Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 212029
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
229 PM MDT TUE JUL 21 2015

.SHORT TERM...TONIGHT THROUGH WEDNESDAY

WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS
WESTERN AND CENTRAL WYOMING THIS EVENING...WITH MOST OF THE
ACTIVITY EXPECTED TO BE OVER THE WESTERN MOUNTAINS AS ANOTHER
DISTURBANCE OVER IDAHO...AS OF ABOUT 2 PM THIS AFTERNOON...
CONTINUES TO TRACK EAST. STORMS ARE EXPECTED TO HOLD TOGETHER A
LITTLE LONGER EARLY THIS EVENING WITH A BETTER CHANCE OF SOME
THUNDER MAKING IT INTO SOME OF THE BASINS AS THIS DISTURBANCE
ARRIVES AND SOME WEAK TO MARGINAL SHEAR DEVELOPS...ESPECIALLY
ACROSS THE NORTHWEST. STORMS ARE NOT EXPECTED TO BE SEVERE BUT
THERE COULD BE A FEW STRONGER WIND GUSTS IN EXCESS OF 40 MPH AS
STORMS COLLAPSE.

WEDNESDAY IS EXPECTED TO BE MORE ACTIVE AS A STRONGER WAVE ARRIVES
WITH SUPPORT ALOFT FROM THE RIGHT ENTRANCE REGION OF A JET STREAK
IN WESTERN MONTANA/NORTHERN IDAHO AND WITH BROAD LIFT ASSOCIATED
WITH AN APPROACHING TROUGH AND A BROAD AREA OF QG FORCING ALSO
ENCOURAGING UPWARD MOTION WEDNESDAY AFTERNOON. ADDITIONALLY THERE
WILL BE SOME ABNORMALLY HIGH MOISTURE IN THE AREA AS THE REMNANTS
OF TS DOLORES STREAM INTO OUR WESTERN MOUNTAINS THAT WILL
CONTRIBUTE TO EFFICIENT RAINFALL AND PROVIDE SOME FUEL FOR
THUNDERSTORM DEVELOPMENT ON BOTH SIDES OF THE DIVIDE. MOST OF THE
LOW LEVEL MOISTURE WILL STRIP OFF IN THE WESTERN
MOUNTAINS...THEREFORE A FLASH FLOOD WATCH HAS BEEN HOISTED BEYOND
18Z WEDNESDAY TO COVER THE STRONGER STORMS EXPECTED TO DEVELOP.
EAST OF THE DIVIDE...MOST OF THE MOISTURE WILL REMAIN AT THE MID
LEVELS AND ABOVE SO THE PRIMARY THREAT FROM STORMS EAST OF THE
DIVIDE AND ACROSS FAR SOUTHERN WYOMING 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...ESPECIALLY AS WE GET FURTHER INTO THE AFTERNOON.

.LONG TERM...WEDNESDAY NIGHT THROUGH THURSDAY

INCREASINGLY MOIST SW FLOW AHEAD OF DEVELOPING WEST COAST TROUGH
LATE WEDNESDAY THROUGH THURSDAY WILL LEAD TO A HIGH LIKELIHOOD OF
THUNDERSTORMS ACROSS THE WEST. HIGH SURFACE DEW POINTS TO THE
SOUTH WILL COMBINE WITH SOME MID LEVEL MONSOONAL/REMNANT DOLORES
MOISTURE TO GRADUALLY INCREASE THE PW`S ACROSS ESPECIALLY THE NW
WEDNESDAY INTO THURSDAY. IN ADDITION...THE RIGHT ENTRANCE REGION
OF A JET STREAK MAY HELP WITH THE FORCING IN THE NW WED EVENING.
ON THURSDAY ANOTHER JET STREAK MOVES UP FROM THE SW WITH A
POSSIBLE COUPLET FORMING OVER THE NW AND N FOR AIDED TSTM/HEAVY
RAIN POTENTIAL. WE WILL HAVE A FLASH FLOOD WATCH OUT THAT STARTS
WED AFTN AND CONTINUES INTO THURSDAY EVENING FOR MOST OF THE FAR
WEST. THE NW LOOKS BEST BUT AREAS A LITTLE FURTHER SOUTH WILL
STILL HAVE TO BE WATCHED AND THUS THE WATCH FROM THE SALT/WYOMING
RANGE/UPPER GREEN NWD TO YNP AND THE ABSAROKAS. TROUGH WEAKENS AND
SWINGS ACROSS ON FRIDAY WITH A CHANCE OF SHOWERS AND THUNDERSTORMS
ALONG IT ALONG WITH BREEZY TO WINDY CONDITIONS. THE MOUNTAINS WILL
SEE INCREASING WIND THE NEXT COUPLE DAYS...ESPECIALLY THU INTO
FRIDAY. ASSOCIATED FRONT MAY HELP WITH STORMS IN THE FAR NORTH
LATE THURSDAY. THE GFS IS SHOWING MORE ENERGY WITH THIS TROUGH ON
FRIDAY FOR MORE MTN TSTMS CHANCES AND HAVE NUDGED FORECAST THAT
WAY. DRIER OVER THE WEEKEND AS HEIGHTS REBUILD BUT A NEW
APPROACHING SHORTWAVE MAY HELP WITH TSTMS IN THE NW AS EARLY AS
LATE SUN AFTN OR EVENING AS AN ASSOCIATED COLD FRONT HITS THE
NORTH AND WEST. GENERALLY VERY WARM TO EVEN HOT AND DRY SOUTH AND
EAST WITH INCREASING WIND LATE IN THE WEEKEND INTO EARLY NEXT WEEK
AS THE NEXT TROUGH APPROACHES. A STRONGER COLD FRONT LOOKS TO
IMPACT THE MONDAY INTO MONDAY NIGHT WITH VERY WARM AND WINDY CONDS
AHEAD OF IT IN THE SE HALF WITH SOME TSTMS CHANCES ALONG IT
FURTHER NORTH. TUESDAY WILL LIKELY BE COOLER...ESPECIALLY NORTH
WITH LIMITED SHOWER/TSTM CHANCES.

