Severe Thunderstorm Warning 16, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
139 PM MDT TUE JUL 18 2000

THE LATEST SFC CHART SHOWS A LARGE AREA OF LOW PRESSURE EXTENDING
FROM SRN SASKATCHEWAN ACROSS WY TO CENTRAL CO. RADAR/SATELLITE/LTG
PLOT SHOWING TSTMS OVER ERN ID AND NW WY AS WELL AS A RECENT
DEVELOPMENT SOUTH OF RKS. A SHORTWAVE CAN BE SEEN ON WATER VAPOR
IMAGERY IN SE ID WITH TSTMS LIKELY TO FIRE IN AN ARC FROM RKS NORTH
TO CURRENT CONVECTION IN THE BIG HORN BASIN.

WX PATTERN OF SHORTWAVES MOVING THROUGH THE PERIPHERY OF THE UPPER
HIGH WILL CONTINUE NEXT 48 HOURS. AT THE SFC...A BROAD AREA OF WEAK
LOW PRESSURE REMAINS OVER THE FA. A COOL FRONT/HIGH PRESSURE WILL
MOVE INTO THE NE WED NIGHT BUT COOL AIR WILL HAVE LITTLE IF ANY
EFFECT AS NEXT AREA OF LOW PRESSURE PUSHES FRONT BACK ON THURSDAY
AND HIGH SHIFTS EAST INTO THE PLAINS. FOR TONIGHT...CURRENT
SCT CONVECTION WILL MOVE EAST ACROSS THE FA WITH THE STRONGEST
STORMS POSSIBLE OVER JOHNSON COUNTY IN AREA OF HIGHER DEWPOINTS AND
CAPE. STORMS SHOULD BE MORE NUMEROUS OVER THE NRN FA. VISIBLE
SATELLITE INDICATING CU DEVELOPMENT OVER THE REST OF THE FA FOR
ISOLD TO SCT POPS. ON WED...ANOTHER WEAK WAVE APPROACHES THE WEST
WITH UVVS SO WILL GO WITH ISOLD AFT/EVE POPS OVER THE FA. THIS
SAME SCENARIO CONTINUES ON THU WITH ISOLD -TSRA FIRING ON THE
MTNS AND SHIFTING EAST OVER THE BASINS. FWC/FAN GUIDANCE IN THE
BALLPARK WITH FAN WARMER SO WILL GO WITH BLEND.

IN THE EXTENDED...NEW MRF BRINGS A FRONT ACROSS THE FA FRI/SAT WITH
TSTMS POSSIBLE AS SHORTWAVES PASS THROUGH PERIPHERY OF UPPER HIGH.
SUNDAY LOOKS DRY WITH HIGH PRESSURE BUILDING IN BEHIND THE FRONT
AND THE UPPER RIDGE AXIS SHIFTING WEST OF WY? CAUSING SHORTWAVES TO
BE SHUNTED NORTH AND DOWNSLOPE OVER A LARGE PORTION OF THE FA.

.RIW...NONE

FS

WYZ028-190315-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
1226 PM MDT TUE JUL 18 2000

THE SEVERE WEATHER POTENTIAL IN NORTHEAST WYOMING WILL BE SLIGHT THIS
AFTERNOON AND EVENING.

SPOTTER ACTIVATION MAY BE NECESSARY LATER TODAY.

DISCUSSION...AFTERNOON HEATING WILL COMBINE WITH AMPLE MOISTURE TO
PRODUCE ENOUGH INSTABILITY FOR THUNDERSTORMS TO DEVELOP AND MOVE OFF
THE BIG HORN MOUNTAINS THIS AFTERNOON. THESE STORMS SHOULD THEN
DRIFT EAST ACROSS JOHNSON COUNTY THIS AFTERNOON AND EVENING. A
DISTURBANCE PASSING OVER THE REGION SHOULD HELP INTENSIFY A FEW OF
THESE STORMS TO PRODUCE SOME LARGE HAIL AND STRONG GUSTY WIND.

THIS OUTLOOK IS FOR THE FOLLOWING COUNTIES IN WESTERN AND CENTRAL
WYOMING:

JOHNSON

FS

WCJIN-WYNE

NNNN

WYZ004-005-008-009-182115-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
210 PM MDT TUE JUL 18 2000

...THUNDERSTORMS MOVING ACROSS THE BIG HORN BASIN...

AT 210 PM NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED STRONG
THUNDERSTORMS MOVING ACROSS THE BIG HORN BASIN. THE STRONGEST STORMS
WERE ABOUT 5 MILES NORTH OF THERMOPOLIS...OVER MEETEETSE AND ABOUT
5 MILES EAST OF CODY.  THESE STORMS WERE MOVING EAST AT 15 MPH AND
WERE PRODUCING HEAVY DOWNPOURS OF RAIN...SMALL HAIL AND FREQUENT
LIGHTNING.

ALL OUTDOOR INTERESTS SHOULD KEEP AN EYE ON THE SKY AND MOVE INTO A
SAFE SHELTER IF THREATENING WEATHER APPROACHES.

WCJIN-WYNW-
DF

WYZ001-002-004-005-008-009-182150-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
246 PM MDT TUE JUL 18 2000

...THUNDERSTORMS MOVING ACROSS NORTHERN WYOMING...

AT 245 PM...RIVERTON DOPPLER WEATHER RADAR INDICATED AN AREA OF
THUNDERSTORMS APPROACHING THE NORTHWEST PART OF YELLOWSTONE NATIONAL
PARK FROM EASTERN IDAHO.  THE LEADING EDGE OF THESE STORMS WILL
MOVE INTO THE NORTHWESTERN PART OF YELLOWSTONE PARK AROUND 3 PM.

ANOTHER AREA OF STRONGER THUNDERSTORMS WAS MOVING EASTWARD AT 25
MPH ACROSS HOT SPRINGS...WASHAKIE...AND BIG HORN COUNTIES. THE
STRONGEST THUNDERSTORM WAS LOCATED 15 MILES EAST OF THERMOPOLIS.
THIS THUNDERSTORM WAS CAPABLE OF PRODUCING QUARTER SIZE HAIL
AND STRONG WIND GUSTS TO 60 MPH...AS WELL AS VERY HEAVY RAIN.

HIKERS AND VACATIONERS SHOULD KEEP A WEATHER EYE TO THE SKY
AND SEEK SHELTER IF THREATENING WEATHER APPROACHES.  REPORT ANY SEVERE
WEATHER TO YOUR LOCAL LAW ENFORCEMvENT AGENCY.  THEY WILL RELAY YOUR
REPORT TO THE NATIONAL WEATHER SERVICE.

WCJIN-WYNW

RR

N