Area Forecast Discussion
Issued by NWS Riverton, WY
FXUS65 KRIW 140556
Area Forecast Discussion
National Weather Service Riverton WY
1156 PM MDT THU OCT 13 2016
Allowed red flag warning to expire at 7 PM this evening as wind
gusts have decreased below 25 MPH, and RH across the area is above
Decided with this update to expand the high wind warning for
tonight through Friday evening to include the eastern slopes of
the Wind River Mountains, SE Fremont County (zone 19), and much of
the lower elevations of Natrona County (zone 20). Would like to
see a tighter surface gradient too have more confidence in the new
zones issued this evening, but 700mb winds around 50KT and a
decent lee surface trough should be sufficient to produce a low
end high wind event. The eastern slopes of the Wind Mountains will
be harder to verify since need 50 sustained or gust of 75 mph, but
the mountain wave signature is strong enough to include them.
These high winds could impact South Pass at times with the
strongest wind impacting that area between 21Z Friday and 03Z
Saturday. Also wanted to include the Wind Mountains due to the
number of hunters.
.PREV DISCUSSION... /issued 219 PM MDT THU OCT 13 2016/
Short Term...Tonight Through Friday
High winds are expected tonight and Friday in the Absaroka
mountains and Cody foothills. Strong winds will also occur from
Crowheart to Togwotee Pass and along the east slopes of the Wind
River mountains to South Pass. Windy conditions can also be
expected from Beaver Rim to Muddy Gap...and east into the Casper
area. Downslope winds will warm temperatures. Clouds moving into
the west this afternoon are the leading edge of clouds associated
with a Pacific low pressure trough. Some mountain showers will
develop over night. Precipitation is expected to develop late
tonight with snow levels from 8000 to 8500 feet. Precipitation is
expected to become more widespread Friday afternoon. The western
valleys should see mainly rain.
Long Term...Friday night Through Thursday
High winds will remain a threat friday evening in the Absaroka
mountains and Cody foothills with strong winds remaining across
much of the area along and east of the Continental Divide.
Mountain snow and valley rain will increase Friday night. A break
between Pacific lows is expected Saturday but some higher mountain
snow will still be possible. The next batch of heavier
precipitation with heavy snow possible above 8000 feet is expected
Sunday continuing Sunday night through early afternoon on Monday.
Through the period snowfall above 8500 feet may be around 12 to 15
inches. Strong west winds in the higher mountains are also
possible. The western valleys could see 1 to 2 inches of rain by
late Monday. Windy and rather mild temperatures will occur with
variable cloud cover east of the Continental Divide. Tuesday will
see precipitation end in the west with a cold front cooling
temperatures and decreasing wind east. The flow aloft will become
north northwest Wednesday and Thursday with cooler temperatures
but overall dry conditions continuing through Thursday.
WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES
Increasing mountain snow/valley rain showers Friday morning,
becoming widespread during the afternoon and evening especially
across the far west. The bulk of the precipitation will be along and
northwest of a line from 20N KEMM-KBPI-10W KDUB. KJAC terminal will
be most impacted by this activity with persistent MVFR conditions
possible especially by late afternoon/early evening. Also breezy to
windy southwest to west wind will be common...more southerly in
Jackson Hole with some low level wind shear. Mountains will
increasingly become obscured Friday morning with mountain passes
obscured much of the time in IFR conditions in the afternoon into
tonight. The exception will be South Pass where ceilings will be
last to lower with the least amount of precipitation, but strong
southwest flow and mountain turbulence will persist.
EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES
The main concern will be strong southwest flow resulting in strong
surface winds, low level wind shear at times, and strong mountain
turbulence. Mountain snow showers will be mainly confined to along
and west of the Divide. Mountain tops along the Divide will
increasingly become obscured by midday Friday into the afternoon as
mountain snow showers become established along the Divide.
Otherwise, VFR conditions with considerable mid/high level clouds.
A red flag warning remains until 7 pm for wind and low relative
humidity in Natrona county. A high wind warning is in effect
tonight through Friday evening for the Absaroka mountains and
Cody foothills. Strong winds will be common across the southwest
and areas east of the Continental Divide with warming
temperatures. Valley rain and mountain snow will increase across
the west Friday continuing through Monday with a break in the
heavier precipitation Saturday. Significant snow and significant
valley rainfall is expected in the west.
High Wind Warning until 9 PM MDT Friday for WYZ002-003.
High Wind Warning from midnight tonight to midnight MDT Friday
night for WYZ015-019.
High Wind Warning from midnight tonight to 9 PM MDT Friday for