Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 270840
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
240 AM MDT SAT AUG 27 2016

.SHORT TERM...Today Through Monday Night

Satellite and radar trends demonstrating a drier air mass moving
over the forecast area this morning. This system will bring a
forecast period of warming temperatures, lowering humidity, and
mostly free of shower activity. As flow becomes more zonal today with
the movement of nearby areas of low pressure, wind across much of
the forecast area will be able to increase this afternoon,
especially over the mountains and areas west of the Continental
Divide. The combination of dry conditions, warm temperatures, and
gusty wind will bring critical fire behavior for portions of western
and southern Wyoming, along with Natrona county and the northern
mountains. Consequently, a Red Flag Warning is in effect for
these areas. Any agricultural burning is strongly discouraged today.

High pressure will work to build over the area Sunday. Lighter wind
is anticipated for much of the area. Some discussion was had about
fire weather concerns for Sunday, but confidence was not high enough
to extend the warning out into Sunday afternoon. Instead, subsequent
shifts can evaluate the threat over the next one or two model runs.

Otherwise, warm and dry conditions persist into Monday with an
amplifying area of high pressure expected over the state.

.LONG TERM...Tuesday Through Saturday

Synopsis...Dry and unseasonably warm conditions will prevail on
Tuesday.  A large upper trough will move slowly east across the
western U.S. Thursday through Saturday bringing chances of showers
and thunderstorms into the west on Wednesday.  A cold front will
spread showers and thunderstorms into central and eastern Wyoming on
Friday, with cooler and unsettled conditions to follow through Labor
Day weekend.

Discussion...Medium-range guidance shows better overall agreement
this morning with large-scale pattern across the Pacific and North
America, featuring a ridge across the east central Pacific, upper
trough off the west coast and ridge centered over the High Plains.
This overall pattern will progress slowly through the period with
upper trough amplifying over the western U.S. as strong Pacific
jetstream digs down its backside. Tuesday is expected to be the
warmest day as Wyoming remains under influence of upper ridge over
the High Plains. Southwest flow will bring some weak shortwave
energy and chances of showers and thunderstorms across the west on
Wednesday, while lee side surface trough develops bringing breezy,
dry and warm conditions across central Wyoming along with elevated
to possibly critical fire weather conditions. These elevated fire
weather conditions will likely remain across central areas through
Thursday, with some thunderstorm activity beginning to spread in
from the south and west. The outlook for Labor Day Weekend is
looking increasingly cool and wet with the large upper trough
expected to slowly progress across the Rockies, with the
possibility of some snow in the mountains in the latter part of
the weekend. Good news for fire concerns, not so good if you are
planning to be in the great outdoors.

&&

.AVIATION.../12Z ISSUANCE/

Cannot rule out patchy fog through 15Z where rain occurred Friday
evening such as at CPR terminal. However confidence is too low and
overall boundary layer is not high enough to include at KCPR for
now. Otherwise expect VFR conditions through the period with
variable high level cloudiness. Breezy west to southwest winds will
be observed in many locations this afternoon and evening.

&&

.FIRE WEATHER...

Warm, dry, and windy conditions anticipated across areas west of the
Continental Divide, Natrona county, and portions of the central
mountains today. Critical fire weather conditions are expected, with
a Red Flag Warning in effect into this evening. Agricultural burning
is not advised today. Sunday could be another interesting fire
weather day, as Haines Index values increase across the area.
However, with the increasing high pressure, winds should relax a bit
by Sunday afternoon, potentially easing some of the threat. Dry
conditions will still be present, and the increasing Haines values
may necessitate fire weather highlights for Sunday. For now,
confidence was not high enough to extend the current warning.

&&

.RIW Watches/Warnings/Advisories...
Red Flag Warning from noon today to 8 PM MDT this evening for
WYZ140-277>280-285>289-414>416.

&&

$$

SHORT TERM...Branham
LONG TERM...AEM
AVIATION...WM
FIRE WEATHER...Branham



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