Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 241704
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1103 AM MDT WED JUN 24 2015

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

A FEW SHOWERS CONTINUE TO STREAM INTO SOUTHERN WYOMING THIS MORNING.
STRONGER STORMS HAD PREVIOUSLY MOVES THROUGH JOHNSON COUNTY...AND
NOW THOSE STRONGER STORMS CONTINUE TO MOVE THROUGH PORTIONS OF
NORTHEASTERN WYOMING. SHOWERS AND THUNDERSTORMS WILL RETURN THIS
AFTERNOON WITH THE CONTINUATION OF SOMEWHAT ZONAL FLOW. SHOWERS AND
THUNDERSTORMS LOOK MORE FAVORABLE ACROSS NORTHEAST
WYOMING...ESPECIALLY THE BIGHORN MOUNTAINS AND JOHNSON COUNTY.

SHOWERS WILL REMAIN OVER THIS AREA THROUGH THURSDAY
AFTERNOON....WITH SLIGHTLY COOLER TEMPERATURES ANTICIPATED. AN
AMPLIFYING RIDGE OF HIGH PRESSURE WILL BEGIN STRENGTHEN OVER THE
INTERMOUNTAIN WEST THURSDAY AFTERNOON...WITH ITS NORTHWESTERLY FLOW
MOVING ACROSS THE FORECAST AREA. A SURGE OF MOISTURE AND INSTABILITY
ACROSS THE NORTHEASTERN HALF OF THE FORECAST AREA WILL BRING SHOWER
AND THUNDERSTORM ACTIVITY THURSDAY AFTERNOON. COVERAGE WILL WEAKEN
THROUGH THE OVERNIGHT HOURS AS THE RIDGE GAINS STRENGTH.

THE AMPLIFYING RIDGE WILL PUSH LINGERING SHOWERS OUT OF THE FORECAST
AREA BY FRIDAY MORNING WITH GENERALLY DRY CONDITIONS EXPECTED
THROUGH FRIDAY NIGHT.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

SYNOPSIS...UPPER HIGH PRESSURE WILL STRENGTHEN OVER THE GREAT
BASIN OVER THE WEEKEND INTO EARLY NEXT WEEK BRINGING HOT
TEMPERATURES AND MAINLY DRY CONDITIONS. AN UPPER LEVEL DISTURBANCE
DIVING SOUTHEAST INTO THE NORTHERN HIGH PLAINS WILL BRING THE NEXT
CHANCE OF BETTER THUNDERSTORM COVERAGE ACROSS EASTERN AREAS ON
TUESDAY.

DISCUSSION...MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT WITH
STRENGTHENING UPPER HIGH OVER THE GREAT BASIN THROUGH THE WEEKEND
WITH A NORTHWARD DRIFT THROUGH EARLY NEXT WEEK.  H7 TEMPERATURES OF
18-20C CLOSER TO THE HIGH CENTER WORK THERE WAY INTO THE SW.  THIS
WILL BRING SOME HIGHS INTO THE LOWER 90S INTO THE WESTERN VALLEYS
WHILE LOWER CENTRAL BASINS PUSH INTO THE MID TO UPPER 90S WITH SOME
TRIPLE DIGITS IN THE LOWER BIGHORN BASIN.  WITH WARM AIR
ALOFT...ONLY EXPECTING A FEW THUNDERSTORMS ALONG MOUNTAIN/VALLEY
BREEZE BOUNDARIES MAINLY AROUND WASHAKIE NEEDLES WITH SOME NOCTURNAL
CLOUD TOP COOLING POSSIBLY SUSTAINING THE STORMS FURTHER INTO THE
BASINS EITHER SIDE OF THE OWL CREEK MOUNTAINS.  BOTH THE ECMWF AND
GFS SHOW A SHORTWAVE ROUNDING THE PERIPHERY OF THE UPPER HIGH ACROSS
NORTHERN MONTANA MONDAY NIGHT...THEN DIVING SE INTO THE NORTHERN
HIGH PLAINS ON TUESDAY.  THIS WILL BRING A BETTER CHANCE OF
THUNDERSTORMS MAINLY ALONG AND EAST OF THE BIGHORN RANGE AND
INTERSTATE 25 TUESDAY AFTERNOON/EVENING.  TEMPERATURES SHOULD COOL A
FEW DEGREES BEHIND THIS SYSTEM ON WEDNESDAY.

&&

.AVIATION.../18Z ISSUANCE/

EXCEPT FOR BRIEF IFR/MVFR IN THUNDERSTORMS...VFR CONDITIONS WILL
PREVAIL THROUGH THE FORECAST PERIOD. LOW CLOUDS OVER JOHNSON
COUNTY...WHICH COULD IMPACT KBYG...WILL LINGER INTO THE MID
AFTERNOON. OTHERWISE THE MAIN AVIATION CONCERN TODAY WILL BE
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS MAINLY ALONG NORTH AND
EAST OF KCOD...20W KBYG...40W KCPR LINE. ALSO SOME CONVECTION COULD
PUSH OFF THE UINTA MTS AND A NEARBY FRONT...IMPACTING SOUTHERN
SWEETWATER COUNTY THIS AFTERNOON/EVENING. THE STORMS OVER THE FAR
NORTH AND EAST COULD BE STRONG WITH LARGE HAIL AND STRONG
WIND...WHILE THE ACTIVITY OVER SWEETWATER COUNTY COULD SEE ISOLD DRY
MICROBURSTS.

&&

.FIRE WEATHER...

SHOWERS AND THUNDERSTORMS WILL REMAIN ACROSS NORTHEASTERN WYOMING
TODAY WITH COVERAGE INCREASING THROUGH THE AFTERNOON AND EVENING
HOURS. A RIDGE OF HIGH PRESSURE WILL STRENGTHEN OVER THE
INTERMOUNTAIN WEST THURSDAY...THOUGH A RETURNING SURGE OF MOISTURE
AND INSTABILITY WILL KEEP SHOWERS AND THUNDERSTORMS AROUND THURSDAY
AFTERNOON...AND EVEN ALLOW COVERAGE TO INCREASE TO COVER THE
COMPLETE NORTHEASTERN HALF OF THE FORECAST AREA. SLIGHTLY COOLER
TEMPERATURES ANTICIPATED THURSDAY. THE RIDGE OF HIGH PRESSURE WILL
STRENGTHEN TO CONTROL MUCH OF THE AREA BY FRIDAY. WARMING
TEMPERATURES AND MOSTLY DRY CONDITIONS WILL ACCOMPANY THE ARRIVAL OF
THE RIDGE.

&&

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

$$

SHORT TERM...BRANHAM
LONG TERM...AEM
AVIATION...JB
FIRE WEATHER...BRANHAM



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