Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 190918

Area Forecast Discussion
National Weather Service Riverton WY
318 AM MDT TUE JUL 19 2016

.SHORT TERM...Today through Thursday night

...Fire Weather Watch for portions western and central Wyoming
Wednesday afternoon and evening...

Fire danger moderate to elevated today (with less wind overall)then
elevated to extreme across the lower elevations east of the Divide
and also over the west central and southwest mountains Wednesday.
As fuel status has now changed across the FA and includes more
zones, the Fire Weather Watch for Wednesday now includes the west
central/southwest mountains along with portions of lower
elevations of central WY. Natrona county lays at the far eastern
extension of the Watch and may end up not being included in the
Red Flag Warning at issuance time.

Imagery shows broad ridge across the central CONUS with bookend
trofs over each coast. Upper broad central high pressure is
located over the plains. Embedded disturbance continue riding
through/around the ridge touching off showers/storms where sfc/mid
level fronts exist (high/central plains) or capping is weak...such
as higher terrain features. Mid level moisture flowing around the
high out of the tropics and across the desert SW...then southern and
central Rockies. Surface has generally weak high pressure across
southern WY with lower pressure off to the north, west and southwest
from the northern Great Basin into the desert southwest. This is
setting up a brief period of monsoonal type flow through the
southern and central Rockies into the central plains...but mostly
missing WY except across the far south and southeast.

Through the forecast period: Upper ridge moves further east into the
plains while the ridge center sets up across the southern/central
plains. With good mid-level moisture feeding around the high and
heat induced low pressure setting up across the Great Basin and
Desert Southwest, a monsoonal type flow is setting up across the
southern and central Rockies. However, and unfortunately, the
moisture at this time is being directed through the southern/central
Rockies and then eastward into the eastern high/central
plains...including mainly eastern/southern portions of WY and
leaving most of the FA, except for the south, rain free. Through
Wednesday, a lee side trof/weak surface low will try to build over
central/eastern WY. With the upper ridge axis then tilted slightly
from southeast to northwest, the upper level flow over most of the
CWA will be from the southwest and quite dry and capped. Today
through Wednesday, convection will then lay across
southern/southeastern WY with only a few isolated showers/storms
over possibly initiating across the higher terrain of the areas
mountains with little to offer but light rain and gusty winds. The
Uinta and Medicine Bow mountains will have the best chances for
laying down measurable precip. Thursday, a front moves through
eastern Wyoming from north to south in the morning...effectively
shutting off what little moisture was getting into the FA...with
only a few late day/evening showers/storms possible across mainly
the southwest mountains...which could only provide gusty erratic
winds to the fires instead of any helpful rainfall.

.LONG TERM...Friday Through Tuesday

Hot and breezy to windy on Friday ahead of our MT shortwave which
will push a front sewd into at least our nrn zones Friday night.
A little moisture may be drawn up ahead of this system with a few
light showers around mainly the mountains in the morning with
isolated, gusty thunderstorms late in the day in the mtns and sern
zones. Saturday looks dry in the wly flow behind this shortwave
and not as hot. Temps may cool as much as 10 to 15 degrees in the
far north with only a few degrees of cooling in the southwest.
Temperatures start to rebound again Sunday into Monday a few
degrees each day with limited tstm chances. There is a significant
difference though between the Euro and GFS on a potential
shortwave moving in from the wsw late Sunday. The GFS is much
stronger and generates more potential for a few storms just about
anywhere but especially mtns and sern zones. Just have a few
storms in some of the mtns right now but we`ll see how this
evolves because the evolution is already different than last
night. A few storms still possible Monday mainly around the
mountains as weak ripples will likely be around with limited
moisture in the w/sw flow. Another shortwave is forecast to move
ewd across us on Tuesday with potential for a higher low level
moisture in our far ern zones. Will add in isolated storms in the
ern zones for this. Not a lot of hope for any real rain during
this period so the main weather concern will be elevated fire
concerns due to ever drying fuels, breezy periods, hot temps and
isolated thunderstorms.



The main aviation concerns:

1. Very isolated high based convection mainly on the lee side of
mountain ranges east of the Divide, as well as between KRKS-KCPR.
Gusty/Dry microburst winds will be the main hazard. Have elected to
have VCTS at KRKS/KCPR terminals, but could have easily left it out
as coverage will be isolated at best.

2. Smoke from ongoing wildfires across western Wyoming will cause
MVFR restrictions at times especially on routes between KJAC-KRIW
and KJAC-KBPI/KPNA. KJAC terminal could see MVFR restrictions from
smoke this morning, and will have 6SM FU in KJAC TAF for now.



...Fire Weather Watch for portions of the southwest/west central
mountains in addition to central Wyoming lower elevations...

Fire danger will elevated for all lower elevation zones over the
next several days with moderate to elevated conditions in the
mountains as warm/hot, dry conditions prevail with little chance for
rainfall relief across most of the forecast area (except for perhaps
the far southern zones. Otherwise, extreme fire conditions expected
again Wednesday this time possibly across portions of the
southwest/west central mountains in addition to portions of the
lower elevations of central Wyoming in the afternoon through early
evening as low rh and very gusty winds combine with Haines
instability values of 5 to 6 and critically dry fuels. Natrona
county, fire wx zone 280, is definitely the most marginal of the
Watch group and may end up not making the cut at Warning issuance. Three
large incident fires are currently burning in the west
central/southwest forecast area.


.RIW Watches/Warnings/Advisories...
Fire Weather Watch from Wednesday afternoon through Wednesday
evening for WYZ280-283-414>416.



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