Area Forecast Discussion
Issued by NWS Riverton, WY
FXUS65 KRIW 201733
Area Forecast Discussion
National Weather Service Riverton WY
1133 AM MDT FRI MAY 20 2016
.SHORT TERM...Friday through Sunday night
Unsettled will be the word of the weather for the next few days as
an upper level low takes up residence to the west and sends a few
waves of energy over the area. Some showers are still ongoing this
morning but most are rather light at this time. As for lightning,
most has gone away with only an isolated strike or two. There should
be a general waning in coverage through the night with most areas
mainly dry for Friday morning.
The break will be brief through as more showers and thunderstorms
fire up this afternoon. The lion`s share will be West of the Divide.
but one or two could pop up in the eastern mountains and possibly
drift into the adjacent foothills. The most noticeable feature east
of the divide will be wind today as the pressure gradient begins to
tighten ahead of an approaching cold front. At this point, 700
millibar winds do not look strong enough to warrant high wind wind
highlights. However, it will be quite windy this afternoon for many
areas with gusts over 40 mph certainly possible for many areas.
These winds should decrease a bit tonight as the winds decouple with
the loss of mixing this evening although it will still be breezy at
There will be one more warm and windy day ahead of the front on
Saturday. However, things could get more interesting in the
convection department. Model soundings are showing a decent amount
of shear. This, in addition to the added forcing from the passing
cold front could bring some stronger storms. The best threat for
these would be further east where more CAPE and instability will be
found. The Storm Prediction Center has Johnson and Natrona County
under a marginal risk with a slight risk just to the
east.Hightemperatures could be tricky though depending on the
passage of the front. Precipitation should taper off and
temperatures fall behind the front Saturday night.
As for Sunday look for a cooler day with less wind, although still
breezy. With the low heights still around and another shortwave
moving through the area there will once again be the threat of
afternoon convection. With the cooler conditions and lower wet bulb
zero temperatures...small hail may be the main threat with these
.LONG TERM...Monday through Friday
This forecast period will feature an overall trough pattern over
the Rocky Mountain region. A series of weather disturbances will
move through this flow during the week. The given long range
models have various timing of these weather systems as they move
through the area. It appears that convection will be the issue
each afternoon and night with lingering late night/morning
showers. Instability and lapse rates support the daily rounds of
showers and storms. Thus the forecast will have the chance for
showers and storms each day with varying coverage. Surface
convergence areas will certainly occur which will enhance
convection in those locations. 700mb temps and 500mb temps are on
the cool side for the most part during the week and do not
fluctuate much from day to day. Thus not a lot of day to day
changes in highs and lows over the region Mon through Fri.
West of the Continental Divide...KJAC/KRKS/KPNA/KBPI Routes
Mountain showers this morning will give way to the development of
more widespread showers and thunderstorms this afternoon,
especially after 20z. Gusty and erratic wind may accompany
thunderstorm development, with gusts of 40kt or stronger possible.
Thunderstorm activity will weaken after 03z this evening, though
light showers will continue through the overnight hours. Low
pressure moving closer to western Wyoming will send another push
of moisture across the area after 15z Saturday. Mountain snows and
ongoing shower activity will leave the potential for obscured
mountain tops through the TAF period.
East of the Continental Divide...KCPR/KCOD/KRIW/KWRL/KLND Routes
The majority of the area can expect generally dry conditions
today, though northeastern Wyoming including KBYG may see some
isolated showers and thunderstorms this afternoon. Coverage is not
anticipated to be significant, though some storms may produce
gusty and erratic wind at terminal sites. Additionally, it remains
difficult to completely rule out shower activity at those
terminals adjacent to shower receiving mountains, including KLND.
A rogue shower may remain possible this afternoon. The central and
northern mountains will see the potential for showers and
thunderstorms, with lowered ceilings to create obscured mountain
tops. Showers at the terminals will weaken after 06z this evening,
with VFR conditions then anticipated. Showers and related mountain
obscurations will remain possible.
After a break this morning, more showers and thunderstorms will fire
this afternoon mainly west of the Divide and across the higher
elevations. Erratic winds from these thunderstorms will be possible.
Across the lower elevations east of the Divide, gusty southwest
winds will develop in the afternoon and continue into the evening.
Mixing and smoke dispersal will be good to excellent after any
morning inversions break. A cold front will move across the state on
Saturday with another chance of showers and thunderstorms.