Flash Flood Warning 4, NWS Riverton, WY

067 
WGUS75 KRIW 272026
FFSRIW

Flash Flood Statement
National Weather Service Riverton WY
226 PM MDT SUN MAY 27 2018

WYC037-272145-
/O.CON.KRIW.FF.W.0004.000000T0000Z-180527T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sweetwater-
226 PM MDT SUN MAY 27 2018

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 345 PM MDT FOR
NORTHEASTERN SWEETWATER COUNTY...

At 223 PM MDT, Doppler radar indicated thunderstorms that produced 
the heavy rain have moved north and east of the warned area. Two to 
three inches of rain is estimated to have fallen in the warned area. 
Flash flooding is likely occurring.

Flash flooding will remain over mainly rural areas of northeastern 
Sweetwater County. The heaviest rain fell near Crooks Gap Road north 
of Wamsutter.

Additional rainfall amounts of less than one-quarter inch are 
possible in the warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 4181 10778 4176 10812 4204 10836 4214 10794

$$

CNJ

994 
WGUS75 KRIW 272146
FFSRIW

Flash Flood Statement
National Weather Service Riverton WY
346 PM MDT SUN MAY 27 2018

WYC037-272155-
/O.EXP.KRIW.FF.W.0004.000000T0000Z-180527T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sweetwater-
346 PM MDT SUN MAY 27 2018

...THE FLASH FLOOD WARNING FOR NORTHEASTERN SWEETWATER COUNTY HAS
EXPIRED...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Motorists on Crooks Gap Road, Mineral Exploration Road, and 
other gravel roads in northeast Sweetwater County may still 
experience minor flooding into Sunday evening.

LAT...LON 4181 10778 4176 10812 4204 10836 4214 10794

$$

CNJ

Area Forecast Discussion
National Weather Service Riverton WY
1147 AM MDT Sun May 27 2018

.SHORT TERM...(Today through Tuesday night) Issued at 231 AM MDT
Sun May 27 2018

Strong southerly difluent flow and left front quad dynamics over
our CWA, out ahead of the prominent low spinning around the vcnty
of Las Vegas early this morning, has produced training convection,
mainly over our northern CWA since earlier this evening.
Currently, training convection is ongoing across the Interstate
25/90 corridor from south to north in Johnson County, laying the
ground work for increasingly saturated soil for this next round of
convection expected this afternoon and evening. Todays convection
will result from the 500mb low tracking east northeast into Utah
with an asct 700mb circulation out ahead of the main 700mb low
(also over Utah) expected to develop over Southwest Natrona County
before tracking east to the vcnty of Casper later today. This
weak 700mb circulation will likely be a bulls eye for the heaviest
precip to fall from afternoon and evening thunderstorms. In
addition, Johnson County will be under the gun later today where
the lifted indices are progged to be -6 to -7 along with the
highest capes. Since this area is already getting heavy rainfall
from ongoing thunderstorms followed by relatively strong
convection expected later today, decided to issue a flash flood
watch to cover the lower elevations of Johnson/Natrona counties as
well as Casper Mountain, valid from 18z this afternoon to 06Z
Monday. A 35 knot easterly wind will aid in drawing in juicy air
into the area from the east and influence back building along east
slopes today. SPC has the entirety of Natrona County under a
slight risk today.

The flood watch for most of the northern half of the CWA, west of
the flash flood watch remains in effect through Monday morning to
account for the warm temps as well as for rain on snow melt.

The 700mb low is progged to take an odd turn to the northwest
tonight and into Monday as it becomes more well defined over
Southern montana by later Monday. With the low just to our north,
instability and moisture will again influence another round of
convection Monday afternoon and evening, Our eastern zones will be
in a marginal risk so the potential for significant convection is
expected Monday, although, not quite to the degree we are expecting
today. Some convection will take place behind the exiting low
Tuesday under dirty nw flow. After a cool down expected today and
Monday, temps will begin a warming trend again Tuesday.

.LONG TERM...(Wednesday through Sunday) Issued at 231 AM MDT Sun
May 27 2018

The next Pacific trough will move onto the west coast and into
the Intermountain West on Thursday and Thursday night, and then
shear northeast across the area Friday and Saturday. The area will
see a break between systems on Wednesday with dry and warmer
weather prevailing, except for a few late day thunderstorms over
the mountains. Shortwaves from western trough should begin to
eject northeast across western Wyoming on Thursday, bringing
isolated to scattered showers and thunderstorms to the west and
far north, while dry, warm and breezy conditions prevail across
south and central Wyoming. Southwest flow with lee side low near
the Bighorn mountains will bring modest instability across
northern Johnson County and the northern Bighorn basin Thursday
where stronger thunderstorms are likely to develop.

