Severe Thunderstorm Warning 48, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
242 PM MDT Sat Jun 23 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 233 PM MDT Sat Jun 23 2018

A Pacific low pressure trough moving through the Northern Rockies
will bring afternoon and evening showers with isolated thunderstorms,
most numerous in the north and central tonight, decreasing in coverage
on Sunday. Heavy thunderstorms rains may cause flooding across the
north, central and east through Sunday afternoon.  Temperatures will
decrease with increasing relative humidity.  The south will be mainly
dry with breezy to windy areas and lower relative humidity.  With high
pressure ridging over the west and decreasing west flow aloft, drying
will occur with warming Monday and Tuesday.

.LONG TERM...(Tuesday night through Saturday)
Issued at 233 PM MDT Sat Jun 23 2018

West flow aloft will bring dry conditions Wednesday and Thursday with
some limited moisture and instability increasing across the north
Friday and Saturday for limited showers and thunderstorms.  Temperatures
will continue to warm through Thursday then cool Friday and Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday)
Issued at 233 PM MDT Sat Jun 23 2018

VFR conditions expected at all terminals through the forecast period
with a few exceptions. Depending upon rainfall and a moist boundary
layer, there could be a period of MVFR ceilings at KCPR and KWRL
between 08Z-15Z/Sunday. Confidence is still low and a prevailing
group is not included with this forecast issuance. However, a TEMPO
group or prevailing group may be needed with 06Z/Sunday issuance.
Brief MVFR conditions possible east of the Continental Divide with
strongest convection between 21Z/Saturday and 03Z/Sunday. Mountain
top obscurations will continue through at least 12Z/Sunday across
the northwest and north. Upper low over western Montana will slowly
progress southeast Saturday night and Sunday morning. The showers
and thunderstorms associated with this system will push south as
well with the most widespread convection between 21Z/Saturday and
03Z/Sunday. Coverage and intensity of showers and storms will
decrease after that time but will continue through the night. Upper
low will eventually set-up over western portions of South Dakota and
Nebraska later Sunday. This will allow for lingering showers at KCPR
and KWRL through at least Sunday morning. High pressure will push
into southwest Wyoming Sunday afternoon with dry conditions and less
wind anticipated Sunday afternoon. Gusty west-northwest surface wind
of 15-25kts Saturday afternoon ahead of a south-moving cold front.
This front will reach a KLND-KCPR line by 01Z/Sunday with gusty
north wind in its wake through 06Z/Sunday. Surface winds will be
much less at all terminals Sunday afternoon.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 233 PM MDT Sat Jun 23 2018

A Pacific low pressure trough moving through the Northern Rockies
will bring afternoon and evening showers with isolated thunderstorms,
most numerous in the north and central tonight, decreasing in coverage
on Sunday.  Temperatures will decrease with increasing relative
humidity.  The south will be mainly dry with breezy to windy areas and
lower relative humidity.   The lower and mid levels will be unstable
and well mixed Sunday and Monday with sufficient winds for excellent
smoke dispersal in the afternoons.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 6 PM MDT this evening through Sunday afternoon
for WYZ005>011-017-019-020-022.

&&

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

Hazardous Weather Outlook
National Weather Service Riverton WY
138 AM MDT Sat Jun 23 2018

WYZ001>020-022>030-241300-
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-
138 AM MDT Sat Jun 23 2018

...Flood Watch is in effect from Saturday evening through Sunday
afternoon for central and eastern portions...

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight

Saturday and Saturday night...Showers and thunderstorms will
become more numerous by the afternoon and continue through the
overnight hours. Localized flooding is possible Saturday night.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Sunday...Scattered showers with isolated thunderstorms, with
locally heavy rain, will continue through the day. Precipitation
will end by late Sunday evening.

Thursday and Friday...Isolated afternoon and evening thunderstorms
mainly over the north.

.SPOTTER INFORMATION STATEMENT...

Spotters are urged to report hail, wind gusts past 45 mph and any
flooding. Thank you.

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Special Weather Statement
National Weather Service Riverton WY
253 PM MDT SAT JUN 23 2018

WYZ007>009-232130-
Owl Creek and Bridger Mountains-Bighorn Mountains Southeast-Bighorn
Mountains West-
253 PM MDT SAT JUN 23 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN JOHNSON...
NORTHWESTERN NATRONA AND SOUTHEASTERN WASHAKIE COUNTIES UNTIL 330 PM
MDT...

At 251 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles east of Cottonwood Pass, or 40 miles south of Ten Sleep,
moving east at 25 mph.

Hail up to the size of pennies, brief heavy rain, wind gusts to
around 45 mph, and dangerous lightning will be possible with this
storm.

This storm will remain over mainly rural areas of southwestern
Johnson...northwestern Natrona and southeastern Washakie Counties.
Bighorn Trail Road and Bighorn Mountain Road are both in the path of
this storm.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4337 10695 4338 10748 4356 10748 4367 10696
      4341 10690
TIME...MOT...LOC 2051Z 269DEG 22KT 4347 10738

CNJ

Special Weather Statement
National Weather Service Riverton WY
305 PM MDT SAT JUN 23 2018

WYZ007-017-232130-
Owl Creek and Bridger Mountains-Wind River Basin-
305 PM MDT SAT JUN 23 2018

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL FREMONT COUNTY UNTIL
330 PM MDT...

At 303 PM MDT, Doppler radar was tracking a strong thunderstorm over
Boysen State Park Headquarters, or 12 miles north of Shoshoni,
moving east at 25 mph.

Hail of pea to dime size, wind gusts around 40 mph, brief heavy
rain, and dangerous lightning will be possible with this storm.

Boysen Dam and Bosyen State Park Headquarters will be impacted by
this storm. The storm should move along the base of the Bridger
Mountains east of the dam through 330 PM MDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4330 10829 4346 10830 4347 10781 4323 10774
TIME...MOT...LOC 2102Z 268DEG 22KT 4341 10815

CNJ