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fxus65 kriw 182258 

Area forecast discussion
National Weather Service Riverton Wyoming
458 PM MDT Wed Sep 18 2019

Short term...(this evening through Saturday night)
issued at 228 PM MDT Wed Sep 18 2019

A trough over the West Coast currently will push very slowly
eastward into the intermountain west Thursday/Thursday night and
then across The Rockies Friday and Saturday. The associated cold
front will approach far western Wyoming late tonight, but the
front is expected to retreat westward Thursday as the flow backs
to the south. Windy south to southwest winds and unseasonably warm
temperatures are expected Thursday ahead of the storm system with
elevated to critical fire weather conditions.

The cold front is expected to push across much of the forecast
area Thursday night and Friday. Precipitation chances remain slim
through Thursday, but will increase Thursday night and Friday as
the best synoptic lift overspread the area. The best chance will
be across the northwest and north. Snow levels look to lower to
around 8500 feet by sunrise Friday over the far west. Much of the
area should see snow levels dip into the 8500/9000 feet range by
Friday evening while the far west/northwest dip to around 7500
feet. The big question mark is how much wrap around moisture will
be in the northwest flow in wake of the trough/upper low. The
European model (ecmwf) is much more bullish than the GFS for a few model runs. A
few to several inches could accumulate generally above 9000/9500
feet before the system exits late Saturday. Not expecting enough
snow accumulation for any winter highlights at this time.

Long term...(sunday through wednesday)
issued at 228 PM MDT Wed Sep 18 2019

Warmer to much warmer temperatures and dry conditions are
expected Sunday as a transitory ridge pulls across The Rockies
ahead of another trough/upper low impacting The Rockies Monday and
Tuesday. 12z deterministic global models are indicating this
trough splitting with the bulk of the energy remaining south of
the area. Plenty of time to watch how models trend over the next
few days. Will have some slight to chance pops for now at times
Monday and Tuesday.


Aviation...(for the 00z tafs through 00z friday)
issued at 455 PM MDT Wed Sep 18 2019

VFR conditions will occur at the terminal sites through the period
with light wind speeds through Thursday morning for all sites except
krks and kcpr. These sites will see gusty winds around 20 to 25 kts
through 01z, then increase again Thursday morning. Otherwise, winds
will begin to increase in the mountains early Thursday morning. By
Thursday afternoon expect gusty winds at most sites, especially at
krks and kcpr. Additionally, clouds will increase as a system
approaches from the west Thursday evening.


Fire weather...
issued at 228 PM MDT Wed Sep 18 2019

Elevated to marginally critical fire weather conditions are
expected over the central and southern areas this afternoon and
again Thursday afternoon ahead of a Fall storm system. Most
confident for red flag conditions over fire zone 280. Could see
red flag conditions over S. Johnson, Sweetwater, Uinta, and S.
Lincoln counties, but an increase in moisture should result in relative humidity
between 15 and 20 percent.

A storm system will push a cold front across the area Thursday
night and Friday. The best chance of precipitation will be over
the northwest and north where a wetting precipitation event is
likely while areas between Rock Springs and Casper will only have
only a slim chance.

The storm system will gradually pull away Friday night and
Saturday with the best chance of mountain Snow/Valley rain over
the northwest.

A few to several inches of snow could accumulate generally above
9000 feet by the time the precipitation ends late Saturday.


Riw watches/warnings/advisories...

Red flag warning until 7 PM MDT Thursday for wyz280.



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