Special Weather Statement, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1132 AM MDT THU JUL 4 2013

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
UPDATED TO ADD A FLASH FLOOD WATCH FOR ALL THE MOUNTAINS THIS
AFTERNOON AND EVENING. ABNORMALLY MOIST ATMOSPHERE WITH
PRECIPITABLE WATER VALUES OF 150 TO NEARLY 200 PERCENT OF NORMAL
AND LIGHT STEERING FLOW UNDER 10 KNOTS WILL COMBINE TO PRODUCE THE
THREAT OF HEAVY RAIN PRODUCING CELLS. THE MOUNTAINS WILL BE THE
MOST LIKELY AREA BUT ANY AREA COULD SEE A HEAVY RAIN PRODUCING
CELL WITH A LESSER RISK OF STRONG TO SEVERE CELLS MAINLY FOR HAIL.
HAVE INCREASED POPS CONSIDERABLY TO MATCH THIS THINKING.

A FEW SHOWERS CONTINUE TO IMPACT SWEETWATER COUNTY THIS
MORNING...WITH A COUPLE OTHERS ATTEMPTING TO MOVE INTO THE WESTERN
MOUNTAINS AND VALLEYS. OTHERWISE...CLEARING SKIES GENERALLY NOTED
EAST OF THE CONTINENTAL DIVIDE.

A SURGE OF MOISTURE WILL BUILD OVER THE FORECAST AREA THIS
MORNING...WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
ANTICIPATED BY THE LATE MORNING TO EARLY AFTERNOON HOURS. SOME
STORMS WILL HAVE THE CAPABILITY TO PRODUCE SMALL HAIL AND GUSTY
WIND...ESPECIALLY DURING THE AFTERNOON. A DECENT SLUG OF CAPE AND
NEGATIVE LIFTED INDEX VALUES WILL BE FOUND ACROSS THE NORTHERN THIRD
OF THE FORECAST AREA...THOUGH LACK OF SIGNIFICANT SHEAR SHOULD KEEP
AN OUTBREAK OF SEVERE WEATHER FROM HAPPENING. CERTAINLY NOT TO SAY
THAT A ROGUE STORM OR TWO MAY NOT HAVE THE CAPABILITY TO PRODUCE
MORE SIGNIFICANT WEATHER...JUST THAT WIDESPREAD SEVERE STORMS ARE
NOT CURRENTLY ANTICIPATED.

STORMS WILL WEAKEN WITH THE LOSS OF DAYLIGHT THIS EVENING.
HOWEVER...STORMS WILL NOT DISSIPATE COMPLETELY...WITH SOME LINGERING
ACTIVITY ANTICIPATED OVER MUCH OF THE FORECAST AREA. A STRONGER SLUG
OF MOISTURE IS ANTICIPATED FRIDAY...WITH INCREASED COVERAGE OF
SHOWERS AND THUNDERSTORMS ANTICIPATED. THE ENVIRONMENT LOOKS MUCH
MORE FAVORABLE FOR THE DEVELOPMENT OF STRONG TO SEVERE
STORMS...MAINLY ACROSS THE BIG HORN BASIN AND JOHNSON COUNTY AS A
TROUGH WORKS THROUGH THE AREA. CAPE AND LIFTED INDEX VALUES APPEAR
TO WANE THROUGH THE AFTERNOON ACROSS THE BIG HORN BASIN WHICH MAY
INDICATE AN EARLIER SHOW FOR THAT AREA. HOWEVER...CONDITIONS REMAIN
FAIRLY FAVORABLE INTO THE EARLY EVENING HOURS FOR JOHNSON COUNTY.
THE FORECAST HAS INCLUDED THE MENTION OF SEVERE STORMS BEGINNING
FRIDAY AFTERNOON FOR THESE TWO AREAS...WITH JOHNSON COUNTY LINGERING
INTO THE EVENING. AGAIN...STORMS WILL WEAKEN OVERNIGHT...BUT WILL
NOT END COMPLETELY.

