FXUS65 KRIW 171759 AAA

Area Forecast Discussion...UPDATED
National Weather Service Riverton WY
1159 AM MDT Tue Jul 17 2018

.SHORT TERM...Tuesday through Thursday night

There is still some activity on the radar this evening although it has
lightened significantly from earlier this evening. Right now, it
looks like we will have one more active day before we enter into a
quieter pattern. We will still have low level east to
southeasterly flow moving moisture into the area. Instability does
not look quite as impressive as yesterday although it is still
enough. We also still have some shear. Timing will be different as
well as it looks to be an earlier show today across most of the
area and this may limit surface instability a bit more. The
exception may be across portions of Johnson and northern Natrona
Counties where a shortwave moving south may bring some more storms
in the evening hours before ending before midnight. As for the
chance of any strong to severe storms, the Storm Prediction Center
does have a marginal risk roughly from the Bighorn Mountains and
eastward. The main threat today looks to shift to hail given
cooling temperatures aloft that could allow for better ice growth
rates. We have allowed for small hail with all thunderstorms and
added heavy rain and gusty winds further east where the deeper
moisture and greater instability will be found today.

For Wednesday and Thursday, we will dominated by mainly dry
northwesterly flow. That means mainly dry conditions and warm to
hot temperatures. A gusty breeze may develop in some areas in the
afternoon, and this could result in elevated fire behavior later
each day. This would especially be the case in southern Wyoming
where the wind gusts would be the strongest.

.LONG TERM...Friday through Tuesday

Models are now trending back to an increasing threat of monsoonal
moisture moving nwd over the upcoming weekend. Early next week we
may keep some of this moisture around while we transition to a nw
flow with disturbances passing to the north allowing for cold front
to settle in east of the divide Monday into Monday night and hang
around through Tuesday. Friday looks to be the driest and possibly
hottest day before monsoonal moisture edges nwd Friday night into
Saturday leading to potential showers as early as late Friday night
or Saturday morning. The chance of showers/storms will then be
around over the weekend. How much of a monsoonal surge we get is
still uncertain with the models overall still struggling and
changing with each run where the high will be. At least, it looks
better than last night's model runs. Early next week, we may cool
off, east of the divide especially with cooler nw flow and frontal
boundary sagging swd and setting along the continental divide Monday
night into Tuesday. We may see some storms with the initial front
dropping south but it may just set the stage for a better convective
day next Tuesday with moist upslope and good directional shear
profiles. Temps start out in the 90s east of the divide Friday (and
probably Saturday) before temps start to cool with more clouds and
higher moisture levels. Monday and Tuesday definitely look cooler
with lower heights and developing wnw/nw flow aloft and cooler mid
level temps. MEX guidance is already showing 70s up north at the end
of this period compared to upper 80s and 90s Friday and Saturday.


.AVIATION...18Z Issuance

VFR conditions to rule through 12Z/Wednesday with the exception
of the strongest thunderstorms.Active westerly flow will track
other disturbances across the north and central Tuesday morning
with another to track to our north over Montana Tuesday afternoon.
This afternoon the best chance for thunderstorms will shift to
the far north and east, though any terminal east of the
Continental Divide could see lingering convection. The best chance
for stronger convection will be along and east of a line from
KCOD to KCPR. Heavy rain and small hail are the primary hazards
along with wind gusts 30 to 40 mph. However, there is a
possibility of damaging winds and large hail in Natrona and
Johnson Counties including KCPR and KBYG. Drier air will being to
push into the far west and southwest this afternoon and continue
and eastward push overnight.



Another round of thunderstorms are expected this afternoon; storms
will be scattered in the north and east and more isolated
southwest. There is only a marginal chance of severe weather in
eastern Wyoming. Relative humidities will be moderate and
temperatures comparable to yesterday. Winds however, are expected
to increase today and become breezy in the south and west by this
afternoon. The remainder of the work week looks to be mostly dry.




SHORT TERM...Hattings
LONG TERM...Skrbac
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