Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 222114
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
314 PM MDT WED JUL 22 2015

.SHORT TERM...TONIGHT THROUGH THURSDAY

A SHORT WAVE ARRIVES IN THE SOUTHWEST FLOW WITH SUPPORT ALOFT FROM
THE RIGHT ENTRANCE REGION OF A JET STREAK IN WESTERN
MONTANA/NORTHERN IDAHO THIS EVENING. BROAD LIFT ASSOCIATED WITH AN
APPROACHING TROUGH AND A BROAD AREA OF QG FORCING WILL ALSO
ENCOURAGE UPWARD MOTION LATE THIS AFTERNOON AND TONIGHT.
ADDITIONALLY THERE WILL BE SOME ABNORMALLY HIGH MOISTURE IN THE AREA
AS TROPICAL MOISTURE STREAMS INTO OUR WESTERN MOUNTAINS...THAT
WILL CONTRIBUTE TO EFFICIENT RAINFALL FROM THE STRONGER STORMS AND
PROVIDE SOME FUEL FOR THUNDERSTORM DEVELOPMENT ON BOTH SIDES OF
THE DIVIDE. GENERALLY WE ARE EXPECTING ANYWHERE FROM ONE QUARTER
TO ONE HALF OF AN INCH ACROSS THE WESTERN MOUNTAINS WITH ANY OF
THE STRONGER STORMS CAPABLE OF PRODUCING AN INCH AND A HALF IN
LESS THAN AN HOUR...WHICH IN THE COMPLEX TERRAIN OF THE WEST COULD
INITIATE FLASH FLOODING...ESPECIALLY AS WE MOVE INTO THURSDAY AND
MORE RAIN FALLS OVER THE SAME AREAS.

EAST OF THE DIVIDE...MOST OF THE MOISTURE WILL REMAIN AT THE MID
LEVELS AND ABOVE SO THE PRIMARY THREAT WILL BE STRONG DOWNBURSTS IN
EXCESS OF 50MPH WITH THE MORE ORGANIZED CELLS. THERE WILL BE SOME
DECENT BULK SHEAR IN THE LOW TO MID LEVELS...SO A FEW OF THE MORE
ORGANIZED STORMS COULD HAVE SOME NICKEL SIZED HAIL OR LARGER.

ON THURSDAY ANOTHER JET STREAK MOVES UP FROM THE SW WITH A POSSIBLE
COUPLET FORMING OVER THE NORTHWEST AND NORTH FOR AIDED
THUNDERSTORM/HEAVY RAIN POTENTIAL. THE NORTHWEST LOOKS LIKE THE MOST
LIKELY AREA FOR STRONGER STORMS AND HEAVY RAIN BUT AREAS A LITTLE
FURTHER SOUTH WILL STILL HAVE TO BE WATCHED AND THUS THE WATCH FROM
THE SALT/WYOMING RANGE/UPPER GREEN UP TO YELLOWSTONE AND THE
ABSAROKAS EXTENDING THROUGH THURSDAY AFTERNOON AND INTO THE EVENING.
THE GRADIENT WILL INCREASE A BIT ON THURSDAY WITH STEADY 20 TO 30
MPH WIND EXPECTED THURSDAY AFTERNOON ALONG THE SOUTHERN WIND
CORRIDOR FROM ROCK SPRINGS TO CASPER. THE MOUNTAINS WILL SEE
INCREASING WIND THE NEXT COUPLE DAYS TOO.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

BEGINNING OF FCST...UPR LV SWRLY FLOW WITH EMBEDDED SW TROF MOVING
NEAR OR OVR NWRN WY W/ MODEST BUT DECREASING MID LVL MOISTURE ACROSS
THE NWRN HALF OF THE STATE. GENERALLY WIDELY SCATTERED STORMS
AROUND...MAINLY OVR THE W/NW AND NRN FA. SOUNDINGS SHOW LONG SKINNY
RELATIVELY LOW CAPE IN THIS AREA WITH LOTS OF SHEAR. STRONG TO
OCCASIONAL BORDERLINE SVR DOWNDRAFTS WITH SMALL HAIL POSSIBLE.
OTHERWISE...GUSTY WINDS ACROSS THE S/SERN ZONES SHOULD BE ON THE
DECREASE...SO BORDERLINE RED FLAG CONDITIONS...IF THEY EXISTED IN
THE AFTERNOON.

FRIDAY...UPR RIDGING BEGINNING WITH DECREASING MOISTURE THROUGHOUT
THE ATMOSPHERE...AND ISOLATED TO WIDELY SCATTERED STORMS OVR ROUGHLY
THE SAME AREA AS ON THURSDAY...JUST LESS OF THEM. AGAIN...LOW CAPE
AND HIGH SHEAR WITH GUSTY STRONG...ISOLATED SVR...WINDS POSSIBLE.

