Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 262023
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
223 PM MDT Mon Jun 26 2017

.SHORT TERM...(This evening through Thursday)
Issued at 225 PM MDT Mon Jun 26 2017

The high pressure ridge over eastern Idaho will move east as a
Pacific low pressure trough moving into the Pacific Northwest
coast spreading southwest winds across the area tonight and Tuesday.
Temperatures will warm with increasing instability with Scattered
showers and thunderstorms Tuesday.  Relative humidity will be low
with strong gusty winds in the afternoon and evening across the south.
Showers and thunderstorms will become more widespread Wednesday and
Thursday with some cooling beginning as cloud cover and precipitation
increase. Strong gusty winds will be an increasing threat with
thunderstorms.

.LONG TERM...(Thursday night through Monday)
Issued at 225 PM MDT Mon Jun 26 2017

In wake of the cold front Thursday, an unseasonably cool end to June
is expected Friday with highs about 10 degrees cooler than average
east, and about 5 degrees cooler west. Some energy in the northwest
flow on Friday could result in some convection across the northern
mountains spreading southeast into the basins and valleys. However
instability is weak so expecting any thunderstorms to be quite
isolated. The ECMWF and GFS show a more zonal flow developing this
weekend with relatively weak shortwaves in the flow with the GFS a
bit more amplified. This will keep afternoon/evening thunderstorms
in the forecast across the north and central portions of the area
mainly over the mountains and adjacent foothills, with dry
conditions prevailing over the south. Global models then show a
drier and warmer airmass pushing into the region for the 4th of July
with little or no chance of thunderstorms. However looks like
temperatures will be above average with a westerly breeze.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 225 PM MDT Mon Jun 26 2017

A few showers could develop over the western/northwestern mountains
this evening, but should not impact area terminals except for some
gusty outflow winds. After 06Z, an increase in shower activity is
expected over northwest Wyoming with considerable mid-level
cloudiness expanding across the rest of the area. The main terminal
to be impacted would be KJAC terminal, but only enough to have VCSH
for now. Some of the shower activity could spread south and east
Tuesday morning, but will keep terminals dry for now with only some
mid-level cloudiness. A Pacific cold front will sweep east/southeast
across the area during the day Tuesday with windy west to northwest
wind developing at most locations. The greatest instability as the
front pulls across the area will be across northern Wyoming where
some strong thunderstorms could occur. Looks like KCOD would be
impacted first by the strong convection between 18Z and 21Z then
east southeast impacting KWRL and then possibly KCPR after 21Z.
Across the far south, including the KRKS terminal a drier air mass
should keep a lid on convection. Except for brief IFR/MVFR near any
convection Tuesday, VFR conditions are expected.

&&

.FIRE WEATHER...
Issued AT 205 PM MDT Mon Jun 26 2017

The high pressure ridge over eastern Idaho will move east as a
Pacific low pressure trough moving into the Pacific Northwest
coast spreading southwest winds across the area tonight and Tuesday.
Temperatures will warm with increasing instability with Scattered
showers and thunderstorms Tuesday.  Relative humidity will be low
with strong gusty winds in the afternoon and evening across the south.
Showers and thunderstorms will become more widespread Wednesday and
Thursday with some cooling beginning as cloud cover and precipitation
increase. Strong gusty winds will be an increasing threat with
thunderstorms. The lower air mass will be unstable enough with
sufficient wind for very good to excellent smoke dispersal from late
morning to mid evening each day.

&&

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

$$

SHORT TERM...Baker
LONG TERM...Murrell
AVIATION...Murrell
FIRE WEATHER...Baker


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