Special Weather Statement, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
1252 PM MDT Thu Aug 2 2018

.SHORT TERM...This evening through Sunday
Issued at 1223 PM MDT Thu Aug 2 2018

Monsoonal moisture in the sw will aid convection down there
spreading ne into the evening hours. Thermal trough/shortwave noted
on the upper air and satellite analysis this morning is moving into
ern ID and far swrn MT and this will be the focus for storms as it
moves into YNP through the afternoon hours and then spreads across
the north. A little better mid level westerlies and mid level
cooling will create the potential for a few stronger storms. A lot
of the area will have the threat of storms through the evening hours
with a few lingering overnight. Another round of storms is expected
Friday. The next approaching shortwave for Friday may draw another
round of monsoonal moisture nwd while some forcing across the north
with the trough and exiting jet may aid in storms across the far
north. The subtle front from today's wave washes out Friday before
the 'stronger' front drops down Friday night into Saturday hanging
around our central zones on Saturday. South of the boundary over
Sweetwater, Uinta and srn Lincoln County up to the Greens and
Rattlesnakes may have critical fire weather conds. The two critical
fuels zones 277 and 279 will have a fire weather watch for Saturday
from noon to 9 pm. If the front washes out further north, then 280
and even 283 could become critical. On Sunday, the system that is
currently out near 31-32N/142W will move onshore Saturday night and
move across us on Sunday. It could be an active day, especially
along and east of the divide as front remains in place while trough
approaches and dual jet structure develops in the nern zones.

.LONG TERM...Monday night through Thursday
Issued at 1223 PM MDT Thu Aug 2 2018

Pattern transition is forecast to be underway next week, as upper
low from the Gulf of Alaska dives south and cuts off over the
eastern Pacific, pumping up a ridge over the western U.S. Medium-
range models show an overall trend westward with this trough/ridge
pattern. This shift will put Wyoming under the influence of NW flow
aloft rather than under the dome of hot air; so forecast
temperatures, at least east of the Divide, have been trended
slightly cooler. Some adjustments further downward may be necessary
if this trend further westward of the ridge continues. A similar
pattern was responsible for severe weather outbreaks in late July;
however, models are placing mean surface trough and higher CAPES
along and east of Wyoming's eastern border, drier air over west and
central Wyoming. We have slight chances of thunderstorms over the
Bighorn Mountains on Monday; otherwise, dry conditions are expected
to prevail Monday through Thursday.

&&

.AVIATION...For the 00Z TAFS through 00Z Friday afternoon
Issued at 1223 PM MDT Thu Aug 2 2018

Showers and thunderstorms will continue through 06Z. Expect showers
and storms to persist through 06Z Fri in the central and east. VFR
conditions will occur at the terminal sites through the period.
Local MVFR conditions will occur with some of the stronger storms
due to heavy rain which would reduce visibility. Mountains will be
obscured at times. Another round of showers and thunderstorms is
likely tomorrow afternoon.

&&

.FIRE WEATHER...
Issued AT 1223 PM MDT Thu Aug 2 2018

...Fire Weather Watch Saturday from Noon to 9 pm for zones 277 and
279...

Scattered thunderstorms will move east across the area through this
evening. Isolated to widely scattered showers will continue through
the overnight hours, especially over southern portions. Another bout
of widely scattered to scattered thunderstorms will occur Friday
afternoon and evening. A Fire Weather Watch is in effect for fire
zones 277 and 279 from noon to 9 pm Saturday, due to very low RH
values and gusty winds up to 35 mph.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday afternoon through Saturday
evening for WYZ277-279.

&&

SHORT TERM...Skrbac
LONG TERM...Hulme
AVIATION...Hulme
FIRE WEATHER...Skrbac

Hazardous Weather Outlook
National Weather Service Riverton WY
147 AM MDT Thu Aug 2 2018

WYZ001>020-022>030-031100-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Big Horn Basin-Southwest Big Horn Basin-
Southeast Big Horn Basin-Owl Creek and Bridger Mountains-
Bighorn Mountains West-Bighorn Mountains Southeast-
Northeast Johnson County-Southeast Johnson County-
Teton and Gros Ventre Mountains-Jackson Hole-
Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
147 AM MDT Thu Aug 2 2018

This Hazardous Weather Outlook is for Western and Central
Wyoming.

