Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 210500

Area Forecast Discussion
National Weather Service Riverton WY
1100 PM MDT SAT AUG 20 2016

.SHORT TERM...Tonight Through Tuesday (Issued at 350 PM MDT)

After one of the coldest days in recorded history across Central
Wyoming on Friday, the rapid rebound has begun. Highs Sunday will
soar into the 80s in many of the lower elevations with a few of the
lowest elevations touching 90 already east of the divide. The
mountains will warm into the 70s with 60s confined to the highest
elevations. Monday looks just a touch warmer yet ahead of our next
weather system currently over the nrn Gulf of Alaska. This system
should skim across far southern Canada Monday night into Tuesday
pushing a cold front into Nrn Wyoming by Monday evening and further
into Central Wyoming on by Tuesday morning. Front looks shallow
initially and may mix out in Fremont and Natrona Counties before
making another push just beyond this period. Sunday looks dry with
some buildups over the highest locations, mainly nrn Winds and srn
Absarokas. On Monday, we may get a little moisture being drawn up
from the south to spark a few late day storms in the far sw and may
in the nwrn corner with the approaching cold front. Late Monday
Night or Tuesday morning, we may get a little moisture sneaking into
the sw/west central areas ahead of the weak front enough to
produce a few late night or morning showers or sprinkles out
there. On Tuesday, limited instability across the north behind the
front with maybe just a few mountain showers. Further south, the
western moisture band gets shunted to the far srn/southeastern zones
where a few showers/tstms are possible. Not as warm overall with
shallow front north and west and cooler mid levels, especially
north half (cooler the further north you go).

.LONG TERM...Tuesday Night Through Saturday

Tuesday evening into Wednesday morning will see the next serious
cold front move down from the north into Wyoming, as the decent
shortwave trough moves across the Canada/US border. Not really
expecting much precipitation with the front, except for possibly
some showers from Johnson County into central WY. Primary impact
of the front will certainly be to cool down northern, eastern, and
central WY again, but also establish a mid level boundary along
the continental divide. Models are indicating a secondary
shortwave trough sliding southeastward along this boundary from
western MT into WY on Wednesday. The resulting instability should
provide for some showers and thunderstorms across NW WY and in the
higher terrain of central and northern WY. Afternoon temperatures
will cool once again into the low 70s. As a broad weak trough
moves into the SW US off the Pacific Ocean at the same time,
general troughiness over the western US will result in relatively
cool temperatures for the rest of the week. Some moisture looks to
move northward into southern and SE WY from the four corners area
Thu and Fri, as yet another shortwave trough drops out of Canada
into MT and northern WY. This feature should provide a good focus
for showers and thunderstorms across northern and north central WY
Friday into early Saturday morning. Saturday then looks to be a
typical late August day with weak zonal flow. Overall, a continued
active pattern across WY with the hopes of producing more
precipitation for the dry areas of the state. Temperatures likely
to be slightly below normal for the mid to end of the week. Medium
range models are showing some differences with the flow and
resulting surface weather, so confidence is average to just below
for the period.



VFR conditions will occur through Sunday night. It will be breezy
across much of the area Sunday afternoon into early evening. Wind
speeds of 12 to 18 knots will be common at most terminal sites with
gusts to 22 knots. Areas of smoke from wildfires in NW WY may impact
visibility downwind of the fires.



...Fire Weather Watch for Fire Zones 140 and 415 From 1 PM to 9 PM

Fire conditions will become a concern again by Sunday afternoon in
the northwest portions as some very dry air moves in with warm
temperatures and increasing wind. Monday looks windier but Sunday
looks very dry with low rh`s and at least breezy at times. Some rh`s
on Sunday could briefly dip below 10 percent in the northwest zones.
Fire danger will increase further on Monday for most of the area
with very warm to hot temperatures, breezy to windy conditions and
low rh`s.


.RIW Watches/Warnings/Advisories...

Fire Weather Watch from Sunday afternoon through Sunday evening
for WYZ140-415.



LONG TERM...McDonald
FIRE WEATHER...Skrbac is the U.S. government's official web portal to all federal, state and local government web resources and services.