Winter Storm Warning 5, NWS Riverton, WY

547 
WWUS45 KRIW 282353
WSWRIW

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE RIVERTON WY
553 PM MDT SAT APR 28 2012

...MODERATE TO HEAVY SNOW EXPECTED IN THE BIGHORN MOUNTAINS TONIGHT...

.A VIGOROUS LOW PRESSURE SYSTEM OVER THE NORTHERN HIGH PLAINS WILL
SLOWLY LIFT NORTHWARD OVERNIGHT. BANDS OF MODERATE TO HEAVY SNOW
WILL CONTINUE TO ROTATE SOUTH ON THE BACK SIDE OF THIS SYSTEM INTO THE
BIGHORN MOUNTAINS THROUGH EARLY SUNDAY MORNING...ESPECIALLY ALONG
THE WEST SLOPES NORTH OF HIGHWAY 16. THE SNOW COMBINED WITH
NORTHWEST WIND AT 20 TO 30 MPH WITH GUSTS TO 40 MPH WILL CAUSE
AREAS OF SUBSTANTIAL BLOWING AND DRIFTING SNOW OVER POWDER RIVER
PASS AND OPEN AREAS ABOVE 8500 FEET.

WYZ008-009-291200-
/O.CON.KRIW.WS.W.0005.000000T0000Z-120429T1200Z/
BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST-
553 PM MDT SAT APR 28 2012

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 AM MDT SUNDAY...

A WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 AM MDT SUNDAY. 

* SUMMARY AND TIMING...BANDS OF MODERATE TO HEAVY SNOW WILL
  CONTINUE THROUGH EARLY SUNDAY MORNING...GRADUALLY TAPERING OFF
  BETWEEN 2 AM AND 6 AM.

* SNOWFALL SO FAR AS OF 500 PM MDT...SNOWFALL RANGED FROM 10 TO
  20 INCHES ALONG THE WEST SLOPES ABOVE 9000 FEET...NORTH OF
  HIGHWAY 16. AROUND A FOOT OF NEW SNOW WAS ESTIMATED OVER POWDER
  RIVER PASS. SNOWFALL AMOUNTS ACROSS THE REST OF THE BIGHORN
  RANGE GENERALLY RANGED FROM 5 TO 10 INCHES.

* SNOW ACCUMULATIONS...15 TO 25 INCHES IN THE NORTH WITH 6 TO 14 INCHES
  IN THE SOUTH.

* WIND AND VISIBILITY...NORTHWEST WIND AT 20 TO 30 MPH WITH GUSTS
  TO 40 MPH THIS EVENING...DIMINISHING AFTER MIDNIGHT. VISIBILITY
  WILL BE REDUCED TO BELOW ONE QUARTER MILE AT TIMES IN HEAVIER
  SNOW AND BLOWING SNOW.

* IMPACTS...CONDITIONS OVER POWDER RIVER AND GRANITE PASSES WERE
  SLICK WITH SNOWFALL...BLOWING AND DRIFTING SNOW AND LIMITED
  VISIBILITY. THIS TREACHEROUS CONDITIONS WILL PERSIST OVERNIGHT. TRAVEL
  WILL BE DIFFICULT AND IS NOT ADVISED BUT IF YOU MUST TRAVEL MAKE
  SURE YOU HAVE A WINTER SAFETY KIT IN YOUR VEHICLE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHER
CONDITIONS ARE EXPECTED OR OCCURRING.  SIGNIFICANT AMOUNTS OF
SNOW ARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL IN
AN EMERGENCY. IF YOU MUST TRAVEL...KEEP AN EXTRA FLASHLIGHT...
FOOD...AND WATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY.

THE LATEST ROAD CONDITIONS PROVIDED BY THE WYOMING DEPARTMENT OF
TRANSPORTATION ARE AVAILABLE BY CALLING 5-1-1 OR ON THE INTERNET
AT WYOROAD.INFO.

&&

$$

003 
WWUS45 KRIW 291118
WSWRIW

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE RIVERTON WY
518 AM MDT SUN APR 29 2012


WYZ008-009-291230-
/O.CAN.KRIW.WS.W.0005.000000T0000Z-120429T1200Z/
BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST-
518 AM MDT SUN APR 29 2012

...WINTER STORM WARNING IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN RIVERTON HAS CANCELLED THE WINTER
STORM WARNING. 

