Area Forecast Discussion
Issued by NWS Riverton, WY

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406
FXUS65 KRIW 250920
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
320 AM MDT SUN SEP 25 2016

.SHORT TERM...Today through Tuesday night

Imagery shows deep amplified upper trof now located from the south
Canadian Plains, through the western Dakotas, south through Colorado
and on to AZ/NM boundary. Upper ridging following and building
across the western CONUS. Surface has occluded cyclone over ND and
moving quickly northeastward into Canada. High pressure now
building into WY from the west.

Through the forecast period: With the upper trof now east of the FA
and the surface cyclone well off to the northeast over ND, rather
deep high pressure will envelop WY through most of the forecast
period with no significant weather occurring and clouds even hard to
come by. This pattern will also keep winds relatively light and
fire danger low.

.LONG TERM...Wednesday through Sunday

Wednesday looks dry for the region. The models bring moisture into
southwest WY Wed afternoon into Wed night. Will add isolated
showers and storms into parts of SW WY Wed night. The models still
keep the moisture flowing into WY on Thursday as a weak weather
system moves into the area. Isolated to scattered showers with
some thunderstorms around as well. Most of the activity will be in
the west, south, and the mountains. However, any other place could
see a shower or storm. The showers and storms linger into Thurs
night and should end by midnight. A southwest flow aloft develops
Friday and continues through Sunday as a trough forms along the
west coast. Weather disturbances will swing northeast toward WY
during this period. Timing these disturbances is the challenge
this far out. Will maintain the chance of showers and storms in
the west zones each day with isolated activity east of the divide.
A cold front will push into northwest WY Saturday and across the
rest of the area Sat evening or early Sunday morning. Mild high
temps Wed through Fri then cooler over the west Saturday. Cooler
all areas on Sunday.

&&

.AVIATION.../12Z ISSUANCE/

As the upper level low moves to the NE into the northern Dakotas
this morning, clearing has begun from west to east across the
area, and showers have essentially dissipated except for light
activity around the Bighorn mountains. These light showers should
finish up by 14Z with the mountains remaining obscured. Wind has
also decreased this evening and should remain light overnight. Fog
is likely to develop or continue in some locations due to recent
precipitation and clearing skies, continuing through mid morning.
Locations not certain though, so VCFG has been included in
forecast for some TAF sites. Other than possible fog for MVFR to
IFR conditions, VFR conditions are expected for the next 24 to 30
hours. Later today will bring continued scattered mid level
ceilings to northern WY in NW flow. Some gusts over 15 knots are
possible with west wind across southern WY this afternoon.

&&

.FIRE WEATHER...

Fire danger low all areas today...lasting through the work week.
Upper level ridging and surface high pressure will combine to
provide very stable conditions over the forecast area for the next
several days...with no rainfall, sunny/clear skies and relatively
light winds. The next chance for isolated to widely scattered
precipitation will not arrive until next Thursday...and even then
will likely only be available to the mountains.

&&

.RIW Watches/Warnings/Advisories...None.

&&

$$

SHORT TERM...Braun
LONG TERM...AR
AVIATION...McDonald
FIRE WEATHER...Braun



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