Severe Thunderstorm Warning 18, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
131 PM MDT THU JUN 4 2015

.SHORT TERM...TONIGHT THROUGH FRIDAY

MOIST AIRMASS CONTINUES EAST OF THE DIVIDE WITH WEAK FRONTAL
BOUNDARY HUNG UP NEAR THE DIVIDE. SIMILAR TEMP/DP NOW COMPARED TO
YESTERDAY AT THIS TIME WITH LAPS SHOWING CONSIDERABLE BUILDING CAPE
EAST OF THE DIVIDE...ESPECIALLY IN JOHNSON AND NATRONA. STILL HAVE
SOME CIN TO ERODE BUT WITH PLENTY OF SUNSHINE THAT SHOULD NOT BE A
PROBLEM. THE DRIER AIR REMAINS JUST TO THE SOUTH ALSO SIMILAR TO
YESTERDAY. THE BIG DIFFERENCE TODAY IS NO APPARENT UPPER SUPPORT AS
MENTIONED YESTERDAY. SO THE DURATION AND COVERAGE SHOULD NOT BE AS
IMPRESSIVE AS YESTERDAY...THE THREAT OF STRONG TO SEVERE STORMS WITH
HEAVY RAIN REMAINS. SEVERE WORDING REMAINS IN THE FORECAST FOR A
SIMILAR AREA TODAY. WE'RE WATCHING THE FLOOD THREAT VERY
CAREFULLY AGAIN THROUGH THIS EVENING AS MANY AREAS ARE TOTALLY
SATURATED WITH A FEW AREAS GETTING SEVERAL INCHES OF RAIN
YESTERDAY...ESPECIALLY JOHNSON AND NE NATRONA.

ON FRIDAY...THE FRONT IS EXPECTED TO REMAIN NEAR THE DIVIDE WITH
MOIST...E-SE FLOW CONTINUING. SIMILAR TO WEDNESDAY...WE HAVE AN
APPROACHING SHORTWAVE AND JET STREAK THAT HAS THE POTENTIAL TO HELP
INCREASE AND ORGANIZE THE STORMS ONCE AGAIN EAST OF THE DIVIDE. HAVE
ADDED IN SEVERE TSTM WORDING ALONG WITH HEAVY RAIN FOR ALL AREAS
ALONG AND EAST OF THE DIVIDE LATE FRIDAY AFTERNOON. WITH THIS
POTENTIAL...WE HAVE DECIDED TO ISSUE A FLASH FLOOD WATCH FOR MOST
AREAS EAST OF THE DIVIDE FROM 2 PM FRIDAY THROUGH MIDNIGHT FRIDAY
NIGHT. ANOTHER BUSY COUPLE DAYS.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY

FRIDAY NIGHT...STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE INTO
THE EVENING HOURS ACROSS PORTIONS OF CENTRAL WYOMING...MORE
SPECIFICALLY ACROSS PARK...BIGHORN...JOHNSON AND NATRONA COUNTIES.
IT APPEARS AS THOUGH SIGNIFICANT 0-6KM BULK SHEAR...ON THE ORDER OF
40-50KT WILL REMAIN THROUGH MIDNIGHT...ALONG WITH THE PASSAGE OF A
SHORT WAVE DISTURBANCE DURING THIS TIME ADDING TO THE OVERALL
FORCING FOR ASCENT ACROSS THE REGION...IN ADDITION TO INCREASINGLY
DIFLUENT FLOW ALOFT AND THE ARRIVAL OF THE NOSE OF A 90KT JET STREAK
INTO SOUTHERN WYOMING. LARGE HAIL...OVER AN INCH IN DIAMETER AND
DAMAGING WIND CONTINUE TO BE POSSIBLE AFTER SUNSET...ESPECIALLY IN
JOHNSON AND NATRONA COUNTIES. ADDITIONALLY...PWAT VALUES COULD BE
OVER AN INCH ACROSS THIS AREA...SO FLASH FLOODING CONTINUES TO BE
A CONCERN AS SOILS ARE SATURATED. IN ADDITION...LCL HEIGHTS REMAIN
LOW AND LOW LEVEL SHEAR AND EHI REMAIN ELEVATED SO TORNADOES ARE
ALSO WITHIN THE REALM OF POSSIBILITY AS WELL.

ON SATURDAY...AS THE UPPER LOW SWINGS INTO UTAH AND A COLD FRONT
DROPS OUT OF THE NORTH...IT LOOKS TO BE ANOTHER RAINY DAY WITH
CONVECTION FOCUSED OVER THE HIGHER TERRAIN BUT WITH A GOOD CHANCE OF
A WETTING RAIN JUST ABOUT EVERYWHERE.

SUNDAY CONTINUES TO BE UNSETTLED WITH STRONGER STORMS POSSIBLE ALONG
AND NEAR A LINE FROM SOUTH PASS TO CASPER WHERE THE COLD FRONT MAY
SETTLE. OTHERWISE...IT WILL BE MARGINALLY UNSTABLE JUST ABOUT
EVERYWHERE ACROSS THE STATE AS THE UPPER LOW CONTINUES TO APPROACH AND
EVENTUALLY ELONGATE INTO MORE OF AN OPEN WAVE.