Forecast generally follows ECMWF's slower and more consistent
solution lifting the main upper trough northeast across the area
late Friday into Saturday; the associated Pacific cold front pushing
across the area Friday-Friday evening.  Higher chances of
precipitation will remain across the west and north Friday, with a
few strong thunderstorms still possible east of the Bighorn Range.
Cooler conditions and mainly dry conditions are expected to prevail
through the day Saturday behind the cold front.

&&

.AVIATION...For the 18Z TAFS through 18Z Monday
Issued at 1145 AM MDT Sun May 27 2018

Scattered showers and thunderstorms will develop over the area and
continue through 06Z Monday. Isolated showers and storms will
linger after 06Z Monday. Wind gusts to 35 knots and hail will be
likely with stronger storms. Heavy rain will also be possible.
Mountains will be obscured at times. Expect VFR conditions at the
terminal sites, but MVFR conditions will occur in thunderstorms.
See TAFs for further details.

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 231 AM MDT Sun May 27 2018

As a Pacific low pressure trough over the western Great Basin
shifts slowly east, moisture and instability will increase in the
southwest flow bringing a significant increase in showers and
thunderstorms on Sunday. Temperatures will begin to cool today.
The still relatively warm temperatures and breezy conditions will
accelerate snow melt runoff with most rivers and streams expected
to rise to near bankfull with some flooding. Please check on local
flood products in your area. Today and Monday significant
rainfall of 1 to 2 inches will be possible adding to flooding
concerns. Showers and isolated thunderstorms will decrease in
overall coverage on Tuesday with warming temperatures. Mixing
heights in the afternoons should be high enough for good smoke
dispersal except in areas with heavier precipitation.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday afternoon for WYZ002>004-006-008-009-
012-015>017.

Flash Flood Watch through this evening for WYZ010-011-020-022.

&&

SHORT TERM...Lipson
LONG TERM...Meunier
AVIATION...Hulme
FIRE WEATHER...Lipson

Hazardous Weather Outlook
National Weather Service Riverton WY
242 AM MDT Sun May 27 2018

WYZ001>020-022>030-281100-
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-
242 AM MDT Sun May 27 2018

...Flash Flood Watch in effect from noon through this evening for
Natrona and Johnson Counties...

...Flood Watch from this morning through Monday afternoon...

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight

Scattered showers and thunderstorms developing over most
of the area. Locally heavy rainfall is possible and will elevate
the flood threat along rivers and creeks already running high from
snowmelt. Isolated strong to severe thunderstorms are possible.

.DAYS TWO THROUGH SEVEN...Memorial Day through Saturday

Memorial Day...Scattered showers and thunderstorms developing
over most of the area. Locally heavy rain may elevate the flood
threat along rivers and creeks already running high from snowmelt.

Tuesday...Isolated to scattered showers and thunderstorms across
the area.

Thursday and Friday...Isolated to scattered showers and
thunderstorms mainly in the north and west.

.SPOTTER INFORMATION STATEMENT...

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

Special Weather Statement
National Weather Service Riverton WY
1103 AM MDT SUN MAY 27 2018

WYZ014-015-018-019-271745-
Wind River Mountains West-Wind River Mountains East-Green Mountains
and Rattlesnake Range-Lander Foothills-
1103 AM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL FREMONT COUNTY
UNTIL 1145 AM MDT...

At 1102 AM MDT, Doppler radar was tracking a strong thunderstorm
near Frye Lake, which is 11 miles southwest of Lander, moving
northwest at 15 mph. Additional thunderstorms were developing over
the southern end of the Wind River Range near Red Canyon and Sinks
Canyon.

Heavy rain, pea-sized hail, wind gusts to 35 mph, and dangerous
lightning are all possible with these storms.

Other impacted locations included Upper Silas Lake, Worthen Meadows
Reservoir, and Louis Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with these storms, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4229 10881 4283 10926 4297 10900 4294 10898
      4292 10896 4297 10890 4297 10888 4230 10821
TIME...MOT...LOC 1700Z 123DEG 15KT 4268 10883

CNJ

Special Weather Statement
National Weather Service Riverton WY
1142 AM MDT SUN MAY 27 2018

WYZ030-271815-
East Sweetwater County-
1142 AM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN SWEETWATER COUNTY
UNTIL 1215 PM MDT...