SNOW HAS TAPERED OFF ACROSS THE BIGHORN MOUNTAINS THIS MORNING.
LIGHT SNOW SHOWERS WILL LINGER THROUGH MID-MORNING...WITH LITTLE
ADDITIONAL ACCUMULATIONS EXPECTED. 

$$

TL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
410 AM MDT SAT APR 28 2012

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

MOSTLY STACKED LOW OVER NE WY/SE MT HAS BECOME ORPHANED FROM THE
MAIN UPPER FLOW AS JET REMAINS REMOVED TO THE SOUTH.  THIS WILL
ALLOW THE LOW TO SLOWLY DRIFT AROUND TODAY BRINGING WRAPAROUND SNOW
SHOWERS TO THE BIGHORN MOUNTAINS.  6 TO 12 INCHES ARE POSSIBLE OVER
MUCH OF THE RANGE THROUGH EARLY SUNDAY.  EAST SLOPES ALONG THE NORTH
END OF THE BIGHORNS WILL SEE THE GREATEST ACCUMULATION.  AS
SUCH...HAVE ISSUED A WINTER WEATHER ADVISORY FOR THIS AREA.  LIGHTER
SNOW CAN BE EXPECTED IN THE MOUNTAINS OF WESTERN WYOMING AND THE
WIND RIVER RANGE.  SEASONABLY COOL TEMPERATURES CAN BE EXPECTED IN
THE WAKE OF YESTERDAYS COLD FRONT PASSAGE. A WARMING TREND CAN BE
EXPECTED SUNDAY AND MONDAY AS THE OCCLUDED LOW MOVES OFF TO THE
NORTHEAST AND THE PARENT TROUGH WEAKENS ACROSS THE WESTERN CONUS.
LIGHT SNOW MAY LINGER IN THE FAR NORTHERN MOUNTAINS THROUGH SUNDAY
EVENING BUT SUBSIDENCE ASSOCIATED WITH WEAK HIGH PRESSURE WILL
INHIBIT PRECIPITATION ELSEWHERE.  ZONAL FLOW DEVELOPS BY MONDAY
BRINGING AN UNIMPEDED STREAM OF PACIFIC MOISTURE TO THE WESTERN
MOUNTAINS.  A WEAK SHORTWAVE TROUGH WITHIN THE ZONAL FLOW WILL HELP
BRING A FEW SHOWERS TO THE WESTERN WYOMING MOUNTAINS.  SHOWERS WILL
BE SNOW AT HIGHER ELEVATIONS.

.LONG TERM...TUESDAY THROUGH SATURDAY

MEDIUM RANGE GLOBAL MODELS 00Z RUNS ARE CONSISTENT WITH BRINGING
THE NEXT WEATHER SYSTEM TO THE COWBOY STATE BY TUESDAY MORNING.
MOST OF THE PRECIPITATION WILL BE CONFINED TO WESTERN AND SOUTHERN
PORTIONS WITH RAIN SHOWERS AND ISOLATED THUNDERSTORMS. SNOW
SHOWERS WILL BE CONFINED TO THE HIGHER ELEVATIONS DURING THE
OVERNIGHT HOURS. THIS SYSTEM WILL QUICKLY EXIT THE AREA BY EARLY
WEDNESDAY...REPLACED BY ZONAL WESTERLY FLOW THROUGH SATURDAY. A
FEW WEAK SHORTWAVES WILL BRING ISOLATED SHOWERS AND THUNDERSTORMS
TO THE WEST AND SOUTH DURING THIS TIME. BREEZY TO WINDY
CONDITIONS WILL ALSO OCCUR WITH THIS PATTERN ACROSS WIND PRONE
LOCATIONS IN CENTRAL AND SOUTHERN PORTIONS. THERE IS TIMING
DISCREPANCIES BETWEEN THE GFS AND ECMWF WITH THE SATURDAY
SYSTEM...WITH THE GFS SLOWER AND STRONGER...AND THE ECMWF FASTER
AND WEAKER...ONLY IMPACTING NORTHERN PORTIONS OF THE STATE. BOTH
SOLUTIONS HAVE TEMPERATURES RETURNING TO WELL ABOVE NORMAL FRIDAY
AND SATURDAY WITH A RIDGE AXIS BUILDING OVER THE PLAINS. WILL
CONTINUE TO MONITOR THIS SYSTEM AS THE POTENTIAL FOR ANOTHER
RECORD BREAKING DAY IS FORECAST FROM THE GFS.