SATURDAY LOOKS TO BE ANOTHER DAY OF SHOWERS AND THUNDERSTORMS WHICH
MAY IMPACT MUCH OF THE FORECAST AREA. SMALL HAIL AND GUSTY WIND MAY
ACCOMPANY STORMS SATURDAY AFTERNOON AND INTO THE EARLY EVENING
HOURS. AGAIN...SHOWERS ARE EXPECTED TO WEAKEN THROUGH SATURDAY NIGHT.

.LONG TERM...SUNDAY THROUGH THURSDAY

MODELS CONTINUE TO SHOW DRIER AIR WORKING INTO THE AREA SUNDAY IN
THE WEST/SOUTHWEST FLOW. HOWEVER ENOUGH MOISTURE WILL REMAIN
AVAILABLE FOR MAINLY DIURNAL CONVECTION...ESPECIALLY ACROSS THE
EAST. HOWEVER CONVECTION WILL BE LESS WIDESPREAD AND WEAKER THAN
WHAT OCCURS IN THE SHORT TERM.  ON MONDAY AND TUESDAY...ATTENTION
TURNS TO A SHORTWAVE TROUGH PUSHING EAST FROM THE PACIFIC NORTHWEST
ACROSS THE NORTHERN ROCKIES MONDAY/MONDAY NIGHT INTO THE NORTHERN
PLAINS TUESDAY. THE 00Z GFS KEEPS THE BULK OF THE MOISTURE/DYNAMICS
NORTH AND EAST OF THE AREA MONDAY AND TUESDAY...BUT STILL ENOUGH TO
WARRANT ISOLATED TO LOCALLY SCATTERED POPS...ESPECIALLY ALONG AND
EAST OF THE DIVIDE. THE 00Z ECMWF IS A BIT SLOWER AND DEEPER WITH
THIS SYSTEM...WITH A BETTER DEFINED COLD FRONT AFFECTING AREAS
EAST OF THE DIVIDE LATE MONDAY INTO TUESDAY. THIS RESULTS IN A
BETTER CHANCE OF CONVECTION AND COOLER CONDITIONS TUESDAY...MAINLY
ALONG AND EAST OF THE DIVIDE. AFTER TUESDAY MODELS TREND TOWARD
RIDGING BUILDING BACK INTO THE AREA...WITH WARMER AND MAINLY DRY
CONDITIONS.

TEMPERATURES ARE EXPECTED TO BE SLIGHTLY ABOVE AVERAGE FOR MUCH OF
THE EXTENDED. THE MAIN EXCEPTION COULD BE TUESDAY IF THE ECMWF
SOLUTION COMES TO FRUITION WITH A DECENT SUMMERTIME COLD FRONT
AFFECTING AREAS EAST OF THE DIVIDE.

.AVIATION.../18Z ISSUANCE/

ACTIVE THUNDERSTORM PERIOD ACROSS THE ENTIRE AREA THROUGH FRIDAY.
EVEN THE NIGHTTIME AND MORNING PERIODS WILL SEE AT LEAST ISOLATED
THUNDERSTORMS WITH SCATTERED TO NUMEROUS STORMS IN THE AFTERNOON
AND EVENING. ALL TERMINALS COULD BE IMPACTED AT ONE TIME OR ANOTHER.
THE PEAK PERIODS WILL BE DURING THE AFTERNOON AND EVENING BUT ANY
PERIOD COULD BE IMPACTED BY A THUNDERSTORM.

.FIRE WEATHER...

