Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Riverton Wyoming
211 PM MST Wednesday Feb 10 2016
Short term...tonight through Thursday
A couple of concerns in the short range. The first is for wind. The
usual suspects in the Cody foothills...mainly america's favorite
crossroad...Aka Clark has reported some wind gusts around 60 miles per hour.
However...so far this is only at one sensor and impacts look minimal
so we will stick with a Special Weather Statement and not issue any
highlights. 700 millibar winds continue to not look strong enough
for any widespread high wind in that area. Gusty winds are also
blowing through the southwestern wind corridor but these nothing
unusual and should remain below highlight criteria. Winds should
decrease tonight with decoupling of the atmosphere and a weakening
of upper level winds. The other issue is some fog in the western
valleys...it is starting to lift but should return later tonight.
The previous forecast had patchy fog and will maintain that
forecast. Meanwhile...elsewhere east of The Divide expect a mix of
sunshine and high clouds along with near to somewhat above normal
temperatures. These clouds have kept temperatures a bit cooler
than expected in some areas...such as here at National Weather Service Riverton. Places
like Cody and Buffalo will have downsloping flow that will push
temperatures close to 60 though.
Thursday at this point looks like another quiet day with more of the
same. Temperatures will be a bit cooler across areas that were close
to 60 but still above normal. The GFS does show a bit of
precipitation approaching the northwestern portion of the state late
Thursday. The NAM is dry however. For now...we will keep the
forecast dry since a vast majority of the day would be precipitation
Long term...Thursday night through Wednesday
A long wave high pressure ridge will be established over the western
United States through the middle and long term while a series of
Pacific short wave low pressure troughs will come over the top of
the ridge bringing Pacific moisture and lift into western Wyoming at
times. Some light snow showers will be over the northwest Thursday
night with a cold front moving south from Montana into northern
Wyoming. Central and southern areas will have breezy to windy west
winds with dry conditions east of the Continental Divide. Showers
will decrease as the trough moves east and the ridge rebounds. A few
snow showers will remain in the northwest on Friday then dissipate
Friday night. A second Pacific short wave low pressure trough will
then move east reaching the northwest Saturday morning with
increasing areas of light snow in the western and northern mountains
through the day...continuing through Saturday night as another cold
front moves out of Montana with increasing chances of snow in the
north and east late Saturday night and Sunday morning. A second
Pacific short wave low pressure trough will move into western
Wyoming Sunday not allowing the ridge to rebound. This should
result in a prolonged period of light to moderate snowfall in the
west as the Pacific moisture fetch increases and the timing of a
series of Pacific troughs keeps suppressing the ridge. East of the
Continental Divide could become quite windy Sunday and Sunday night.
Late Sunday night or Monday morning another cold front should brush
the north and east with some areas of light snow. Another Pacific
trough then moves east towards western Wyoming with increasing
chances of snow in the west Monday and Monday night. Then the high
pressure ridge rebounds and becomes more dominant with drying across
the western United States. This will decrease snow chances through
the day Tuesday with dry conditions Tuesday night through Wednesday
morning. Some light snow showers may return Wednesday afternoon.
With a very progressive flow pattern with significant changes in
cloud cover...precipitation and wind...temperatures will be more
difficult to nail down.
VFR conditions are expected through most areas through 00z Friday.
Most areas will see areas of passing high clouds with a gusty breezy
continuing across the southwestern wind corridor from krks to kcpr.
Across the western valleys...fog may reform in the western valleys
after 09z Thursday and persist through the morning hours.
Steep temperature inversions...especially in the western valleys
will lead to very poor smoke dispersion this week.
Winds...however...will be on the breezy side across the usual wind
prone area of central Wyoming...which will improve smoke dispersion
in these areas. No major snow storms or widespread strong wind
events are on the horizon although some light snow showers are
possible in the northern mountains Thursday night into Friday.