Severe Thunderstorm Warning 76, NWS Riverton, WY

000 
WWUS55 KRIW 232331
SVSRIW

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
531 PM MDT THU AUG 23 2007

WYC037-232341-
/O.EXP.KRIW.SV.W.0076.000000T0000Z-070823T2330Z/
SWEETWATER WY-
531 PM MDT THU AUG 23 2007

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN SWEETWATER COUNTY
HAS BEEN ALLOWED TO EXPIRE AT 530 PM MDT...

THE STORM HAS DECREASED IN INTENSITY AND IS NO LONGER SEVERE. 
THEREFORE...THE WARNING HAS BEEN ALLOWED TO EXPIRE.

ALTHOUGH THE WARNING HAS BEEN ALLOWED TO EXPIRE...THUNDERSTORMS WITH
SMALL HAIL...WIND GUSTS TO 40 MPH AND FREQUENT LIGHTNING WILL STILL
BE POSSIBLE.

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

LAT...LON 4207 10794 4188 10795 4181 10751 4205 10751

$$

MCDONALD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
231 PM MDT THU AUG 23 2007

.SHORT TERM...TONIGHT THROUGH SUNDAY
CONVECTION IS OCCURRING OVER THE AREA AS INSTABILITY IS INCREASING.
A SHORTWAVE IS EVIDENT ON SATL PICS WITH SOME UPPER LEVEL DIVERGENCE
FORECASTED AS THE WAVE MOVES INTO THE ROCKIES TONIGHT. HAVE RAISED
THE PRECIP CHANCE OVER THE NORTH AND NORTHEAST ZONES TONIGHT THRU
12Z FRIDAY. WOULD EXPECT THE ACTIVITY TO END IN THE WEST AND
CENTRAL AROUND MIDNIGHT. ON FRIDAY THE SHORTWAVE COULD STILL BRING
SOME SHOWERS TO THE NE ZONES UNTIL 18Z...THEN THE DRYING SHOULD WORK
INTO THAT AREA...WITH COOL HIGHS. REST OF THE REGION WILL BE DRY
FRIDAY WITH WARMER HIGHS THAN TODAY. WEST NORTHWEST FLOW FOR
SATURDAY WITH DRY WEATHER AND LIGHT WIND. HIGH TEMPS WILL WARM AS
WELL. ON SUNDAY THE RIDGE AXIS WILL PASS THROUGH WY WITH A WEST
SOUTHWEST FLOW ALOFT AND LEE TROF FORMING. THIS WILL BRING SOME
WIND TO THE FAVORED AREAS OF THE CENTRAL AND SOUTH. WARMER AS WELL
ON SUNDAY WITH ONLY ISOLATED AFTERNOON STORMS OVER THE NW ZONES.

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
MEDIUM-RANGE MODELS CONTINUE TO SHOW DECREASING SPREAD IN HANDLING
ENERGY MOVING ACROSS GULF OF ALASKA THIS MORNING. THUS FOR THIS
PERIOD UPPER TROUGH WILL MOVE ACROSS THE NORTHERN ROCKIES SUNDAY
NIGHT AND MONDAY. SOME SHOWERS AND THUNDERSTORMS MAY CLIP THE
YELLOWSTONE NATIONAL PARK AREA WITH SURFACE COLD FRONT PUSHING
ACROSS THE AREA SUNDAY NIGHT AND MONDAY. UPPER RIDGE THEN BUILDS
INTO THE INTERIOR WEST BEHIND THIS TROUGH WITH GFS SHOWING SOME
SUB-TROPICAL MOISTURE ALONG WITH EMBEDDED DISTURBANCES ROTATING
THROUGH THE GREAT BASIN ACROSS SOUTHERN WYOMING. THUS...THE BEST
CHANCES OF THUNDERSTORMS TUESDAY THROUGH THURSDAY WILL BE
PRIMARILY ALONG AND SOUTH OF A CPR-RKS LINE. ABOVE NORMAL
TEMPERATURES SUNDAY WILL BE FOLLOWED BY NEAR OR SLIGHTLY ABOVE
NORMAL TEMPERATURES TO CLOSE OUT AUGUST 2007.

&&

.AVIATION...
SCATTERED THUNDERSTORMS WILL CONTINUE THIS EVENING...MOST NUMEROUS
IN AND NEAR THE MOUNTAINS...WITH A FEW LINGERING SHOWERS OVERNIGHT.
VISIBILITIES COULD BRIEFLY DROP BELOW 3 STATUTE MILES IN HEAVY RAIN
AT THE SURFACE NEAR THE THUNDERSTORMS...AREAS THAT RECEIVE HEAVY
RAIN THIS EVENING CAN EXPECT IFR CONDITIONS IN THE LOWER VALLEYS
WITH LOW CEILINGS AND VISIBILITY IN AREAS OF FOG LATER TONIGHT AND
FRIDAY MORNING.  WESTERLY FLOW WILL DECREASE MOISTURE ACROSS THE
AREA ON FRIDAY LIMITING THUNDERSTORMS TO ISOLATED COVERAGE.

&&

.FIRE WEATHER...SHOWERS AND STORMS WILL OCCUR THIS EVENING OVER THE
FIRE ZONES WITH THE BEST COVERAGE OVER THE NORTH AND EAST ZONES.
SHOWERS WILL OCCUR OVER THE NORTH AND EAST ZONES AFTER MIDNIGHT
WHILE THE REST OF THE AREA SEES DECREASING CLOUDS. SOME SHOWERS
WILL PERSIST OVER THE NORTHEAST FIRE ZONES FRIDAY MORNING...WITH
SOME DRYING IN THE AFTERNOON. ELSEWHERE FRIDAY...DRY WEATHER WILL
OCCUR WITH A MOSTLY SUNNY SKY. THE DRYING TREND WILL CONTINUE INTO
SATURDAY AND SUNDAY WITH WARMING TEMPERATURES AND LOWER AFTERNOON
HUMIDITY. THE WIND WILL INCREASE SOME ON SUNDAY WITH A LEE SIDE
TROUGH FORMING. THERE MAY BE SOME CONCERN ON SUNDAY IN THE
SOUTHERN FIRE ZONES DUE TO CRITICAL DRY FUELS. WILL ADDRESS THIS
IN THE COMING DAYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SHORT TERM...AR
LONG TERM...AEM
AVIATION...C.BAKER
FIRE WEATHER...AR

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
500 AM MDT THU AUG 23 2007

WYZ001>020-022>030-241100-
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-
500 AM MDT THU AUG 23 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS
WYOMING THIS AFTERNOON AND EVENING IN ADVANCE OF A STRONG UPPER LEVEL
LOW PRESSURE SYSTEM. THE MAIN CONCERN WITH THESE STORMS WILL BE
SEVERE WIND GUSTS...ALTHOUGH LARGE HAIL WILL ALSO BE POSSIBLE IN
STRONGER STORMS. THE STRONGEST THUNDERSTORMS WILL DEVELOP FROM
SWEETWATER COUNTY TO SOUTHERN NATRONA COUNTY FROM EARLY AFTERNOON
THROUGH THIS EVENING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

BREEZY...WARMER AND DRIER CONDITIONS ON SUNDAY MAY BRING A RETURN TO
CRITICAL FIRE WEATHER CONDITIONS ACROSS MUCH OF WEST AND CENTRAL
WYOMING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND THIS EVENING.
PLEASE REPORT WINDS GUSTS GREATER THAN 40 MPH AND ANY HAIL TO THE
NATIONAL WEATHER SERVICE.

TEAM RIVERTON