Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 212119
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
315 PM MDT Mon Aug 21 2017

.SHORT TERM...Tonight through Thursday

Now that the eclipse has passed...it was spectacular with the high
clouds moving away about 10 minutes before totality, perfect timing.
As I said, now back to the regularly scheduled weather. And through
tonight and most of tomorrow, things look relatively quiet. Just
about all areas look dry through tonight. And for tomorrow, expect
more of the same. A bit of moisture may begin to creep in from the
south on Tuesday afternoon and may touch off a couple of
thunderstorms, but these would likely be restricted to south of
Interstate 80 as well as few and far between. Temperatures will
remain rather warm but not hot, generally running lightly above
normal for most locations.

By Wednesday and Thursday, some monsoonal moisture will begin
returning to the area this will mean an increase in clouds as well
as an increase in coverage of showers and thunderstorms. With the
additional kick of an weak approaching shortwave, a few of
thunderstorms may become a bit stronger with the usual chance of
small hail, gusty winds and locally heavy rain. Humidity will also
increase a bit and help with fire conditions a bit. With the
increased cloud cover, expect high temperatures to average 3 to 5
degrees cooler than on Tuesday.

.LONG TERM...Thursday night through Monday

Weak ridge over the central Rockies gets pushed eastward into the
plains from Thursday into Friday as a moderate low pressure system
is forecast to move through southern Canada.  All models are
indicating a cool front dragging across Montana and Wyoming Thursday
night into Friday.  This looks to be the best chance for showers and
precipitation during the long term period.  Best chances should be
across northern Wyoming and gusty winds should be the main threat.
Friday afternoon should see a northerly push east of the divide as
weak high pressure moves in behind the system.  Saturday will see
weak NW flow and only a very slight chance of afternoon mountain
storms. Temperatures should warm slightly to the mid to upper 80s
Saturday into Sunday. Sunday should see high pressure build nicely
over the Great Basin, bringing mostly clear skies for the weekend
and generally light wind, though afternoon humidities should reach
the low teens across much of the lower elevations.  A similar
pattern continues into Monday though western and NW WY should see an
increase in cloudiness from moisture wrapping around the high.  With
700mb temps forecast to top out around 16C over central and southern
WY, temps will be above normal, but do not appear to hit record
levels.

&&

.AVIATION...00Z Issuance

VFR conditions expected through 06Z/Wed with weak high pressure
building just to the west of WY on Tuesday.  Some gusts late this
afternoon and early this evening of 15 to 20 kts, diminishing after
02-03Z/Tue.  Weak northeast flow east of the divide will wash out by
12Z/Tue.  Mostly clear Tuesday with no ceiling or visibility issues
expected.  Slight chance of thunderstorms late Tuesday afternoon
into the evening across southern WY border.  Tuesday afternoon to
also see 15 to 20 kts NW gusts across SW WY with weak NE flow east
of the divide.

&&

.FIRE WEATHER...

Mainly dry weather will continue through Tuesday. Relative humidity
will also continue to be rather low, below 15 percent in many of the
lower elevations. However, winds should remain light to moderate for
most areas. However, areas of near critical fire conditions are
possible on Tuesday afternoon. Mixing and smoke dispersal will range
from fair in the basins to very food across portions of moisture.
Increased monsoonal moisture moving in from the south on Wednesday
and Thursday should raise relative humidity somewhat and decrease
fire concerns somewhat for the middle of the week.

&&

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

$$

SHORT TERM...Hattings
LONG TERM...McDonald
AVIATION...McDonald
FIRE WEATHER...Lipson


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