&&

.AVIATION.../00Z ISSUANCE/

VCTS/VCSH CONTINUING INTO THE LATE EVENING ACROSS THE WEST. THE
TWO MAIN AREAS OF SHOWERS AND THUNDERSTORMS INTO THE EVENING WILL
OCCUR MAINLY ALONG AND SOUTH OF A KRKS- KCPR LINE AND ACROSS
NORTHWEST WYOMING...OR MAINLY VCNTY AND NORTH OF A KJAC- KCOD
LINE. A DRIER AND MORE STABLE AIRMASS WILL HOLD IN BETWEEN ACROSS
THE CENTRAL BASINS...BUT SOME HIGH-BASED SHOWERS OFF THE HIGH
TERRAIN MAY MOVE INTO THESE AREAS (VCNTY KLND-KRIW- KWRL) AND
PRODUCE ISOLD MICROBURSTS 30-40KTS THROUGH 03Z. THE MOST ACTIVE
PERIOD FOR CONVECTION IS EXPECTED THROUGH 05Z WED...WITH PARTLY
CLEARING SKIES AFTER 06Z WED. SHOWERS AND THUNDERSTORMS RETURN
AFTER 18Z WEDNESDAY WITH HEAVY RAIN IN THE WESTERN MOUNTAINS AND
40-50KT MICROBURSTS POSSIBLE EAST OF THE DIVIDE THROUGH 05Z
THURSDAY.

&&

.FIRE WEATHER...

AFTERNOON SHOWERS AND THUNDERSTORMS WILL REMAIN A THEME FOR THE NEXT
COUPLE DAYS. STORMS EXPECTED TO IMPACT WESTERN AND CENTRAL WYOMING
THROUGH THURSDAY. STORMS MAY CONTAIN GUSTY AND ERRATIC WIND AND SMALL
HAIL JUST ABOUT EVERYWHERE WITH HEAVY RAIN EXPECTED ACROSS MUCH OF
TETON DISPATCH AND NORTHERN CODY DISPATCH...AS WELL AS PORTIONS OF
WESTERN RAWLINS DISPATCH. BREEZY WIND WILL BE POSSIBLE WEDNESDAY
AFTERNOON ACROSS THE WIND CORRIDOR BETWEEN ROCK SPRINGS AND
CASPER BUT THE AREAS WITH THE STRONGEST ANTICIPATED WIND ARE NOT
CURRENTLY EXPECTED TO SEE CRITICALLY LOW HUMIDITY. PORTIONS OF THE
BIG HORN BASIN MAY APPROACH THE MID TEENS FOR HUMIDITY ON
WEDNESDAY... BUT WILL HAVE NEITHER THE CRITICAL WINDS NOR THE
CRITICAL FUELS. HOWEVER...THE STORMS WILL BE DRIER IN THE BIGHORN
AND WIND RIVER BASINS ON WEDNESDAY SO THERE COULD BE SOME NATURAL
STARTS AND SOME IA ACTIVITY.

&&

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

&&

$$

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


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