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fxus65 kriw 300446 

Area forecast discussion
National Weather Service Riverton Wyoming
1046 PM MDT Mon may 29 2017

Short term...(this evening through thursday)
issued at 250 PM MDT Mon may 29 2017

Weak isold convection attm spawning off the common convergence
zones, namely off the southern Wind River mtns where a sfc
boundary appears to be located. There is also a stream of weak
convection coming off the Big Horn mtns as well as off the
southern absaroka mtns with the cells tracking south southeast.
Only isold ltg strikes attm. Then there are a few other isold
cells around as well. The prominent circulation spinning over Lake
Superior is extending way out to northeast Wyoming where kbyg is
still experiencing Post frontal/synoptic scale cyclonic bora winds
currently blowing 32025g32 knots. North-northwest winds are also blowing to a
lesser degree over the northern Big Horn basin. The 700mb temps
will still be influenced by the aforementioned Great Lakes cold
low with h7 temps over the Big Horn mtns progged to be cold enough
to support snowfall at 8500 feet this evening should additional
shower activity occur over any mtns at these elevations. By
Tuesday, the ridge will build in from the west which will slacken
the pressure gradient and the resultant NW winds currently blowing
east of The Divide in northern WY. The confluent backing upper
flow flow will keep convective activity in check, relegating much
of the convection over the western mtns. Temperatures will be
milder Tuesday with highs in the 70s at the lower elevations east
of The Divide and will remain in 60s west as the sfc boundary
retreats northeast, east of The Divide. On Thursday, highs will
continue to warm to the 80s east and 70s west when the h7 temp
rises to 13c as the ridge continues to build into the area from
the west. Only isold convection is expected. Then by Thursday, the
backside of the ridge will exit to the east and the next
shortwave now out at 150w will track inland across the
intermountain west and a Pacific cold front will initiate much
more widespread thunderstorm activity along with continued warm
temperatures east of The Divide with temperatures 5 to 10 degrees
cooler west.

Long term...(thursday night through monday)
issued at 250 PM MDT Mon may 29 2017

Weakening splitting trough will move slowly across the area
Thursday night through Friday night with minimal forcing but
enough moisture and modest instability for quite a few showers and
some thunderstorms in the mountains and a chance across the lower
elevations. Surface low is still expected to form over our ern
zones Thursday night with some return flow moisture Thursday
evening/night which increases Friday into Friday evening. If temps
warm enough behind the front, we could see some stronger storms
around the low and front in our nrn/nern zones late Thursday and
in our ern zones Friday/Friday evening. Heights will try and
rebuild Saturday but generally hold off until Saturday night and
Sunday. A shortwave in the developing SW flow Sunday may clip the
nwrn zones late Sunday with some stronger tstms. In addition, the
more moist E-se flow May Draw moisture wwd into the central zones
Saturday night and Sunday which could set the stage for some
stronger storms east of The Divide Sunday afternoon and evening.
Models vary considerably on our next upper low approaching from
the west. GFS 5-wave pattern shows mean ridge building in which
would support a weaker or further north low passage like the 12z
Gem and Euro (mt and further north). 12z op GFS seems way too far
south with the upper low over Idaho next Monday night. Will lean
further north with a front impacting the far west/NW Monday with
increasing SW flow east of The Divide and retreating higher dew
points to the far north and east which would focus some stronger
storms along and north of the retreating frontal boundary.


Aviation...(for the 06z tafs through 06z wednesday)
issued at 1045 PM MDT Mon may 29 2017

West of the Continental Divide...kbpi/kjac/kpna/krks terminals

VFR conditions will prevail through Tuesday night. Scattered showers
and isolated thunderstorms will develop after 20z and continue
through 03z Wed. Gusty wind to 35 knots and small hail are likely
with some of the storms. The best concentration of activity will be
in northwest Wyoming...from a kjac to kcod line. Showers will become isolated
after 03z and end around 06z Wednesday.

East of the Continental Divide...kcod/kcpr/klnd/kriw/kwrl terminals

VFR conditions will prevail through Tuesday night. Isolated showers
and thunderstorms will develop after 20z over and near the
mountains. This activity will end by 05z Wednesday. Gusty outflow
wind to 35 knots will occur near the storms. Kcod Airport will see
the best chance for showers and storms. Klnd Airport will also have
thunderstorms in the vicinity due to its close proximity to the mountains.


Fire weather...
issued at 250 PM MDT Mon may 29 2017

Fire danger relatively low across the forecast area at the moment as
all fuels are currently in green-up. However, afternoon temperatures
will increase across areas east of The Divide Tuesday and
everywhere by Wednesday with highs in the 80s at the lower
elevations east of The Divide and 70s west by Wednesday. The
minimum relative humidity will begin to dip into the upper teens
east of The Divide and over Sweetwater County by Tuesday and into
the mid teens over these areas by Wednesday. Isolated showers or
storms Tuesday most likely to occur over the higher terrain and
closely adjacent foothills. Gusty winds with this activity
possible into the evenings. Wednesday, fire danger will elevate
with the aforementioned lower relative humidity and increasing temperatures along
with west winds gust 20 to 25 mph at times. Smoke dispersion will
be good to excellent in the afternoons. The chance of late
thunderstorm activity will increase by Thursday. Flooding
potential will also begin to go up from Wednesday going forward as
warming temperatures greatly increase snowmelt along with an
increasing chance of thunderstorm activity by Thursday.


Riw watches/warnings/advisories...none.



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