Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

000
FXUS65 KRIW 192009
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
209 PM MDT Sun Mar 19 2017

.SHORT TERM...(This evening through Monday)
Issued at 113 PM MDT Sun Mar 19 2017

Next shortwave in the sw flow is moving quickly towards western
Wyoming. This this will bring a quick shot of lgt to mdt snow to
mainly the nw mtns this evening before decreasing to lighter snow.
The valleys will see mostly rain. After a lull/lessening, another
shortwave (actually more like two) will move ne across the area on
Monday into Monday evening with another period of light to ocnl
moderate mtn snow (esp nw mtns) with some light rain showers for the
west and sw. Enough instability for isold tstms possibly in the same
area. Isold tstms are still a possibility til around sunset in the
far west today. The systems in the west have enough break and
movement to them to likely preclude any winter weather advisories.
We still likely see 2 to 5 inches in the nw/wcntrl mtns with up to 7
inches or so in the Tetons between tonight and late Monday afternoon.
East of the divide, the cold front just entering the north will drop
swd overnight to near Casper and at least the nrn and ern parts of
the Wind River Basin. In the far north, a few light
showers/sprinkles may develop overnight but the odds increase as we
head into Monday afternoon and night. As shortwaves aloft, possible
right entrance region jet support and weak instability build up
showers that move over the cool dome Monday afternoon. Upslope
increases Monday night as shortwave over srn Canada strengthens the
high to the north and increases the gradient over nrn Wyo causing a
good chance of lower elevation rain and mtn snow. Temps could drop
enough to potentially change the lower elevations of mainly nrn
Johnson over to snow late Monday night before pcpn ends. Will
continue to indicate that with a couple inches possible and likely
pops. If temps drop near or below freezing, we could see some
freezing drizzle/lgt freezing rain in nrn Johnson County including
around Buffalo early Tuesday. Saturated sub-freezing boundary layer
showing up in multiple models with no ice crystals above that layer.
Will add a chance of that too into the mix. Front will likely hang
around the ern, especially nern zones through Tuesday for a cool,
cloudy day with some instability showers around and near the higher
terrain of our area. Next shortwave in the sw flow moves into the
west Tuesday night for another round of mountain snow and valley
rain (possibly mixing with snow late in the higher parts of the
valleys). The more potentially interesting weather with this
developing trough will be covered by my esteemed colleague below.

.LONG TERM...(Monday night through Sunday)
Issued at 113 PM MDT Sun Mar 19 2017

The next troughpa is progged for Thursday. Except for one odd ball
run of the GFS which pushed the southern stream low with this trough
right across Central Wyoming on Thursday, the latest run of the GFS,
the Canadian, and the Euro all advertise a much more southerly track
of the low tracking across extreme southern Co Thursday. This makes
sense as this will be a splitting trough with the mean ridge over
the Rockies. However, increased pops a bit in the mtns and in the
northern half of the CWA Wednesday night and Thursday to account for
the northern stream energy with this splitting trough. The east
slope of the Wind River Mtns, Lander, and Casper Mtn should see a
limited amount of upslope precip Thursday and Thursday evening as
the sfc low develops over Southeast Co when the low becomes
vertically stacked by late Thursday. In addition, extreme Eastern
Sweetwater County and extreme Southeast Natrona County should see
added precip with the closer proximity of the dynamics directly
related to the low center. The precip west of the divide looks to be
more showery in nature with this trough with the added instability.
A mixture of rain and snow showers can be expected Wednesday night
through Thursday evening in the west with mostly snow from 06z Thu
through 18z Thu. By the time the cooler air behind this trough
reaches areas east of the Divide to turn the rain to snow at the
lower elevations Thursday night, most of the moisture will exit to
the east. After 06z Friday, precip will taper off to a few scattered
snow showers in the mtns.

Friday will be a precip free day with milder temps. Then more high
elevations snow and low elevation rain will spread into Western
Wyoming later Friday night as the next digging Pacific trough
approaches Wyoming with snow levels rising to about 7500 feet by
Sunday. This precip will increase in coverage in Western Wyoming
through Sunday. Low-elevations snowmelt causing localized flooding
will continue on/off through the extended.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday afternoon)
Issued at 113 PM MDT Sun Mar 19 2017

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

Mostly VFR conditions will prevail at the terminal sites through
tonight. One exception will be the rain showers and high elevation
snow showers will that will redevelop during the remainder of this
afternoon in northwest WY and continue through tonight. Local MVFR
conditions will occur in NW WY at this time with some mountain
obscuration. These showers will dissipate by 14z Monday morning but
will continue in Northwest Wyoming. Another weather disturbance will
push the low elevation rain and high elevation snow showers south
across the rest of the area again by 21Z Monday.

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

VFR conditions will prevail through the period. A gusty wind will
occur today into this evening at some of the terminal sites. A cold
front slides into Northern WY after 01Z with a wind shift to the
north. This front will push south to a KRIW to KCPR line by 12Z
Monday. Showers will develop north of the Owl Creek Mtns and
southeast into Natrona County behind the front by 22z Monday.

&&

.FIRE WEATHER...
Issued AT 113 PM MDT Sun Mar 19 2017

A cold front will drop down into Central Wyoming east of the divide
tonight lowering the fire danger to generally low Monday through
Tuesday. The west will remain with a low fire danger with a good
chance of occasional mountain snow and lower elevation rain or
mixed rain and snow. Only the far south, mainly around Sweetwater
County will have drier conditions with a gusty sw flow and
somewhat elevated fire concerns during the afternoon hours mainly.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for WYZ013-023-027.

&&

$$

SHORT TERM...Skrbac
LONG TERM...Lipson
AVIATION...Lipson
FIRE WEATHER...Skrbac



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.