Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 150521

Area Forecast Discussion
National Weather Service Riverton WY
1121 PM MDT Wed Mar 14 2018

.SHORT TERM...(This evening through Saturday)
Issued at 1239 PM MDT Wed Mar 14 2018

Approaching shortwave and associated cold front will aid in lines of
convection forming over nrn UT and sern ID which will move nwd/nnewd
across far west and sw into this evening, then gradually lifting nwd
into nw and ncntrl WY overnight with increasing shower potential. A
few of the storms in especially the swrn corner could produce some
pea hail (<.5"), gusty wind and brief heavy rain (higher elevation
snow). Some heavier rain showers could fall on the snow in the Star
Valley but temperatures will fall quickly during heavier convection.
Could be 50 at the start and then suddenly fall into the upper 30s
with a rain snow mixture. It`ll definitely be a crazy 6-9 hours with
a little bit of everything possible, thunder, small hail,
accumulating snow with spurts of heavy mtn snow showers, and valley
rain showers mixing with or changing to snow during heavier showers.
Will update the SPS as this seems to cover everything just fine.
Local advisory amounts still possible but not confident on
widespread advisory amounts in the west. Snow levels will start
mainly above 8K but that will lower overnight and during heavier
convective showers. Some concern about a quicker changeover to snow
in the far west valleys, especially the Jackson Valley. Will mention
this in the SPS and have the evening crew watch developments
closely. This swath of showers will lift nwd with the shortwave with
an increasing chance of showers spreading into the Cody Foothills
and Bighorn Basin overnight. We also expect some gusty to strong
south wind as this system lifts nwd overnight, including parts of
Central WY. Some snow showers will persist at times in the west
during the day Thursday. Models have backed off on the amount of
moisture wrapping nwwd around our developing surface (and mid level)
low that moves from nern CO into nwrn KS Thursday night. The end
result in most of the convective pcpn that forms stays east of our
area Thursday night. We still have a weaker shortwave lifting nwd
during the day Thursday with some showers developing east of the
divide. A potential stronger shortwave lifts nwd on Friday with
colder mid level temps and some snow showers. Moisture looks quite
limited with this system so most of the snow showers will likely be
in the higher terrain/mtns on Friday. The main upper low then
approaches the far west by Saturday morning with an increasing
chance of snow once again out west through the day Saturday.

.LONG TERM...(Saturday night through Wednesday)
Issued at 1239 PM MDT Wed Mar 14 2018

The aforementioned upper low will be moving across Wyoming
through Sunday. We still expect some snow and rain across the
area. However, the models continue to have the same issues as
yesterday with placement of the steadiest and heaviest
precipitation. As a result, we are still having difficulty
pinpointing where the heaviest will fall. Sunday night into Monday
will see a decrease in the amount of showers as the low moves into
the Plains with the best chance during these periods across
northern Wyoming. With unstable northwesterly flow though, some
showers will remain possible as the system departs. We should
these gradually come to an end as we head into Monday night.

At this point, Tuesday looks mainly dry with high pressure
building into the area. The GFS at this point looks like it is
overdoing showers across the northwest. The models then diverge a
bit for the middle of next week with the approach of the next
system. The GFS is faster in bring the next Pacific trough and
front in on Wednesday while the European is about 12 to 24 hours
slower. Right now, I am inclined to believe the European more
since the GFS has a nasty habit of bringing Pacific systems in a
day or two too quickly this far out.

.AVIATION...(For the 06Z TAFS through 06Z Friday)
Issued at 1120 PM MDT Wed Mar 14 2018

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

Rain and snow showers will occur overnight. Areas of MVFR and IFR
conditions will occur. Scattered snow showers will continue through
the day Thursday, decreasing to isolated snow showers after 00Z
Friday. Mountains will be frequently obscured through 00Z Fri.

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

Scattered rain showers will occur overnight through 15Z. Then
isolated showers will occur the rest of Thursday into Thursday
night. VFR conditions will prevail at the terminal sites through the


Issued AT 1239 PM MDT Wed Mar 14 2018

The effects of the next spring/winter weather system begin to be
felt west of the Continental Divide this afternoon and evening with
a little everything from rain and snow to thunderstorms with small
hail possible across southwestern Wyoming. 6 to 10 inches of new wet
snowfall will be possible above 8500 feet through the day
Thursday...with rain/snow mixes and much less accumulation below
7500 feet. Cool and showery most locations east of the Divide from
later tonight through Friday. Gustiest winds most probable across
the Wind Corridor from eastern Sweetwater through Natrona Counties
both into this evening and Thursday afternoon again.





LONG TERM...Hattings
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