HEIGHTS BUILD ON MONDAY WITH WARMER TEMPERATURES AND HIGHS BACK INTO
THE 80S TO NEAR 90 INTO MID WEEK. THE RIDGE BEGINS TO BREAK DOWN
ACROSS THE WEST AS EARLY AS TUESDAY AFTERNOON WITH MORE
THUNDERSTORMS POSSIBLE ACROSS THE WEST...SPREADING ACROSS THE CWA BY
WEDNESDAY WITH ANOTHER UPPER LEVEL LOW DIGGING TO THE WEST WITH A
COLD FRONT AND WIDESPREAD PRECIPITATION POSSIBLE AGAIN BY THURSDAY
AND CONTINUING INTO SATURDAY MORNING.

&&

.AVIATION.../00Z ISSUANCE/

AFTER A PERIOD OF MOSTLY VFR CONDITIONS...AFTER 21Z MORE SHOWERS
AND THUNDERSTORMS WILL REDEVELOP OVER WESTERN AND CENTRAL WY AND
THESE WILL CONTINUE THROUGH ABOUT 06Z FRI. ONLY ISOLATED SHOWERS
AND STORM ARE EXPECTED IN SOUTHERN WY FROM 21Z UNTIL 03Z. AREAS OF
MVFR CONDITIONS AND MOUNTAIN OBSCURATION CAN BE EXPECTED. WIND
GUSTS TO 40 KNOTS WILL BE POSSIBLE ALONG WITH HAIL. HEAVY RAINFALL
WILL REDUCE VISIBILITY AT TIMES TO LESS THAN 5 MILES. AREAS OF
MVFR CONDITIONS/LOW CLOUDS WILL REDEVELOP AGAIN TONIGHT EAST OF
THE DIVIDE AFTER 06Z TONIGHT...ESPECIALLY IN AREAS THAT RECEIVE
SUBSTANTIAL RAINFALL. THESE LOW CLOUDS WILL DISSIPATE BY 16Z
FRIDAY. A STRONGER ROUND OF THUNDERSTORMS IS EXPECTED AGAIN FRIDAY
AFTERNOON WITH MVFR CONDITIONS...LCL IFR CONDITIONS...MTN
OBSCURATIONS...GUSTS TO 40 KNOTS ALONG WITH POSSIBLE HAIL.

&&

.FIRE WEATHER...

ANOTHER DAY OF SHOWERS AND THUNDERSTORMS WILL BE FOUND ACROSS THE
AREA...THOUGH ACTIVITY IS NOT EXPECTED TO BE AS WIDESPREAD. STORMS
MAY STILL INCLUDE GUSTY AND ERRATIC WIND AND SMALL HAIL. SOME STORMS
ACROSS JOHNSON AND NATRONA COUNTIES MAY CONTAIN DAMAGING WIND IN THE
LATE AFTERNOON AND EARLY EVENING HOURS. OVERALL...A COOLING TREND IS
IN STORE FOR THE NEXT COUPLE OF DAYS...HELPING TO ALSO INCREASE
DAYTIME HUMIDITY. OUTSIDE OF POTENTIAL STARTS FROM LIGHTNING
ACTIVITY...OR INFLUENCE FROM STORM RELATED WIND...EXPECTING A LOW
FIRE BEHAVIOR ACROSS THE AREA FOR THE NEXT COUPLE DAYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING
FOR WYZ002>011-016>018-020-022.

FLASH FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR WYZ008>011.

&&

SHORT TERM...PS
LONG TERM....ALLEN
AVIATION...LIPSON
FIRE WEATHER...LIPSON

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
123 PM MDT THU JUN 4 2015

WYZ001>020-022>030-051200-
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-
123 PM MDT THU JUN 4 2015

...FLASH FLOOD WATCH IN EFFECT FROM 3 PM THROUGH MIDNIGHT FOR
JOHNSON COUNTY...
...FLASH FLOOD WATCH FOR MUCH OF CENTRAL WYOMING FROM 2 PM FRIDAY
THROUGH MIDNIGHT FRIDAY NIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND WESTERN WYOMING.

.DAY ONE...TODAY AND TONIGHT

SCATTERED AFTERNOON AND EVENING THUNDERSTORMS. SOME STORMS WILL
BE STRONG WITH GUSTY WIND AND SMALL HAIL. A FEW STORMS MAY BECOME
SEVERE ACROSS THE EASTERN HALF OF THE AREA WITH DAMAGING WIND AND
LARGE HAIL. ADDITIONALLY...STORMS MAY PRODUCE PERIODS OF MODERATE
TO HEAVY RAINFALL...WHICH COULD RESULT IN FLASH FLOODING
ESPECIALLY ACROSS JOHNSON COUNTY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

FRIDAY...STRONG TO SEVERE THUNDERSTORMS ALONG WITH HEAVY RAIN
POSSIBLE ACROSS MOST OF CENTRAL WYOMING DURING THE AFTERNOON AND
EVENING.

SATURDAY THROUGH SUNDAY...ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS. SOME STORMS MAY PRODUCE GUSTY WIND...SMALL
HAIL AND HEAVY RAIN.

MONDAY AND TUESDAY...ISOLATED THUNDERSTORMS POSSIBLE...MAINLY OVER
THE MOUNTAINS AND ADJACENT FOOTHILLS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT HAIL SIZES...WIND SPEEDS OVER 45
MPH...AND ANY FLOODING. THANK YOU.

TEAM RIVERTON

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