Alert archive / Wyoming / Flash Flood Watches in 2018

Flash Flood Watch 4, NWS Riverton, WY

July 16, 2018Johnson County, Natrona County, Washakie County, Wyoming

NWS Riverton, WY issued this flash flood watch at Jul 16, 2018, 2:14 PM MDT for Johnson County, Natrona County, Washakie County, Wyoming. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued
Jul 16, 2018, 2:14 PM MDT (20:14 UTC)
Expired
Jul 16, 2018, 11:26 PM MDT
In force
9 hr
Issued by
NWS Riverton, WY
Flood severity
None

Counties Johnson County, WY, Natrona County, WY, Washakie County, WY

The radar

The Riverton/Lander radar (KRIW), 134 km from the middle of the area, began a volume at 20:14 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Riverton, WY (KRIW), launched 12:00Z, 8.2 hours before the alert went out and 128 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Riverton, WY at 12:00Z on 2018-07-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 36 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Riverton, WY at 12:00Z on 2018-07-16The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -14 square meters per square second.1939587897Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
36 J/kg
Mixed-layer CIN
-282 J/kg
Mixed-layer LCL
1825 m above ground
0-6 km bulk shear
20 kt
0-1 km storm-relative helicity
-14 m²/s²
0-3 km storm-relative helicity
43 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Riverton, WY wrote its last area forecast discussion before this flash flood watch went out at Jul 16, 12:10 PM MDT, 2 hours 4 minutes earlier.

Area forecast discussion, Jul 16, 12:10 PM MDT, 2 hours 4 minutes before
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Hazardous weather outlook, Jul 16, 2:22 AM MDT, 11 hours 52 minutes before
Hazardous Weather Outlook
National Weather Service Riverton WY
222 AM MDT Mon Jul 16 2018

WYZ001>020-022>030-171200-
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-
222 AM MDT Mon Jul 16 2018

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight

Scattered thunderstorms will develop this afternoon and evening.
Some could become strong to severe in northern and central Wyoming
with large hail and damaging winds.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Tuesday...Isolated to locally scattered thunderstorms; especially
in the northern half of the state.

Saturday and Sunday...Isolated thunderstorms, mainly in the
afternoon and evening hours.

.SPOTTER INFORMATION STATEMENT...

Spotters are urged to report hail, wind gusts over 45 mph and
heavy rainfall. Thank you.

Team Riverton

In the hours before

Special weather statement, Jul 16, 8:35 AM MDT, 5 hours 39 minutes before
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Special weather statement, Jul 16, 12:22 PM MDT, 1 hour 52 minutes before
Special Weather Statement
National Weather Service Riverton WY
1222 PM MDT MON JUL 16 2018

WYZ002>007-161900-
Owl Creek and Bridger Mountains-North Big Horn Basin-Southeast Big
Horn Basin-Cody Foothills-Southwest Big Horn Basin-Absaroka
Mountains-
1222 PM MDT MON JUL 16 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN HOT SPRINGS...
SOUTHWESTERN BIG HORN...NORTHWESTERN WASHAKIE AND SOUTHEASTERN PARK
COUNTIES UNTIL 100 PM MDT...

At 1221 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Meeteetse, moving east at 35 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of northwestern Hot
Springs...southwestern Big Horn...northwestern Washakie and
southeastern Park Counties, including the following locations...
Badlands Overlook, Sunshine Reservoir and Grass Creek.

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 4388 10910 4430 10911 4441 10845 4383 10837
TIME...MOT...LOC 1821Z 250DEG 32KT 4399 10894

Baker

The office that day

Everything else NWS Riverton, WY issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 15, 6:11 PM MDTSpecial Weather StatementRIWJohnson34 min
Jul 15, 6:41 PM MDTSpecial Weather StatementRIWJohnson49 min
Jul 15, 6:54 PM MDTSpecial Weather StatementRIWJohnson36 min
Jul 15, 7:00 PM MDTSpecial Weather StatementRIWJohnson45 min
Jul 15, 7:31 PM MDTSpecial Weather StatementRIWJohnson29 min
Jul 16, 8:35 AM MDTSpecial Weather StatementRIWNatrona25 min
Jul 16, 12:22 PM MDTSpecial Weather StatementRIWHot Springs38 min
Jul 16, 1:52 PM MDTAreal Flood AdvisoryRIWJohnson, Natrona4 hr
Jul 16, 3:02 PM MDTSpecial Weather StatementRIWNatrona43 min
Jul 16, 3:33 PM MDTSpecial Weather StatementRIWNatrona42 min
Jul 16, 3:48 PM MDTAreal Flood AdvisoryRIWJohnson4 hr
Jul 16, 4:09 PM MDTSpecial Weather StatementRIWNatrona36 min
Jul 16, 4:17 PM MDTSpecial Weather StatementRIWNatrona43 min
Jul 16, 4:52 PM MDTSpecial Weather StatementRIWNatrona38 min
Jul 16, 5:02 PM MDTSevere Thunderstorm WarningRIWNatrona43 min
Jul 16, 5:32 PM MDTSpecial Weather StatementRIWNatrona28 min

Nearby

Flash Flood Watches in Wyoming, 2018Every flash flood watch in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.