Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 080527
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1027 PM MST Thu Dec 7 2017

.SHORT TERM...(This evening through Sunday)
Issued at 104 PM MST Thu Dec 7 2017

A very stagnant pattern will continue with a very large high
pressure ridge along the west coast extending north well above
the Arctic Circle producing cool dry northerly flow over
western Wyoming through the weekend.  As the ridge moves slowly
east wind aloft will decrease with gradual warming.

.LONG TERM...(Sunday night through Thursday)
Issued at 104 PM MST Thu Dec 7 2017

The next in a series of clipper type weather systems will sideswipe
mainly our eastern zones Sunday night and Monday with mainly
increased nnw winds and increasing clouds. However, snowfall should
remain east of our CWA for the most part. This system does not
appear to be as cold as the clipper currently exiting the region.
The GFS gives our CWA more residence time with this system than the
Euro so will reflect this idea in the forecast for both Sunday night
and into Monday, where as the Euro sweeps this system into the
Southern Plains by 18z Monday. Will choose the GFS for the sake of
persistence as well as for the fact that the long wave ridge will
amplify over the far Western United States as will the trough over
the Midwest. Tuesday and Wednesday of next week should see
relatively benign weather. Then the next in a series of clippers
will arrive Thursday along with breezier and cooler conditions once
again along with spotty snowfall in the northern mtns. Will keep
temps in the valleys and basins colder than guidance to account for
temperature inversions through the period. One side note, with the
temperature inversions in place, patchy morning fog is likely
through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1026 PM MST Thu Dec 7 2017

VFR conditions are expected through the forecast period. The only
exception could be patchy fog across the extreme far western
valleys Friday morning, but KJAC has remained fog free over the
past couple of nights, and this trend of no fog should continue.
Breezy west to northwest wind along with marginal LLWS will be
found in a few locations.

&&

.FIRE WEATHER...
Issued AT 104 PM MST Thu Dec 7 2017

A very stagnant pattern will continue with a very large high
pressure ridge along the west coast extending north well above
the Arctic Circle producing cool dry northerly flow over
western Wyoming through the weekend.  As the ridge moves slowly
east wind aloft will decrease with gradual warming.

&&

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

$$

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


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