Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 191908
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
108 PM MDT Fri Oct 19 2018

.SHORT TERM...This evening through Saturday

Quiet period of weather continues in the forecast tonight and
Saturday. A ridge of high pressure will be in place over the PACNW
and the Canadian Rockies this afternoon. The cold front, associated
with the clipper system, moved through the area earlier this
morning. Apart from gusty northwesterly winds at Buffalo and an area
of SCT to BKN mid level clouds from Sheridan to Judith Gap, there
was little fanfare. Afternoon temperatures will remain several
degrees cooler today, as a result of the cold front. By Saturday,
the high center moves over central ID/SW MT. This will allow 700mb
temperatures to warm to +5 to +7C over the Cowboy State, which in
turn will bring afternoon temperatures back to the lower to middle
60s. Readings in the lower 70s will be possible from Thermopolis
to Greybull, as well as southern portions of Johnson County.
Clear skies and generally light winds will also continue across
the area tonight and Saturday. A cutoff low will begin to form
tonight into Saturday along the CA coast. The remnants of this
feature could bring the next chance of precipitation (mainly west
of the Divide) by Monday.

.LONG TERM...Saturday night through Friday night

Saturday night through Sunday will see continued fair weather as the
ridge overhead slowly weakens. The upper low is still forecast to be
over central CA/western NV Monday and then gradually drift northeast
over us into Tuesday night/Wednesday morning before finally
dying/exiting stage right. Shower chances will increase in the far
west by Monday afternoon, especially in the mountains. Shower and
possible isolated tstms will peak in the west on Tuesday as what`s left
of the cold core moves in.

As the remnants of this upper low swing east of the divide, a few
showers will likely pop up but the best chance will be over the
mountains and higher terrain. Mid level temps are still quite mild
(+2 to +3C at H7) so temps will be cooler than what we`ll see over
the weekend but still not bad for late October with 50s across the
lower elevations and even some lower 60s east of the divide.
Depending on the exact timing, a few showers may linger into
Wednesday across the mountains but otherwise, just some lingering
clouds and still mild with 50s to lower 60s across the lower
elevations and 40s in the mountains. Brief shortwave ridging is
possible Thursday ahead of a fast moving system that will likely
impact us on Friday.

Models are still struggling with this system and how much of an
impact it will have on us. The GFS 5-wave is holding a mean ridge
over us through the week. It`s weaker by Friday but still a mean
ridge. The most likely scenario is for a strong jet move across MT
with most of the energy well to the north. The Euro is now keeping
most of the energy to the north much like the GFS. The Canadian is
currently bringing activity furthest south, impacting both sides of
the divide by Friday afternoon. We could still see some light
rain/snow showers in the mountains up north but not looking great
for pcpn chances further south or across the lower elevations (per
GFS). We will probably see a cold front impact the north and far ern
zones by Friday night. Besides the strong to possible high winds in
the Cody Foothills Friday, the wind corridor and most mountain
locations will also see increasing wind Friday with some 40-50kt H7
winds developing.

&&

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

VFR conditions will occur through the period. Wind speeds are
expected to be less than 12 knots at the terminal sites.


&&

.FIRE WEATHER...

Dry conditions, clear skies and light winds will continue through
the weekend. Temperatures Saturday will be similar to Thursday, with
above normal readings returning through the weekend. Isolated
showers could be possible for areas west of the Divide by Monday.

&&

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

$$

SHORT TERM...LaVoie
LONG TERM...Hulme/Skrbac
AVIATION...LaVoie
FIRE WEATHER...LaVoie


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