SATURDAY...DRY ACROSS MOST OF THE SRN CWA...ISOLATED TO WIDELY
SCATTERED STORMS W AND N...MAINLY MOUNTAINS. LOW CAPE AND DECREASING
SHEAR...WITH STRONGER STORMS SHOWING WITHIN THE FIRST HR OR SO OF
CI. GUSTY WINDS AGAIN THE MAIN THREAT.

SUNDAY THRU THE END OF THE FCST...MAINLY DRY FCST WITH A FEW
ISOLATED...MAINLY OROGRAPHICALLY DRIVEN...STORMS ACROSS THE NW AND N
FA. UPR LVL SW FLOW REMAIN UNTIL MON NIGHT ONWARD WHEN A STRONG UPR
TROF PASSES ACROSS THE NRN CONUS...FLATTENING THE FLOW AND PUSHING A
FRONT THRU THE REGION...DROPPING HIGH TEMPS TO JUST BELOW SEASONAL
THRU THE END OF THE FCST.

&&

.AVIATION.../00Z ISSUANCE/

THUNDERSTORMS WITH OCCNL MVFR CONDITIONS WILL CONTINUE TO FORM ALONG
A COLD FRONT AS IT MOVES THROUGH WESTERN WYOMING. ISOLATED STRONG TO
SEVERE THUNDERSTORMS ARE POSSIBLE VCNTY AND WEST OF A KAFO- KJAC-
KCOD LINE WITH LARGE HAIL AND DAMAGING WIND OVER 50KTS POSSIBLE
THROUGH AROUND 4Z THURSDAY. AFTER 4Z THURSDAY...ISOLATED
THUNDERSTORMS AND SCATTERED SHOWERS MAY THEN BE POSSIBLE ALONG THIS
SAME KAFO-KJAC-KCOD LINE THROUGH 12Z THURSDAY. SHOWERS AND STORMS
WILL BECOME STRONGER AND MORE NUMEROUS AGAIN AFTER 18Z THURSDAY AND
WILL CONTINUE THROUGH THE TAF PERIOD.

A DISTURBANCE WILL CONTINUE TO PUSH NORTHEASTWARD ACROSS WYOMING
THIS EVENING. A LINE OF HIGH-BASED SHOWERS AND STORMS WILL LIKELY
DEVELOP AHEAD OF THIS SYSTEM WITH THE MAIN HAZARD OF MICROBURST
WINDS OVER 40KTS THROUGH 06Z THURSDAY MAINLY ACROSS THE SOUTH AND
EAST OF THE DIVIDE. MOST TERMINALS COULD AT LEAST EXPERIENCE VCTS
WITH THIS DISTURBANCE...WITH BETTER CHANCES OF THUNDERSTORMS COMING
ACROSS THE KRKS...KLND...AND KCPR AREAS. ON THURSDAY...STORMS WILL
OCCUR MAINLY ALONG AND NORTHWEST OF A LINE FROM KBYG TO KRIW TO KEMM
BUT THE MAIN STORY EAST OF THE DIVIDE ON THURSDAY WILL BE PERSISTENT
15 TO 30 KNOT SOUTHWEST WIND WITH OCCASIONAL ERRATIC GUSTS FROM
STORMS OVER THE MOUNTAINS.

&&

.FIRE WEATHER...

AFTERNOON SHOWERS AND THUNDERSTORMS WILL REMAIN IN THE FORECAST FOR
TONIGHT AND TOMORROW. MAIN THREAT WITH THE STORMS EAST OF THE DIVIDE
WILL BE LIGHTNING AND STRONG WIND WHILE THE PRIMARY THREATS ACROSS
THE WEST WILL BE HEAVY RAIN AND HAIL.

A GUSTY 15 TO 30 MPH ACROSS THE WIND CORRIDOR BETWEEN ROCK SPRINGS
AND CASPER AS WELL AS OVER THE MOUNTAINS. THE GOOD NEWS IS THAT THE
RELATIVE HUMIDITY WILL BE MARGINAL IN AREAS WITH CRITICAL FUELS BUT
WITH WIND THAT STRONG AND PERSISTENT...THERE COULD BE SOME LOCAL
ISSUES SHOULD A FIRE START AND GET INTO CERTAIN FINER FUELS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THURSDAY EVENING FOR WYZ001-002-012-
013-023>026.

&&

$$

SHORT TERM...ALLEN
LONG TERM...BRAUN
AVIATION...ALLEN
FIRE WEATHER...ALLEN



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