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Area forecast discussion 
National Weather Service Riverton Wyoming
1105 PM MDT Monday Sep 1 2014

Short term...tonight through Tuesday

Upper low quickly exiting east into northern plains will keep a
few showers and thunderstorms early this evening then ridging
takes hold. Dry west flow will dominate later tonight and Tuesday
with increasing winds Tuesday as stronger winds aloft mix to
surface central and south areas. Waring will result.

Long term...Tuesday night through Monday

Through Wednesday night...probably the significant weather parameters of this
forecast period are directly as result of upper zonal flow beginning
to transition to strong SW flow while at the same time...rapid
drying near surface occurs as deepening Lee side low develops across
eastern Wyoming along with a tightening pressure gradient/frontogenesis to the
west/northwest. This is directly related to the influence of the
approach of yet another large northwest Continental U.S. Upper level trough. Additionally
and associated with this disturbance...upper level wind speeds will
increase dramatically through the day Wednesday as jet level winds range
between 80 and 100 kts ahead of this trough. This situation along
with surface to 500 mb lapse rates ranging between 9 and 11 degree
c/km...albeit near dry adiabatic...with still be more than
unstable enough to bring down some of the increased upper level flow
and reinforce the p gradient induced winds at the surface. At this time...winds
look to remain below High Wind Warning...however fire danger
elements look to easily exceed min criteria for red flag
conditions Wednesday afternoon...wind gusts >= 25 kts and rh<= 15
percent...so looking to add fire weather zones 279 280 283 and 289 into
watch/warning. Thankfully these conditions look to be short-lived
as the front mentioned above sweeps through the forecast area from north to
S...eliminating red flag conditions Thursday. Also...with very dry
air in place for most of the County Warning Area ahead of the front and its upper
level cousin...and no time to reload moisture...very little precipitation
will have a chance to fall and what little does will have to take
advantage of elevation gains in the northern mountains.

Through the rest/end of the forecast...inasmuch as Wednesday will be the
warmest day of the extended...Thursday will be Post frontal and
likely the coolest with highs struggling to get out of the 60s
across the lower reaches while the mountains only get into the upper
30s to lower 40s.

Otherwise...lr models are struggling somewhat with how to treat the
western Continental U.S. Trough through the entire extended...starting on Friday.
However there are commonalities through the extended which have the
most merit with respect to the forecast. Overall...relatively dry
extended forecast as we continue to lose contact with monsoonal
moisture through the end of the period...especially across the
central and northern forecast area when compared to the past few weeks. Even
with periods of upper level instability and a brush with another (back
door this time) front near the end of the work week...and another
weaker one next Monday...higher precipitation probs and quantitative precipitation forecast will likely
stay nearer the southern or southeastern zones...closer to a little better
moisture and forcing. Have tweaked forecast to reflect this trend.

&&

Aviation.../06z issuance/

VFR conditions with sky clear skies. Light winds through Tuesday
morning...with breezy southwest wind developing mainly in the
rks-cpr corridor...as well as Jackson Hole. The breezy winds could
mix down into the Wind River basin after 21z. The winds will then
subside between 01z and 03z Wednesday.

Note...FAA informs National Weather Service that observation fro kcod will be unavailable
until sometime Tuesday when repairs are expected. Taf continued as
VFR conditions are anticipated at kcod through the forecast period.

&&

Fire weather...

Dry west southwest flow aloft will move over southwest and
central Wyoming Tuesday afternoon and remain through Wednesday
evening. Very low relative humidity and strong gusty winds will
develop across the southwest and central portions of Wyoming after
noon on Tuesday continuing until around 8 PM MDT Tuesday evening.
The very low relative humidity and strong gusty winds will
redevelop after noon on Wednesday continuing until around 8 PM MDT
Wednesday evening. Red flag warning in effect from noon to 8 PM MDT
Tuesday for wind and low relative humidity for fire weather zones
279...280... 283 and 289. Red flag warning again in effect from
noon to 8 PM MDT Wednesday for wind and low relative humidity for
fire weather zones 279...280...283 and 289.

&&

Riw watches/warnings/advisories...
red flag warning from noon to 8 PM MDT Tuesday
wyz279-280-283-289.

Red flag warning from noon to 8 PM MDT Wednesday
wyz279-280-283-289.

&&

$$

Short term...c.Baker
long term...Braun
aviation...wm
fire weather...c.Baker

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