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Area forecast discussion 
National Weather Service Riverton Wyoming
302 am MDT Wednesday Jul 30 2014

Short through Friday night

Upper circulation appears to be over the Idaho/Wyoming border acdg to
satellite loop with the middle level circulation over Lincoln Colorado SW Wyoming acdg
to radar. These circulations will drift to the southeast as the
remaining stratiform precipitation becomes more focused primarily over
Sweetwater and southeast Natrona counties. The upper circulation will
make its way to the Red Desert today with the middle level circulation
drifting from NE Utah to northwest Colorado. The asct rainfall will exit southern
Wyoming around middle day just as fresh convection forms over northwest Wyoming
this afternoon. The prevailing surface wind will be from the east
north of the low...especially over Sweetwater County keeping US under a
relatively mild and moist airmass but warmer than Tuesday.
On Thursday...more convection will form mainly in northwest Wyoming where
the best lifted indices/convective available potential energy will be. Then on Friday another weak upper
low will ride up and over the stationary ridge over The Rockies and
is prognosticated to be over northwest Wyoming by Friday afternoon. This will result in
a good chance of thunderstorms across the County Warning Area Friday aft/eve. Temperatures
will slowly recover during the remainder of the work week but will
remain at or below normal for high temperatures.

Long term...Saturday through Wednesday

Weekend looks to start with the ridge axis nearly overhead with the
best moisture and instability forecast to be in the western and
especially northwestern mountains. Isolated showers may drift across the
lower elevations during the late afternoon and early
evening...mainly central and north. GFS dries out the airmass
slightly on Sunday for mainly Western Mountain storms. Early next week looks
quite interesting again with another chance of decent rainfall as
the ridge axis shifts slightly east of US opening the door for
increasing monsoonal moisture and disturbances. The GFS has the
moisture returning to the west Monday with some increase east of The
Divide by evening. The European model (ecmwf) is faster with the higher precipitable water air over
the entire County warning forecast area Monday. The Gem is closer in timing to the GFS. All
the models seem to bring up the remnants of an Ely wave originating
on the bottom of the 4-corners high for later Monday into Tuesday.
Details are still uncertain but early next week looks to be another
potentially moist and unsettled period with a good chance of more
rain for a large part of the area. European model (ecmwf) is showing rapid drying
Tuesday in a northwest flow as the ridge redevelops to our west. The GFS is
slower to develop the northwest flow...more west-northwest yet Tuesday...with the
remnant wave still hanging over the eastern part of the area. Sticking
with scattered probability of precipitation yet Tuesday before some drying occurs Wednesday with
scattered probability of precipitation confined to the mountains and generally isolated across the
lower elevations. Depending on exact timing the warmest days look to
be Sunday and potentially Monday if the slower monsoonal GFS timing
occurs. Cooler with more clouds and precipitation then Tuesday. Temperatures
will likely rebound some Wednesday but still below normal.


Aviation.../12z issuance/
widespread shower activity ongoing this morning...mainly over
southern Lincoln and Sweetwater counties...will gradually dissipate
to only isolated activity by around 15/16z. Before then...widespread
MVFR and possibly IFR conditions are expected in this area impacting
krks. Farther north...the primary concern will be patchy fog
impacting terminals where rain fell yesterday. Any fog is expected
to lift/dissipate by around 15/16z. In the afternoon...isolated to
locally scattered convection will mainly occur over the west and
south. The best instability will be over the far west and will have
thunderstorms in the vicinity only at jac terminal for now...with vcsh over the rest of the
terminals west of The Divide. Although there could be some isolated
convection east of The Divide...coverage and confidence is not high
enough to have even vcsh. During the evening...convection should
quickly wane. Winds will generally be light easterly in most areas
today...with the exception of breezy east winds expected across
Sweetwater County impacting krks. One side note...fog is expected
across the southern two thirds over Wyoming this morning with small
deep/temperature spreads as a result of the widespread significant rainfall
Tuesday through early this morning.


Fire weather...
an area of light to moderate rainfall will exit Sweetwater County
to the south this morning. Soon afterward...widely scattered
thunderstorms will develop over western Wyoming this afternoon.
Expect east winds 15 to 30 miles per hour today across zone 279. Thursday
will be a repeat of today with more widely scattered thunderstorms
developing over western Wyoming. An upper level disturbance will
ride up and over the ridge of high pressure parked over The
Rockies Friday which will increase the coverage of thunderstorms
Friday with the most numerous shower activity expected over
western Wyoming as far east as the western edges of the central basins.
Temperatures will slowly recover during the remainder of the work
week but will remain at or below normal for high temperatures.


Riw watches/warnings/advisories...none.



Short term...lipson
long term...skrbac
fire weather...lipson

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