&&

.AVIATION.../12Z ISSUANCE/

A CUT OFF UPPER LOW OVER NE WYOMING/SE MONTANA/EASTERN DAKOTAS
REGION WILL KEEP A STEADY FLOW OF MOISTURE/LIFT ACROSS NORTHERN
WYOMING THROUGH THE FORECAST PERIOD. THIS WILL RESULT IN SCATTERED
TO NUMEROUS SHOWERS ACROSS NORTHERN WYOMING. MOUNTAINS WILL RECEIVE
ALL SNOW...WHILE VALLEYS WILL BE RAIN OR SNOW. THE BIGHORN MTS WILL
BE HIT THE HARDEST WITH LIFR CONDITIONS EXPECTED FROM POWDER RIVER
PASS NORTHWARD THROUGH THE ENTIRE FORECAST PERIOD. WESTERN AND
CENTRAL WYOMING COULD ALSO SEE SOME ISOLATED TO LOCALLY SCATTERED
CONVECTION. MVFR/SOME IFR CONDITIONS ARE LIKELY AT TIMES ACROSS THE
BIG HORN BASIN AND JOHNSON COUNTY INCLUDING KCOD AND KWRL TAF SITES.
OTHER TAF SITES SHOULD REMAIN MAINLY VFR THROUGH THE FORECAST
PERIOD. HOWEVER...KCPR...KJAC...KLND AND KRIW WILL HAVE CONSIDERABLE
LOW/MID LEVEL CLOUDS WITH CEILINGS GENERALLY BETWEEN 12-18 KFT MSL
WITH BRIEF MVFR CONDITIONS POSSIBLE WITH ANY SHOWER ACTIVITY. WIND
WILL BE MUCH LIGHTER TODAY...BUT STILL GENERALLY FROM THE WEST TO
NORTHWEST.

&&

.FIRE WEATHER...

RECENT PRECIPITATION HAS MOISTENED THE ATMOSPHERE OVER MUCH OF THE
AREA.  DRIER AREAS INCLUDE SWEETWATER COUNTY AND THE CASPER AREA.
COOL TEMPERATURES WILL KEEP RH VALUES UP AROUND THE AREA TODAY.
WIND WILL REMAIN BREEZY TO WINDY ALONG RIDGETOPS AND THE SOUTHERN
WIND CORRIDOR.  MOUNTAIN SNOW AND PERIODIC VALLEY RAIN WILL CONTINUE
THROUGH MUCH OF THE DAY IN THE NORTHERN ZONES TODAY.  DRIER
CONDITIONS WITH LIGHTER WINDS DEVELOP SUNDAY AND MONDAY WITH A
WARMING TREND EXPECTED TO LOWER HUMIDITY ACROSS THE AREA.  CRITICAL
FIRE WEATHER CONDITIONS ARE NOT EXPECTED OVER THE NEXT FEW DAYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM MDT SUNDAY WYZ008-009.

&&

SHORT TERM...BERC
LONG TERM...LAVOIE
AVIATION...WM
FIRE WEATHER...BERC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
544 AM MDT SAT APR 28 2012

WYZ001>020-022>030-291100-
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-
544 AM MDT SAT APR 28 2012

...WINTER WEATHER ADVISORY FOR THE BIG HORN MOUNTAINS THROUGH EARLY
SUNDAY MORNING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

SIGNIFICANT SNOWFALL EXPECTED IN THE BIGHORN MOUNTAINS. SNOW WILL
DECREASE EARLY SUNDAY. 6 TO 12 INCHES ARE POSSIBLE WITH THE HIGHEST
ACCUMULATIONS TOWARD THE NORTH END OF THE RANGE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT SNOW ACCUMULATION. THANK YOU.

TEAM RIVERTON