WARM TEMPERATURES AND SLIGHTLY INCREASED DAYTIME HUMIDITY WILL BE
FOUND OVER THE AREA TODAY AS ANOTHER SURGE OF MOISTURE IMPACTS THE
FORECAST AREA. SHOWERS AND THUNDERSTORMS WILL BE PRESENT ACROSS MUCH
OF WESTERN AND CENTRAL WYOMING TODAY...WITH GUSTY WIND AND SMALL
HAIL BEING THE PRIMARY THREATS OUTSIDE OF LIGHTNING. SHOWERS AND
THUNDERSTORMS WILL REMAIN PRESENT OVER THE NEXT COUPLE OF
DAYS...WITH FRIDAY APPEARING TO BE A FAVORABLE FOR STRONGER
THUNDERSTORMS...ESPECIALLY OVER THE BIG HORN BASIN AND JOHNSON
COUNTY. THESE STORMS MAY PRODUCE VERY STRONG WIND AND LARGER HAIL.
TEMPERATURES WILL DIP SLIGHTLY UNDER THE CONTINUED PRESENCE OF
THUNDERSTORMS...WITH DAYTIME HUMIDITY ALSO INCREASING SLIGHTLY EACH
DAY.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THIS EVENING
WYZ001-002-007>009-012-014-015-022-024.

&&

SHORT TERM...SKRBAC
LONG TERM...WM
AVIATION...SKRBAC
FIRE WEATHER...SKRBAC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
919 AM MDT THU JUL 4 2013

WYZ001>020-022>030-051200-
ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST-
BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS-
EAST SWEETWATER COUNTY-FLAMING GORGE-
GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS-
NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN-
NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS-
ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES-
SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN-
SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY-
TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN-
UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN-
WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST-
YELLOWSTONE NATIONAL PARK-
919 AM MDT THU JUL 4 2013

...FLASH FLOOD WATCH FOR ALL THE MOUNTAINS THIS AFTERNOON AND
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

SCATTERED TO NUMEROUS THUNDERSTORMS...MAINLY IN THE AFTERNOON AND
EVENING. SOME STORMS MAY PRODUCE VERY HEAVY RAIN AND POSSIBLE FLASH
FLOODING...ESPECIALLY IN THE MOUNTAINS. THOSE WITH OUTDOOR INTERESTS
SHOULD REMAIN AWARE OF CHANGING WEATHER CONDITIONS AND SEEK SHELTER
IF STORMS APPROACH. AVOID CAMPING IN LOW LYING OR CANYON AREAS. ALSO
BE ALERT FOR FREQUENT LIGHTNING WITH SOME STORMS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

FRIDAY AND SATURDAY...ISOLATED TO SCATTERED THUNDERSTORMS. SOME
STORMS COULD BE SEVERE IN THE AFTERNOON AND EVENING...ESPECIALLY
ACROSS THE NORTH...WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT ANY WIND OVER 40 MPH AND ANY SIZED
HAIL...THANK YOU.

TEAM RIVERTON

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
1221 PM MDT THU JUL 4 2013

WYZ009>011-041900-
BIGHORN MOUNTAINS SOUTHEAST WY-NORTHEAST JOHNSON COUNTY WY-SOUTHEAST
JOHNSON COUNTY WY-
1221 PM MDT THU JUL 4 2013

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL JOHNSON COUNTY UNTIL 100
PM MDT...

AT 1218 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A STRONG THUNDERSTORM 5 MILES NORTHEAST OF U.S. HWY 16 MILE MARKER
70...OR 9 MILES SOUTHWEST OF BUFFALO...MOVING SOUTHEAST AT 20 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN. A FLASH FLOOD WATCH
IS ALSO IN EFFECT FOR THE BIGHORN MOUNTAINS THROUGH MIDNIGHT.

THIS STORM WILL BE NEAR...
U.S. HWY 16 MILE MARKER 70 AROUND 1225 PM MDT.
STATE HWY 196 MILE MARKER 290 AND I25 MILE MARKER 290 AROUND 1240 PM
MDT.
STATE HWY 196 MILE MARKER 280 AND I25 EXIT 280 AROUND 100 PM MDT.

THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 278 AND
298.

THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS... FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

BRIEF HEAVY RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES
AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A
FLOODED ROADWAY.

REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.

LAT...LON 4403 10648 4391 10678 4429 10702 4437 10680
TIME...MOT...LOC 1820Z 331DEG 16KT 4425 10685

SKRBAC