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Area forecast discussion 
National Weather Service Riverton Wyoming
1152 am MDT Monday Jul 6 2015

Short term...Monday through Wednesday night

What a difference a day makes across the cowboy state. It feels a
lot more like April than July this morning with widespread 50s
across the area along with clouds. Areas of rain continue across
much of the area...mainly of the light to moderate variety but with
some pockets of heavier rain. And yes...there could be some of the
white stuff in the higher elevations...but remaining above pass
level and probably above 11000 feet. The rain should continue
through the remainder of the night. After that...there should be a
decrease in the coverage of the showers as some drier air works its
way in from the north courtesy of an area of high pressure that will
drop in from Montana. The models are fairly consistent in bringing
in lower precipitable waters through the day from the north to the
south. As a result the the showers should become more sparse that
way as well east of The Divide.As for the chance of
thunderstorms...the best chance would be west of The Divide where
the best instability is still found. We left it in everywhere for
this afternoon...but most areas should not see once since
instability is lacking with the cloud cover. The next question is
temperatures. If this was January...we could be talking about
falling temperatures during the day. But this is that will
not happen. A lot depends on if there is any clearing. The warmest
temperatures would be in the Big Horn basin where the clearing will
be earlier. For now...we left continuity alone since it seemed like
a reasonable compromise. Showers will linger across the west tonight
with mainly dry conditions to the east.

By looks to become more active once again as a weak
area of low pressure develops to the north and a shortwave moves
across the state. This will again increase the chance of showers and
thunderstorms across the area. At this time...these look like more
of the garden variety of thunderstorms as models have as instability
parameters and precipitable water values are not overly impressive.
With more sunshine in the morning temperatures should be a few
degrees warmer...but still below normal for this time of year. There
should taper off again as we head into the night hours but a few
will linger even into the overnight hours.

As we head into Wednesday it looks like more of the same with
easterly flow continuing. Another shortwave will cross the area with
a chance for additional convection. There a better chance for a few
stronger storms on this day as there will be a bit more moisture to
work with. In addition...northern portions of the area will be see
some better upper level divergence courtesy of the right rear quadrant
of a jet streak. As a result...the best chance of a stronger storm
would be in the Big Horn basin and Johnson County. Temperatures will
warm as well as the air mass becomes more modified.

Long term...Thursday through Monday

The GFS and European model (ecmwf) models continue to bring the upper low inland
into California Thursday with a south southwest flow aloft over
Wyoming. Upper level difluent flow will aid in thunderstorm
development. Storm coverage looks better over the west and
southwest Thursday afternoon. Thursday evening should see coverage
increase east of The Divide. The upper low opens up Thursday night
as it moves into Nevada. Then the system tracks into Idaho Friday
and moves through western Wyoming Friday night. Southwest flow aloft
Friday with best storm chances in the west and northwest part of
Wyoming with mainly isolated coverage elsewhere. Saturday looks drier
for most places with slight chance of storms over the northwest.
Isolated activity over the southwest and far northern Wyoming Saturday.
Upper level high pressure builds over the southern rockies and
pushes northward into the central and northern rockies for Sunday
and Monday. 700mb temperatures warm up and summertime heat returns to the
area both days. Storm coverage will be isolated at best and mainly
over or near the mountains.


Aviation.../18z issuance/

All routes...VFR to prevail rest of today into tonight. Patchy
areas of fog could develop later tonight both sides of The Divide.
Otherwise...middle level...cumulus...ceilings to remain especially
east of The Divide. Only isolated low-topped thunderstorms
possible until 03z Tuesday.


Fire weather...

Unseasonably cool today with a continuing chance of showers. Drier
air may work into northern and eastern areas this afternoon and
tonight. Some snow is possible above 10500 feet but accumulation
will be small given recent warm weather and ground temperatures.
Relative humidity will remain well above critical levels with winds
generally light to moderate. Below normal temperatures and the
chance of showers will continue into Tuesday and Wednesday.


Riw watches/warnings/advisories...none.



Short term...99
long term...hattings
fire weather...hattings

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