At 1141 AM MDT, Doppler radar was tracking a strong thunderstorm 10
miles north of Wamsutter, moving northwest at 15 mph.

Heavy rain, half inch diameter hail, winds around 40 mph, and
dangerous lightning are all possible with this storm.

This storm will remain over mainly rural areas of northeastern
Sweetwater County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4173 10779 4167 10816 4195 10848 4208 10802
TIME...MOT...LOC 1741Z 141DEG 14KT 4182 10805

CNJ

Special Weather Statement
National Weather Service Riverton WY
1150 AM MDT SUN MAY 27 2018

WYZ014-015-019-271830-
Wind River Mountains West-Wind River Mountains East-Green Mountains
and Rattlesnake Range-
1150 AM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL FREMONT COUNTY
UNTIL 1230 PM MDT...

Nickel size hail, heavy rain, wind gusts around 40 mph, and
dangerous lightning will be possible with this storm.

This strong thunderstorm will be near South Pass City and South
Pass Rest Area around 1220 to 1230 PM MDT.

Other locations impacted by this storm include Atlantic City and
State Highway 28 over South Pass.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4234 10895 4237 10895 4240 10899 4240 10903
      4246 10909 4260 10879 4222 10836 4218 10878
TIME...MOT...LOC 1749Z 141DEG 14KT 4232 10872

Jones

Special Weather Statement
National Weather Service Riverton WY
1158 AM MDT SUN MAY 27 2018

WYZ015>018-271845-
Wind River Basin-Upper Wind River Basin-Wind River Mountains
East-Lander Foothills-
1158 AM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN FREMONT COUNTY UNTIL
1245 PM MDT...

At 1156 AM MDT, Doppler radar was tracking a strong thunderstorm
near Dickinson Park, which is 9 miles west of Lander, moving
northwest at 15 mph. Additional thunderstorms were located west of
Fort Washakie and moving northwest at 15 mph.

Heavy rain, nickel sized hail, winds in excess of 40 mph, and
dangerous lightning will be possible with these storms.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4319 10952 4324 10902 4265 10857 4256 10890
      4257 10897 4261 10899 4261 10901 4263 10902
      4265 10905
TIME...MOT...LOC 1754Z 141DEG 14KT 4285 10892

CNJ

Special Weather Statement
National Weather Service Riverton WY
1215 PM MDT SUN MAY 27 2018

WYZ030-271900-
East Sweetwater County-
1215 PM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN SWEETWATER COUNTY
UNTIL 100 PM MDT...

At 1214 PM MDT, Doppler radar was tracking a strong thunderstorm 14
miles north of Wamsutter, moving slowly north at 10 to 15 mph.

Heavy rain, nickel sized hail, wind gusts to 40 mph, and dangerous
lightning will all be possible with this storm.

This storm will remain over mainly rural areas of northeastern
Sweetwater County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Heavy rainfall is also occurring with this storm, and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4211 10856 4219 10805 4215 10805 4214 10796
      4212 10799 4210 10798 4211 10792 4183 10778
      4177 10813
TIME...MOT...LOC 1814Z 163DEG 11KT 4188 10801

CNJ

Special Weather Statement
National Weather Service Riverton WY
1239 PM MDT SUN MAY 27 2018

WYZ002-015>017-271930-
Wind River Basin-Upper Wind River Basin-Wind River Mountains
East-Absaroka Mountains-
1239 PM MDT SUN MAY 27 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN FREMONT COUNTY UNTIL
130 PM MDT...

At 1239 PM MDT, Doppler radar was tracking a strong thunderstorm over
Crowheart, which is 23 miles northwest of Fort Washakie, moving
northwest at 20 mph.

Nickel size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Fort Washakie, Crowheart, Diversion Dam Rest Area, Torrey Lake,
Burris, Bull Lake and Crowheart Elementary School.

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.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

A severe thunderstorm watch remains in effect until 800 PM MDT for
central Wyoming.

LAT...LON 4302 10883 4289 10908 4348 10964 4364 10921
TIME...MOT...LOC 1839Z 153DEG 16KT 4328 10920

Hulme