Area Forecast Discussion
Issued by NWS Riverton, WY
FXUS65 KRIW 221652
Area Forecast Discussion
National Weather Service Riverton WY
1052 AM MDT MON AUG 22 2016
.SHORT TERM...Monday through Wednesday night
The main concern for the next couple of days remains high fire
danger. This will definitely be the case. As a cold front moves
toward the area from the north and west. Ahead of it expect a warm
to hot and breezy day. Highs in the 90s will be commonplace in many
of the lower elevations East of the Divide. As the front approaches,
the pressure gradient will tighten and increase west to
southwesterly flow across the state. The result will be a gusty west
to southwesterly wind developing. The fire weather warning was
continued for all locations. We also added the southern Big Horn
Range with a new fire showing up there. As for the chance of
thunderstorms, all of the models are fairly unimpressed. The best
chance would be across southern Wyoming and possibly portions of
Yellowstone Park. But even here, they would be few and far between
and maybe of the dry variety. Fire danger should decrease tonight
after the front passes and the wind decreases as the atmosphere
Tuesday looks to be a cooler day but not cool by any means. In
addition, relative humidity will remain fairly low, although a bit
higher than Tuesday. It is a decent possibility more fire weather
highlights may be needed, although possibly for a smaller area. A
gusty breeze will also continue, although maybe a bit less. The
biggest threat of fire danger may shift further south into southern
Wyoming however. As for the chance of thunderstorms with the second
front, again there is little moisture to work with. Far southern
Wyoming at this point looks to be the only chance on the edge of the
monsoonal moisture but even here, coverage will be isolated at best.
The second cold front with cooler air will push through Tuesday
Wednesday at this point looks to be noticeably cooler and more
importantly, a bit more humid, especially East of the Divide. This
should finally lower fire danger a bit. And upper level disturbance
moving in from the northwest could bring some showers and
thunderstorms to northern Wyoming Wednesday afternoon and evening.
And, there could even be enough cold air for a bit of snow in the
higher elevations. At this point, amounts look to be light if any
.LONG TERM...Thursday through Monday
1025 MB surface high over the region Thursday will shift east
into the Plains/Midwest Friday. Aloft the forecast area will be on
the cyclonic side of an upper jet with a couple weak
perturbations pushing across the area. Thus will have a chance of
seeing isolated to locally scattered convection despite weak
forcing and minimal instability. Best shot will be over the
mountains and adjacent foothills along and east of the Divide on
Thursday with the driest conditions across the far west and
Medium range models are showing the flow becoming relatively light
westerly across the forecast area for the weekend into early next
week. Models are trying to pull up some modified monsoonal
moisture into the area early next week. This combined with any
weak disturbances could cause isolated diurnal convection mainly
Sunday and Monday. This solution would limit any red flag
potential. However, one concern or something too watch is an upper
low pushing into southern British Columbia Saturday. Global
models want to deamplify this feature quickly as it moves east,
and are a bit farther north than last night. If this upper low
would take a track/strength of the past couple of upper lows that
have moved across southern Canada...then fire weather concerns
would return. Forecast goes with model consensus.
VFR conditions will occur through Tuesday. Expect breezy to windy
conditions at times during the afternoon and evening hours. Isolated
showers or thunderstorms may drift into far southern WY after 21Z
through 06Z. Gusty wind to 35 knots will occur near that activity.
KRKS airport is not expected to be impacted by showers or storms.
Areas of smoke from wildfires in NW WY may impact visibility across
northern WY through Tuesday morning.
...RED FLAG WARNING FOR MUCH OF THE AREA...
A combination of warm to jot temperatures, low relative humidity and
a gusty west to southwest wind will bring critical fire conditions
to much of western and central Wyoming. Elevated fire danger for a
period of time in the afternoon will be possible in other locations.
Mixing and smoke dispersal will range be good to excellent. Fire
danger may remain high on Tuesday, especially in southern Wyoming.
Fire conditions should improve on Wednesday with cooler temperatures
and higher relative humidity.
Red Flag Warning from noon today to 9 PM MDT this evening for