Severe Thunderstorm Warning 35, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
130 PM MDT THU JUL 29 2004

.TONIGHT THROUGH SUNDAY...
FORECAST STILL LOOKING ON TRACK FOR LATER THIS AFTERNOON AND EVENING
FOR POSSIBLE STRONG THUNDERSTORMS ACROSS OUR EASTERN ZONES...
ESPECIALLY AROUND NATRONA COUNTY. SHORTWAVE IS DROPPING THROUGH SRN
MT ATTM AND PRESSURES ARE FALLING ACROSS WYOMING. SURFACE LOW IS
BEGINNING TO INTENSIFY NEAR CASPER. LOW SHOULD BEGIN TO DRIFT SE
AND INTENSIFY INTO THE EVENING HOURS. SOUTH TO SOUTHEAST FLOW AROUND
THIS LOW COULD ASSIST WITH KEEPING HIGHER DEWPOINTS INTO AT LEAST
EASTERN NATRONA COUNTY INTO THE EVENING HOURS. SPEEDMAX ROTATING
THROUGH BASE OF MT SHORTWAVE AND POSSIBLE BRIEF DUAL JET STRUCTURE
WITH NRN HIGH PLAINS JET COULD ASSIST IN A FEW SEVERE STORMS
(COMBINED WITH CAPES OF 1000-1500J/KG AND GOOD DIRECTIONAL SHEAR).
CAPES ARE ALSO BUILDING IN OUR CENTRAL ZONES BUT LATE AFTERNOON
DOWNSLOPE FLOW COULD INHIBIT MORE ORGANIZED STORMS. WITH THAT SAID...
STILL LIKE IDEA OF SCATTERED THUNDERSTORMS INTO THE EVENING HOURS FOR
ERN AND AT LEAST PART OF OUR CENTRAL ZONES NEAR OR JUST EAST OF
RIVERTON WITH BEST AREA LIKELY NATRONA COUNTY. DRIER MORE STABLE AIR
MOVES IN ON FRIDAY AS UPPER RIDGE BEGINS TO TAKEOVER. ETA KEEPS
AIRMASS DRY THROUGH SATURDAY WHILE THE GFS BRINGS IN SOME MID LEVEL
MOISTURE FROM DEVELOPING LOW OFF THE CA COAST. DRY FORECAST STILL OK
FOR NOW AS MOISTURE LIKELY TO BE SHALLOW YET AND NOT ENOUGH TO
SUPPORT AFTERNOON CONVECTION. CHALLENGE BEGINS SUNDAY WITH GFS
SPREADING SIGNIFICANT AMOUNT OF MID LEVEL MOISTURE THROUGHOUT THE
STATE ALONG WITH VERY STEEP LAPSE RATES AND LIFTED INDICES NEAR OR
SLIGHTLY BELOW ZERO. THE ETA SHUNTS WHAT MOISTURE IT HAS TO THE NORTH
WITH NEUTRAL OR SLIGHTLY POSITIVE LIS. WITH THE FAVORABLE 4-CORNERS
HIGH...I WILL EXPAND THE SLIGHT CHANCE OF THUNDERSTORM INTO THE
SALT/WYOMING RANGE AND THE WIND RIVERS FOR SUNDAY AFTERNOON. LATER
SHIFTS CAN SEE IF WE NEED TO EXPAND THAT FURTHER.

.SUNDAY NIGHT THROUGH THURSDAY...
MUCH WARMER SOUTHWEST FLOW DOMINATES THROUGH THE PERIOD WITH H7
TEMPS 16C-18C. SOUTHWEST FLOW MONDAY THROUGH THURSDAY WILL FAVOR
SHORTWAVES CLIPPING NORTHWEST MOUNTAINS WITH DRY...HOT AND BREEZY
CONDITIONS ACROSS REST OF AREA.

&&

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

&&

SKRBAC/AEM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
500 AM MDT THU JUL 29 2004

WYZ001>020-022>030-301100-
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 JUL 29 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING

.DAY ONE...TODAY AND TONIGHT

A SURFACE LOW PRESSURE SYSTEM WILL DEVELOP SOUTHEAST OF CASPER...AND
ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP THIS AFTERNOON
AND EVENING. SOME OF THE STORMS HAVE THE POTENTIAL TO BECOME SEVERE
THROUGH THE AFTERNOON AND EVENING HOURS...GENERALLY EAST OF AN
ALCOVA...TO RIVERTON...TO CODY LINE. THE STRONGEST STORMS HAVE THE
POTENTIAL TO PRODUCE VERY HEAVY RAIN...HAIL LARGER THAN PENNIES...
AND THUNDERSTORM WIND GUSTS IN EXCESS OF 55 MPH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

HOT...DRY AND BREEZY CONDITIONS WILL PREVAIL OVER WEST AND CENTRAL
WYOMING MONDAY THROUGH WEDNESDAY...RAISING THE FIRE DANGER
SIGNIFICANTLY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT HEAVY RAIN RESULTING IN FLOODING...
PENNY SIZED HAIL OR LARGER...AND STRONG THUNDERSTORM WINDS.

HAHN/AEM