Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 160905
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
305 AM MDT Sun Jun 16 2019

.SHORT TERM...Today through Tuesday night

It was a bit more active than thought yesterday with numerous
thunderstorms around. As I write this around one we still have
some convection in eastern portion of the area but it is moving
east and most of it should be out of the area by dawn, which is
very early right now (Solstice is in 5 days). Today again looks
like a rather active day with a stationary boundary over the area
and plenty of moisture to work with precipitable waters near and
over an inch in many areas. As a result, many areas will see
another chance of showers and thunderstorms. Coverage looks fairly
similar to yesterday with the best coverage further north and the
smallest chance in southwestern Wyoming. And like yesterday, some
showers will likely linger into the overnight hours.

Monday looks like another active day when it comes to convection.
There is a little more disagreement in the placement of the storms
though with some models a bit further south than others. At this
point I have low confidence in nailing down an area of more activity
since the models have been doing a poor job in that regard the past
few days. For now, we went with isolated to scattered POPs for most
areas for now. Temperatures will continue to average below normal as
well given the ample cloud cover as well. There are some differences
in that some of the models are showing some somewhat drier air
moving in later at night and this could shut the storms off before
midnight. For now, we rolled the dice and went dry for later Monday
night.

As for Tuesday, with precipitable waters running on average about 20
percent lower than Monday and some weak ridging trying to build into
the area from the west, coverage of storms should decrease somewhat,
although many areas will still have the chance of one. Of the three
days though, this one will likely have the longest rain free
durations of the three days. Most of these storms should also be
over by late evening with later Tuesday night largely dry.

.LONG TERM...Wednesday through Sunday

Wednesday will be dry for most areas. Isolated showers and storms
will occur in the north in the afternoon and night. Breezy in the
central and south zones in the afternoon into early evening.
Seasonably warm day Wed with 70s to lower 80s. Thursday looks
similar to Wed with the best chance of showers and storms over the
north with isolated activity in the central portion. The south and
southwest is to be dry. A cold front moves into the north for
Thursday. Still breezy to windy in the central and south Thursday
with a west wind. Cooler highs over the north with slightly cooler
highs central and south.

The weather pattern seems to be evolving into another trough over
the northern and central Rockies Friday through next Sunday. The
ECMWF model is quite unsettled while many of the GFSensemble
members are also leaning toward the ECMWF solution. Thus Friday
will see scattered showers over the region with less activity over
the south. Then a better chance of showers and storms is expected
over the area next Saturday and Sunday. Cooler high temps Friday
through Sunday. Will keep an eye on this pattern in the coming
days and adjust forecast as needed.

&&

.AVIATION...

Another round of showers and thunderstorms is expected to develop
around the noontime Sunday, starting initially in the northern
mountains, then spreading across the Big Horn and Wind River
basins, then into Natrona and Johnson counties later in the
afternoon. Most areas west and south of the divide should remain
free of rainfall through the day. Showers will linger after
sunset, but should become more isolated in nature. Wind Sunday
night after midnight should again drop to light and variable,
except near any remaining thunderstorms. VFR conditions will occur
at the terminal sites, but brief MVFR conditions can be expected
if a storm directly impacts any airport.

&&

.FIRE WEATHER...

Unsettled conditions will continue with another round of scattered
showers and thunderstorms, most numerous in the afternoon and east
of the Continental Divide. A wetting rain will be possible where
storms persist for longer. Relative humidity will remain above
critical levels. Wind should remain light to moderate except in and
around any shower or thunderstorm. Mixing and smoke dispersal will
generally range from fair to good East of the Divide to good to very
good West of the Divide and in Sweetwater County.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...Hattings
LONG TERM...AR
AVIATION...Straub
FIRE WEATHER...Hattings


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