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 29 30 31 32

000
FXUS65 KRIW 110502
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1002 PM MST Fri Nov 10 2017

.SHORT TERM...(This evening through Monday)
Issued at 148 PM MST Fri Nov 10 2017

Southwest flow aloft will bring areas of Pacific moisture
into the western mountains of wyoming tonight and Saturday
with light snow accumulations in the 3 to 6 inch range
with locally higher amounts above 9500 feet. Across the
south and east of the Continental divide clouds with generally
dry and breezy to windy conditions are expected.  The strongest
winds will be along and near the east slopes of the mountains.
Some warming will result with the downslope winds.  High
pressure will bring dry and cool conditions withe less wind
on Sunday with warming on Monday.

.LONG TERM...(Monday night through Friday)
Issued at 148 PM MST Fri Nov 10 2017

Beginning of fcst, a shortwave ridge passes to the east and the
upper levels transition to southwesterly with an (the) advancing
trof on the way toward the region along with a 100 to 130 kt jet
undercutting/and on its leading side. A brief, but decent, strong
wind pattern will become possible by Monday night over the nrn
Mountains and Foothills as mid/upper level flow across this region
(mountains) will be favorable to the formation of good amplitude
mountain waves...continuing into Tuesday morning. The Wind Corridor
is also expected to react to the approach of this system with
increased winds...and a very brief period of marginal High Wind
possible ahead of the cold front Tuesday morning (probably not
enough for a Warning). Over the same period, moisture, clouds and
precip chances will increase across wrn WY Monday night...continuing
into/through Tuesday morning...with some very low (generally < 15
percent) chances east of the Divide by afternoon/evening Tuesday.
The boundary layer flow pattern with respect to moisture and wind
could/should support continuing lingering -SN(SH) across the
wrn/nwrn mountains even under building post frontal mesoscale high
pressure (although it could shut off for a short period from late
overnight Tuesday into Wednesday morning). Beyond that, renewed EPAC
moisture and better upper level dynamics should return by Wednesday
afternoon/evening/overnight (depending on model - GFS faster, EC
slower) with return chances for precip west of the Divide. The
bigger problem in the extended fcst (from one that previously was in
decent agreement) now occurs from later Thursday onward with severe
out of phase temporal differences through and beyond the end of the
fcst period. Have essentially broad-brushed this latter portion of
the fcst period with slight to chance POPs west of the Divide. Still
should see a decent period of light/moderate snowfall through the
week. Additionally, winds will be favorable for a gusty/high wind
set-up from time to time from mid-week on as increasing SFC pressure
gradients (lee side trof/upwind ridge) combine with continuing
relatively strong flow aloft being nearly orthogonal (+/-) to the
area`s mountains. Currently sometime between Wednesday night Friday
look best for a possible wind event. But until the dichotomy between
GFS and EC gets resolved, will have to wait to narrow.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday)
Issued at 1000 PM MST Fri Nov 10 2017

West of the Divide (KBPI-KJAC-KPNA-KRKS routes)

A weather system will move through the west overnight and exit
Saturday afternoon. Snow will occur in the western mountains. Areas
of snow will occur at the lower elevation of the west with MVFR/IFR
conditions through 19Z. VFR conditions will prevail at the terminal
sites by 21Z through 06Z Sunday. KRKS airport will not see any rain
or snow from this system, just a gusty wind from around 18Z through
01Z Sunday. Please see the latest terminal forecast for more
details.

East of the Divide (KCOD-KCPR-KLND-KRIW-KWRL routes)

A weather system will move through the region late Saturday morning
and afternoon. The system will exit the area by 01Z Sunday. Some
snow will occur in the mountains along and east of the continental
divide. Scattered areas of snow will occur late Saturday morning and
afternoon at the lower elevations. KCOD and KWRL airports look to be
impacted by snow and MVFR/IFR conditions for a few hours. From KLND
to KRIW to KCPR, VCSH will be in the terminal forecasts. VFR
conditions will prevail over the region by 01Z Sunday. Please see
the latest terminal forecast for more details.

&&

.FIRE WEATHER...
Issued AT 148 PM MST Fri Nov 10 2017

Southwest flow aloft will bring areas of Pacific moisture
into the western mountains of wyoming tonight and Saturday
with light snow accumulations in the 3 to 6 inch range
with locally higher amounts above 9500 feet. Across the
south and east of the Continental divide clouds with generally
dry and breezy to windy conditions are expected.  The strongest
winds will be along and near the east slopes of the mountains.
Some warming will result with the downslope winds.  High
pressure will bring dry and cool conditions withe less wind
on Sunday with warming on Monday.

&&

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

&&

$$

SHORT TERM...Baker
LONG TERM...Braun
AVIATION...AR
FIRE WEATHER...Baker



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