Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 220853
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
253 AM MDT SUN MAY 22 2016

.Short Term...Sunday through Tuesday night

The active weather pattern looks to continue into the first part of
the week. The cold front as swept across the state with much cooler
temperatures present in many areas. There is currently a band of
mainly light rain that stretches across the central portion of the
state that is shown quite well by the models with a jet streak
moving across the area. This band should die off by around sunrise
with many areas starting the day mainly dry. However, it will turn
active again this afternoon as a shortwave crosses the area. Showers
will break out across the west this morning and press east through
the area with some thunderstorms developing this afternoon.
Intensity of the storms and rainfall should be much less than
yesterday though. This is due to a cooler temperatures and rather
limited CAPE. Precipitable water values are have also fallen under a
half an inch. As a result we have removed heavy rain from the
wording. Low wet bulb zero levels could mean small hail is a threat
though. Snow will fall across the mountains at times but no
highlights are needed since any substantial accumulations would be
above pass level and any snow that falls on roads would melt with
the strong late May sun. There will also be a gusty wind that will
continue but much less than on Saturday.  Showers should end this
evening with much of the overnight period mainly dry.

Another shortwave will move across the area on Monday. However this
one is weaker than the previous couple. As a result the coverage
should be less. The models are split as to whether or not any
showers can jump the divide with the NAM wet and the GFS dry. At
this point we have kept things dry for most areas. And even in areas
that have one, a vast majority of the area will be dry most of the
time. Temperatures should moderate a few degrees but remain below
normal. A more substantial wave will then move toward the area for
Tuesday and increase the chance of showers once again. The west
looks fairly wet again. Meanwhile, the east will see mainly
afternoon convection with again most of the area dry most of the
time.

.LONG TERM...Wednesday through Sunday

Wednesday looks to have that chance of showers and storms in the
afternoon and evening with lingering showers late Wed night. Will
be keeping an eye on a weather disturbance that may move through
the area Thurs into Thurs night. It appears that the main energy
will stay south. Will maintain the chance of showers and storms
Thursday into Thurs night. Weather pattern this coming Friday
through Sunday may be close to what we just experienced this past
weekend. A storm system settles into the Western U.S. and brings a
south to southwest flow aloft into WY. The GFS model is farther
west than the ECMWF model, which has the storm in close proximity
to the last one. If it stays farther west, then less showers and
storms for WY Fri through Sunday. For now will keep the chance of
storms on Friday but this may be too much coverage if the storm
stays west. Then a lower chance of showers and storms Sat/Sun.

High temps will be near seasonal values Wed through Fri...60s to
lower 70s...upper 50s to lower 60s in the west. Warmer highs
Sat/Sun with 60s west of the divide and 70s east of the divide.

&&

.Aviation.../12Z Issuance/

West of the Continental Divide...KJAC/KRKS/KPNA/KBPI Routes

An upper level disturbance will spread scattered showers into the
southwest, mainly vicinity and south of a KAFO-KPNA line 12z-18z
Sunday along with areas of MVFR conditions and frequent mountain
obscurations.  Isolated thunderstorms will blossom during afternoon
heating across mainly southwest Wyoming with activity more isolated
vicinity KJAC-KDUB and northward.  Showers and thunderstorms will
diminish in the early evening with some clearing and patchy ifr/lifr
ceilings or fog forming overnight, partially obscuring western
valleys (vcnty KJAC-KPNA-KBPI).

East of the Continental Divide...KCPR/KCOD/KRIW/KWRL/KLND Routes

A line of rain showers with areas of MVFR conditions VCNTY of a KRKS-
KRIW-KGEY will slowly drift east and dissipate by 12z, likely not
making it to KCPR beforehand.  The area should be mostly
precipitation free 12z-20z Sunday.  An upper level disturbance will
spread scattered showers and thunderstorms along and south of a
KRKS-KLND-KCPR line through the afternoon with activity more
isolated further north. Brief MVFR conditions are possible KRKS-
KLND-KRIW-KCPR through 01z Monday. Clearing will occur with VFR
conditions prevailing 3z-12z Monday.

&&

.FIRE WEATHER...

Fire weather concerns should remain low for the next few days.
Another upper level disturbance will cross the area today and bring
another chance of showers and afternoon thunderstorms. However,
coverage and intensity of any thunderstorms should be less than on
Saturday. A gusty west wind will continue, but relative humidity
will remain above critical levels. The chance of showers will linger
into Monday although coverage will be much less; especially east of
the Divide. Temperatures will remain below normal the next few days.

&&

.RIW Watches/Warnings/Advisories...None.

&&

$$

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



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