with this system looks to be
squeezed between a ridge trying to build northward from the Four
Corners region and a separate upper low over OR/CA. For now, it
looks like this front will only impact eastern portions
(Johnson/Natrona counties). However, isolated to scattered
afternoon and evening thunderstorms will occur over the area, as
shortwaves from the SW move over the area. Isolated thunderstorms
will be possible Tuesday, especially over northern and western
portions, as the remnants of the OR/CA upper low move over the
region. Conditions look to be dry Wednesday, in the wake of this
remnant low.

Friday will be the warmest day of the period, with pleasant
temperatures Saturday through Monday. Readings will be at or
slightly below normal across the area through these days, before
retuning to normal by Wednesday.

&&

.AVIATION...For the 00Z TAFS through 00Z Friday

Smoke may increase in thickness tonight. Otherwise, mainly SKC
conditions will prevail across the area with some lower VFR
visibilities in smoke/haze through 00z Friday. Isolated
thunderstorms are possible in far Southwest Wyoming after 21Z
Thursday.

&&

.FIRE WEATHER...

|...RED FLAG WARNING IN EFFECT FOR SOUTHWESTERN WYOMING THROUGH
EARLY THIS EVENING INCLUDING ZONES 277, 278, 279, AND 414.

The combination of relative humidity falling to around 10 percent
and a gusty westerly breeze will continue to bring critical fire
conditions across much of southwestern Wyoming through early this
evening. Wind should remain light to moderate outside of the Red
Flag warning area. Mixing and smoke dispersal will range from fair
in some of the northern basins to excellent across southern Wyoming.
Lighter winds are expected Thursday, but low RH is expected to
continue. A few isolated thunderstorms are possible in zone 277 late
Thursday afternoon.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ277>279-414.

&&

$$

SHORT TERM...Lipson
LONG TERM...LaVoie
AVIATION...Lipson
FIRE WEATHER...Lipson


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