.DAY ONE...Today and Tonight.

Scattered afternoon and evening thunderstorms. The main threat
will be gusty outflow winds of 50 to 55 mph possible. Warm
conditions and gusty winds will elevate fire weather conditions
across central and eastern portions this afternoon and early
evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Friday through Sunday...Warm with gusty west wind will elevated
fire weather conditions across southern Wyoming during the
afternoon and early evening. Isolated to scattered afternoon and
evening thunderstorms across mainly northern Wyoming.

.SPOTTER INFORMATION STATEMENT...

Spotters are urged to report wind gusts past 45 mph. Thank you.

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Special Weather Statement
National Weather Service Riverton WY
820 PM MDT THU AUG 2 2018

WYZ017-030245-
Wind River Basin-
820 PM MDT THU AUG 2 2018

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL FREMONT COUNTY UNTIL 845
PM MDT...

At 820 PM MDT, Doppler radar was tracking a strong thunderstorm near
Kinnear, or 10 miles south of Pavillion, moving east at 20 mph.

Winds in excess of 40 mph will be possible with this storm.

This strong thunderstorm will be near...
  Riverton around 840 PM MDT.

Other locations impacted by this storm include Riverton Country Club,
Arapahoe Elementary School, Midvale, St Stephens, Fremont County
Fairgrounds, Riverton Regional Airport, Wyoming Indian Elementary
School and Riverton Landfill.

LAT...LON 4295 10870 4296 10871 4298 10877 4317 10873
      4327 10830 4289 10821
TIME...MOT...LOC 0220Z 260DEG 19KT 4310 10861

TL

Special Weather Statement
National Weather Service Riverton WY
824 PM MDT THU AUG 2 2018

WYZ004-008-009-030300-
North Big Horn Basin-Bighorn Mountains Southeast-Bighorn Mountains
West-
824 PM MDT THU AUG 2 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN JOHNSON AND CENTRAL
BIG HORN COUNTIES UNTIL 900 PM MDT...

At 824 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 14 miles north of Medicine Wheel to 12 miles
north of Greybull. Movement was east at 55 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Strong thunderstorms will be near...
  Shell Canyon around 845 PM MDT.
  Shell Falls around 850 PM MDT.

Other locations impacted by these storms include Porcupine
Campground, Bald Mountain Campground and Shell Creek Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4490 10785 4487 10786 4479 10783 4477 10775
      4471 10774 4471 10768 4468 10767 4470 10762
      4466 10752 4463 10752 4464 10750 4461 10747
      4460 10739 4456 10737 4456 10706 4440 10712
      4465 10829 4500 10796 4500 10791
TIME...MOT...LOC 0224Z 278DEG 49KT 4504 10792 4468 10810

Troutman

Special Weather Statement
National Weather Service Riverton WY
833 PM MDT THU AUG 2 2018

WYZ004-008-009-030300-
North Big Horn Basin-Bighorn Mountains Southeast-Bighorn Mountains
West-
833 PM MDT THU AUG 2 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN JOHNSON AND CENTRAL
BIG HORN COUNTIES UNTIL 900 PM MDT...

At 832 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 17 miles northeast of Medicine Wheel to 9 miles
northwest of Shell. Movement was east at 55 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Strong thunderstorms will be near...
  Shell Falls around 845 PM MDT.

Other locations impacted by these storms include Porcupine
Campground, Bald Mountain Campground and Shell Creek Campground.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4490 10785 4487 10786 4479 10783 4477 10775
      4471 10774 4471 10768 4468 10767 4470 10762
      4466 10752 4463 10752 4464 10750 4461 10747
      4460 10739 4456 10737 4456 10706 4440 10712
      4465 10829 4500 10796 4500 10791
TIME...MOT...LOC 0232Z 278DEG 49KT 4501 10769 4465 10787

Troutman