Area Forecast Discussion
Issued by NWS Riverton, WY
FXUS65 KRIW 301942
Area Forecast Discussion
National Weather Service Riverton WY
142 PM MDT TUE AUG 30 2016
.SHORT TERM...Tonight Through Friday
Upper ridge currently on top of us will gradually shift eastward
over the next couple days allowing our cold upper low off the B.C.
coast to move into the Pacific Northwest on Friday. Gradually
increasing southwest flow will start to draw up a little moisture
with possible embedded waves. Wednesday doesn`t look a lot different
than today. There could be a subtle wave with a little mid level
moisture close to the northwest corner but not sure it`ll even
impact our area. Mainly just another day with cu building over the
mountains leading to a few late day showers/storms. A somewhat
more organized batch of moisture is still looking like it will get
drawn newd into Western Wyoming later Wednesday night into
Thursday with a few late night more showers/slight chance of a
tstm and then a better chance of showers and thunderstorms over
the west during the day gradually spreading east of the divide.
Moisture levels look like they`ll rise enough in the west for most
of the area to avoid the 15 percent fire weather parameter. The
southwest looks driest. Tomorrow will actually be the driest but
winds look marginal at best. Friday will likely see the most wind
with the approaching cold front into Eastern Idaho by 00z
Saturday. Some showers/isold storms will continue overnight
Thursday night. Showers and thunderstorms should be a decent bet
in the far west, especially northwest on Friday ahead of the front
with the southeast quadrant the other area. Decent wind at times
Thursday into Friday with the lower rh`s being mainly east of the
divide. Quite warm east of the divide through the period while the
west starts to cool with increased moisture and clouds Thursday
.LONG TERM...Friday Night Through Tuesday
An approaching wave of low pressure will keep southwest flow over
western and central Wyoming Friday night. Expect some lingering
mountain showers and thunderstorms through the evening. The axis of
this wave will move through the area through Saturday afternoon,
moving some shower activity along with it. This system will result
in cooling temperatures across the state with decreases of 5 to 15
degrees between Friday and Saturday.
Meanwhile, another area of low pressure will be right on its
heels, moving another area of low pressure over the pacific northwest
by Saturday evening. The area of low pressure will continue to move
eastward on Sunday, with the core moving over north-central Idaho by
late Sunday evening. Continued southwest flow will keep afternoon
showers and thunderstorms over the area mountains...with generally
dry conditions otherwise. Cooler temperatures will persist, with
values decreasing another 5 degrees between Saturday and Sunday.
As this next area of low pressure moves across northeastern Montana,
the axis of its associated wave will move into western Wyoming by
Monday evening, and then progressing quickly through the state. The
wave is generally expected to be east of Wyoming by early Tuesday
evening. Cooler temperatures will persist through the remainder of
the forecast period, with below normal temperatures anticipated
across the state.
Quiet conditions overnight with shower activity weakening through
the evening. Smoke from nearby wildfires may have the greatest
impact on area aviation through the overnight hours...with smoke
bringing limited visibilities and partially to fully obscured
mountain tops. Another round of isolated mountain showers and
thunderstorms is expected by 18z Wednesday, with some threat of
gusty wind reaching into adjacent terminals. Otherwise, VFR
conditions are generally anticipated.
...Red Flag Warning for fire zone 281 until 8 pm this evening...
Elevated fire weather conditions will continue through Wednesday
with warm to very warm temperatures, min rh`s in the teens and
isolated gusty showers and thunderstorms in the mountains. Winds
will increase across the area Thursday into Friday with increasing
fire weather concerns east of the divide. West of the divide, even
though the winds increase and a few storms are around, the min rh`s
will generally be over 20 percent.
Red Flag Warning until 8 PM MDT this evening for WYZ281.