Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 150447

Area Forecast Discussion
National Weather Service Riverton WY
1047 PM MDT Mon May 14 2018

.SHORT TERM...(This evening through Thursday)
Issued at 1253 PM MDT Mon May 14 2018

Cool mid levels, warming temps and several disturbances around our
pesky upper low to the sw is aiding in showers and thunderstorms
across the area. A few storms with hail up 1/2-3/4 inch and heavy
rain will be a possibility into the early evening, especially in
the sern/ern portions. On Tuesday, the mid levels warm 1-2C with
less instability to work with. However, there is a vort lobe that
rotates nwd out of our upper low over NV which impacts the swrn
portion where the best instability is expected (due to cooler mid
levels). So a few decent tstms may occur in the sw/wcntrl areas
Tue aftn. Limited chances east of the divide. A few showers may
linger into the early morning hours in the nw as this shortwave
lifts nwd. The remnant low itself finally lifts nwd and then gets
absorbed into the new upper low which replaces it over NV on
Thursday. This system is currently near 32N/148W. On Wednesday,
the best instability is in the far west, especially wcntrl/nw
areas where slightly cooler mid level temps exist. In addition
several weak disturbances are expected to move ne from the upper
low across the area increasing the shower/tstm risk in the
afternoon thru evening. One other area of potential instability
and convergence is over nrn Johnson County where a weak boundary
drops swd for increased convergence and instability. It will also
likely be the warmest day of the period as heights build east of
the divide. On Thursday, as the new upper low moves into the Great
Basin, we see increasing QG forcing and decent instability for a
decent shot of showers and tstms in the west. But even east of the
divide, there is some instability and a weak boundary to aid in
convection in the central to nern areas. Things get more unsettled
beyond this period. More on that below.

.LONG TERM...(Thursday night through Monday) Issued at 1253 PM
MDT Mon May 14 2018

The upper level trough in the Western US will slowly push towards WY
Thursday night and become very disorganized Friday morning. As it is
disorganized I do not expect overly strong winds with this system
but widespread showers and isolated thunderstorms will occur during
the day Friday. saturday morning GFS and the Canadian indicate a low
forming over North CO/South WY. This will continue shower and
thunderstorm activity in the FA and it will cause gusty northeast
winds in the wind corridor from Lincoln County to the Green
Mountains. Temperatures will drop a little but not significantly.
As the low moves away from the area Sunday, winds will decrease
but spotty shower activity will continue through the afternoon.
Monday will see much dryer weather and temperatures returning to
the 70s.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday)
Issued at 1045 PM MDT Mon May 14 2018

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

VFR conditions to prevail through the period. Isolated showers will
end by 12Z. Patchy fog with local IFR conditions are possible in the
western valleys until 15Z. Scattered showers and thunderstorms will
develop after 18Z in the west and occur through 05Z. Local MVFR
conditions will occur with the thunderstorms. Mountains will be
obscured at times. The shower activity will decrease after 06Z Wed.

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

VFR conditions to prevail through the period. Isolated showers will
end by 09Z. Isolated showers and thunderstorms will develop after
19Z, mainly over and near the mountains. Local MVFR conditions will
occur with thunderstorms. The activity will decrease after 04Z with
any lingering showers ending around 06Z. Mountains will be obscured
at times.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.


Issued AT 1253 PM MDT Mon May 14 2018

Scattered showers and isolated thunderstorm will continue into the
evening hours before gradually decreasing and ending in most areas.
A warming trend will continue through Wednesday with min rh`s
dropping into the 20s east of the divide and in the upper teens by
Wednesday in eastern 279. Scattered showers and thunderstorms will
develop again in mainly in southwest WY late Tuesday morning and
spread northward through the day. Only isolated showers and
thunderstorms are possible east of the divide and mainly in and near
the mountains/higher terrain. Later in the week, a new potentially
wet storm system will first spread into the west later Thursday into
Thursday night and then spread east of the divide Friday through





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